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7.4.1.1 Unless otherwise necessary for a specific project, the analysis of themulti-component analytes employs a single-point calibration. A single calibrationstandard near the mid-point of the expected calibration range of each multi-componentanalyte is included with the initial calibration of the single component analytes for patternrecognition, so that the analyst is familiar with the patterns and retention times on eachcolumn.7.4.1.2 For calibration verification (each 12-hour shift) all target analytesrequired in the project plan must be injected.7.4.2 Establish the GC operating conditions appropriate for the configuration (singlecolumnor dual column, Sec. 7.3) using Tables 4, 5, 7, or 8 as guidance. Optimize theinstrumental conditions for resolution of the target analytes and sensitivity. An initial oventemperature #140 -150EC is required to resolve the four BHC isomers. A final temperature of240 - 270EC is required to elute decachlorobiphenyl. Use of injector pressure programmingwill improve the chromatography of late eluting peaks.NOTE:Once established, the same operating conditions must be used for bothcalibrations and sample analyses.7.4.3 A 2 µL injection volume of each calibration standard is recommended. Otherinjection volumes may be employed, provided that the analyst can demonstrate adequatesensitivity for the compounds of interest.7.4.4 Because of the low concentration of pesticide standards injected on a GC/ECD,column adsorption may be a problem when the GC has not been used for a day or more.Therefore, the GC column should be primed (or deactivated) by injecting a pesticide standardmixture approximately 20 times more concentrated than the mid-concentration standard. Injectthis standard mixture prior to beginning the initial calibration or calibration verification.CAUTION:Several analytes, including Aldrin, may be observed in the injection justfollowing this system priming. Always run an acceptable blank prior torunning any standards or samples.7.4.5 Calibration factorsWhen external standard calibration is employed, calculate the calibration factor for eachanalyte at each concentration, the mean calibration factor, and the relative standard deviation(RSD) of the calibration factors, using the formulae below. If internal standard calibration isemployed, refer to Method 8000 for the calculation of response factors.as:CF '7.4.5.1 Calculate the calibration factor for each analyte at each concentrationPeak Area (or Height) of the Compound in the StandardMass of the Compound Injected (in nanograms)7.4.5.2 Calculate the mean calibration factor for each analyte as:CD-ROM 8081A - 12 Revision 1December 1996
mean CF ' CF 'nj CF ii'1nwhere n is the number of standards analyzed.7.4.5.3 Calculate the standard deviation (SD) and the RSD of the calibrationfactors for each analyte as:SD 'nj (CF i&CF) 2i'1n&1RSD ' SDCF x 100If the RSD for each analyte is # 20%, then the response of the instrument is consideredlinear and the mean calibration factor can be used to quantitate sample results. If theRSD is greater than 20%, then linearity through the origin cannot be assumed. Theanalyst must use a calibration curve or a non-linear calibration model (e.g., a polynomialequation) for quantitation. See Method 8000 for information on non-linear calibrations.7.4.6 Retention time windowsAbsolute retention times are used for compound identification. Retention time windowsare crucial to the identification of target compounds, and should be established by one of theapproaches described in Method 8000.7.4.6.1 Before establishing the retention time windows, make sure the gaschromatographic system is operating within optimum conditions.7.4.6.2 The widths of the retention time windows are defined as described inMethod 8000. However, the experience of the analyst should weigh heavily in theinterpretation of the chromatograms.7.5 Gas chromatographic analysis of sample extracts7.5.1 The same GC operating conditions used for the initial calibration must beemployed for samples analyses.7.5.2 Verify calibration each 12-hour shift by injecting calibration verification standardsprior to conducting any sample analyses. Analysts should alternate the use of high and lowconcentration mixtures of single-component analytes and multi-component analytes forcalibration verification. A calibration standard must also be injected at intervals of not less thanonce every twenty samples (after every 10 samples is recommended to minimize the numberof samples requiring re-injection when QC limits are exceeded) and at the end of the analysissequence. See Sec. 8.4.4 for additional guidance on the frequency of the standard injections.7.5.2.1 The calibration factor for each analyte should not exceed a ± 15 percentdifference from the mean calibration factor calculated for the initial calibration. If a non-CD-ROM 8081A - 13 Revision 1December 1996
Page 1 and 2: METHOD 8081AORGANOCHLORINE PESTICID
Page 3 and 4: CompoundCAS Registry No.Chloropropy
Page 6 and 7: confirmation techniques may be empl
Page 9 and 10: 5.7.2 1-bromo-2-nitrobenzene is sug
Page 11: columns. Table 2 lists average rete
Page 15 and 16: 7.5.6.1 For aqueous samplesConcentr
Page 17 and 18: 7.5.11 Identification of mixtures (
Page 19 and 20: Construct a similar baseline in the
Page 21 and 22: 8.0 QUALITY CONTROL8.1 Refer to Cha
Page 23 and 24: 8000, Sec. 8.0 for information on e
Page 25 and 26: TABLE 1GAS CHROMATOGRAPHIC RETENTIO
Page 27 and 28: TABLE 3aFACTORS FOR DETERMINATION O
Page 29 and 30: TABLE 5GC OPERATING CONDITIONS FOR
Page 31 and 32: TABLE 6 (continued)RETENTION TIMES
Page 33 and 34: TABLE 8GC OPERATING CONDITIONS FOR
Page 35 and 36: TABLE 10ANALYTE RECOVERY FROM DICHL
Page 37 and 38: TABLE 12SINGLE LABORATORY ACCURACY
Page 39 and 40: FIGURE 2GAS CHROMATOGRAM OF INDIVID
Page 41 and 42: FIGURE 4GAS CHROMATOGRAM OF TOXAPHE
Page 43 and 44: FIGURE 6GAS CHROMATOGRAM OF ORGANOC

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