FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

I 8020 / 7 average ratio or calibration factor can be used in place of a calibration curve. 7.2.2.3 The working calibration curve or calibration factor must be verified on each working day by the measurement of one or more calibration standards. If the response for any parameter, varies from the predicted response by more than +10%, the test must be repeated using a fresh calibration standard. Alternatively, a new calibration curve or calibration factor must be prepared for that compound. 7.2.3 Internal standard calibration procedure. To use this approach, the analyst must select one or more internal standards that are similar in analytical behavior to the compounds of interest. The analyst must further demonstrate that the measurement of the internal standards is not affected by method or matrix interferences. Because of these limitations, no internal standard that would be applicable to all samples can be suggested. The compounds recommended for use as surrogate spikes have been used successfully as internal standards, because of their generally unique retention times. 7.2.3.1 Prepare calibration standards at a minimum of three concentration levels for each parameter of interest as described in Section 7.2.2.1. 7.2.3.2 Prepare a spiking solution containing each of the internal standards using the procedures described in Sections 5.3 and 5.4. 7.2.3.3 Analyze each calibration standard according to appropriate methods (direct injection, 5020, 5030), adding the internal standard spiking solution directly to an aliquot of the sample or, in the case of purge -and -trap, to the syringe. Tabu- late peak height or area responses against concentration for each compound and internal standard, and calculate response factors (RF) for each compound as follows: RF = (AsCis)/(AisCs) where: As = Response for the parameter to be measured Ais = Response for the internal standard Cis = Concentration of the internal standard Cs = Concentration of the parameter to be measured