Ethyl-bridged hybrid column as an efficient alternative for HPLC analysis of plasma amino acids by pre-column derivatization with 6-aminoquinolyl- N -hydroxysuccinimidyl carbamate

Determination of 23 Amino Acids and Amines in Plasma and Cortex of C57BL/6 Mice with HPLC-FLD

Using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate as a pre-column derivatization reagent, optimized derivatization and chromatography parameters, a simple high-performance liquid chromatography fluorescence detector (HPLC-FLD) method was developed and validated to determine 23 related amines in plasma and cortex of C57BL/6 mice with cerebral ischemia-reperfusion injury. The prepared samples were separated on a ZORBAX SB-C18 column (4.6 mm × 250 mm, 5 μm) with 60% acetonitrile (ACN) and 20 mM sodium acetate solution (pH adjusted to 5.0 by phosphoric acid). All analytes achieved good separation within 1.2 h at a flow rate of 1 mL/min. The limits of detection and limits of detection quantitation of the method were ranged from (0.1-9.2) to (0.3-30.6) ng/mL, respectively. The analytical method was apt for simultaneously determining 23 amino acids in plasma and cortex. Our results revealed that the relevant amino acids were significantly altered (P < 0.05) in C57BL/6 mice.

Evaluation and optimization of the derivatization reaction conditions of glyphosate and aminomethylphosphonic acid with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate using reversed-phase liquid chromatography

Due to the polar and ionic characteristics of glyphosate and its main metabolite, aminomethylphosphonic acid, a derivatization reaction is required before performing liquid chromatographic determination of these compounds. In this study, reaction conditions using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate as the derivatization reagent are assessed. A two-level full-factorial design is applied here to optimize the derivatization time (ranging from 0.5 to 20 min) and temperature (from 24 to 55°C). It is found that neither of these two variables have a significant effect on the derivatization process and that the reaction is quantitatively achieved in a few seconds at room temperature (24°C). The results obtained indicate that derivatization reaction with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate is achieved in milder conditions, with a faster kinetic reaction, than those required with the most conventional derivatization reagents used today, and the derivatives are more stable. It has been found that the most important parameter affecting the chromatographic separation is the pH of the mobile phase, as it has a significant effect on the retention time of the hydrolyzed excess of reagent. When ammonium acetate is used in the mobile phase, buffered solutions at pH around 5.0 are required.

Adsorptive Removal of Antibiotic Ciprofloxacin from Aqueous Solution Using Protein-Modified Nanosilica

The present study aims to investigate adsorptive removal of molecular ciprofloxacin using protein-modified nanosilica (ProMNS). Protein was successfully extracted from Moringa seeds while nanosilica was synthesized from rice husk. Fourier-transform infrared (FTIR), ultraviolet visible (UV-Vis) and high-performance liquid chromatography (HPLC) were used to evaluate the characterization of protein. Adsorption of protein onto nanosilica at different pH and ionic strength was thoroughly studied to modify nanosilica surface. The removal efficiency of antibiotic ciprofloxacin (CFX) increased from 56.84% to 89.86% after surface modification with protein. Effective conditions for CFX removal using ProMNS were systematically optimized and found to be pH 7.0, adsorption time 90 min, adsorbent dosage 10 mg/mL, and ionic strength 1 mM KCl. A two-step model was successfully used to fit the adsorption isotherms of CFX onto ProMNS at different ionic strength while a pseudo-second-order model could fit adsorption kinetic of CFX onto ProMNS very well. Maximum adsorption capacity was very high that reached to 85 mg/g. Adsorption of CFX onto ProMNS decreased with increasing KCl concentration, suggesting that adsorption of CFX onto ProMNS is mainly controlled by electrostatic attraction between positively charged ProMNS surface and anionic species of CFX. Adsorption mechanisms of CFX onto ProMNS were discussed in detail based on adsorption isotherms, the change in surface charge by zeta potentail and the change in functional groups by FT-IR. The removal of CFX after three regenerations was greater than 73% while CFX removal from an actual hospital wastewater using ProMNS reached to 70%. Our results suggest that ProMNS is a new and eco-friendly adsorbent to remove antibiotics from aqueous solutions.

Well-Defined Materials for High-Performance Chromatographic Separation

Chromatographic separation has been widely applied in various fields, such as chemical engineering, precision medicine, energy, and biology. Because chromatographic separation is based on differential partitioning between the mobile phase and stationary phase and affected by band dispersion and mass transfer resistance from these two phases, the materials used as the stationary phase play a decisive role in separation performance. In this review, we discuss the design of separation materials to achieve the separation with high efficiency and high resolution and highlight the well-defined materials with uniform pore structure and unique properties. The achievements, recent developments, challenges, and future trends of such materials are discussed. Furthermore, the surface functionalization of separation ma-terials for further improvement of separation performance is reviewed. Finally, future research directions and the challenges of chromatographic separation are presented.

A reliable LC-MS/MS method for the quantification of natural amino acids in mouse plasma: Method validation and application to a study on amino acid dynamics during hepatocellular carcinoma progression

A simple and fast LC-MS/MS method was developed and validated for simultaneous quantification of 20 proteinogenic l-amino acids (AAs) in a small volume (5 μL) of mouse plasma. Chromatographic separation was achieved on an Intrada Amino Acid column within 13 min via gradient elution with an aqueous solution containing 100 mM ammonium formate and an organic mobile phase containing acetonitrile, water and formic acid (v:v:v = 95:5:0.3), at the flow rate of 0.6 mL/min. Individual AAs and corresponding stable-isotope-labeled AAs internal standards were analyzed by multiple reaction monitoring (MRM) in positive ion mode under optimized conditions. Method validation consisted of linearity, sensitivity, accuracy and precision, recovery, matrix effect, and stability, and the results demonstrated this LC-MS/MS method as a specific, accurate, and reliable assay. This LC-MS/MS method was thus utilized to compare the dynamics of individual plasma AAs between healthy and orthotopic hepatocellular carcinoma (HCC) xenograft mice housed under identical conditions. Our results revealed that, 5 weeks after HCC tumor progression, plasma l-arginine concentrations were significantly decreased in HCC mice while l-alanine and l-threonine levels were sharply increased. These findings support the utilities of this LC-MS/MS method and the promise of specific AAs as possible biomarkers for HCC.

Rapid Determination of Amino Acids of Nitraria tangutorum Bobr. from the Qinghai-Tibet Plateau Using HPLC-FLD-MS/MS and a Highly Selective and Sensitive Pre-Column Derivatization Method

Amino acids are indispensable components of living organisms. The high amino acid content in Nitraria tangutorum Bobr. fruit distinguishes it from other berry plants and is of great significance to its nutritional value. Herein, using 10-ethyl-acridine-3-sulfonyl chloride as a fluorescent pre-column labeling reagent, a method for the efficient and rapid determination of amino acid content in N. tangutorum by pre-column fluorescence derivatization and on-line mass spectrometry was established and further validated. The limits of detection (signal-to-noise ratio = 3) were between 0.13 and 1.13 nmol/L, with a linear coefficient greater than 0.997 and a relative standard deviation between 1.37% and 2.64%. In addition, the method required a short analysis time, separating 19 amino acids within 20 min. Subsequently, the method was used to analyze the amino acid content of Nitraria tangutorum Bobr. from tissues retrieved from seven regions of the Qinghai-Tibet Plateau. Nitraria tangutorum Bobr. was shown to contain a large amount of amino acids, with the total content and main amino acid varying between the different tissues. This research supports the nutritional evaluation, quality control, and development and utilization of Nitraria tangutorum Bobr.

A sensitive HPLC-FLD method combined with multivariate analysis for the determination of amino acids in l-citrulline rich vegetables

The proposed analytical method reports the separation and quantification of 21 amino acids including l-citrulline from fresh vegetables and commercial juices using a C₈ column. Optimal separation conditions for amino acids analysis were obtained with 20 mM sodium acetate (solvent A) and water with organic modifier acetonitrile and methanol (solvent B; 18/50/32 V/V). The ideal pH and column temperature were found to be 5.40 and 35 °C, respectively. The LOD and LOQ values were obtained in the range of 0.02–0.19 ng/mL and 0.04–0.39 ng/mL for all amino acids respectively. Relative standard deviations (RSD) of intraday and interday analysis were found to be <2.7% and 7.9%, respectively. The recovery of amino acids were found be satisfactory for all the tested crops. The developed method was successfully used for the quantification of amino acids in six fresh vegetable juices including watermelon, cucumber, celery, calabaza squash, zucchini squash, yellow squash and commercial juices. Multivariate analysis was used to determine the significant differences in the amino acids profiles. l-citrulline content was highest in fresh watermelon juice (716.57 ± 24.80 μg/mL) and commercial watermelon lime juice (826.48 ± 34.48 μg/mL). The optimized analytical method is rapid, sensitive, accurate and reproducible for analysis of free amino acids including l-citrulline from different vegetable juices and other food products. To the best of our knowledge, this is the first report to separate OPA derivatives of amino acids using C₈ column from watermelon, cucumber, zucchini squash, yellow squash, calabaza squash, and celery in a HPLC-FLD system.

Skeletal muscle metabolomics and blood biochemistry analysis reveal metabolic changes associated with dietary amino acid supplementation in dairy calves

The effects of different amino acid (AA) supplementations of milk protein-based milk replacers in pre-ruminant calves from 3 days to 7 weeks of age were studied. Animals were divided into 4 groups: Ctrl) Control group fed with milk protein-based milk replacer without supplementation; GP) supplementation with 0.1% glycine and 0.3% proline; FY) supplementation with 0.2% phenylalanine and 0.2% tyrosine; MKT) supplementation with 0.62% lysine, 0.22% methionine and 0.61% threonine. For statistical analysis, t-test was used to compare AA-supplemented animals to the Ctrl group. At week 7, body weight and average daily gain (ADG) were measured and blood samples and skeletal muscle biopsies were taken. Blood biochemistry analytes related to energy metabolism were determined and it was shown that MKT group had higher serum creatinine and higher plasma concentration of three supplemented AAs as well as arginine compared with the Ctrl group. GP group had similar glycine/proline plasma concentration compared with the other groups while in FY group only plasma phenylalanine concentration was higher compared with Control. Although the AA supplementations in the GP and FY groups did not affect average daily gain and metabolic health profile from serum, the metabolome analysis from skeletal muscle biopsy revealed several differences between the GP-FY groups and the Ctrl-MKT groups, suggesting a metabolic adaptation especially in GP and FY groups.

Recent trends in analytical methods for the determination of amino acids in biological samples

Amino acids are widely distributed in biological fluids and involved in many biological processes, such as the synthesis of proteins, fatty acids, and ketone bodies. The altered levels of amino acids in biological fluids have been found to be closely related to several diseases, such as type 2 diabetes, kidney disease, liver disease, and cancer. Therefore, the development of analytical methods to measure amino acid concentrations in biological samples can contribute to research on the physiological actions of amino acids and the prediction, diagnosis and understanding of diseases. This review describes the analytical methods reported in 2012-2016 that utilized liquid chromatography and capillary electrophoresis coupled with ultraviolet, fluorescence, mass spectrometry, and electrochemical detection. Additionally, the relationship between amino acid concentrations and several diseases is also summarized.