Determination of protein content using a solid phase spectrophotometric procedure

We used a conditioned fiberglass paper to perform the reaction and to retai n the reaction products of the Lowry method for protein content. The analyt ical parameter was obtained by measuring directly the absorbance of the sup port. Different influencing chemical, support related and instrumental vari ables were studied and optimized. The usual asymptotic behavior of the anal ytical function response was improved here by linearizing using a quadratic function. Using 10 mul of sample, the applicable concentration range was b etween 25 and 200 mg l(-1), with a detection limit of 17 mg l(-1) and a R,S .D. around 5%. The method was applied to the determination of protein in eg gwhite samples coming from different birds. The method proposed here for pr otein content shows higher sensitivity than solution methods, less dependen ce on protein nature and higher stability of the species fixed on the suppo rt. (C) 2001 Elsevier Science B.V. All rights reserved.