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Human placental factor XI11 (F XIII), purified from a commercial source and activated by calcium, was used to enzymatically cross-link individual whey proteins (a-lactalbumin, @-lactoglobulin, bovine serum albumin) and a mixture of total caseins and bovine serum albumin. Polymerization of DTTreduced a-lactalbumin and @-lactoglobulin was incomplete. Saturation of the response was reached in the time range 2-3 h and the substrate concentration range 10-20 mg/mL. A heat treatment had no effect on the polymerization of a-lactalbumin by F XIII,, whereas @-lactoglobulin gelled. A nonenzymatic gelation of both reduced proteins was observed above 50 mg/mL in the presence of calcium. Analysis of reaction products between BSA and caseins indicated that both proteins were polymerized, in the absence of DTT, through the formation of intermolecular cross-links. In contrast, polymerization of BSA required this reductant.

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We developed a method for the quantitative determination of sodium fluoride (NaF), sodium monofluorophosphate (SMFP) and amine fluoride (AmF) in toothpastes on the Belgian market. Samples were suspended in water and the determination was made using anion chromatography with conductivity detection after chemical suppression. The described ion chromatographic method is an easy and reliable isocratic high-performance liquid chromatography method for the determination of total soluble fluoride content in toothpastes. The analytical repeatability and reproducibility, the matrix effects and the method's decision limit of three different toothpastes containing NaF, SMFP and AmF at a concentration close to the permitted one of 0.15 g % total F are determined. All the samples analysed are in conformity with the Cosmetics Directive 76/768/EC; none exceeds the limit of 0.15 g %.