Analysis of Theanine in Tea (Camellia sinensis) Dietary Ingredients and Supplements by High-Performance Liquid Chromatography with Postcolumn Derivatization: Single-Laboratory Validation, First Action 2016.10.

An HPLC method with postcolumn derivatization was developed and validated for the determination of theanine content in tea dietary ingredients and supplements. A variety of common commercially available supplement forms such as powders, liquid tinctures, tablets, softgels, and gelcaps, as well as three National Institute of Standards and Technology Camellia sinensis Standard Reference Materials were investigated in the study. A simple extraction procedure using citrate buffer at pH 2.2 allowed for the analysis of theanine without additional cleanup or concentration steps, even at low ppm levels. Theanine was separated from other naturally occurring amino acids using a cation-exchange column and detected using a UV-Vis detector after derivatization with ninhydrin reagent. A single-laboratory validation demonstrated that specificity, accuracy, precision, and other method performance parameters have met the requirements set for theanine analysis by the AOAC Stakeholder Panel on Dietary Supplements.

Multiresidue mycotoxin analysis in corn grain by column high-performance liquid chromatography with postcolumn photochemical and chemical derivatization: single-laboratory validation.

A multiresidue method was developed and validated for simultaneous analysis of 5 families of mycotoxins in corn grain. Deoxynivalenol (DON); aflatoxins B1, B2, G1, G2; ochratoxin A; zearalenone; and fumonisins FB1 and FB2 are extracted from corn grain samples with water-methanol, and extracts are cleaned up using immunoaffinity and solid-phase extraction columns. The column high-performance liquid chromatographic method uses postcolumn photochemical derivatization for detection of aflatoxins and derivatization with o-phthalaldehyde for detection of fumonisins. Mean recoveries and relative standard deviation values (%) over studied fortification levels for the chosen matrixes were: DON 89.9, 8.7; aflatoxin B1 85, 9.4; aflatoxin B2 82.4, 9.7; aflatoxin G1 74.8, 13.5; aflatoxin G2 79.2, 10.0; fumonisin B1 96.2, 8.0; fumonisin B2 84.5, 6.4; zearalenone 91.7, 11.5; and ochratoxin A 87.4, 15.8. The method performance criteria, including specificity, accuracy, repeatability, operational range, and detection limits, were found to be within specifications set by the Feed Additives and Contaminants Group of the AOAC Agricultural Materials Community.

Single-laboratory validation for the quantification of neomycin B and neomycin C in animal feeds by liquid chromatography fluorescence detection with post-column derivatization.

A method using ion-exchange liquid chromatographic (LC) separation, post-column derivatization, and fluorescence detection to quantify neomycin B and neomycin C in animal feeds has been developed and validated. Improved methodology is required to achieve positive identification of antibiotics present and to more accurately determine the amount of antibiotics in feeds. The method sample range covers additive levels found in type A, B, and C medicated feed products (50-0.005% wt/wt neomycin base). The linear range for the method covers 50-150% of expected sample concentrations. Average recovery from type A and B feeds, n = 9, was 100.4% neomycin with %RSD = 2.28. Average recovery from type C feeds and milk replacers, n = 9, was 97.5% neomycin with %RSD = 4.36. There were no interferences from soybean meal and milk replacer matrix components, oxytetracycline, or other aminoglycosides, with the exception of one gentamicin isomer, which co-elutes with neomycin B. However, neomycin and gentamicin are not a legal feed combination, and the presence of gentamicin can easily be discerned by the appearance of the 3 gentamicin homologs that do not interfere. Comparison of the proposed LC method to the microbiological method shows that the LC method provides comparable recoveries of neomycin from feed products throughout the range of concentrations found commercially.