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866 A · ANALYTICAL CHEMISTRY, VOL. 53, NO. 7, JUNE 1981
haustion of the cation suppressor col umn is necessary, more so for stabili zation of the baseline than for peak height changes. The sample container is probably the greatest potential source of sample contamination, not only in the labora tory, but in the various operationsampling-analysis procedures of a field test. Polystyrene was determined to be the optimum sample bottle ma terial for this type of sampling. Another material, polymethylpentene (PMP), is currently undergoing evaluation and shows promise as a via ble sample bottle material. If this can be borne out, P M P would be a sub stantial improvement over the rela tively brittle polystyrene material, which easily crazes (temperature ef fect) and cracks upon shipment to and from sampling sites, resulting in the occasional loss of a valuable sample. Figure 3 shows the results of graph ic analyses of samples collected at one of the sampling locations for a 580-MW plant with a Babcock and Wilcox 2400 psia once-through boiler operating with 1000 °F reheat temper ature. The extreme range of concen trations indicates poor control over steam chemistry. The usefulness of on-site ion chromatography was dem onstrated here, as our testing con firmed a suspected condenser leak. In addition, the detection of ionic im purities at another sampling location, the polisher header, made plant per sonnel aware of improper polisher op eration. Elimination of the condenser leak and a change in polisher operation were directly reflected in the analysis of polisher effluent samples following a shutdown and subsequent restart. The concentration of all species was below 5 ppb following these changes. In contrast, Figure 4 presents four sample sets of analytical data collect ed from various locations throughout a plant that had over eight years of cor rosion-free operation with good con trol of the steam chemistry. This plant was a 326-MW Combustion Engineer ing 2000 psi natural circulation drum boiler operating with 1000 °F reheat temperature. With the exception of a limited number of suspect points, the data from 72 ion chromatographic analyses show concentrations of all species were consistently maintained below 5 ppb. The accuracy and repro ducibility of the data were checked by monitoring impurity concentrations at three selected sample locations throughout an entire test. In over 120 separate anion and cation analyses, only one high SOi~ analysis could be attributed to sample contamination or technique. Figure 5 is a plot of impurity clean up for sodium and chloride following a
