Analytical methods for sulfonamides in foods and feeds. II. Performance characteristics of sulfonamide methods.

Important factors in interpretation of methods for sulfonamides in tissues are value of the blank, use or omission of recovery factors, and precision of the methods. For determining sulfonamide in tissues, no interlaboratory collaborative studies have been performed to provide reproducibility parameters. By assuming comparability with other tissue residue methods at equivalent concentrations, it may be anticipated that the coefficient of variation within-laboratories of the Bratton-Marshall method is about 15% at concentrations of a fraction of a part per million. It is estimated that the limit of reliable measurement of the Bratton-Marshall method is about 0.2 ppm, varying with the individual laboratory. This value is higher than the tolerance it is intended to enforce. Obviously, the method in this case has been stretched beyond its original claimed capabilities. This method also has high blanks and low recoveries. Assignment of sufficient resources to the solution of the problem by regulatory agencies has resulted in methods capable of handling the sulfonamide residue problem at 0.1 ppm.