Abstract
The branched-chain amino acids (BCAAs) including leucine (Leu), isoleucine (Ile) and valine (Val) play a pivotal role in the human body. Herein, we developed capillary electrophoresis (CE) coupled with conventional UV detector to quantify underivatized BCAAs in two kinds of sport nutritional supplements. For direct UV detection at 195 nm, the BCAAs (Leu, two enantiomers of Ile and Val) were separated in a background electrolyte (BGE) consisting of 40.0 mmol/L sodium tetraborate, and 40.0 mmol/L β-cyclodextrin (β-CD) at pH 10.2. In addition, the indirect UV detection at 264 nm was achieved in a BGE of 2.0 mmol/L Na2HPO4, 10.0 mmol/L p-aminosalicylic acid (PAS) as UV absorbing probe, and 40.0 mmol/L β-CD at pH 12.2. The β-CD significantly benefited the isomeric separation of Leu, L- and D-Ile. The optimal conditions allowed the LODs (limit of detections) of direct and indirect UV absorption detection to be tens μmol/L level, which was comparable to the reported CE inline derivatization method. The RSDs (relative standard deviations) of migration time and peak area were less than 0.91% and 3.66% (n = 6). Finally, CE with indirect UV detection method was applied for the quantitation of BCAAs in two commercial sport nutritional supplements, and good recovery and precision were obtained. Such simple CE method without tedious derivatization process is feasible of quality control and efficacy evaluation of the supplemental proteins.
Highlights
The branched-chain amino acids (BCAAs) including leucine (Leu), isoleucine (Ile) and valine (Val) have become a popular sports nutritional supplement for the athletes to meet their metabolic needs [1]
The BCAAs are type of essential amino acids (AAs) that could not be synthesized by human body itself, so sufficient BCAAs must be supplied in the diet or in the nutritional supplements [2]
The present study described a simple and low cost capillary electrophoresis (CE) method for the determination of underivatized BCAAs with direct or indirect UV detection
Summary
The branched-chain amino acids (BCAAs) including leucine (Leu), isoleucine (Ile) and valine (Val) have become a popular sports nutritional supplement for the athletes to meet their metabolic needs [1]. Many studies have showed that indirect UV absorbance detection is an important and alternative tool for the analysis of AAs in their native state [22], but has not been successfully applied in the separation of BCAAs. The present study described a simple and low cost CE method for the determination of underivatized BCAAs with direct or indirect UV detection. The present study described a simple and low cost CE method for the determination of underivatized BCAAs with direct or indirect UV detection For this purpose, two optimal BGEs were respectively proposed to accommodate the isomeric separation of the targets. Two optimal BGEs were respectively proposed to accommodate the isomeric separation of the targets It was demonstrated the direct UV detection was not suitable for the real sample analysis due to the existing strong absorbance interference. The obtained results might be promising for the analysis of BCAAs in human bioliquids to direct the usage of the supplemental proteins, for the purpose of ensuring BCAAs needs but not exceeding tolerable upper intake level
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