APPENDIX‖l Pesticide Analytical Manual Vol I Proper Application of Methods Do not combine a GlC column that contains cyano groups with a nitro- gen-selective detector Adjust GlC column temperature to establish the correct relative retention time (rrt)of the marker chemical(s). Absolute retention times(min)are provided in DG modules to provide an indication of normal behavior, but the temperature should not be adjusted to achieve this Measure retention times on glc columns from the solvent front wher ever possible for both the compound being tested and the marker com- pound. If the instrumentation in use precludes measurement from the solvent front, state this fact in the report. When submitting chromatograms with reporting forms, label them clearly indicate how many nanograms(ng) or picograms(pg)are represented by the peak. Do not label a chromatogram of a standard in ppm For chro- matograms that result from recovery studies, indicate on the chromato- gram label how much sample weight equivalent(mg) was injected For accurate quantitation, detector response to the reference standard should be within +25% of the response to the analyte in the sample, based on observable(on-scale) peak heights. Usual GLC linearity does not sup- port quantitation that compares responses differing in size by more than that amount Injection to elute before the next injection is made. peaks from one Make sure that chromatograms do not overlap; allow when the chromatogram contains multiple peaks representing different components in the standard, report the rrt of each peak >5%0 FSD It is not necessary to evaporate the solvent from the fortification solution once it has been added to the sample, unless there is some reason to expect it to interfere with the analysis. It is preferable for the fortifying solution to be made from the same solvent used to extract the sample Use only the 60/100 mesh PR grade Florisil specified by Sections 303 and 304(Protocols E and F). Other grades of commercially available Florisil are likely to result in different elution patterns Florisil column in a polar solvent, which will affect elution patern. ch During tests of elution from Florisil, do not add reference material to Test Florisil elution by both ethyl ether/petroleum ether (Sections 303 Cl, 304 Cl and C3)and methylene chloride($0% C2, 304 C2 and C4) elution systems when following the steps of Protocols E and F. Even when florisil elution tests with reference standards indicate no elu tion with later eluants amine by GLC all the Florisil eluates of the recovery test from the fortified sample. Sometimes the presence of extract changes the Florisil elution pattern ppendⅸ|4 vo.941(1 2905a(6Transmittal No. 94-1 (1/94) Appendix II–4 Form FDA 2905a (6/92) APPENDIX II Pesticide Analytical Manual Vol. I Proper Application of Methods • Do not combine a GLC column that contains cyano groups with a nitro￾gen-selective detector. • Adjust GLC column temperature to establish the correct relative retention time (rrt) of the marker chemical(s). Absolute retention times (min) are provided in DG modules to provide an indication of normal behavior, but the temperature should not be adjusted to achieve this. • Measure retention times on GLC columns from the solvent front wher￾ever possible for both the compound being tested and the marker com￾pound. If the instrumentation in use precludes measurement from the solvent front, state this fact in the report. • When submitting chromatograms with reporting forms, label them clearly: indicate how many nanograms (ng) or picograms (pg) are represented by the peak. Do not label a chromatogram of a standard in ppm. For chro￾matograms that result from recovery studies, indicate on the chromato￾gram label how much sample weight equivalent (mg) was injected. • For accurate quantitation, detector response to the reference standard should be within ±25% of the response to the analyte in the sample, based on observable (on-scale) peak heights. Usual GLC linearity does not sup￾port quantitation that compares responses differing in size by more than that amount. • Make sure that chromatograms do not overlap; allow peaks from one injection to elute before the next injection is made. • When the chromatogram contains multiple peaks representing different components in the standard, report the rrt of each peak >5% FSD. • It is not necessary to evaporate the solvent from the fortification solution once it has been added to the sample, unless there is some reason to expect it to interfere with the analysis. It is preferable for the fortifying solution to be made from the same solvent used to extract the sample. • Use only the 60/100 mesh PR grade Florisil specified by Sections 303 and 304 (Protocols E and F). Other grades of commercially available Florisil are likely to result in different elution patterns. • During tests of elution from Florisil, do not add reference material to the Florisil column in a polar solvent, which will affect elution pattern. • Test Florisil elution by both ethyl ether/petroleum ether (Sections 303 C1, 304 C1 and C3) and methylene chloride (303 C2, 304 C2 and C4) elution systems when following the steps of Protocols E and F. • Even when Florisil elution tests with reference standards indicate no elu￾tion with later eluants, examine by GLC all the Florisil eluates of the recovery test from the fortified sample. Sometimes the presence of extract changes the Florisil elution pattern