Determination of taurine in infant formulas using ultrafiltration and cation-exchange chromatography

A fast and simple method for determination of taurine in infant formulas has been developed. The sample preparation uses disposable ultrafiltration cartridges to remove protein and clarify the sample. Hydrolysis is avoided, simplifying the procedure and increasing efficiency. One mL sample is centrifuged in a cartridge for 45 min. The filtrate is diluted with pH 2.2 citrate buffer and injected into a high performance amino acid analyzer. A cation-exchange column (sodium phase) is used with a single buffer eluant and an isocratic chromatographic program. Colorimetric detection is performed following post-column ninhydrin reaction. Chromatographic resolution from other ninhydrin-positive compounds is excellent. Average recoveries for 3 levels of spike for various products were 100-102%. Precision is 1-3% RSD, depending on product. Linearity, specificity, and ruggedness are excellent. The method is applicable to quality control testing of milk-based, soy-based, and prehydrolyzed protein-based infant formulas in the ready-to-use, concentrate, and powder forms. A variety of commercially available infant formulas from different manufacturers were analyzed and all were found to contain taurine levels comparable to human milk. Some human milk and cow's milk samples were also analyzed and results compare well with literature values.