Development of a capillary electrophoretic method for the analysis of amino acids containing tablets

Comparative analysis of the chemical and biochemical synthesis of keto acids

Keto acids are essential organic acids that are widely applied in pharmaceuticals, cosmetics, food, beverages, and feed additives as well as chemical synthesis. Currently, most keto acids on the market are prepared via chemical synthesis. The biochemical synthesis of keto acids has been discovered with the development of metabolic engineering and applied toward the production of specific keto acids from renewable carbohydrates using different metabolic engineering strategies in microbes. In this review, we provide a systematic summary of the types and applications of keto acids, and then summarize and compare the chemical and biochemical synthesis routes used for the production of typical keto acids, including pyruvic acid, oxaloacetic acid, α-oxobutanoic acid, acetoacetic acid, ketoglutaric acid, levulinic acid, 5-aminolevulinic acid, α-ketoisovaleric acid, α-keto-γ-methylthiobutyric acid, α-ketoisocaproic acid, 2-keto-L-gulonic acid, 2-keto-D-gluconic acid, 5-keto-D-gluconic acid, and phenylpyruvic acid. We also describe the current challenges for the industrial-scale production of keto acids and further strategies used to accelerate the green production of keto acids via biochemical routes.

Application of independent component analysis, principal component regression and partial least squares methodologies for the simultaneous potentiometric titration of some amino acids

Potentiometric titration and chemometric methods were applied to the simultaneous determination of the four amino acids, alanine (ALA), phenylalanine (PHE), leucine (LEU) and lysine (LYS).

Three-phase hollow-fiber microextraction combined with ion-pair high-performance liquid chromatography for the simultaneous determination of five components of compound α-ketoacid tablets in human urine

The determination of α-ketoacid concentration is demanded to evaluate the absorption and metabolic behavior of compound α-ketoacid tablets taken by chronic kidney disease patients. To eliminate the interference of endogenous substance of urine and enrich the analytes, a three-phase hollow-fiber liquid-phase microextraction combined with ion-pair high-performance liquid chromatography method was established for the determination of d,l-α-hydroxymethionine calcium, d,l-α-ketoisoleucine calcium, α-ketovaline calcium, α-ketoleucine calcium, and α-ketophenylalanine calcium of compound α-ketoacid tablets in human urine samples. The extraction parameters, such as organic solvent, pH of donor phase and acceptor phase, stirring rate, and extraction time were optimized. Under the optimal conditions, the obtained enrichment factors were up to 11-, 110-, 198-, 202-, and 50-fold, respectively. The calibration curves for these analytes were linear over the range of 0.1-10 mg/L for α-ketovaline calcium, d,l-α-ketoisoleucine calcium, and α-ketoleucine calcium, 0.5-10 mg/L for d,l-α-hydroxymethionine calcium, and α-ketophenylalanine calcium with r > 0.99. The relative standard deviations (n = 5) were less than 6.27% and the LODs were 100.7, 10.0, 5.8, 7.8, and 8.6 μg/L (based on S/N = 3), respectively. Good recoveries from spiked urine samples (92-118%) were obtained. The proposed method demonstrated excellent sample clean-up and analytes enrichment to determine the five components in human urine.

A novel ion-pair RP-HPLC method for determination of five components in compound α-ketoacid tablets

A sensitive and reliable ion-pair reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for the simultaneous determination of D,L-α-hydroxymethionine calcium (HMACa), D,L-α-ketoisoleucine calcium (KILCa), α-ketovaline calcium (KVCa), α-ketoleucine calcium (KLCa) and α-ketophenylalanine calcium (KPACa) in the compound α-ketoacid tablets using tetrabutylammonium hydroxide as an ion-pair reagent. The analytes were separated on a C(18) column (250 mm × 4.6 mm, 5 μm) with the mobile phase of methanol-potassium dihydrogen phosphate buffer (pH 3.0; 50mM) (37:63, v/v) at a flow rate of 0.6 mL min(-1). The UV detection wavelength was set at 210 nm. Good linearity with correlation coefficients larger than 0.9990 (n=6) for all analytes were achieved. The average recoveries were within the range of 99.6-100.9%, and the RSDs of the results were within the acceptable limit of 2.0%, which showed that this method was accurate and precise. The limits of detection were 10.44, 5.94, 3.44, 3.60 and 1.63 ng mL(-1), and the limits of quantification were 34.80, 19.80, 10.32, 12.00 and 5.44 ng mL(-1) for HMACa, KILCa, KVCa, KLCa and KPACa, respectively. The method is simple and accurate for quality control of the compound α-ketoacid tablets.

Simultaneous Determination of Essential Basic Amino Acids in Pharmaceuticals by Capillary Isotachophoresis

Capillary isotachophoresis (ITP) in cationic regime of the separation with conductometric detection has been used for the separation and determination of basic amino acids (arginine, histidine, and lysine) in pharmaceutical preparations. Several electrolyte systems of different compositions and pH were examined. The optimized ITP electrolyte system consisted of 10 mmol/L potassium acetate adjusted to pH 4.0 with acetic acid as the leading electrolyte with the electroosmotic-flow (EOF) suppressing additive, 0.2% (w/v) methylhydroxyethylcellulose (m-HEC), and 10 mmol/L beta-alanine as the terminating electrolyte. The proposed electrophoretic method was successfully validated. It was convenient for the sensitive, simple, rapid and highly reproducible assay of these amino acids. Good quantitation was obtained in short analysis times (a single analysis took about 10 min). The minimal sample pretreatment and low running costs make the proposed ITP method a good alternative to commonly used analytical methods. The obtained results suggest that the proposed method is suitable for routine assay of basic amino acids in pharmaceuticals.