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INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
Effectiveness of the Preservation Protocol within EPA Method 200.8 for Soluble
and Participate Lead Recovery in Drinking Water
Regional Applied Research Effort - Addressing Drinking Water Challenges through Science and Innovation
Background
The U.S. Environmental Protection Agency (EPA) is responsible for establishing national regulations under the Safe
Drinking Water Act (SDWA). Regulations protect public health by establishing Maximum Contaminant Levels (MCLs) or
other enforceable thresholds for contaminants including microorganisms, disinfection byproducts, inorganic/organic
chemicals, and radionuclides. Water quality monitoring by drinking water utilities is necessary to demonstrate regulatory
compliance with these enforceable limits.
The Lead and Copper Rule (LCR) is unique when compared with other regulations because compliance sampling for lead
(and copper) occurs at household taps rather than at the entry point to the distribution system. This is because premise
plumbing materials can be primary sources of lead and copper contamination. Furthermore, the LCR established an action
level (AL) rather than an MCL for lead (and copper). If more than 10% of the water samples exceed an AL of 0.015 mg/L for
lead, then the drinking water utility is required to implement certain treatment techniques to control lead corrosion.
EPA Method 200.8
EPA Method 200.8 (Figure 1) is an accepted method
for the determination of total lead and other trace
elements in water (and wastes) by Inductively
Coupled Plasma-Mass Spectrometry (ICP-MS).
Among other instructions, the method provides a
protocol for standard acid preservation of water
samples to pH < 2 because this step can affect lead
quantification. If the sample turbidity is > 1 NTU,
more rigorous subsequent acid digestion is also
required. Adding acid preservative to water samples
aims to prevent metal precipitation and reduce metal
adsorption onto the walls of sampling bottles,
thereby rendering all the metal soluble and thus
quantifiable by ICP-MS.
Review of the literature indicates that the extent of
lead contamination, the form of the lead (dissolved
versus particulate), the preservation pH, the type of
sampling container, and the type of water sample are
important factors affecting acid preservation of
water samples for lead quantification.
Project Purpose
The purpose of this project was to investigate the effectiveness of the sample preservation protocol outlined in Method
200.8 in recovering lead from water samples. Lead recoveries were studied in various water samples spiked with lead by
evaluating lead sorption and desorption from sample bottles using ICP-MS. Specific concerns with the acidification
protocol, bottle types and occurrence of particulates in water were investigated in two phases. Phase One of the study
(Figure 2, left) focused on the recovery of 50 u.g/L dissolved lead within different water sources, bottle types and
preservation pHs. The lead recovery in glass and high-density polyethylene (HOPE) bottles was examined in Dl water,
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Atqmrt Digestion
Add 2 mLHNOi(rrorn 1:1 solution]
and 1 mLHCI (frarn 1:1 solution]
Heat to 85 *C until volume reduced
tD 20 rnL |do not boil]
1 P
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centrifuge until clear
Figure 1. EPA Method 200.8 (ICP-MS) specifies procedures to
quantify total recoverable lead (and other trace metals) in
drinking water samples.
Office of Research and Development
EPA/600/F-14/248 | August 2014
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ground water, surface water and Dl water containing 100 mg/L calcium (Ca). Similarly, lead recovery was compared
between altered sample preservations at pH 2, 4, 5, 6 and 7. Phase Two examined the recovery of particulate lead from
water samples using direct and total recoverable analyses. Specifically, the recovery of lead phosphate, basic lead
carbonate and lead (IV) oxide was evaluated.
Phase One Results & Conclusions
Unpreserved glass bottles showed a significant decrease in lead concentration prior to acidification in all water sources.
Within these glass bottles, Dl water showed the greatest decrease (Figure 2, right), followed by ground water, surface
water and then Dl water spiked with Ca. After acidification to a pH < 2, lead recovery increased and showed no significant
difference to the immediately preserved bottle in the Dl (Figure 2, right), surface, ground and Dl spiked with Ca trials.
I
I
• Preserved HDPE
Duplicate Preserved HOPE
•Unpreserved HOPE
Duplicate Unpreserved HDPE
* Preserved Glass
Duplicate Preserved Glass
• Unpreserved Glass
Duplicate Unpneserved Glass
43 96 144 192 240 2S3 33£ 334 432 430 523 576 624 572
Time (hours)
Figure 2. LEFT: Duplicate 2 ml aliquots from each sample bottle (HDPE versus glass) were collected for lead analysis at specified time intervals in
Phase One. RIGHT: Representative results of lead concentration in Dl water contained in glass and HDPE bottles in Phase 1.
In the trials investigating the relationship between lead recovery and preservation pH in Dl water samples, as pH
increased, lead recovery decreased. As also seen within the other water source trials, the lowest lead recovery occurred in
glass bottles preserved to pH 7 in this trial. It was also determined that pH 4 was not an optimal preservation pH because
it did not always yield as high of a lead recovery as pH < 2. In some cases, there was a significant difference between
preservation to pH 4 and to a pH < 2. This difference was seen in Dl, surface and ground water samples collected in glass
bottle; however, this difference was not seen in the bottles containing Dl water spiked with 100 mg/L Ca. It is believed
that calcium competed with lead to occupy sorption sites on the bottle's surface, thereby forcing lead to remain in
solution at both preservation pHs.
Overall, samples preserved to pH < 2 recovered greater than 90% of the initial spiked dissolved lead concentration of 50
u.g/L, independent of sample container type and delays in acidification.
Phase Two Results & Conclusions
Recovery of lead particulates was more problematic than recovery of dissolved lead. A "well mixed" acid preserved
sample was not always attainable due to particulate inhomogeneity even if samples were vigorously agitated prior to
aliquoting. A concentration of 2% HMOs and 1% HCI provided complete solubilization of the three investigated lead
compounds. This technique would require the addition of large amounts of reasonably expensive high purity acids (i.e., 20
ml nitric and 10 ml hydrochloric acid) to the 1L water samples mandated in the LCR. An alternative pre-filtration
procedure offers advantages over the digestion procedure, specifically given the lower cost associated with the acid
requirements. However, recovery of lead was not complete at 88.6% on average after the pre-filtration procedure.
Contacts
Principal Investigators: Darren Lytle, (513) 569-7432, lytle.darren@epa.gov | Keith Kelty, (513) 569-7414,
kelty.keith@epa.gov | Maily Pham, (513) 569-7212, pham.maily@epa.gov
This work was performed under EPA's Regional Applied Research Effort (RARE) program with EPA Region 6.
Full project report (EPA/600/R 13/222) is available online: http://nepis.epa.gov/Adobe/PDF/P100H8Y6.pdf
Office of Research and Development
EPA/600/F-14/248 | August 2014
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