Use of Statistically Designed Experiments to Minimize the Effect of ...

Published: Journal of Chromatographic Science, Volume 33, Number 2, February 1995, pp. 66-70.

Use of Statistically Designed Experiments to Minimize the Effect of Water on Gas Chromatographic Analysis
Hai Bin Wan, Ming Keong Wong, and Chup Yew Mok

A two-level orthogonal array design is used to study the effects of water content in the samples on the precision of gas chromatographic analysis. Six relevant parameters and possible interactions are examined simultaneously in the statistically designed experiments. Based on the results of the experiments, the following conclusions are drawn: water contained in a sample can reduce the precision of gas chromatographic analysis with electron capture detection; the adverse effect is more serious with less stable analytes; the adverse effect can be minimized by adopting a lower injector temperature and a higher initial oven temperature, reducing the injection volume, adding a cosolvent with a higher boiling point than the water-containing sample, and using a switching valve to discharge the solvent before it reaches the detector. Under the proposed conditions, water has little effect on the analysis of lindane, a very stable pesticide, even when water content reaches 50%. However, the effect is still noticeable with methyl parathion, a less stable pesticide.

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