EPA-821-R-01-004
January 2001
Method 1687
Total Kjeldahl Nitrogen in Water and Biosolids by Automated
Colorimetry with Preliminary Distillation/Digestion
DRAFT
January 2001
U.S. Environmental Protection Agency
Office of Water
Office of Science and Technology
Engineering and Analysis Division (4303)
1200 Pennsylvania Ave. NW
Washington, D.C. 20460
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Method 1687
Acknowledgments
This method was prepared under the direction of William A. Telliard of the U.S. Environmental Protection
Agency's (EPA's) Office of Water. The method was prepared under EPA Contract 68-C-98-139 by
DynCorp Information and Enterprise Technology.
Disclaimer
This draft method has been reviewed and approved for publication by the Analytical Methods Staff within
the Engineering and Analysis Division of EPA. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use. EPA plans further validation of this draft method. The
method may be revised following validation to reflect results of the study. This method version contains
minor editorial changes to the November 1999 version.
EPA welcomes suggestions for improvement of this method. Suggestions and questions concerning this
method or its application should be addressed to:
Maria Gomez-Taylor
Engineering and Analysis Division (4303)
U.S. Environmental Protection Agency
1200 Pennsylvania Ave., NW
Washington, DC 20460
Phone: (202)260-7134
Fax: (202)260-7185
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Method 1687
Note: This method is performance based. The laboratory is permitted to omit any step or modify any
procedure provided that all performance requirements in this method are met. The laboratory may
not omit any quality control analyses. The terms "shall," "must," and "may not" define procedures
required for producing reliable results. The terms "should" and "may" indicate optional steps that
may be modified or omitted if the laboratory can demonstrate that the modified method produces
results equivalent or superior to results produced by this method.
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Method 1687
Total Kjeldahl Nitrogen in Water and Biosolids by
Automated Colorimetry with Preliminary
Distillation/Digestion
1.0 Scope and Application
1.1 This method describes procedures for the determination of total kjeldahl nitrogen (TKN) and/or
organic nitrogen in drinking, ground, and surface water; domestic and industrial waste; and biosolids
(municipal sewage sludge). Digestion/distillation of the TKN from the sample is followed by
analysis using automated colorimetry. This method is based on U.S. Environmental Protection
Agency (EPA) Method 351.1: Nitrogen, Kjeldahl (Colorimetric; Titrimetric; Potentiometric)
(Reference 16.1). This method is associated with Method 1691: Municipal Biosolids Sampling
Guidance (Reference 16.2).
1.2 This method is to be used in EPA's data gathering and monitoring programs under the Clean Water
Act, the Resource Conservation and Recovery Act, the Comprehensive Environmental Response,
Compensation, and Liability Act, the Solid Waste Disposal Act, and the Safe Drinking Water Act.
1.3 Method detection limits and minimum levels for TKN have not been formally established for this
draft method. These values will be determined during the validation of the method.
1.4 This method is performance based. The laboratory is permitted to omit any step or modify any
procedure, provided that all performance requirements in this method are met. Requirements for
establishing method equivalency are given in Section 9.1.2.
1.5 Each laboratory that uses this method must demonstrate the ability to generate acceptable results
using the procedures in Section 9.2.
2.0 Summary of Method
2.1 The kjeldahl nitrogen in the sample is first converted to ammonia by metal-catalyzed acid digestion.
The resulting ammonia is then separated from the sample by distillation. The ammonia released is
captured in a dilute sulfuric acid solution. A procedure is given for removal of the ammonia present
in the sample prior to digestion. A sample so treated then gives a result of organic nitrogen after
digestion/distillation.
2.2 The ammonia concentration of the distillate is determined by automated colorimetric measurement of
indophenol blue, which is formed when ammonia reacts with alkaline phenol and hypochlorite.
2.3 Cupric sulfate has been substituted for the historically-used mercuric sulfate due to toxicity and
waste disposal problems associated with mercury.
2.4 Quality is assured through calibration and testing of the analytical instruments and testing of the
sample preparation.
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Method 1687
3.0 Definitions
Definitions for terms used in this method are given in Section 18.
4.0 Interferences
4.1 Nitrate in large quantities (>10 mg/L) will oxidize ammonia produced by the digestion and cause a
negative bias. No known method exists to prevent this interference, but its effect can be predicted on
the basis of preliminary nitrate determination of the sample.
4.2 Inorganic salts or solids will increase the temperature at which the digestion takes place, and
digestion temperatures in excess of 400°C will cause pyrolitic loss of nitrogen. If high salt/solid
content is suspected, addition of extra volumes of sulfuric acid will stabilize the temperature.
Approximately 1 mL H2SO4 per g of salt/solid will preserve the proper ratio. Monitoring of the
digestion temperature will indicate if problems are occurring.
4.3 Large amounts of organic matter can consume the acid in the digestion reagent, causing the
temperature of the digestion to rise above 400°C. Addition of 10 mL H2SO4 per 3000 mg COD will
prevent this interference. Monitor digestion temperature and pH if this correction is used.
4.4 Residual chlorine, if present, must be removed by pretreatment of the sample with sodium thiosulfate
before digestion/distillation. Typically, this will be necessary if the sample contains free water or is
aqueous.
4.5 Nitrogen occurring in certain organic compounds will not be measured by this method. These
compounds include those having nitrogen in the following forms: azide, azine, azo, hydrazone,
nitrate, nitrite, nitrile, nitro, nitroso, oxime, and semicarbazone.
5.0 Safety
5.1 The toxicity or carcinogenicity of reagents used in this method has not been fully established. Each
chemical and environmental sample should be regarded as a potential health hazard and exposure
should be minimized. Each laboratory is responsible for maintaining a current awareness file of
OSHA regulations regarding the safe handling of the chemicals specified in this method. A reference
file of material safety data sheets (MSDS) should be available to all personnel involved in the
chemical analysis. Additional information on laboratory safety can be found in Reference 16.3.
5.2 If samples originate from a highly contaminated area, appropriate sample handling procedures must
be followed to minimize worker exposure.
5.3 All personnel handling environmental samples known to contain or to have been in contact with
human waste should be immunized against known disease causative agents.
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Method 1687
6.0 Apparatus and Equipment
NOTE: Brand names, suppliers, and part numbers are for illustration only, and no endorsement
is implied. Equivalent performance may be achieved using apparatus and materials other than
those specified here. Meeting the performance requirements of this method is the responsibility of
the sampling team and laboratory.
6.1 Equipment for distillation and digestion
6.1.1 Kjeldahl flask, 800 mL.
6.1.2 Erlenmeyer flasks, 500 mL.
6.1.3 Distillation apparatus, all glass, consisting of a vertical condenser with an outlet tip that can
be submerged below the surface of the receiving solution in a 500 mL Erlenmeyer flask.
6.1.4Heating unit, adjusted so that 250 mL of water is brought to a full boil in 5 minutes.
6.2 Colorimetric analysis—Automated analytical equipment with the capability of delivering the
reagents specified in Figure 1 at the specified rates, and with a colorimeter capable of measuring at
630 - 660 nm.
6.3 General equipment
6.3.1 Analytical balance, capable of weighing to 0.001 g (1 mg).
6.3.2 Hot plate or other heating apparatus.
6.3.3 Boiling chips or glass beads.
6.3.4Watchglasses or dishes for weighing samples
7.0 Reagents and Consumable Materials
7.1 All water and reagents used in this method must be free of ammonia.
7.1.1 Ammonia-free water—Ammonia-free water can be prepared by passing reagent water through
an ion-exchange column containing a mixture of both strongly acidic cation and strongly basic
anion exchange resins. When necessary, regenerate the column according to the
manufacturer's instructions.
7.1.2 All reagents should be ACS Reagent Grade or better.
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Method 1687
7.2 Sulfuric acid
7.2.1 5N Sulfuric acid (H2SO4)—Carefully add 139 mL of concentrated H2SO4 to approximately
500 mL reagent water. Cool to room temperature and dilute to 1 L.
7.2.2 0.04N Sulfuric acid—Carefully add 4 mL of 5N H2SO4 (Section 7.2.1) to approximately 300
mL reagent water. Cool to room temperature and dilute to 500 mL.
7.3 Sodium hydroxide solutions
CAUTION: Considerable heat is generated upon dissolution of sodium hydroxide in
water. It may be advisable to cool the container in an ice bath when preparing sodium
hydroxide solutions.
7.3.1 0.1N Sodium hydroxide (NaOH)—Dissolve 4.0 g NaOH in reagent water, cool, and dilute to
1L.
7.3.2 6N Sodium hydroxide—Dissolve 240 g NaOH in reagent water, cool, and dilute to 1 L.
7.3.3 IN Sodium hydroxide—Dissolve 40 g NaOH in reagent water, cool, and dilute to 1 L.
7.4 Borate buffer
7.4.1 0.025M Sodium tetraborate—Dissolve 5 g anhydrous sodium tetraborate (Na2B4O7) or 9.5 g
sodium tetraborate decahydrate (Na2B4O7»10H2O) in reagent water and dilute to 1 L.
7.4.2 Add 88 mL of 0.1N NaOH solution (Section 7.3.1) to 500 mL 0.025M Na2B4O7 (Section
7.4.1) and dilute to 1 L with reagent water.
7.5 Sodium phenate—Using a 1 L Erlenmeyer flask, dissolve 83 g phenol in 500 mL reagent water.
Add 32 g NaOH cautiously and in small increments while agitating the flask. Periodically cool the
flask under running water. When cool, dilute to 1 L.
7.6 Sodium hypochlorite solution—Dilute 250 mL of a bleach solution containing 5.25% NaOCL (such
as "Clorox") to 500 mL. Available chlorine level should approximate 2 - 3%. Since "Clorox" is a
proprietary product, its formulation is subject to change. The analyst must remain alert to detecting
any variation in this product significant to its use in this procedure. Due to the instability of bleach,
storage over an extended period should be avoided.
7.7 5% Disodium ethylenediamine-tetraacetate (EDTA)—Dissolve 50 g EDTA (disodium salt) and
approximately six pellets NaOH in 1 L of reagent water.
7.8 0.05% Sodium nitroprusside—Dissolve 0.5 g of sodium nitroprusside (Na2Fe(CN)5NO»2H2O) in 1
L reagent water.
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Method 1687
7.9 Blank sand—Bake 500 g diatomaceous earth or clean sand at 400°C for eight hours. Cool and store
in a glass container with a sealing lid.
7.10 Ammonia standards
7.10.1 Ammonia stock solution (1000 mg/L NH3-N)—Dissolve 0.382 g of anhydrous
ammonium chloride (NH4C1) in reagent water and dilute to 100 mL in a volumetric
flask. NH4C1 should be dried at 105 °C prior to use.
7.10.2 Ammonia working standard (10 mg/L NH3-N)—In a volumetric flask, dilute 10 mL of
ammonia stock solution (Section 7.10.1) to 1 L.
7.11 Digestion reagent—Dissolve 134 g potassium sulfate (K2SO4) and 7.3 g cupric sulfate (CuSO4) in
800 mL reagent water. Slowly add 134 mL cone, sulfuric acid. Cool and dilute solution to 1 L.
Mix well. Store the solution at room temperature.
7.12 Sodium hydroxide-sodium thiosulfate solution—Dissolve 500 g NaOH and 25 g Na2S2O3»5H2O in
reagent water and dilute to 1 L.
7.13 Nicotinic acid standard 100 mg/L organic N—Dissolve 21.637 g nicotinic acid (C6H5NO2) in
approximately 150 mL reagent water. Dilute to 200 mL.
7.14 Dechlorinating reagent—Dissolve 0.35 g sodium thiosulfate (Na2S2O3»5H2O) in reagent water and
dilute to 100 mL. One mL of this reagent will neutralize 1 mg/L of residual chlorine in a 500 mL
sample aliquot.
7.15 Quality control sample (QCS)—A prepared quality control sample from a standards vendor (ERA
catalog # 545, or equivalent).
8.0 Sample Collection, Preservation and Storage
8.1 Ammonia is a pervasive contaminant. Minimize exposure of samples to air as much as possible.
8.2 A sufficient volume of sample for analysis must be collected using the procedures found in
Reference 16.2 for biosolids samples and Reference 16.4 for water and wastewater samples.
8.3 Ammonia can be formed or lost during storage due to biological activity or lost by volatilization or
oxidation. The following preservation procedures will help prevent significant changes in the analyte
concentration.
8.3.1 Samples should be collected in wide mouth jars with a minimum of air space.
8.3.2 Aqueous samples or samples that contain free water
8.3.2.1 Samples should be checked for residual chlorine and treated with sodium
thiosulfate, if necessary, during collection.
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Method 1687
8.3.2.2 Samples should be preserved with 2 mL concentrated H2SO4 and cooled to 4°C
as soon as possible after collection. The holding time for samples should not
exceed 28 days from sampling.
8.3.3 If the sample contains no free water or is solid, the sample should be cooled to 4°C as soon as
possible after collection. The holding time for samples should not exceed 28 days from
sampling.
8.4 Collect a separate sample for total solids determination (Appendix A). The holding time for total
solids determination is seven days.
9.0 Quality Control
9.1 Each laboratory using this method is required to operate a formal quality control (QC) program.
The minimum requirements of this program consist of an initial demonstration of laboratory
capability and the ongoing analysis of laboratory reagent blanks, precision and recovery standards,
and matrix-spiked samples as a continuing check on performance. The laboratory is required to
maintain performance records that define the quality of data thus generated. Laboratory
performance is compared to established performance criteria to determine if the results of analyses
meet the performance characteristics of the method.
9.1.1 The analyst shall make an initial demonstration of the ability to generate acceptable accuracy
and precision with this method. This ability is established as described in Section 9.2.
9.1.2 In recognition of advances that are occurring in analytical technology, the analyst is permitted
certain options to improve separations or lower the costs of measurements, provided that all
performance specifications are met. Changes that degrade method performance are not
allowed. If an analytical technique other than the technique specified in this method is used,
that technique must have a specificity equal to or better than the specificity of the techniques
in this method for TKN in the sample of interest. Specificity is defined as producing results
equivalent to the results produced by this method for analytical standards (Section 9.4) and,
where applicable, environmental samples (Section 9.5), and as meeting all of the QC criteria
stated in this method.
9.1.2.1 Each time a modification is made to this method, the analyst is required to repeat
the IPRtest in Section 9.2.2 to demonstrate that the modification produces
results equivalent to or better than results produced by this method. If the
detection limit of the method will be affected by the modification, the analyst
must demonstrate that the MDL (40 CFR part 136, appendix B) is less than or
equal to the MDL in this method or one-third the regulatory compliance level,
whichever is higher. The tests required for this equivalency demonstration are
given in Section 9.1.2.2.4.
9.1.2.2 The laboratory is required to maintain records of modifications made to this
method. These records include the following, at a minimum:
9.1.2.2.1 The names, titles, addresses, and telephone numbers of the
analyst(s) who performed the analyses and modification, and of the
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Method 1687
quality control officer who witnessed and will verify the analyses
and modification.
9.1.2.2.2 A listing of pollutants) measured (TKN).
9.1.2.2.3 A narrative stating reason(s) for the modification.
9.1.2.2.4 Results from all quality control (QC) tests comparing the modified
method to this method, including:
(a) Calibration (Section 10).
(b) Calibration verification (Section 9.6).
(c) Initial precision and recovery (Section 9.2.2).
(d) Analysis of blanks (Section 9.3).
(e) Accuracy assessment (Sections 9.5 and 9.7).
(f) Ongoing precision and recovery (Section 9.4).
(g) Method detection limit (Section 9.2.1)
9.1.2.2.5 Data that will allow an independent reviewer to validate each deter-
mination by tracing the instrument output (weight, absorbance, or
other signal) to the final result. These data are to include:
(a) Sample numbers and other identifiers.
(b) Sample preparation dates.
(c) Analysis dates and times.
(d) Analysis sequence/run chronology.
(e) Sample weight or volume.
(f) Dry weight ratio (solid and semi-solid samples only;
Appendix A).
(g) Distillate solution volume.
(h) Make and model of analytical balance and weights
traceable to NIST.
(i) Copies of logbooks, printer tapes, and other
recordings of raw data.
(j) Data system outputs, and other data to link the raw
data to the results reported.
9.1.3 Analyses of laboratory blanks are required to demonstrate freedom from contamination. The
procedures and criteria for blank analyses are described in Section 9.3
9.1.4 Analyses of ongoing precision and recovery samples are required to demonstrate that the
sample preparation and analysis are within the specified limitations. The procedure and
criteria for OPR sample analysis are described in Section 9.4.
9.1.5 Analyses of matrix spike and matrix spike duplicate samples are required to demonstrate
method accuracy and precision, and to monitor interferences caused by the sample matrix.
The procedure and criteria for spiking are described in Section 9.5.
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Method 1687
9.1.6 Analyses of calibration verification standards are required to demonstrate accuracy and
stability of the initial calibration. The procedure and criteria for calibration verification
analyses are described in Section 9.6.
9.1.7 Analyses of quality control samples (QCS) are required to demonstrate the accuracy of the
calibration standards and the analytical system. The procedure and criteria for the QCS
sample analyses are described in Section 9.7.
9.2 Initial demonstration of laboratory capability—The initial demonstration of laboratory capability is
used to characterize laboratory performance and method detection limits. The MDL and IPR for
solid samples should be determined using blank sand as a reference matrix. The MDL and IPR for
aqueous samples should be determined using reagent water as a reference matrix.
9.2.1 Method detection limit (MDL)—The MDL should be established for TKN according to the
procedures at 40 CFR part 136, appendix B (Reference 16.5). First, spike a reference matrix
with nicotinic acid at a concentration one to five times the estimated detection limit. To
determine the MDL, take seven replicate aliquots of the spiked reference matrix and process
each aliquot through each step of the analytical method. Perform all calculations and report
the concentration values in the appropriate units. Aqueous and/or solid method detection
limits should be determined every year or whenever a modification to the method or analytical
system is made that will affect the MDL.
9.2.2 Initial precision and recovery (IPR)—To establish the ability to generate acceptable precision
and accuracy, the analyst shall perform the following operations:
9.2.2.1 Prepare four spiked samples as detailed in Section 9.4. Using the procedures in
Section 11, prepare and analyze these spiked samples for TKN.
9.2.2.2 Using the results of the set of four analyses, compute the average percent
recovery (X) and the standard deviation (s) of the percent recovery for TKN.
9.2.2.3 Compare s and X with the corresponding limits for initial precision and recovery
in Table 1. If s and X meet the acceptance criteria, system performance is
acceptable and analysis of samples may begin. If, however, s exceeds the
precision limit or X falls outside the range for recovery, system performance is
unacceptable. In this event, correct the problem, and repeat the test.
9.3 Laboratory blanks—Laboratory blanks are analyzed to demonstrate freedom from contamination.
Aqueous samples should be run with an aqueous blank, and solid samples should be run with a solid
blank.
9.3.1 Prepare and analyze a laboratory blank initially (i.e., with the tests in Section 9.2) and with
each analytical batch. The blank must be subjected to the same procedural steps as a sample,
and will consist of 250 mL of ammonia-free reagent water (aqueous blank) or 5 g aliquot of
blank sand in 250 mL of ammonia-free reagent water (solid blank).
9.3.2 If material is detected in the aqueous or solid blank at a concentration greater than the
aqueous or solid MDL (Section 1.3), analysis of samples is halted until the source of
contamination is eliminated and a blank shows no evidence of contamination. All samples
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Method 1687
must be associated with an uncontaminated laboratory blank before the results may be
reported for regulatory compliance purposes.
9.4 Ongoing precision and recovery (OPR)—The laboratory must analyze at least one ongoing precision
and recovery sample with each analytical batch. A solid OPR should be run with solid samples, and
an aqueous OPR should be run with aqueous samples. An aqueous OPR is prepared by spiking
reagent water with nicotinic acid standard at a concentration so that the concentration of TKN in the
OPR is one to five times the ML. A solid OPR is prepared by mixing 5 g of blank sand with 250
mL reagent water and spiking with nicotinic acid standard so that the concentration of TKN in the
OPR is one to five times the ML. The spiked aliquot is carried through the entire analytical process
(Section 11). Calculate accuracy as percent recovery. If the recovery of the analyte falls outside the
control limits in Table 1, the system performance is unacceptable, and the source of the problem
should be identified and resolved before continuing analyses.
9.5 Matrix spike and matrix spike duplicates (MS/MSD)—To assess the performance of the method on
a given sample matrix, the laboratory must spike, in duplicate, a minimum of 10% (one sample in
10) of the samples from a given sampling site or, if for compliance monitoring, from a given
discharge. Blanks may not be used for MS/MSD analysis.
9.5.1 The concentration of the MS and MSB shall be determined as follows:
9.5.1.1 If, as in compliance monitoring, the concentration of analytes in the sample is
being checked against a regulatory concentration limit, the spiking level shall be
at that limit or at 1-5 times the background concentration of the sample,
whichever is greater.
9.5.1.2 If the concentration of TKN in a sample is not being checked against a
regulatory concentration limit, the spike shall be at 1-5 times the background
concentration.
9.5.1.3 For solid and sludge samples, the concentration added should be expressed as
mg/kg and is calculated for a one gram aliquot by multiplying the added analyte
concentration (mg/L) in solution by the conversion factor 100 (mg/L x
0.1L/0.001kg= 100).
9.5.2 Assessing spike recovery
9.5.2.1 To determine the background concentration, analyze one sample aliquot from
each set of 10 samples from each site or discharge according to the procedure in
Section 11. If the expected background concentration is known from previous
experience or other knowledge, the spiking level may be established a priori.
9.5.2.2 Prepare the MS/MSD samples by adding the appropriate concentration of
nicotinic acid standard (Section 7.13) to two sample aliquots. Analyze the
MS/MSD aliquots as described in Section 11 to determine the concentration of
TKN in the samples after spiking.
9.5.3 Calculate the percent recovery (P) and relative percent difference (RPD) of the two matrix
spike samples for the analyte, corrected for the background concentration measured in the
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Method 1687
sample, and compare these values to the control limits given in Table 1. Percent recovery is
calculated in units appropriate to the matrix, using Equation 1. RPD is calculated using
Equation 2.
Equation 1
(c -c}
percent recovery = -— —*100
where: Cs = Measured sample concentration after spiking
Ch = Measured sample background concentration
S = known concentration of the spike
Equation 2
(A+A)
where: D, = concentration TKN of MS sample
D2 = concentration TKN ofMSD sample
9.5.4 If the percent recovery or the RPD of the analyte in the MS/MSD samples falls outside the
designated range, and the laboratory performance on the OPR for the analyte is within the
specified limits (Section 9.4), the recovery problem encountered with the MS/MSD sample is
judged to be matrix-related instead of method-related.
9.5.5 Recovery for samples should be assessed and records maintained.
9.5.5.1 After the analysis of five samples of a given matrix type (wastewater, heat-dried
biosolids, etc.) for which the results pass the tests in Section 9.5.3, compute the
average percent recovery (R) and the standard deviation of the percent recovery
(SR) for the analyte(s). Express the accuracy assessment as a percent recovery
interval from R - 2SR to R + 2SR for each matrix. For example, if R=90% and
SR = 10% for five analyses of wastewater, the accuracy interval is expressed as
70-110%.
9.5.5.2 Update the accuracy assessment for each matrix regularly (e.g., after each five to
ten new measurements).
9.6 Calibration verification (CV)—The laboratory must analyze a calibration verification standard
before running any samples and once per ten analyses thereafter. The CV should be prepared at a
concentration that is at or near the midpoint of the calibration curve. The source of the CV standard
should be different from the source used to prepare the calibration standards. If a different
ammonium compound is used for the CV stock, the amount weighed will have to be adjusted
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Method 1687
according to the ratio of ammonia-nitrogen atomic weight to the molecular weight. Results of the
CV analysis should be evaluated according to the specifications in Table 1. If the CV does not meet
acceptance criteria, the problem must be identified and corrected, including possible recalibration of
the instrument.
9.7 Quality control sample (QCS)—It is suggested that the laboratory analyze a QCS with each day's
distillations, or every twelve hours, whichever is more frequent. The results of the QCS analysis
should be evaluated according to the manufacturer's specifications.
10.0 Calibration and Standardization
10.1 Calibrate the colorimeter with a minimum often standards that cover the expected range of the
samples and a blank. If the autoanalyzer is linked to a data system, follow the manufacturer's
instructions for calibration. Alternatively, prepare a calibration graph relating absorbance to the
concentration of TKN, or develop a weighted linear regression formula from the calibration data
using concentration versus absorbance. If the correlation coefficient falls below 0.995, check the
system for faults, correct them if found, and reanalyze the calibration standards.
10.2 Preparation of calibration curve—Prepare the standards (Table 2) and analyze them according to the
procedure in Section 11.3, beginning with the lowest standard. It is not necessary to distill or digest
the calibration standards
10.3 An OPR run after the calibration must be within the specified limits (Table 1). Unacceptable OPR
results require corrective action before analysis of samples may continue; they may indicate
problems with the distillation procedure.
10.4 Balance calibration—Calibrate the analytical balance at 2 mg and 1000 mg using class "S" weights.
The calibration shall be within ± 10% at 2 mg and ± 0.5% at 1000 mg. If values are not within
these limits, recalibrate the balance.
11.0 Procedure
11.1 Digestion
11.1.1 Sample preparation
11.1.1.1 Solid samples—Thoroughly homogenize the sample. Weigh 5 g of
sample in a clean dish or watchglass, and transfer to the kjeldahl flask.
Dilute to 300 mL with reagent water and add a few boiling chips or glass
beads.
11.1.1.2 Aqueous samples—Mix the sample thoroughly. Transfer 300 mL of
sample to the kjeldahl flask and add a few boiling chips or glass beads.
11.1.2 Ammonia removal-If a result of organic nitrogen is desired, perform the following
procedure before digestion.
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Method 1687
11.1.2.1 Add 25 mL borate buffer (Section 7.4.2) and then 6N NaOH (Section
7.3.2) until the pH is 9.5.
11.1.2.2 Boil the solution until 10-20 mL remains and cool. Add 250 mL reagent
water.
11.1.3 Carefully add 5 0 mL digestion reagent (7.11) to the kj eldahl flask. Boil until the
volume is reduced to approximately 25 mL and dense fumes appear above the liquid.
Continue to digest for an additional 30 minutes.
11.1.4 Cool the flask and solution, then dilute to 300 mL with reagent water.
11.1.5 Slowly add 50 mL sodium hydroxide-sodium thiosulfate reagent. Slowly mix the
solution. Connect the flask to a steamed-out distillation apparatus and verify that the
pH is greater than 11.
11.2 Distillation
11.2.1 Place the tip of the condenser below the surface of solution in the receiving flask. The
receiving flask should contain 50 mL of 0.04N H2SO4 (Section 7.2.2).
11.2.2 Distill at a rate of 6-10 mL/min until 200 mL of distillate is collected.
11.2.3 Dilute the distillate to 300 mL with reagent water.
11.3 Colorimetric analysis
11.3.1 Since the intensity of the color used to quantify the concentration is pH dependent, the
acid concentration of the wash water and the standard ammonia solutions should
approximate that of the samples.
11.3.2 Set up the autoanalyzer and reagents according to the manufacturer's instructions,
using the information in Figure 1 as a guide.
11.3.3 Allow both colorimeter and recorder (if applicable) to warm up for 30 minutes. Obtain
a stable baseline with all reagents, feeding reagent water through the sample line.
11.3.4 Switch the sample line from reagent water to the first sample and begin analysis.
11.4 The solid sample dry weight/wet weight ratio must be determined separately (Appendix A).
12.0 Calculations
12.1 Aqueous samples-Compare the absorbance reading for each sample to the calibration curve and
determine the sample concentration. Report all values in mg/L to three significant figures.
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Method 1687
12.2 Solid samples—Compare the absorbance reading for each sample to the calibration curve and
determine the sample concentration using Equations 3 and 4. Report all values in mg/kg to three
significant figures.
Equation 3
TKN (mg/kg) =
(Ws)WOOmL/L
where: Cd = Concentration ofNH3-Nin distillate (mg/L)
Vd = Volume of distillate collected (300 mL)
F = Dilution factor (1 if no dilution)
Ws = Weight of sample distilled (g)
Equation 4
TKN (mg /kg)=^-
where: Cs = Amount of TKN in sample (mg/kg, Equation 3)
W = Dry weight ratio (Appendix A)
12.3 Report all results below the ML as "less than the ML." If the ammonia removal procedure (Section
11.1.2) was performed, report results as organic nitrogen.
12.4 The QC data obtained during the analysis provides an indication of the quality of the sample data
and should be provided with the sample results.
13.0 Method Performance
This is a draft method, and is currently undergoing validation. Method performance criteria will be set
following the validation of the method.
14.0 Pollution Prevention
14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of
waste at the point of generation. Many opportunities for pollution prevention exist in laboratory
operation. The EPA has established a preferred hierarchy of environmental management techniques
that places pollution prevention as the management option of first choice. Whenever feasible,
laboratory personnel should use pollution prevention techniques to address their waste generation.
When wastes cannot be feasiblely reduced at the source, the EPA recommends recycling as the next
best option. The acids used in this method should be reused as practicable by purifying by
electrochemical techniques. The only other chemicals used in this method are the neat materials used
in preparing standards. These standards are used in extremely small amounts and pose little threat
to the environment when managed properly. Standards should be prepared in volumes consistent
with laboratory use to minimize the volume of expired standards to be disposed.
Draft, January 2001 13
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Method 1687
14.2 For information about pollution prevention that may be applicable to laboratories and research
institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction,"
available from the American Chemical Society's Office of Society Services, 1155 16th Street NW,
Washington, D.C. 20036, 202/872-4600.
15.0 Waste Management
15.1 The laboratory is responsible for complying with all Federal, State, and local regulations governing
waste management, particularly hazardous waste identification rules and land disposal restrictions,
and for protecting the air, water, and land by minimizing and controlling all releases from fume
hoods and bench operations. Compliance with all sewage discharge permits and regulations is also
required. An overview of requirements can be found in Environmental Management Guide for
Small Laboratories (EPA 233-B-98-001).
15.2 Samples containing strong acids or bases are hazardous and must be either neutralized before being
disposed or handled as hazardous waste.
16.0 References
16.1 U.S. Environmental Protection Agency, 1979. Methods for Chemical Analysis of Water and Wastes.
Publ. 600/4-79-020, rev. March 1983. Environmental Monitoring and Support Lab., U.S.
Environmental Protection Agency, Cincinnati, Ohio.
16.2 U.S. Environmental Protection Agency, 1998. Method 1691: Municipal Biosolids Sampling
Guidance. Draft, September 1998. Office of Water, Washington, DC.
16.3 Sax, N.I. and Lewis, Sr., R.I., Dangerous Properties of Industrial Materials. 5th. ed.. Van Nostrand
Reinhold, New York, 1989.
16.4 U.S. Environmental Protection Agency, 1982. Handbook for Sampling and Sample Preservation of
Water and Wastewater. Publ. 600/4-82-029, Environmental Monitoring and Support Lab., U.S.
Environmental Protection Agency, Cincinnati, Ohio.
16.5 Code of Federal Regulations 40, Ch. 1, Part 136, Appendix B.
17.0 Tables, Diagrams, and Validation Data
Table 1. Quality Control—Sample Acceptance Criteria (to be established from validation study results)
Analyte
TKN
Blank
limit
IPR recovery
(x) limit
IPR precision
(s) limit
OPR
recovery limit
CV recovery
limit
QCS recovery
limit
14
Draft, January 2001
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Method 1687
Table 2. The volume of working standard necessary to make the
calibration standards in 100 mL volumetric flasks
Volume of standard Concentration of
(Section 7.10.2) calibration
added (mL) standard (mg/L)
0.1 0.01
0.2 0.02
0.5 0.05
1.0 0.10
2.0 0.20
5.0 0.50
8.0 0.80
10.0 1.00
15.0 1.50
20.0 2.00
Draft, January 2001 15
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Method 1687
Peristaltic Pump Manifold
O.23 mL/min Air*
Mixing ooil
•4—r
Mixing ooil
SOdeg C
heating
bath
Colorimeter w/15mm flow cell
to Waste
Recorder or data system
O.42 mL/min Sample
O.8O mL/min
EPTA
O.42 Sodium Phenolate
O.32 mL/min Hypochlorite
O.42 mL/min Nitroprusside
1.6 mL/min Waste
2.O mL/min Sampler Wash
*scrubbed through 5N sulfuric acid
Figure 1. Continuous Flow Diagram
16
Draft, January 2001
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Method 1687
18.0 Glossary of Terms
The definitions and purposes below are specific to this method, but have been conformed to common
usage as much as possible.
18.1 Ammonia—N—The quantity of nitrogen occurring in the ammonium ion.
18.2 Analyte—A compound or element tested for by the methods referenced in this method.
18.3 Analytical Batch—The set of samples analyzed at the same time, to a maximum of 10 samples.
18.4 Apparatus—The sample container and other containers, filters, filter holders, labware, tubing,
pipettes, and other materials and devices used for sample collection or sample preparation, and
that will contact samples, blanks, or analytical standards.
18.5 Biosolids—The treated residuals from wastewater treatment that can be used beneficially.
18.6 Calibration Standard—A solution prepared from a dilute mixed standard and/or stock solution
and used to calibrate the response of the instrument with respect to analyte concentration
18.7 Calibration Verification standard (CV)—A solution prepared from a different source than the
calibration standards that is used to confirm the accuracy of the instrument's calibration.
18.8 Initial Precision and Recovery (IPR)—Four aliquots of the OPR standard analyzed to establish
the ability to generate acceptable precision and accuracy. IPR is performed before a method is
used for the first time and any time the method or instrumentation is modified.
18.9 Kjeldahl Nitrogen (TKN)—the sum of ammonia-nitrogen and organic nitrogen.
18.10 Laboratory Blank—An aliquot of reagent water that is treated exactly as a sample including
exposure to all glassware, equipment, solvents, reagents, internal standards, and surrogates that
are used with samples. The laboratory blank is used to determine if method analytes or
interferences are present in the laboratory environment, the reagents, or the apparatus (Section
9.3).
18.11 Matrix Spike (MS) and Matrix Spike Duplicate (MSD)—Aliquots of an environmental sample
to which known quantities of the method analytes are added in the laboratory. The MS and MSD
are analyzed exactly like a sample. Their purpose is to quantify the bias and precision caused by
the sample matrix. The background concentrations of the analytes in the sample matrix must be
determined in a separate aliquot and the measured values in the MS and MSD corrected for
background concentrations (Section 9.5).
18.12 May—This action, activity, or procedural step is optional.
18.13 May Not—This action, activity, or procedural step is prohibited.
Draft, January 2001 17
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Method 1687
18.14 Method Detection Limit (MDL)—The minimum concentration of an analyte that can be
identified, measured, and reported with 99% confidence that the analyte concentration is greater
than zero (Section 9.2.1).
18.15 Minimum Level (ML)—The lowest level at which the entire analytical system gives a
recognizable signal and acceptable calibration point.
18.16 Must—This action, activity, or procedural step is required.
18.17 Ongoing Precision and Recovery (OPR) Standard—A laboratory blank spiked with known
quantities of the method analytes. The OPR is analyzed exactly like a sample. Its purpose is to
determine whether the methodology is in control and to assure that the results produced by the
laboratory remain within the method-specified limits for precision and accuracy (Section 9.4).
18.18 Organic Nitrogen—Nitrogen present in organic molecules in the trinegative oxidation state.
18.19 Reagent Water—Water demonstrated to be free from the method analytes and potentially
interfering substances at the MDL for the method.
18.20 Sewage Sludge—Sewage sludge is solid, semi-solid, or liquid residue generated during the
treatment process of domestic sewage in a treatment works. Sewage sludge includes but is not
limited to, domestic septage; scum or solids removed in primary, secondary, or advanced
wastewater treatment processes; and a material derived from sewage sludge. Sewage sludge does
not include ash generated during the firing of sewage sludge in a sewage sludge incinerator or grit
and screenings generated during preliminary treatment of domestic sewage in a treatment works.
18.21 Shall—This action, activity, or procedural step is required.
18.22 Should—This action, activity, or procedural step is suggested but not required.
18.23 Stock Standard Solution—A solution containing one or more method analytes that is prepared
using a reference material traceable to EPA, the National Institute of Science and Technology
(NIST), or a source that will attest to the purity and authenticity of the reference material.
18.24 Total Kjeldahl Nitrogen—See Kjeldahl Nitrogen.
18 Draft, January 2001
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Method 1687
Appendix A: Total Solids in Solids and Biosolids
1.0 Scope and Application
1.1 This procedure is applicable to the determination of total solids in such solid and semisolid samples
as soils, sediments, biosolids (municipal sewage sludge) separated from water and wastewater
treatment processes, and sludge cakes from vacuum filtration, centrifugation, or other sludge
dewatering processes.
1.2 This procedure is taken from EPA Method 1684: Total, Fixed, and Volatile Solids in Solid and
Semisolid Matrices.
1.3 Method detection limits (MDLs) and minimum levels (MLs) have not been formally established for
this draft procedure. These values will be determined during the validation of Method 1684.
1.4 This procedure is performance based. The laboratory is permitted to omit any step or modify any
procedure (e.g. to overcome interferences, to lower the cost of measurement), provided that all
performance requirements in this procedure are met. Requirements for establishing equivalency are
given in Section 9.1.2 of Method 1687.
1.5 Each laboratory that uses this procedure must demonstrate the ability to generate acceptable results
using the procedure in Section 9.2 of this appendix.
2.0 Summary of Method
2.1 Sample aliquots of 25-50 g are dried at 103 °C to 105 °C to drive off water in the sample.
2.2 The mass of total solids in the sample is determined by comparing the mass of the sample before and
after each drying step.
3.0 Definitions
3.1 Analytical batch-The set of samples analyzed at the same time, to a maximum of 10 samples. Each
analytical batch of 10 or fewer samples must be accompanied by a laboratory blank, an ongoing
precision and recovery sample, and a set of MS/MSD samples, resulting in a minimum of five
analyses (1 sample, 1 blank, 1 OPR, and 2 matrix spike samples) and a maximum of 14 samples.
3.2 Total Solids-The residue left in the vessel after evaporation of liquid from a sample and subsequent
drying in an oven at 103°C to 105 °C.
3.3 Additional definitions are given in Sections 3.0 and 18.0 of Method 1687.
Draft, January 2001 A-l
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Method 1687
4.0 Interferences
4.1 Sampling, subsampling, and pipeting multi-phase samples may introduce serious errors (Reference
16.1). Make and keep such samples homogeneous during transfer. Use special handling to ensure
sample integrity when subsampling. Mix small samples with a magnetic stirrer. If visible suspended
solids are present, pipet with wide-bore pipets. If part of a sample adheres to the sample container,
intensive homogenization is required to ensure accurate results. When dried, some samples form a
crust that prevents evaporation; special handling such as extended drying times are required to deal
with this. Avoid using a magnetic stirrer with samples containing magnetic particles.
4.2 The temperature and time of residue drying has an important bearing on results (Reference 16.1).
Problems such as weight losses due to volatilization of organic matter, and evolution of gases from
heat-induced chemical decomposition, weight gains due to oxidation, and confounding factors like
mechanical occlusion of water and water of crystallization depend on temperature and time of
heating. It is therefore essential that samples be dried at a uniform temperature, and for no longer
than specified. Each sample requires close attention to desiccation after drying. Minimize the time
the desiccator is open because moist air may enter and be absorbed by the samples. Some samples
may be stronger desiccants than those used in the desiccator and may take on water. If uptake of
water by a sample is suspected, the operator should weigh the sample to see if it gains weight while
in the desiccator. If the sample is indeed taking on water, then a vacuum desiccator should be used.
4.3 Residues dried at 103 °C to 105 °C may retain some bound water as water of crystallization or as
water occluded in the interstices of crystals. They lose CO2 in the conversion of bicarbonate to
carbonate. The residues usually lose only slight amounts of organic matter by volatilization at this
temperature. Because removal of occluded water is marginal at this temperature, attainment of
constant weight may be very slow.
4.4 Results for residues high in oil or grease may be questionable because of the difficulty of drying to
constant weight in a reasonable time.
4.5 The determination of total solids is subject to negative error due to loss of ammonium carbonate and
volatile organic matter during the drying step at 103 °C to 105 °C. Carefully observe specified
ignition time and temperature to control losses of volatile inorganic salts if these are a problem.
5.0 Safety
5.1 Refer to Section 5.0 of Method 1687 for safety precautions
6.0 Equipment and Supplies
NOTE: Brand names, suppliers, and part numbers are cited for illustrative purposes only. No endorsement
is implied. Equivalent performance may be achieved using equipment and materials other than those specified
here, but demonstration ofequivalent performance that meets the requirements of this method is the responsibility
of the laboratory.
6.1 Evaporating Dishes-Dishes of 100-mL capacity. The dishes may be made of porcelain (90-mm
diameter), platinum, or high-silica glass.
A-2 Draft, January 2001
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Method 1687
6.2 Watch glass-Capable of covering the evaporating dishes (Section 6.1).
6.3 Steam bath for evaporation of liquid samples.
6.4 Desiccator-Moisture concentration in the desiccator should be monitored by an instrumental
indicator or with a color-indicator desiccant.
6.5 Drying oven-Thermostatically-controlled, capable of maintaining a uniform temperature of 103 °C
to 105 °C throughout the drying chamber.
6.6 Analytical balance-Capable of weighing to 0.1 mg for samples having a mass up to 200 g.
6.7 Reference weights-2 mg, 1000 mg, and 50 g class "S" weights.
6.8 Container handling apparatus-Gloves, tongs, or a suitable holder for moving and handling hot
containers after drying.
6.9 Sample handling apparatus-Spatulas, spoonulas, funnels, or other equipment for transfer and
manipulation of samples.
6.10 Bottles-Glass or plastic bottles of a suitable size for sample collection.
6.11 Rubber gloves (Optional).
6.12 No. 7 Cork borer (Optional).
6.13 Desiccant (Optional).
7.0 Reagents and Standards
7.1 Reagent water-Deionized, distilled, or otherwise purified water.
7.2 Quality control spiking solution-If a commercially available standard can be purchased that contains
standard total solids, the laboratory may use that standard. The laboratory may also prepare a
spiking solution. One possible recipe is given below for a NaCl-KHP solution.
7.2.1 Dissolve 0.10 g sodium chloride (NaCl) in 500 mL reagent water. Mix to dissolve.
7.2.2 Add 0.10 g potassium hydrogen phthalate (KHP) to the NaCl solution (Section 7.2.1) and
mix. If the KHP does not dissolve readily, warm the solution while mixing. Dilute to 1 L
with reagent water. Store at 4°C. Assuming 100% volatility of the acid phthalate ion, this
solution contains 200 mg/L total solids, 81.0 mg/L volatile solids, and 119 mg/L fixed solids.
Draft, January 2001 A-3
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Method 1687
8.0 Sample Collection, Preservation, and Storage
8.1 Use resistant-glass or plastic bottles to collect sample for solids analysis, provided that the material
in suspension does not adhere to container walls. Sampling should be done in accordance with
Reference 16.2. Begin analysis as soon as possible after collection because of the impracticality of
preserving the sample. Refrigerate the sample at 4 °C up to the time of analysis to minimize
microbiological decomposition of solids. Preferably do not hold samples more than 24 hours. Under
no circumstances should the sample be held more than seven days. Bring samples to room
temperature before analysis.
9.0 Quality Control
9.1 Quality control requirements and requirements for performance-based methods are given in Section
9.1 of Method 1687.
9.2 Initial demonstration of laboratory capability—The initial demonstration of laboratory capability is
used to characterize laboratory performance and method detection limits.
9.2.1 Method detection limit (MDL)—The method detection limit should be established for total
solids using the QC spiking solution (Section 7.2). To determine MDL values, take seven
replicate aliquots of the diluted QC spiking solution and process each aliquot through each
step of the analytical method. Perform all calculations and report the concentration values in
the appropriate units. MDLs should be determined every year or whenever a modification to
the method or analytical system is made that will affect the method detection limit.
9.2.2 Initial precision and recovery (IPR)—To establish the ability to generate acceptable precision
and accuracy, the analyst shall perform the following operations:
9.2.2.1 Prepare four samples by diluting the QC spiking solution (Section 7.2) to 1 to 5
times the MDL. Using the procedures in Section 11, analyze these samples for
total solids.
9.2.2.2 Using the results of the four analyses, compute the average percent recovery (x)
and the standard deviation (s, Equation 1) of the percent recovery for total solids.
Equation 1
n-l
Where:
n = number of samples
x = % recovery in each sample
s = standard deviation
A-4 Draft, January 2001
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Method 1687
9.2.2.3 Compare s and x with the corresponding limits for initial precision and recovery
in Table 2 (to be determined in validation study). If s and x meet the acceptance
criteria, system performance is acceptable and analysis of samples may begin.
If, however, s exceeds the precision limit or x falls outside the range for
recovery, system performance is unacceptable. In this event, correct the
problem, and repeat the test.
9.3 Laboratory blanks
9.3.1 Prepare and analyze a laboratory blank initially (i.e. with the tests in Section 9.2) and with
each analytical batch. The blank must be subjected to the same procedural steps as a sample,
and will consist of approximately 25 g of reagent water.
9.3.2 If material is detected in the blank at a concentration greater than the MDL (Section 1.3),
analysis of samples must be halted until the source of contamination is eliminated and a new
blank shows no evidence of contamination. All samples must be associated with an
uncontaminated laboratory blank before the results may be reported for regulatory compliance
purposes.
9.4 Ongoing precision and recovery
9.4.1 Prepare an ongoing precision and recovery (OPR) solution identical to the IPR solution
described in Section 9.2.2.1.
9.4.2 An aliquot of the OPR solution must be analyzed with each sample batch (samples started
through the sample preparation process (Section 11) on the same 12-hour shift, to a maximum
of 20 samples).
9.4.3 Compute the percent recovery of total solids in the OPR sample.
9.4.4 Compare the results to the limits for ongoing recovery in Table 2 (to be determined in
validation study). If the results meet the acceptance criteria, system performance is
acceptable and analysis of blanks and samples may proceed. If, however, the recovery of
total solids falls outside of the range given, the analytical processes are not being performed
properly. Correct the problem, reprepare the sample batch, and repeat the OPR test. All
samples must be associated with an OPR analysis that passes acceptance criteria before the
sample results can be reported for regulatory compliance purposes.
9.4.5 Add results that pass the specifications in Section 9.4.4 to IPR and previous OPR data.
Update QC charts to form a graphic representation of continued laboratory performance.
Develop a statement of laboratory accuracy for each analyte by calculating the average
percent recovery (R) and the standard deviation of percent recovery (SR). Express the
accuracy as a recovery interval from R-2SRto R+2SR. For example, if R=05% and SR=5%,
the accuracy is 85-115%.
Draft, January 2001 A-5
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Method 1687
9.5 Duplicate analyses
9.5.1 Ten percent of samples must be analyzed in duplicate. The duplicate analyses must be
performed within the same sample batch (samples whose analysis is started within the same
12-hour period).
9.5.2 The total solids of the duplicate samples must be within 10% of the solids determination.
10.0 Calibration and Standardization
10.1 Calibrate the analytical balance at 2 mg and 1000 mg using class "S" weights.
10.2 Calibration shall be within ± 10% (i.e. ±0.2 mg) at 2 mg and ± 0.5% (i.e. ±5 mg) at 1000 mg. If
values are not within these limits, recalibrate the balance.
10.3 Place a 50 g weight and a 2 mg weight on the balance. Verify that the balance reads 50.002 ±10%
(i.e. ±0.2 mg)
11.0 Procedure
11.1 Preparation of evaporating dishes-Heat dishes and watch glasses at 103 °C to 105 °C for 1 hour in
an oven. Cool and store the dried equipment in a desiccator. Weigh each dish and watch glass prior
to use (record combined weight as "Wdlsh").
11.2 Preparation of samples
11.2.1 Fluid samples-If the sample contains enough moisture to flow readily, stir to
homogenize, place a 25 to 50 g sample aliquot on the prepared evaporating dish. If the
sample is to be analyzed in duplicate, the mass of the two aliquots may not differ by
more than 10%. Spread each sample so that it is evenly distributed over the
evaporating dish. Cover each sample with a watch glass, and weigh (record weight as
"Wsample"). Evaporate the samples to dryness on a steam bath.
NOTE: Weigh wet samples quickly because wet samples tend to lose weight by evaporation. Samples should
be weighed immediately after aliquots are prepared.
11.2.2 Solid samples-If the sample consists of discrete pieces of solid material (dewatered
sludges, for example), take cores from each piece with a No. 7 cork borer or pulverize
the entire sample coarsely on a clean surface by hand, using rubber gloves. Place a 25
to 50 g sample aliquot of the pulverized sample on the prepared evaporating dish. If
the sample is to be analyzed in duplicate, the mass of the two aliquots may not differ by
more than 10%. Spread each sample so that it is evenly distributed over the
evaporating dish. Cover each sample with a watch glass, and weigh (record weight as
^* sample / •
A-6 Draft, January 2001
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Method 1687
11.3 Dry the samples at 103 °C to 105 °C for a minimum of 12 hours, cool to balance temperature in an
individual desiccator containing fresh desiccant, and weigh. Heat the residue again for 1 hour, cool
it to balance temperature in a desiccator, and weigh. Repeat this heating, cooling, desiccating, and
weighing procedure until the weight change is less than 5% or 50 mg, whichever is less. Record the
final weight as "Wtotal."
NOTE: It is imperative that dried samples be weighed quickly since residues often are very hygroscopic and
rapidly absorb moisture from the air. Samples must remain in the desiccator until the analyst is ready to weigh
them.
12.0 Data Analysis and Calculations
12.1 Calculate the % solids or the mg solids/kg sample for total solids (Equation 2).
Equation 2
% total solids = W'°'al Wdi* *100
"sample ~ "dish
or
me total solids W. ., - W,.,
— = —^ ^-* 1,000,000
kg sludge Wsample - Wdish
Where:
Wdish=Weightofdish (mg)
WsampU=Weight of wet sample and dish (mg)
Wtotal=Weight of dried residue and dish (mg)
12.2 Sample results should be reported as % solids or mg/kg to three significant figures. Report results
below the ML as less than the ML, or as required by the permitting authority or in the permit.
13.0 Method Performance
13.1 Method performance (MDL and quality control acceptance criteria) will be determined during the
multi-lab validation of this method.
13.2 Total solids duplicate determinations must agree within 10% to be reported for permitting purposes.
If duplicate samples do not meet this criteria, the problem must be discovered and the sample must
be run over.
14.0 Pollution Prevention
14.1 Pollution prevention details are given in Section 14 of Method 1687.
Draft, January 2001 A-7
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Method 1687
15.0 Waste Management
15.1 Waste management details are given in Section 15 of Method 1687.
16.0 References
16.1 "Standard Methods for the Examination of Water and Wastewater," 18th ed. and later revisions,
American Public Health Association, 1015 15th Street NW, Washington, DC 20005. 2-59: Section
2540 G (Total, Fixed, and Volatile Solids in Solid and Semisolid Matrices), 1992.
16.2 U.S. Environmental Protection Agency, 1992. Control of Pathogens and Vector Attraction in
Sewage Sludges. Publ 625/R-92/013. Office of Research and Development, Washington, DC.
17.0 Tables, Diagrams, Flowcharts, and Validation Data
17.1 Tables containing method requirements for QA/QC will be added after the validation study has been
performed.
A-8 Draft, January 2001
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