PubMed · 13938298
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C L NG. 1963. Differential proportioning. A micro technique using the autoanalyser.. https://pubmed.ncbi.nlm.nih.gov/13938298/
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Five synthetic and five natural colorants were determined in lyophilized dairy products and fatty foods using an automatic method based on lixiviation and a solid-phase extraction process that includes cotton and RP-C(18) columns for the sequential retention of synthetic colorants and natural colorants, respectively. The lyophilization of the sample coupled with the separation procedure provides clean extracts despite the complexity of the matrices studied. In addition, the lyophilization process preserves the sample for at least 2 months without changes in the concentrations of the colorants. Identification and determination of synthetic and natural colorants were carried out using a liquid chromatograph equipped with a diode array detector. The detection limits achieved for all of the colorants (0.03-75 microg/g of lyophilized sample) allowed their determination within the limits established by the European Union, with good precision (approximately 4.5%). In addition, colorants spiked to different foods provided average recoveries (spiked at three concentration levels in four types of dairy samples and in three types of fatty foods) near 94 +/- 4%.
The determination of folic acid, nicotinamide, nicotinic acid, riboflavin, riboflavin-5'-phosphate, pyridoxine and thiamine in tablets has been successfully automated using a bench-top robotic system (Zymark Tablet Processing Workstation II) coupled to reversed-phase (RP-18) HPLC with UV-detection. The new automated methods have been validated and were found to be applicable in routine analysis for all common types of multivitamin tablets. The precision is exemplified by relative standard deviations of 5.4% for folic acid, 2.1% for nicotinamide, 1.6% for pyridoxine, 0.7% for riboflavin and 1.1% for thiamine using film-coated tablets as sample. Mean recoveries obtained during spiking experiments were in the range of 95.2-103.9%.