USGS-NWQL: O-4024-03: Volatile organic compounds, whole water, gas chromatography/mass spectrometry, heated purge and trap

Summary
Analytes
Revision
Data and Sites

Official Method Name

Volatile organic compounds, whole water, gas chromatography/mass spectrometry, heated purge and trap

Current Revision

2003

Media

WATER

Instrumentation

Gas Chromatography with Mass Spectrometry Detection

Method Subcategory

Organic

Method Source

USGS-NWQL

Citation

Rose, D.L., and Sandstrom, M.W., 2003, Methods of Analysis of the U.S. Geological Survey National Water Quality Laboratory - Determination of Gasoline Oxygenates, Selected Degradates, and BTEX in Water by Heated Purge and Trap/Gas Chromatography/Mass Spectrometry, U.S. Geological Survey Water-Resources Investigations Report 03-4079, 39 p.

Brief Method Summary

Volatile organic compounds are purged from the sample matrix by simultaneously bubbling helium through a 25-mL aqueaous sample and heating at 65^oC. The compounds are trapped in a tube containing suitable sorbent materials and then thermally desorbed into a capillary gas chromatographic column interfaced to a mass spectrometer system. Selected compounds are identified by using strict identification criteria, which include analyzing standard reference materials and comparing retention times and relative ratios of the mass spectra. Compounds are quantitated using interal standard procedures. Quantitation that is extrapolated less than the lowest calibration standard is qualified as "estimated" to signify the lower confidence in the extrapolated concentration. Compounds are not quantitated if they do not strictly adhere to identification criteria. Compounds identified with concentrations within the calibration range are reported without qualification, unless quality control or holding times are compromised.

Scope and Application

This method is suitable for the determination of gasoline oxygenates, selected degradates, and BTEX (benzene, toluene, ethylbenzene, and xylenes) at low concentrations in whole-water samples. The method is applicable to analytes that can be efficiently removed from the water matrix by heating and purging with helium.

Applicable Concentration Range

0.035 - 0.62

Interferences

Samples can be contaminated during collection or analysis. Several types of laboratory and field blanks are used in this method to identify sources of contamination. Possible contamination sources include vehicle exhaust fumes, industrial stack emissions, outgassing of solvents from vehicle carpets and upholstery, copier machines, paint, and cleaning solutions. Sampling equipment used at contaminated sites might contain residual contaminants if not cleaned properly. During sample preparation and analysis in the laboratory, samples can be contaminated by common extraction solvents that are present in the laboratory atmosphere.
Carryover contamination can occur when samples containing high concentrations of VOCs (greater than 20 ug/L) contaminate the next analysis at detectable concentrations because of residual VOCs in the trap, purge vessel, or transfer lines, which were not eliminated during the routine bake procedure. Samples suspected of being contaminated by carryover will be reanalyzed. The field-sampling personnel should note on the analytical service request form (ASR) if it is known that a given sample contains high concentrations of VOCs. The laboratory analysts should separate contaminated samples from clean samples. Knowledge of carryover characteristics by instrument and compound is necessary for this method.
Hydrogen sulfide will interfere with the response of the mass spectrometer and can damage columns, traps, multipliers, and quadropoles. If field personnel detects any odor of hydrogen sulfide, they should note this on the ASR.
Foamy samples can interfere with the analysis by raising the baseline, decreasing instrument response, and shifting peak retention times. Samples that are excessively foamy are diluted until no foam is produced.
Care needs to be taken to eliminate all potential organic contaminants from the volatiles laboratory by limiting exposure to laboratories using organic solvents, and exposed clothing.

Quality Control Requirements

Sample Handling

Samples known to contain bacteria adapted to degrading fuels should be preserved to pH 2 if analysis of BTEX compounds is desired and methyl acetate is not a concern.

Maximum Holding Time

14 days

Relative Cost

Sample Preparation Methods

This method has 15 analytes associated with it.

Analyte	Detection Level	Bias	Precision	Spiking Level
Acetone(67-64-1) 2-Propanone Acetone Dimethylketone Pyroacetic ether beta-Ketopropane	0.625 ug/L	81% Rec (SL)	14.90 % RSD (SL)	40.00 ug/L
Benzene(71-43-2) Benzene Benzol Coal naptha Cyclohexatriene Phene Pyrobenzol	0.007 ug/L	97% Rec (SL)	5.40 % RSD (SL)	1.00 ug/L
Diisopropyl ether(108-20-3) 2,2'-Oxybispropane 2-Isopropoxypropane Bis(isopropyl) ether Di-1-methylethyl ether Diisopropyl ether Diisopropyl oxide Isopropyl ether (8CI) Propane, 2,2'-oxybis- (9CI)	0.041 ug/L	84% Rec (SL)	9.40 % RSD (SL)	4.00 ug/L
Ethylbenzene(100-41-4) Benzene, ethyl Ethyl benzene Ethylbenzene Ethylbenzol Phenylethane	0.016 ug/L	82% Rec (SL)	14.80 % RSD (SL)	1.00 ug/L
MTBE(1634-04-4) 2-Methoxy-2-methyl propane MTBE Methyl tert butyl ether Methyl tert-butyl ether Methyl tertiary butyl ether Methyl-t-butylether Propane, 2-methoxy-2-methyl- tert-Butyl methyl ether	0.038 ug/L	91% Rec (SL)	8.10 % RSD (SL)	4.00 ug/L
Methyl acetate(79-20-9) Acetic acid, methyl ester (6CI,8CI,9CI) Devoton Methyl acetate Methyl ethanoate NSC 405071 Tereton	0.216 ug/L	105% Rec (SL)	19.40 % RSD (SL)	8.00 ug/L
Tert-Butyl Alcohol(75-65-0) 2-Methyl-2-Propanol Tert-Butyl Alcohol t-Butyl Alcohol	0.499 ug/L	130% Rec (SL)	7.50 % RSD (SL)	40.00 ug/L
Toluene(108-88-3) Benzene, methyl Methacide Methylbenzene Methylbenzol Phenylmethane Toluene Toluol	0.005 ug/L	84% Rec (SL)	4.70 % RSD (SL)	1.00 ug/L
Volatile organic compounds(E-12419) Organic compounds, volatile VOCs Volatile organic compounds	N/A	N/A	N/A
m-Xylene(108-38-3) 1,3-Dimethylbenzene 3-Xylene Benzene, 1,3-dimethyl- m-Xylene m-Xylol	0.036 ug/L	71% Rec (SL)	16.00 % RSD (SL)	2.40 ug/L
o-Xylene(95-47-6) 1,2-Dimethylbenzene 2-Xylene Benzene, 1,2-dimethyl- o-Xylene o-xylol	0.020 ug/L	83% Rec (SL)	15.30 % RSD (SL)	1.20 ug/L
p-Xylene(106-42-3) 1,4-Dimethylbenzene 4-Xylene Benzene, 1,4-dimethyl- p-Xylene p-Xylol	0.036 ug/L	71% Rec (SL)	16.00 % RSD (SL)	2.40 ug/L
tert-Amyl alcohol(75-85-4) 1,1-Dimethyl-1-propanol 2-Butanol, 2-methyl- (9CI) 2-Ethyl-2-propanol 2-Hydroxy-2-methylbutane 2-Methyl-2-butanol 2-Methyl-2-hydroxybutane Amylene hydrate Dimethylethylcarbinol Ethyldimethylcarbinol NSC 25498 tert-Amyl alcohol tert-Pentanol tert-Pentyl alcohol (8CI)	0.216 ug/kg	93% Rec (SL)	4.40 % RSD (SL)	40.00 ug/kg
tert-Amyl methyl ether(994-05-8) 1,1-Dimethylpropyl methyl ether 2-Methoxy-2-methylbutane 2-Methyl-2-methoxybutane Butane, 2-methoxy-2-methyl- (9CI) Ether, methyl tert-pentyl (6CI,7CI,8CI) Methyl 1,1-dimethylpropyl ether Methyl tert-amyl ether Methyl tert-pentyl ether t-Amyl methyl ether tert-Amyl methyl ether tert-Pentyl methyl ether	0.035 ug/L	91% Rec (SL)	7.40 % RSD (SL)	4.00 ug/L
tert-Butyl ethyl ether(637-92-3) 1,1-Dimethylethyl ethyl ether 2-Ethoxy-2-methylpropane Ether, tert-butyl ethyl (6CI,7CI,8CI) Ethyl 1,1-dimethylethyl ether Ethyl tert-butyl ether Ethyl tert-butyl oxide NSC 1069 Propane, 2-ethoxy-2-methyl- (9CI) tert-Butyl ethyl ether	0.052 ug/L	90% Rec (SL)	11.10 % RSD (SL)	4.00 ug/L

Precision Descriptor Notes:	Bias and precision estimates for this method were evaluated by analyzing seven spiked replicates in volatile-grade blank water (VBW), surface-water, and ground-water samples at concentrations ranging from 0.5 to 5 ug/L and 5 to 50 ug/L. The water was collected in 1-L amber bottles and stored in a VOC refridgerator. Then, 50 mL of the water was spiked and transferred to a 40-mL VOC vial and analyzed. Replicate spikes were analyzed in the same analytical sequence. All three sample matrices for each concentration were spiked and analyzed randomly. A sample of the unspiked matrix water was analyzed to determine if detectable VOCs were present.
Detection Level Note:	The MDLs are determined from a minimum of seven-replicate low-level spikes analyzed over a minimum of 3 days using the method described in USEPA report Part 135, Appendix B, Revision 1.11.

Precision Descriptor Notes:

Bias and precision estimates for this method were evaluated by analyzing seven spiked replicates in volatile-grade blank water (VBW), surface-water, and ground-water samples at concentrations ranging from 0.5 to 5 ug/L and 5 to 50 ug/L. The water was collected in 1-L amber bottles and stored in a VOC refridgerator. Then, 50 mL of the water was spiked and transferred to a 40-mL VOC vial and analyzed. Replicate spikes were analyzed in the same analytical sequence. All three sample matrices for each concentration were spiked and analyzed randomly. A sample of the unspiked matrix water was analyzed to determine if detectable VOCs were present.

Detection Level Note:

The MDLs are determined from a minimum of seven-replicate low-level spikes analyzed over a minimum of 3 days using the method described in USEPA report Part 135, Appendix B, Revision 1.11.

Revision	PDF/Link
2003

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USGS-NWQL: O-4024-03: Volatile organic compounds, whole water, gas chromatography/mass spectrometry, heated purge and trap

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