Development of a new analytical method for the determination of sulfites in fresh meats and shrimps by ion-exchange chromatography with conductivity detection

An accurate and reliable analytical method, based on ion chromatography and suppressed conductivity detection, has been developed and validated for the quantitative determination of sulfites in fresh meats and shrimps. The chromatographic separation was accomplished by using an anion-exchange column eluted with sodium carbonate and sodium hydroxide. The optimized step-change elution, followed by column re-equilibration at the initial mobile phase composition, guaranteed a good resolution even toward endogenous interfering peaks, and an excellent retention time repeatability (1.1%, n=6). Good results in terms of sample extract stability, recovery efficiency were achieved with an extraction solvent mixture based on sodium hydroxide, fructose and EDTA. The method validation, performed by an in-house model according to Decision 657/2002/EC and Regulation 882/2004/EC, provided excellent results with respect to linearity (correlation coefficient up to 0.9998), limits of detection and quantification (2.7 and 8.2 mg kg(-1), respectively, expressed as SO(2)), expanded measurement uncertainty (below 10%), recovery values (ranging from 85% to 92%) and repeatability (down to 8%), demonstrating the conformity of the proposed method with the European directives. Finally, by major changes ruggedness studies, the method applicability to the quantitative analysis of cow hamburger, pork and horse sausage, and shrimps was demonstrated.