定价： 571元 加购物车

定价： 646元 加购物车

4.1 Gas chromatography with sulfur selective detection provides a rapid means to identify and quantify sulfur compounds in various petroleum feeds and products. Often these materials contain varying amounts and types of sulfur compounds. Many sulfur compounds are odorous, corrosive to equipment, and inhibit or destroy catalysts employed in downstream processing. The ability to speciate sulfur compounds in various petroleum liquids is useful in controlling sulfur compounds in finished products and is frequently more important than knowledge of the total sulfur content alone.1.1 This test method covers the determination of volatile sulfur-containing compounds in light petroleum liquids. This test method is applicable to distillates, gasoline motor fuels (including those containing oxygenates) and other petroleum liquids with a final boiling point of approximately 230 °C (450 °F) or lower at atmospheric pressure. The applicable concentration range will vary to some extent depending on the nature of the sample and the instrumentation used; however, in most cases, the test method is applicable to the determination of individual sulfur species at levels of 0.1 mg/kg to 100 mg/kg.1.2 The test method does not purport to identify all individual sulfur components. Detector response to sulfur is linear and essentially equimolar for all sulfur compounds within the scope (1.1) of this test method; thus both unidentified and known individual compounds are determined. However, many sulfur compounds, for example, hydrogen sulfide and mercaptans, are reactive and their concentration in samples may change during sampling and analysis. Coincidently, the total sulfur content of samples is estimated from the sum of the individual compounds determined; however, this test method is not the preferred method for determination of total sulfur.1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 加购物车

定价： 646元 加购物车

定价： 646元 加购物车

定价： 590元 加购物车

定价： 646元 加购物车

定价： 712元 加购物车

定价： 571元 加购物车

定价： 571元 加购物车

定价： 590元 加购物车

定价： 646元 加购物车

定价： 590元 加购物车

定价： 646元 加购物车

5.1 The N-methyl carbamate (NMC) pesticides: aldicarb, carbaryl, carbofuran, formetanate hydrochloride, methiocarb, methomyl, oxamyl, pirimicarb, propoxur, and thiodicarb have been identified by EPA as working through a common mechanism. They affect the nervous system by reducing the ability of the enzyme cholinesterase. Cholinesterase inhibition was the primary toxicological effect of regulatory concern to EPA in assessing the NMC’s food, drinking water and residential risks. In most of the country, NMC residues in drinking water sources are at levels that are not likely to contribute substantially to the multi-pathway cumulative exposure. Shallow private wells extending through highly permeable soils into shallow, acidic ground water represent what the EPA believes to be the most vulnerable drinking water.45.2 This test method has been investigated for use with reagent and surface water for the selected carbamates: aldicarb, carbofuran, oxamyl, and methomyl.1.1 This procedure covers the determination of aldicarb, carbofuran, oxamyl and methomyl (referred to collectively as carbamates in this test method) in surface water by direct injection using liquid chromatography (LC) and detected with tandem mass spectrometry (MS/MS). These analytes are qualitatively and quantitatively determined by this test method. This test method adheres to multiple reaction monitoring (MRM) mass spectrometry.1.2 This test method has been developed by U.S. 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 carbamates are listed in Table 1.TABLE 1 Detection Verification Level and Reporting RangeAnalyte DVL (ng/L) Reporting Range (μg/L)Aldicarb 100 1–100Carbofuran 100 1–100Oxamyl 100 1–100Methomyl 100 1–1001.4.1 The DVL is required to be at a concentration at least 3 times below the Reporting Limit (RL) and have a signal/noise ratio greater than 3:1. Fig. 1 displays the signal/noise ratios of the primary single reaction monitoring (SRM) transitions and Fig. 2 displays the confirmatory SRM transitions at the DVLs for the carbamates.FIG. 1 Example Primary SRM Chromatograms Signal/Noise RatiosFIG. 2 Example Confirmatory SRM Chromatograms Signal/Noise Ratios1.4.2 The reporting limit is the concentration of the Level 1 calibration standard as shown in Table 2 for the carbamates.TABLE 2 Concentrations of Calibration Standards (PPB)Analyte/Surrogate LV 1 LV 2 LV 3 LV 4 LV 5 LV 6Aldicarb 1 5 10 25 50 100Carbofuran 1 5 10 25 50 100Oxamyl 1 5 10 25 50 100Methomyl 1 5 10 25 50 100BDMC (Surrogate) 2 10 20 50 100 2001.5 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.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 加购物车