Abstract
The precision and accuracy of quantifying semi-volatile organic compounds (SVOCs) in solution by GC/MS, particularly when volume errors are unpredictable or difficult to control, are improved by utilizing internal standards (IS). Not obvious though is the extent to which timing IS addition affects measurement. To illustrate this fact, the mean concentrations of 60 SVOCs (40 or 80 μg/mL) in two identical solutions into which IS were added at different times are compared in this study. In one solution, IS were added promptly on preparation (reference); in the other, IS were added after 36 days of incubation (treatment). To investigate the role that temperature might play here as well, equal fractions of each solution were incubated at − 20 °C, 4 °C or 22 °C. Results, as determined by one-way ANOVA, show that there were no differences between the reference solutions at the beginning and after 36 days (F3,236 = 0.244, p = 0.865), but that significant differences exist between the reference solutions collectively and the treatment irrespective of temperature (F6,413 = 6.76, p = 1.99e−06). These results, confirmed by a post hoc analysis, suggest that uncertainty is introduced into SVOC quantitation when internal standards are not added promptly into SVOCs solutions on preparation.
Highlights
The precision and accuracy of quantifying semi-volatile organic compounds (SVOCs) in solution by GC/MS, when volume errors are unpredictable or difficult to control, are improved by utilizing internal standards (IS)
We have noticed that measuring SVOCs concentrations by this practice, at times, have led to larger values when IS were not added on the day of solutions preparation
We focused on a bulk property of solutions and as a result, we mostly used the mean concentrations of 60 SVOCs in our analysis
Summary
The precision and accuracy of quantifying semi-volatile organic compounds (SVOCs) in solution by GC/MS, when volume errors are unpredictable or difficult to control, are improved by utilizing internal standards (IS). As determined by one-way ANOVA, show that there were no differences between the reference solutions at the beginning and after 36 days (F3,236 = 0.244, p = 0.865), but that significant differences exist between the reference solutions collectively and the treatment irrespective of temperature (F6,413 = 6.76, p = 1.99e−06). These results, confirmed by a post hoc analysis, suggest that uncertainty is introduced into SVOC quantitation when internal standards are not added promptly into SVOCs solutions on preparation. Similar anomaly was pointed out in principle a while a go[6] and because no study has so far been done to verify the existence of this phenomenon (with potentially a costly regulatory consequence), we chose to compare statistically the concentrations of SVOCs in two identical sets of solutions which were stored at three commonly used temperatures as described below
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