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0 <br />F <br />0 <br />11 <br />0 <br />I I <br />G <br />i <br />IIi <br />[I <br />J <br />J <br />J <br />METHODS <br />The GC/MS method is in a real sense more accurate than alternate <br />methods because it is virtually interference free. It is the only method <br />in which the identities of sample constituents can be confirmed by <br />comparison with such multivariate data as authentic fragmentation <br />patterns. Recoveries are typically 80 to 120 percent. Representative <br />data have been appended. These are established by means of spiked <br />samples. <br />When calibration curves such as are appended to this document are <br />available, linear regression analysis provides a further measure of <br />precision as well as an estimate of the detection limit. The curves shown <br />are not extended for enough to determine the upper limit of the linear <br />range. Unlike the methods, samples suspected of being beyond the linear <br />range for the extracted ion area normally employed for the analysis of a <br />given compound con be reexamined by extracting a less abundant ion from <br />both the standards and the samples. In this way reruns can often be <br />avoided without compromising accuracy. The extraction of more than one <br />ion for quantitation is yet another example of how the quality of the data <br />can be improved when mass spectrometry is employed as the analytical <br />tool. We intend to employ two ions per compound (where possible) for the <br />purposes of the proposed study. In this way ion ratios con be checked in <br />addition to retention times. The data processing step has been set up in <br />such a way that independent results are calculated for each ion. The two <br />results are then averaged to provide the answer presented in the reports. <br />If the two answers are not similar, the matter is investigated. If a <br />reason for the difference is not discovered, the lower of the two answers <br />is presented. Typical results are appended. <br />Standard operating procedures such as are provided in the ARB <br />Guidelines have been developed by CCAS for Calderon procedures. These <br />step-by-step instructions are made available to our analysts for quick <br />reference as in the event they encounter an unusual situation. New <br />analysts are required to study the written operating procedures as a part <br />of their training. These are periodically updated by senior staff as <br />improvements are made. <br />USE OF APPROPRIATE SAMPLING CONTAINERS <br />In the analysis of the listed organics, hydrocarbons, and fixed gases, <br />extremely reactive species such as sulfides and mercoptans are not to be <br />determined. Accordingly, samples destined for these types of analyses may <br />be collected in specially passivated steel containers. Passivation and <br />electropolishing are necessary in order to minimize degradation and memory <br />effects from previous samples prior to analysis. <br />