EPA Method 8033 Acetonitrile by Gas Chromatography with Nitrogen-Phosphorus Detection
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166AD75BAF714E14826B3C27BAF2C86B |
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文件大小(MB)： |
0.07 |
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页数： |
7 |
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日期： |
2009-12-11 |
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CD-ROM 8033 - 1 Revision 0,December 1996,METHOD 8033,ACETONITRILE BY GAS CHROMATOGRAPHY WITH,NITROGEN-PHOSPHORUS DETECTION,1.0 SCOPE AND APPLICATION,1.1 Method 8033 may be used to determine the concentration of acetonitrile (CAS No. 75-,05-8) in aqueous matrices.,1.2 The method detection limit in water is approximately 1.7 to 2.8 picograms (1.7 to 2.8 μg/L,with a 1 μL injection) at 40 and 20 volts offset, respectively. The upper limit of the range is,approximately 5000 μg/L and is limited by the non-linearity of the nitrogen-phosphorus detector,(NPD). The range may be extended by diluting the sample. This procedure may be applicable to,other matrices where the target compound can be extracted into water.,1.3 This method is also applicable to aqueous condensate collected from the VOST or semi-,VOST sampling trains.,1.4 This method is restricted to use by or under the supervision of analysts experienced in,the use of gas chromatographs and skilled in the interpretation of gas chromatograms. Each,analyst must demonstrate the ability to generate acceptable results with this method.,2.0 SUMMARY OF METHOD,Water samples containing acetonitrile are introduced into a GC/NPD using cool on-column,direct aqueous injection. The GC/NPD system is externally calibrated using a series of acetonitrile,standards diluted in organic-free reagent water. A series of blank organic-free reagent water,samples are directly injected until no peaks are observed in the chromatogram. The acetonitrile,concentration is quantitated using the external calibration method.,3.0 INTERFERENCES,3.1 There are no known chromatographic interferants when samples are analyzed using the,optimum operating conditions. However, at column temperatures greater than 60EC, water,becomes an interferant, as it coelutes with acetonitrile and produces a negative disruption of the,baseline, thereby preventing accurate quantitations. This problem is eliminated by operating the,column at 35EC. At this temperature, water will eventually elute and produce a positive disruption,of the baseline. However, this effect can be minimized by heating the column to 120EC for 1 hour,after a day's analysis.,3.2 Glassware containing traces of chromium should not be used because chromium will,form a complex with acetonitrile, thereby reducing the amount of acetonitrile available for,quantitation.,3.3 Reagents, glassware, and other sample processing hardware may yield discrete artifacts,and/or elevated baselines causing misinterpretation of gas chromatograms. All these materials,CD-ROM 8033 - 2 Revision 0,December 1996,must be demonstrated to be free from interferences under the conditions of the analysis, by,analyzing reagent blanks.,4.0 APPARATUS AND MATERIALS,4.1 Gas chromatograph,4.1.1 Gas chromatograph, analytical system complete with gas chromatograph suitable,for cool on-column injections and all required accessories, including detector, analytical,columns, recorder, gases, and syringes. A data system for measuring peak heights and/or,peak areas is recommended.,4.1.2 Column: DB-WAX, 15 m X 0.53 mm, 1.0 μm capillary column (J&W Scientific,or equivalent).,4.1.3 Detector: Nitrogen-Phosphorus (NPD).,4.2 Bubble flow-meter: 0-10 and 0-100 cm3/min, for measuring GC gas flows.,4.3 Syringes: 10 μL capacity, equipped with fused silica needles. Use of a syringe with a,stainless steel needle has not been evaluated.,4.4 Volumetric flasks: Class A, sizes as appropriate.,4.5 Pipets: Class A, assorted sizes.,5.0 REAGENTS,5.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is,intended that all reagents shall conform to the specifications of the Committee on Analytical,Reagents of the American Chemical Society, where such specifications are available. Other grades,may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit,its use without lessening the accuracy of the determination.,5.2 Organic-free reagent water - All references to water in this method refer to organic-free,reagent water, as defined in Chapter One.,5.3 Gases,5.3.1 Helium gas - 99.9999% purity, for carrier and make-up gas. Helium is preferred,as the make-up gas over nitrogen because helium produces a more stable baseline with less,noise.,5.3.2 Air - zero grade.,5.3.3 Nitrogen - zero grade.,5.4 Acetonitrile, CH CN - 99.9% purity. 3,CD-ROM 8033 - 3 Revision 0,December 1996,5.5 2-Propanol, (CH ) CHOH - Pesticide quality or equivalent. 3 2,5.6 Stock standard solutions - Prepare from pure standard materials or purchase as certified,solutions.,5.6.1 Prepare stock standard solutions by accurately weighing the appropriate am……
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