Abstract
A sensitive flow-injection spectrophotometric method has been developed for the determination of sodium nitroprusside (SNP). The method is based on the catalytic effect of SNP on the reaction between titanium(III) chloride and an azo dye. The azo dye is formed in a 200-cm reaction coil (0.5mm i.d.) by diazotizing sulfanilamide and coupling with N-(1-naphthyl)ethylenediamine and then mixing with an SNP solution. Titanium(III) chloride solution is injected into a stream of water and merged with an SNP-dye mixture. A decolorizing reaction takes place in a 50cm coil (0.8mm i.d.) and the decrease in absorbance (ΔA), which is proportional to the SNP concentration is measured continuously at 530nm. The RSD is 0.45% (n=10) and 0.6% (n=10) for 5×10-7M and 1×10-6M SNP solutions, respectively. The limit of detection (twice the blank standard deviation) is 5×10-8M (14.9ng ml-1) SNP. EDTA interferes even at 1μg ml-1 level on the determination of SNP.
