Selenium speciation by high-performance anion-exchange chromatography-post-column UV irradiation coupled with atomic fluorescence spectrometry.

A technique for the speciation of selenomethylcysteine (SeMeCys), selenocystine (SeCys), selenite [Se(IV)] and selenomethionine (SeMet) was established in this paper using high-performance anion-exchange chromatography coupled with atomic fluorescence spectrometry (HPAEC-AFS). Analytes were separated on an AminoPac PA10 column and then digested by on-line ultraviolet (UV) irradiation, which destroyed organic compound structure. Hydride generation was used as an available sample introduction technique for atomic fluorescence detection. The detection limits of four compounds were 1-5 microg/L (250 microL injection, 10 times of the baseline noise). The relative standard deviations (RSDs), calculated from seven consecutive injections of 100 microg/L standard mixtures, were from 2 to 4%. Selenious yeast tablet, which had been proposed as selenium supplement, and human urine collected from a volunteer were analyzed. Good spiked recoveries from 86 to 103% were obtained.

Direct amino acid analysis method for speciation of selenoamino acids using high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection.

Speciation analysis of selenomethylcysteine (SeMeCys), selenomethionine (SeMet) and selenocystine (SeCys) has been performed using a direct amino acid analysis method with high-performance anion-exchange chromatography (HPAEC) coupled with integrated pulsed amperometric detection (IPAD). Three selenoamino acids could be baseline-separated from 19 amino acids using gradient elution conditions for amino acids and determined under new six-potential waveform. Detection limits for SeMeCys, SeMet and SeCys were 0.25, 1 and 20 microg/L (25 microL injection, 10 times of the baseline noise), respectively. The relative standard deviations (RSDs) of 200 microg/L SeMeCys, SeMet and SeCys were 3.1, 4.1 and 2.8%, respectively (n=9, 25 microL injection). The proposed method has been applied for determination of selenoamino acids in extracts of garlic and selenious yeast granule samples. No selenoamino acids were found in garlic. Both SeMet and SeCys were detected in selenious yeast tablet with the content of 45 and 129 microg Se/g, respectively. Selenoamino acids standards were spiked in garlic and yeast granule samples and the recovery ranged from 90 to 106%.

Direct determination of free amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection.

Determination of amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection was developed. Amino acids and sugars were separated on an anion-exchange column at a flow-rate of 0.25 ml/min by using ternary gradient elution consisting of deionized water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. Under optimized conditions, theanine was separated from glutamine and three sugars (glucose, fructose, and sucrose) were eluted earlier than the neutral amino acids to avoid their interference with each other. RSDs of the peak area of analytes were lower than 4.6%. Detection limits for the analytes ranged from 0.12 to 4.9 pmol. The linearities for all analytes were two or three orders of magnitude with the correlation coefficients greater than 0.99. This method was applied to determination of amino acids and sugars in green tea with satisfactory results.