EPA-OGWDW/TSC: 524.3:  Purgeable Organic Compounds in Water by GCMS

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
 Measure of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry
Current Revision
Version 1.0, June 2009
Media
 WATER
Instrumentation
 Gas Chromatography with Mass Spectrometry Detection
Method Subcategory
 Organic
Method Source
  EPA-OGWDW/TSC
Citation
 USEPA, 2009, Method 524.3, V. 1: Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectometry, EPA 815-B-09-009.
Brief Method Summary
 Headspace-free samples are collected in amber, glass vials with polytetrafluoroethylene (PTFE)-faced septa. Samples are dechlorinated with ascorbic acid and the pH is adjusted with maleic acid. A 5.0-milliliter (mL) aliquot of the sample is transferred to a glass sparging vessel along with appropriate amounts of internal standard and quality control compounds. The method analytes are purged from the water using helium and trapped on a sorbent material. After purging, the trap may be dry purged for a short period to remove water. Additional water management techniques may be applied. The trap is heated and backflushed with helium to transfer the analytes directly into a gas chromatographic inlet. The inlet is operated in the split mode in order to achieve the desired desorb flow rates and further reduce water transmission. Analytes are transferred onto a capillary GC column, which is temperature programmed to optimize the separation of method analytes. Compounds eluting from the GC are directed into a mass spectrometer for detection and quantitation. The method analytes are identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical GC/MS conditions. The concentration of each analyte is calculated using the internal standard technique and response curves obtained via procedural calibration (Sect. 3.18).
Scope and Application
 This is a gas chromatography/mass spectrometry (GC/MS) method for the determination of purgeable organic compounds in finished drinking waters. Discontinuous scanning modes such as selected ion monitoring (SIM) and selected ion storage (SIS) are permitted for determining selected analytes that are monitored at levels too low for the full scan detection mode.
Applicable Concentration Range
Interferences
 Volatile organic compounds (VOCs) present in ambient air, shipping containers, and in the laboratory environment may permeate the PTFE-lined septa of the sample vials or be present at high concentrations in the headspace of the vial. Commercially available purge-and-trap concentrators and autosamplers have complex sample paths that are subject to cross contamination. All laboratory reagents must be routinely demonstrated to be free from interferences under the conditions of the analysis. Matrix interferences are caused by contaminants that are present in the sample.
Quality Control Requirements
 At a minimum, collect all samples in duplicate. Duplicate field reagent blanks must accompany each sample set, which is composed of the samples collected from the same general sampling site at approximately the same time.
Sample Handling
 Samples must be acidified with maleic and ascorbic acid to ensure a pH of about 2. Samples must be chilled during shipment and must not exceed 10 degrees C during the first 48 hours after collection.
Maximum Holding Time
 Samples must be analyzed within 14 days of collection.
Relative Cost
 $201 to $400
Sample Preparation Methods
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