Hexadecylpyridinium chloride micelles for the simultaneous kinetic determination of cysteine and cystine by their induction of the iodine-azide reaction

✍ Scribed by María Loreto Lunar; Soledad Rubio; Dolores Pérez-Bendito; María López Carreto; Cameron W. McLeod

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 769 KB
• Volume: 337
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/s0003-2670(96)00430-8

✦ Synopsis

The associate formed by triiodide ion and hexadecylpyridinium chloride (cetylpyridinium chloride; CPC) micelles was used to enhance the kinetic spectrophotometric determination of cysteine and cystine by their inductor effect on the iodine-azide reaction. The reaction rate was monitored at 500 nm, the maximum absorption wavelength of the triiodide-CPC associate. The micellar medium allowed the determination of cysteine and cystine at concentrations between 1 and IS ng ml-' and 0.2 and 1.3 pg ml-~ ' , respectively, the detection limits (3g) for the two inductors being 0.6 and 0.12 pg ml ' . respectively. Cysteine and cystine were simultaneously determined by measuring the absorbance at two fixed times, 3 min and I h. Cysteine : cystine ratios between 1 : 50 and 1 : 300 were determined with relative standard deviations of 1.2% for cysteine and 2.3% for cystine. The proposed method was applied for the determination of cysteine in pharmaceuticals.