Vapour phase Fourier transform infrared spectrometric determination of L-cysteine and L-cystine.
A novel and selective procedure for the determination of l-cysteine and l-cystine based on vapour-generation Fourier transform infrared spectrometry is described. Potassium iodate solution was injected into a glass vessel containing l-cysteine and/or l-cystine. The evolved CO was swept by a stream of nitrogen to an infrared gas cell. The vapour phase FTIR spectra were continuously recorded, as a function of time, between 2240 and 2000cm(-1), which includes the CO absorption band. The maximum absorbance at 2170cm(-1) was selected as a measurement criterion. The calibration curve was linear over the range 6-300mgL(-1). The method provided a limit of detection of 2mgL(-1) of l-cysteine, a throughput of 12samples h(-1) and an R.S.D. of 1.76% for five independent analyses of a 75mgL(-1)l-cysteine solution. For the measurement of l-cysteine and l-cystine separately, after measuring total concentration of l-cysteine and l-cystine, l-cysteine was masked with p-benzoquinone at a pH of 3 and individual l-cystine was determined. The amount of l-cysteine was obtained by difference. The method was applied to the determination of l-cysteine and l-cystine in pharmaceutical and urine samples. Results obtained for real samples compared well with those obtained by a reference spectrometric method.
Kargosha
K
K
Chemistry and Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Iran. K.Kargosha@ccerci.ac.ir
Ahmadi
S H
SH
Zeeb
M
M
Moeinossadat
S R
SR