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Section No: 8 Page: 2 of 5 Revision No: 2.0 Date: January 15, 1994 Calibration Procedures and Frequency 8.3.3 Selection of Quantitation Technique (Organics) For organic analysis, a decision must be made during the validation process (and detailed in the SOP) as to whether an internal or external quantitation technique will be routinely employed. The internal standard method of quantitation cannot be employed unless all of the following conditions are met: (1) The internal standard must be added post -extraction. (2) The internal standard must be added quantitatively. (3) Any analyte that is a target analyte in the method of interest may not be selected for use as an internal standard. (4) The concentration of the internal standard(s) must not exceed the calibration range of the method target analyte. In cases where the target analytes are associated with more than one calibration range (i.e. analytes 1114" are calibrated from 1 to 10 ppb, while analyte °'S°' is calibrated from 10 to 100 ppb, all target analytes should be prepared at a level between the highest and lowest calibration standard (e.g. approximately 50 ppb in the example given). ' The use of internal standard quantitation is of greatest benefit in those methods subject to injection variability, and thus, variability in the absolute mass injected onto the column(s) employed. The drawback to this technique, for GC methods, is that any compound which exhibits a similar retention time as the compound used for the internal standard will be identified as the internal standard, leading to erronous quantitation. For this reason, the internal standard technique is most useful for GC/MS where deuterated analytes not naturally occuring can be detected and quantified. 8.3.4 Selection of Calibration Method As part of the validation process, the specific calibration range and calibration method must be determined and documented in the SOP. Once determined in this manner, the same protocols must be followed each time the method is employed. This will ensure that data reduction is not performed differently on separate data sets by different analysts. The calibration acceptance criteria are listed in section 8.3.8. A least squares (linear) regression is initially tried as a calibration method. For organics, if a linear regression is used, a single average response factor may be used. For inorganics, if the acceptance criteria cannot be met using a linear regression, then a second order polynomial can be used to fit the data, with the same acceptance criteria being applied. In the event that neither a simple linear regression nor a second order polynomial fit result in an equation which meets the calibration acceptance criteria, then the calibration range must be reduced. 8.3.5 Minimum Number of Calibration Levels Most calibrations include a minimum of three or five initial calibration standards plus a blank. Specific SOPs may have other requirements. is