Automated Polarographic Determination of Sulfide as Contaminant in Parenteral Amino Acid Solutions

Abstract

A method for the automated polarographic determination of sulfide in a gas-diffusion flow system was developed. The volatile sulfide, existing as a contaminant in parenteral amino acid solutions, was measured after gas diffusion using 0.1 mol l ^{- 1} NaOH solution as acceptor. The linear range of calibration, for measurements at a dropping-mercury electrode (DME), was from 5 to 100 µg of sulfide with r = 0.999 and RSD = 7.5% (n = 5) for 10 µg of sulfide. For measurements at the hanging mercury-drop electrode (HMDE), with a preconcentration time of 30 s, the linear range of calibration was from 0.9 to 20 µg of sulfide with r = 0.998 and RSD = 5.8% (n = 5) for 2 µg of sulfide. Detection limits of 59 and 11 µg l ^{- 1} at the DME and HMDE, respectively, were calculated and the recoveries of sulfide from spiked samples were 91.5–104.5%. Parameters that affect the sulfide determination using this method, such as the organic content of the matrix, pH, flow rate and sample size, were investigated.