Study on the performance of the headspace liquid-phase microextraction, gas chromatography-mass spectrometry in the determination of sorbic and benzoic acids in soft drinks and environmental water samples.

A simple, efficient and virtually solventless headspace liquid-phase microextraction (HS-LPME) technique, combined with gas chromatography-mass spectrometry (GC-MS), was developed for the analysis of sorbic acid (SA) and benzoic acid (BA) in soft drinks and environmental water samples. A microdrop of organic solvent was suspended from the tip of a microsyringe needle over the headspace of the stirred sample solution, containing the analytes for a desired time. The microdrop was then retracted into the microsyringe and directly injected into the GC-MS, without any further pretreatment. Initially, microextraction efficiency factors were optimized, and the optimum experimental conditions found were as follows: 2.5 microL toluene microdrop exposed for 20 min over the headspace of a 6.5 mL aqueous sample (45 degrees C), containing 3 M of NaCl with pH of 1.5 and stirred at 1000 rpm. Under the optimized extraction conditions, preconcentration factors of 154 and 198, limits of detection of 0.3 and 0.1 microg L(-1) (S/N=3) with dynamic linear ranges of 1-500 and 0.5-500 microg L(-1), were obtained for SA and BA respectively. A good repeatability (RSD<10.3%, n=8) and satisfactory linearity (r(2) >or= 0.99) of results were achieved. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 90 to 113%. The method proved to be rapid and cost-effective and is a green procedure for screening purposes.