A salting-out assisted liquid-liquid microextraction procedure for determination of cysteine followed by spectrophotometric detection.

A new analytical method for sensitive determination of cysteine based on its interaction with phenazine methosulfate was developed using salting-out liquid-liquid microextraction followed by spectrophotometric detection. The mechanism of the reaction was studied and confirmed by Fourier transform infrared and mass spectroscopy. Experimental parameters affecting the extraction efficiency were investigated and under the optimal conditions, good linearity was observed in the range 0.2 - 6.0 µg mL-1 with a correlation coefficient of 0.9972. The limit of detection and limit of quantification were found to be 0.07 and 0.21 µg mL -1, respectively. The enrichment factor was 25. The developed methodology was applied for analysis of cysteine in food supplements. The obtained data were in good agreement with LC-MS/MS analysis.