PB88-104344
Preliminary Evaluation of a Method Using an
FID (Flanie lonization Detector) for
Measurement of Methanol in Auto Emissions
(U.S.) Environmental Protection Agency
Research Triangle Park, NC
Sep 37
U.S. Department of Commerce
Techrscri Information Service
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pBtia-10434
EPA/600/3-87/035
September 1987
PRELIMINARY EVALUATION OF A METHOD USING AN FID FOR
MEASUREML'NT 01' METHANOL IN AUTO EMISSIONS
by
Peter A. Gabele and William D. Ray
Emissions Measurement nnd Characterization Division
Atmospheric Sciences Research Laboratory
Research Triangle Park, N.C. 27711
John Duncan and Charles Burton
Northrop Services Inc.
Research Triangle Park, N.C. 27709
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OK KKStARCH AND DFA'EI.OPMENT
I'.S. ENVIRONXENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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TECHNICAL REPORT DATA
(Please read Inslnicr.cm on the if-tne beiore completing
I. REPORT NO.
EPA/600/3-87/035
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
PRELIMINARY EVALUATION OF A METHOD USING AN FID FOR
MEASUREMENT OF METllANOL IN AUTO EMISSIONS
5. REPORT DATE
September 1987
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
Peter Cabele, William Ray, USEPA
John Duncan, Charles Burton, Northrop Services
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME ANO AOCFIESS
Atmospheric Sciences Research Laboratory
Office of Research and Developnent
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
1O. PROGRAM ELEMENT NO.
A101/D/73/022 . 2QS2 (FY-37)
II. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME ANO ADDRESS
Atmospheric Sciences Research Laboratory - RTP,
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT ANO PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
' This report evaluates a simplified technique for estimating -ethanol e-ission
rates in auto exhaust. The technique, referred to as the FID Bubbled Method or FBM,
is based in priciple on the fact that while hydrocarbons are not readily absorbed in
water, methanol is. Kence, by using a heated flaze ionization detector to measure
the organic tr.ass in sample's before and after bubbling them in water, the quantity of
methanol origir.aily present can be estimated by taking the difference between the
measurements. Evaluation of the method was done by comparing methanol measurements
using the FBM with measurements made using an established reference method. Results
shewed poor to fair agreement between the two nethods. The FID -Bubbled Method
appeared better at estimating methanol emission rates from evaporative tests than
from exhaust tests and also exhibited betteraccuracy for samples containing higher
levels of r.ethar.ol.
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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ABSTRACT
Tliis report evaluates a simplified technique for estimating methanol
emission rates in auto exhaust. The technique, referred to as the FID Bubbled
Method or FBM, is based in priciple on the fact that vhile hydrocarbons are
not readily absorbed in water, rnethanol is. Hence, by using a heated flame
ionization detector to measure the organic mass in samples before and after
bubbling them in water, the quantity of tnethanol originally present can be
estimated by taking the difference between the measurements. Evaluation of
the method was done by comparing nethanol measurements using the FBM with
measurements made using an established reference method. Results showed poor
to fair agreement between the two methods. The FID Bubbled Method appeared
better at estimating nethanol emission rates from evaporative tests than from
exhaust tests and also exhibited better accuracy for samples containing higher
levels of taethanol.
111
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ACKNOWLEDGEMENTS
The author would like to thank Susan Bass for her . assistance in the
preparation of this document.
i v
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SECTION 1
INTKODUCTION
In August 1986, the EPA published a notice of proposed rulemaking for
standards for enissions from methanol-fueled motor vehicle engines(l). Since
that time, concents regarding the proposed standard have been solicited from a
number of automobile manufacturers. Of the comments received, many have
addressed the "overly complex" instrumentation requirement set forth in the
standard for measurement of organic compounds. In accordance with the
proposed standard, gas and liqv.id chromatographs (GCs and LCs) would be
required for cethanol and formaldehyde analyses in addition to the heated
flame ionization detector (FID) required for regulated hydrocarbon analyses.
The consensus of recommendations received from commentators proposes that
the separate measurements of viethanol and formaldehyde not be required, thus
eliminating the need for GC and LC analyses. Manufacturers contend that
reasonably accurate measurement of total organics can be had through the sole
application of a heated FID, in one form or another. Some further suggest or
recoranend the use of correction factors to account for differences in FID
response and photochemical reactivity between the organic components.
VCith regard to these comments, the concerns of instrument complexity are
valid and sole use of th'> heated FID to measure total organics vould greatly
simplify the procedure. The use of a correction factor to compensate for the
FID's low response to methanol would be appropriate if the fraction of
methanol to total organic emissions remained constant; however, the fraction
varies significantly with fuel type and vehicle. For example, 80 percent of
the FTP total organic emissions were methanol from a methanol-car tested in
1984 versus 60 percent for one tested in 1986 (2,3). Both vehicles were
Methanol Escorts, but the earlier tests were performed using a 90 percent
methanol fuel while ';he later tests used an 85 percent methanol fuel.
This study was undertaken to evaluate a simplified method for estimating
methar.ol emissions from automobiles using a technique which employs a heated
FID. Based in principle on the high solubility of mcthanol and low solubility
of hydrocarbons i.i water, the technique measures total organics of the sample
with the FID, bubbles the sample through water to remove the methanol portion,
then reneasures the remaining organic traction with the same FID. The
difference between the total organics (initial FID measurement) and the
remaining orga-iics (final FID measurement) is corrected for FID response to
methanol and taken as an estimate of the sample's methanol concentration.
While it is known that any hydrocarbons which would be absorbed in
solution, during the bubbling process would be counted as methanol by the.
method, the inpact of this occurrence on the technique's accuracy requires
investigation. Because a greater quantity of the more soluble automobile
hydrocarbon emissions occur immediately following a cold start, the highest
methnnol measurement errors with the technique likely occur during the FTP
cold transient test phase (Bag 1). On the other hand, the Lowest errors
likely occur with evaporative emissions which contain relatively few water
soluble hydrocarbon components.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
An experimental study was carried out to evaluate a simplified method
(FID Bubbled Method) for measuring methanol emissions from a methanol-fueled
automobile. Conclusions based on a comparison of results obtained using the
GC method (reference method) and the FID Bubbled Method (FBM) are as follow:
1. Comparisons between the FBM and CC msthod for methanol measurement are
fair to poor with differences between methods ranging from 11 to 112 percent
(see Table 1).
2. Comparison between the methods is better with methanol evaporative
emissions than with methanol exhaust emissions.
3. Methar.ol measurement differences, expressed as a percent of the GC valua,
are inversely related to the raethanol content of exhaust samples.
4. Accuracy of the FBM is compromised by the absorption of hydrocarbons in
water, particularly during the CT (cold transient) Test Phase of the FTP.
Net all of the difference between GC and FBM methanol measurements could
be attributed to the absorption of hydrocarbons in the water solution used for
removal of the methanol. When FBM methanol measurements were corrected to
account for the loss of the soluble hydrocarbons, the resulting values were
still significantly higher than those from the CC. Another factor thought to
perhaps have an impact on FBN accuracy by altering the FID's response to
normal hydrocarbons was the increase in humidity of the bubbled sample
compared to the unbubbled sample. Preliminary tests were carried out to
qualify any effect this factor might be having on analyzer response but no
significant effect vas observed. Future tests are recommended to thoroughly
examine the humidity effect on FID response to organic emissions samples from
a methanol-fueled automobile.
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SECTION 3
EXPERIMENTAL PROCEDURES
The procedure adopted was designed to enable an evaluation of a
simplified technique fcr measuring methanol emissions from a methanol-fueled
automobile. Basically it consisted of comparing methanol nicsureraents made
using a technique known as the FID Bubbled Method or FBM with, measurements
made using an established reference method. The reference method utilized a
gas chroir.atograph (CC) to analyze methanol which had been trapped in a chilled
water solution (4).
TEST VEHICLES AND IUELS
The principal test vehicle used to generate methanol emissions for the
study was a Methanol Escort which was equipped with a 3-way catalyst. It was
a modified version of its gasoline-fueled counterpart designed to operate on
"nearly neat" nethanol fuel. Engine modifications featured an increased
compression ratio, recalibrated carburetor, and a retimed ignition system.
Many of the parts in the Escort's fuel tank and fuel delivery system had been
replaced with materials designed to withstand the corrosive effects of
methanol.
Experiments with the Methanol Escort were carried out in a "piggyback"
fashion as testing proceeded during a higher priority program. When tests on
the Escort v:ere concluded, a few exhaust samples were obtained from a
conventionally fueled, 1987 Plymouth Caravellc. These were combined with
appropriate quantities of methanol to simulate a methanol car's exhaust, then
used to examine the effects of methanol and sample humidity on FID response to
hydrocarbons. Use of the Caravelle for these purposes was justified because
the character of exhaust hydrocarbons from a methanol car was found to
resemble that from similarly controlled gasoline-fueled cars (2).
Fuels used by the Methanol Escort during the study were M85 (85 percent
methanol/15 percent unleaded winter grade gasoline) and M100 (pure methanol).
The owner's manual for the Escort recommended use of M85 because the gasoline
fraction of the fuel provides good front-end volatility for engine starting in
cold weather. Suns with M100 were conducted to assist in evaluating the FBM
over a wider range of possible methanol emission rates and exhaust gas
compositions. Regular unleaded vintergrade gasoline was used in the
experiments conducted on the Plymouth Carvclle.
SAMPLE GENERATION, COLLECTION, AND ANALYSIS
The Xethanol Escort was driven through a series of FTP driving cycles on
an electric chassis dynamometer. For each test run, three sets of exhaust
data wtre obtained corresponding to the cola transient (CT) , hot stabilized
(HS) , sr.d warr. transient (V.'T) test phases. Evaporative emissions were
collected only during the diurnal tests.
Exhaust gripes from the car were ducted into a dilution tunnel where they
were thoroughly mixed with filtered diluent. The diluted exhaust gas mixture
was drawn through the system by a constant volume system (CVS) which had a
flowrate of about 650 scfm. Methanol. was sampled using the procedures set
forth in reference 4 (the reference method for sampling and analysis of
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methanol), and in accordance with procedures specified for sampling regulated
FTP gaseous emissions(5). In the former case, the dilute exhaust samples were
bubbled through water using impingers which were later analyzed for methanol
on the CC; in the latter case the samples vere collected in bags which were
analyzed on the heated FID using the FBM (sec Figure 1).
Evaporative emissions were sampled in a Sealed Housing for Evaporative
Determination (SHED). At the conclusion of each diurnal test, samples were
taken from the SHE1) in a 60L Tedlar bag for analyses of methanol using the GC
and F3M.
.The FBM procedure consisted of first using a heated FID to analyze a
portion of the CVS or evaporative sample which had been collected in a-bag.
Next, the remaining sample in the bag was bubbled through water in two series
impingers into a second bag which was re-analyzed using the same heated FID.
The difference in reading between the two bags was taken as a measure of 'he
methanol fraction absorbed in the water. Because the heated FID had been
calibrated using propane, its methanol C response factor was about 0.75 i .02.
Therefore, a correction factor equal to the reciprocal of 0.75, or 1.33, was
applied to the difference measurement to arrive at the concentration of
methanol in the sample.
After adequate samples had been taken for methanol analysis, remaining
sample portions of' both the unbubbled and bubbled bags vere retained as
samples lor separate CC analyses to obtain an. accounting of the detailed
hydrocarbons before and alter the bubbling in water. These analyses were
performed using the chromatographic procedures of Black et al. (6).
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SECTION 4
RESULTS AND DISCUSSION
The FBM and the reference method were used to .simultaneously collect aid
analyse da.a during FTPs with a Methanol Escort. Sumnaries of that d.-ita are
contained in tables 2,3 and 4. The terra "FID Total Organic" used in the
tables refers to the KID raeaourcr.ent of the CVS bag sample taken before it was
bubbled in water. The FID measurement of the bubbled sample is termed "HC
(FBM)" and the decrease in concentration due to bubbling is termed
"CH OH(FBM)". This decrease, adjusted to compensate for the FID's low
response to nethanol, represents the FBM estimate of the methanol
concentration in the sample. The nethanol measured using the CC in accordance
with the reference method is termed "CH OH(CC)".
Table 2 contains data when the Escort was being fuuled with M85.
Comparisons between the methanol measurements with the FBM and the GC are
rather poor in this table. For the CT, US, and WT test phases of the FTP,
the average differences between the CH_OH (FBM) values and t-he CH.,011 (CC)
values are 46%, 112%, and 55%. Sinilar data obtained fron the same nethanol
Escort operating on MIOO (pure nethanol) fuel are shown in Table 3. The
average differences for this case are 11%, 7y%, and 24%.
Evaporative emissions results obtained using M85 and M!00 fuels are shown
in Table i. Evaporative tests using M85 fuel, performed with the charcoal
canister disconnected, resulted in substantially higher emission rates than
when the canister was connected during the Ml 00 tests. Comparisons between
the two irethar.ol measurement methods for evaporative emission tests (average
difference <25-l) were somewhat inprovod over those 'or the exhaust emission
tests, however, methanol determinations with the FBM were still consistently
higher.
FBM mathanol determinations error on the high side when final FID
readings (HC (FBM)) are lower than expected. For example, ibsorption of so~.e
saraple hydrocarbons in the water solution used to absorb methane-1 would result
in a lower final FID reading. Because partial absorption of 'Hydrocarbons was
suspected, an attempt was made to identify and quantify the absorbed HC
species. This was accomplished through detailed HC analyses of bubbled and
ur.bubbled exhaust sar.ples. Integrated HC results iron three of these analyses
(shown in Table 5) indicate that between 2 and 11 percent of the hydrocarbons
were being absorbed in sample? taken during the CT Test Phase of the; FTP.
Results from tiic other two test phases are less dramatic with little or no
rneasureable absorption occurring. This finding is not unexpected since
exhaust gas oiefins and aroma tics, which are normally ir.orc soluble in water
than the paraffinic components, comprise a greater fraction of the CT Test
Phase hydrocarbons.
Manv hydrocarbons which are virtually insoluble in water arc very soluble
in alcohol- Because alcohol (r.ethanoJ ) is being collected i:i the water
solution during bubbling witli t're FBM, the possibi L i tv exists that s^,e
hydrocarbons are being absorbed in this alcohol. Evidence suggesting this
occurrence is the r.ot iceabl t- de-crease in concentration after bubbling of
cis-2-butene, 1-pentone, 2-nethy1-2-butcne, and o-xylene. All of these HC
compounds are listed as being very soluble or niscible in alcohol but
insoluble in wat.er (7). Beyond t:;i:-: observation, the- extent of HC absorption
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in ccthanol with the FBM VMS not examined and thus recains a study for future-
consideration.
Vhen the FBM r.ethanol iseasurucicnts arc corrected to account for the
absorption of hydrocarbons in the water solution, the results are still
significantly hip.hcr than the OC values (see Table fj). This persistent
dlscrepency led to a prclininary examination of another factor thought
possibly to be impacting FID response to hydrocarbons. This was the higher
water vapor in bubbled sanples than in unhubbled samples. Saaple huaiditv
before bubbling, which is est8sated below 50 percent-, increases to saturation
levels after wubbiing. To examine whether or not this increase in humidity
has any effect on r IP response to hvurocarb(>:is, a hydrocarbon sample collected
f r>,-~ the .iMyisouth Caravel le w.is saturated with water vapor and analyzed en the
riD il7ppn). Then the sa-ple w.s dried (1'ermai'uri: Oiler) and red^nlyred to
weterair.i: if sample tumidity had h.id any'ef foe; on FID response. None war.
observe'*. In another test, water wa:. ir.jecti-d into a bag containing 84 ppa
!-.C. Identical FID neasurescnts before and after the injection apain
der.onst rated that sacple tumidity levels had had r.o slp,nit leant eltect rn r ID
rospon-se to norr.al exhaust hydrocarbons. Futur;- tests nr.: recosaended to
ex<;r_ine thorouphlv tlic iiur-idity effert on Fit) response to i-:p.;\r.ic emissions
i :'.i--.p!t'S fro:? a r-.etha;;oi-:tii' led auter.ohilc.
Unfortunately, ti?le restraints have ended the quest to dele mine : !'.e
c-t.-ch.lni sns resp! nsible :«'r FBM r.ethanol neasur er.ent d i:i tlio FiiM "crior" pert ems' presented in
Table ! are a r ranged in order c'. n.ii'.ni ti:dc, the exh.'.i'st neas-urert-nt errors are
ir.ver -.c ly related to the r.cthar.ol coi tent o! *l:e s.irp.e (see Table ^).
L'bv'i-iis ly , THM accuracy :n the study l.i-ise!'i t. teii stihstant ial! y with increase in
r^ethannl conccnrracion ot the exhaust nanplo.
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REFERENCES
1. Federal Register, Vol. 51, No. 168, August, 1986.
2. P. A. Gabele, J.O. Baugh, F. Black, R. Snow. "Characterization of
Emissions from Vehicles Using Nethanol and Mothnnol-Gasoline Blended
Fuels," JAPCA, Vol. 35, No. 11, November, 1985.
3. R. Snow et al., "Chai'acterization of Emissions from a Kethanol Fueled
Metor Vehicle," submitted to JAPCA for publication, preprint available
through EPA, MD-46, RTP, NC, 27711.
4. L.R. Smith, C. Urban, "Characterization of Exhaust Emissions froc
Xethanol end Gasoline Fueled Automobiles," Final Report,
EPA460/3-82-004, U.S. Environmental Protection Agency, Research Triangle
Park, N.C... March, 1982.
5. "Code of Federal Regulations," Title 40, Part 86, U.S. Government
Printing Office, Washington, D.C., July 1978.
6. P.M. Black, L.E. High, J.E. Sigsby, "A Gas Chromatopraphic Method for
Direct Analysis of Photochemically Non-reactive Hydrocnrbcns ," J. Chroir,.
?ci. 14: 257 (1976).
7. Large's Handbook of Cher.-.istry, 13th Edition, McGraw-Hill Book Co., New
Yrrk, 1985.
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REFERENCE
METHOD
FID BUBBLE
METHOD
FI:;AL
BAG
SAMPLE
V
/"
^
S
FID
ANALYSIS
Figure i. Merhanol sampling and analysis flow schematic
s;
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TABLE 1. DIFFERENCES (IN PERCENT) OF METHANOL MEASUREMENTS,
FBM VERSUS GC. . . '
TEST
PHASE/FUEL:
Cold Transient
Hot Stabilized
Warm Transient
Diurnal
M85
+46%
+ 112%
+55%
+25%.
_- __ ____ __ .^ .
M100
. +11%
+ 79%
+ 24%
+20%
TABLE 2. FTP EXHAUST DATA, M85 FUEL
FID TOTAL
Run :
30242
30243
30244
AVG.
30242
30243
302^4
AVG .
30242
30243
30244
AVG.
ORGANIC
(ppm)
82
82
91
85
16
16
1.3
15
56
5b -
50
54
ilC (FBM)
(ppn)
CT TEST PHASE
39
38
44
40 .
HS TEST PHASE
13
13
) L
12
WT TEST PHASE-
30
29 - .
28
29
CH OH (FBM)
fppm)
57.2
58.5
62.5
59.4 .
4.0
4.0
2.7
3.6
34.6
35.9
29.3-
33.3 ;
CH3OH(GC)
(ppm)
38.7'
41.9
41.0
40.5
1.8
1.8
1.4
1.7
23.5
22.5
18.6
21.5 -:.
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TABLE 3. FTP EXHAUST DATA, M100 FUEL
Run f?
FID TOTAL
ORGANIC
(ppra)
HC (FBM)
(ppm)
CH OH . (FBM)
(ppn)
CH CH(GC)
(ppn)
CT TEST PHASE
30245
30246
30248
30249
AVG.
30245
30246
30248
30249
AVG.
30245
30246
30248
30249
AVG.
173
130
89
101
123.2
HS
11
10
10
6
9.2
V,T
23
63
45
52
45.7
12
10
8
8
9.5
TEST PHASE
7
5
5
4
5.2
TEST PHASE
7
7
6
6
6.5
214.1
160.0
107.7
123.7
151.4
5.3
6.6
6.6
2.7
5.3
21.3
74.6
51.9
61.2.
52.2
200.0
135.1
125.7
130.7
147.9
3.0
3.0
3.2
2.4
2.9
16.0
55.0
44.4
55.1
42.6
FUEL
TABLE 4. DIURXAL EVAPORATIVE DATA
FID TOTAL
ORGANIC HC (FBM) CH,OH(FBM) CH OH(GC) CCMMENT
(ppm) (ppm) ""(ppr.) Ippn)
30240
30234
30237
30250
30251
M85
MS 5 '
M85
Ml 00
Ml 00
252
234
237
14.0
12.8
232
210
213
4.0
3.4
_ .
26.6
31.9
31.9
13.3
12.5
21.5
22.3
28.7
11.4
10.1
w/o canister
w/o canister
w/c canister
v/ canister
w/ canister
.10
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TABLE 5. FTP Exhaust Data, M85 Fuel
Run ?
30242
30243
30244
30242
30243
30244
30242
30243
30244
Integrated
THC (GC)
Unbubbled
(ppm)
39.
38.
40.
11.
10.
9.
27.
26.
24.
3
6
1
6
3
9
8
6
.3
Integrated HC's CHOH(FBM).
THC (GC) Absorbed Corrected for
Bubbled In Water HC's Absorbed
(ppm) (ppm) (ppm)
CT TEST PHASE
36.8 2.5
34.2 4.4
. 39.4 . . 0.7 ..
US TE?" PHASE
11.3 0.3
11.1
9.5 0.4
WT TEST PHASE
27.2 0.6
27. 1
24.7
53
52
'..61.
3.6
4.0
2.2
34
36
39
CH OH
(GC)
(ppm)
39
42
41
1.
1.
1.
. 23
22
19
8
8
4
TABLE 6. METHOD COMPARISON VS. MCTHANOL FRACTION AND
CONCENTRATION IN EXHAUST SAMPLES
MsJthanol. . .
Fraction
.11
.29
.36
.43
.76
.92
Methanol .
Cone, (pp.ra)
->
3
21
- 40
43
148
. . .% Diff.
(FBM Error)
. +112%
+79%
+55%
-(46%
+24%
' +11%
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