Certification of vitamins and carotenoids in SRM 3280 multivitamin/multielement tablets.

A new multivitamin/multielement dietary supplement Standard Reference Material (SRM) has been issued by the National Institute of Standards and Technology (NIST), with certified and reference concentration values for 13 vitamins, 24 elements, and 2 carotenoids. The constituents have been measured by multiple analytical methods with data contributed by NIST and by collaborating laboratories. This effort included the first use of isotope dilution mass spectrometry for value assignment of both fat-soluble vitamins (FSVs) and water-soluble vitamins (WSVs). Excellent agreement was obtained among the methods, with relative expanded uncertainties for the certified concentration values typically ranging from <2% to 15% for vitamins.

High-performance liquid chromatographic method for the simultaneous detection of the adulteration of cereal flours with melamine and related triazine by-products ammeline, ammelide, and cyanuric acid.

Melamine has been used for the adulteration of cereal flours in order to increase their apparent protein content. Crude melamine may contain several by-products, i.e. ammeline, ammelide, and cyanuric acid. The simultaneous analysis of all four chemicals is difficult because of the formation of an insoluble salt between melamine and cyanuric acid. A simple and convenient high-performance liquid chromatography (HPLC) method for the detection of the adulteration of cereal flours with all four chemicals is proposed herein. The precipitate formation between melamine and cyanuric acid was prevented by using alkaline conditions (pH 11-12) for both standards preparation and sample extraction. The method uses matrix-matching, which involves the construction of a calibration curve on a blank (negative control) matrix, which is then used for the quantitation of melamine and by-products in adulterated (positive) samples. Matrix-matching compensates for analyte losses during sample preparation, and for matrix effects. The method was successfully applied to wheat, corn, and rice flours, and is expected to be applicable (with some modifications) to soy flour as well. The method allows for the detection of melamine, ammeline, and ammelide at approximately 5 microg g(-1), and cyanuric acid at approximately 90 microg g(-1) in wheat flour.

Trace analysis of perchlorate anion in selected food products by reverse-phase liquid chromatography-tandem mass spectrometry.

An alternative, rapid, and reproducible method of analysis for perchlorate in selected food products (fruit and vegetable juice, milk, and bottled water) was developed and validated. Improvements over previous methods were achieved by the use of a rugged and inexpensive C18 column, a multi-mode OASIS HLB solid-phase extraction cartridge for sample clean-up, and acetic acid for pH adjustment and protein precipitation. The hydrophobicity of the perchlorate anion gives it good retention and separation characteristics on C18 chromatographic columns. The C18 column allowed for the use of 90% of acetonitrile at a low flow rate (0.3 ml min(-1)), without splitting, and could also be regenerated with organic solvents, unlike an ion-exchange column. Perchlorate levels in selected commercial food samples were: <1.0-2.1 ng g(-1) (fruit and vegetable juices, reported here for the first time), <1.0-5.0 ng g(-1) (milk), and <1.0 ng g(-1) (bottled water).