Studies on Ghosting, an Important Source of Error In the Quantitative Estimation of Free Volatile Fatty Acids by GLC II. Effect of Sample VFA Concentration on Ghosting Magnitude and Effectiveness of Remedies to Limit Ghosting

Abstract

Responses of volatile fatty acid (VFA) and corresponding ghostings were examined in two factorial experiments featuring two columns, two injectors, three ghost eluters and with or without formic acid vapor in the carrier gas. No systematic relation between sample VFA concentration and ghosting magnitude was found. The linearity of the calibration graphs and consequently the accuracy of the analysis was markedly improved when using formic acid vapor in the carrier gas. Addition of formic acid to the sample affected peak heights and shapes for samples as well as for the ghosts. Differences were observed between the acids. Only when using formic acid vapor in the carrier gas could quantitative analysis of VFA in aqueous solution be performed with sufficient accuracy and precision.