It is of interest to measure the short chain organic acid content in natural latex serum, and capillary electrophoresis (CE) has proved to be a good tool for this study. However, for some acids, a higher sensitivity than that provided by the standard methods was needed. Therefore, a stacking effect was optimised and applied both for standards and real samples. Large-volume injection of sample solutions prepared in low conductivity matrices containing 50% acetonitrile (v/v) and 0.5% NaCl (w/v) gave the best results with enhancement factors over 17 and recoveries ranging from 83 ± 14 to 122 ± 4%.