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Organophosphate pesticides affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. They were developed during the early 19th century, but their effects on insects, which are similar to their effects on humans, were discovered in 1932. Some are poisonous and were used as chemical weapon agents. Organophosphate pesticides are usually not persistent in the environment. ,
This test method is for the analysis of selected organophosphorous-based chemical weapon agent degradation products from Sarin (GB), Soman (GD), Tabun (GA) and VX. This method has been investigated for use with reagent and surface water.
Область применения1.1 This procedure covers the determination of diisopropyl methylphosphonate (DIMP), ethyl hydrogen dimethylamidophosphate (EHDMAP), ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA), methylphosphonic acid (MPA) and pinacolyl methylphosphonic acid (PMPA) (referred to collectively as organophosphonates in this test method) in surface water by direct injection using liquid chromatography (LC) and detected with tandem mass spectrometry (MS/MS) using electrospray ionization (ESI). These analytes are qualitatively and quantitatively determined by this method. This method adheres to single reaction monitoring (SRM) mass spectrometry.
1.2 This test method has been developed by US EPA Region 5 Chicago Regional Laboratory (CRL).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 The detection verification level (DVL) and reporting range for the organophosphonates are listed in Table 1.
1.4.1 The DVL is required to be at a concentration at least three times below the reporting limit (RL) and have a signal/noise ratio greater than 3:1. Fig. 1 displays the signal/noise ratios at the DVLs for the organophosphonates in the ESI positive mode and Fig. 2 in the ESI negative mode.
1.4.2 The reporting limit is the concentration of the Level 1 calibration standard as shown in Table 2 for the organophosphonates except for MPA in the ESI negative mode which is at Level 2 due to not meeting the DVL criteria at the lower concentration level. The DVL for MPA in the ESI negative mode is at 20 μg/L, which forces a raised reporting limit. However, the multi-laboratory validation required a spike of all target analytes at Level 1 concentrations. The mean recovery for MPA in the ESI negative mode at this level was 98.7 % as shown in Table 3. If your instrument’s sensitivity can meet the requirements in this test method, MPA may have a 50 μg/L reporting limit.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
TABLE 1 Detection Verification Level and Reporting Range
AnalyteESI ModeDVL (μg/L)Reporting Range (μg/L) Diisopropyl methylphosphonatePositive15–150 Ethyl hydrogen dimethylamidophosphateNegative0.255–150 Ethyl hydrogen dimethylamidophosphatePositive0.255–150 Ethyl methylphosphonic acidNegative550–1500 Ethyl methylphosphonic acidPositive550–1500 Isopropyl methylphosphonic acidNegative1050–1500 Isopropyl Methylphosphonic acidPositive550–1500 Methylphosphonic acidNegative20100–1500 Methylphosphonic acidPositive1050–1500 Pinacolyl methylphosphonic acidNegative550–1500 Pinacolyl methylphosphonic acidPositive550–1500TABLE 2 Concentrations of Calibration Standards (PPB)
Analyte/Surrogate LV 1LV 2LV 3LV 4LV 5LV 6LV 7 Diisopropyl methylphosphonate510203550100150 Ethyl hydrogen dimethylamidophosphate510203550100150 Ethyl methylphosphonic acid5010020035050010001500 Isopropyl methylphosphonic acid5010020035050010001500 Methylphosphonic acid5010020035050010001500 Pinacolyl methylphosphonic acid5010020035050010001500 DIMP-D14 (Surrogate)510203550100150 PMPA-13C4 (Surrogate)2550100175250500750 MPA-D3 (Surrogate)2550100175250500750TABLE 3 Multi-Laboratory Recovery Data in Reagent Water
AnalyteESI
FIG. 1 Example ESI Positive Mode SRM Chromatograms Signal/Noise Ratios
FIG. 2 Example ESI Negative Mode SRM Chromatograms Signal/Noise Ratios