Simultaneous Determination of Taurine, N-Acetylcysteine, Glycine and Methionine in Commercial Formulations by High-Performance Liquid Chromatography

A Photoelectrochemical Sensor Based on DNA Bio-Dots-Induced Aggregation of AuNPs for Methionine Detection

Based on DNA bio-dots-induced aggregation of gold nanoparticles (AuNPs), a methionine (Met) photoelectrochemical (PEC) sensor with CS-GSH-CuNCs/TiO2 NPs as the photoelectric conversion element and AuNPs as the specific recognition element was constructed. First, a TiO2 NPs/ITO electrode and CS-GSH-CuNCs were prepared, and then the CS-GSH-CuNCs/TiO2 NPs/ITO photosensitive electrode was obtained by self-assembly. Next, DNA bio-dots were modified to the upper surface of the electrode using a coupling reaction to assemble the DNA bio-dots/CS-GSH-CuNCs/TiO2 NPs electrode. Amino-rich DNA bio-dots were used to induce the aggregation of AuNPs on the electrode surface via Au-N interactions and prepare the AuNPs/DNA bio-dots/CS-GSH-CuNCs/TiO2 NPs electrode. Due to the fluorescence resonance energy transfer (FRET) between CS-GSH-CuNCs and AuNPs, the complexation chance of electron-hole (e--h+) pair in CS-GSH-CuNCs increased, which, in turn, led to a decrease in photocurrent intensity. When Met was present, AuNPs aggregated on the electrode surface were shed and bound to Met since the Au-S interaction is stronger than the Au-N interaction, resulting in the recovery of the photocurrent signal. Under optimal conditions, the photocurrent intensity of the PEC sensor showed good linearity with the logarithm of Met concentration in the range of 25.0 nmol/L-10.0 μmol/L with the limit of detection (LOD) of 5.1 nmol/L (S/N = 3, n = 10).

Determination and Chemometrics-Assisted Comparative Analysis of Active Components in Different Tissue of Rana chensinensis

In this study, the chemical composition of different tissues of Rana temporaria chensinensis David derived from the same individual was analyzed by comparative approach. First, pre-column derivatization combined with high performance liquid chromatography (HPLC) was established to determine the content of 1-methyl hydantoin in samples, which used S1–S5 samples. The results indicated that 1-methyl hydantoin was determined in Oviductus Ranae (OR), Rana chensinensis ovum (RCO), Rana chensinensis meat (RCM), and Rana chensinensis skin (RCS), except for Rana chensinensis bone (RCB). Moreover, the content of it in RCS was the highest. In addition, the contents of six polyunsaturated fatty acids (PUFAs) in different tissues of Rana chensinensis were measured by HPLC, including eicosapentaenoic acid (EPA), α-linolenic acid (ALA), docosahexaenoic acid (DHA), arachidonic acid (ARA), linoleic acid (LA) and oleic acid (OA). The results indicated that OR, RCO, RCM, RCS, and RCB all contained the above six PUFAs. With the aid of chemometrics methods, the results of principal component analysis (PCA), hierarchical cluster analysis (HCA), and orthogonal partial least squares discriminant analysis (OPLS-DA) combined with the sequencing results of the total PUFAs content of each sample, showed that different tissues of Rana chensinensis could be divided into four categories, and the RCO sample was divided into one category because of the highest PUFAs content, which was a good source of PUFA. For comparison, OR and other tissue from the perspective of PUFAs, we also established OPLS-DA models of them. It could be found that the RCM was the most similar to the OR in the diversity and content of PUFAs. This study provided a theoretical basis for the further development and utilization of RCO, RCM, RCS, and RCB as by-products of OR.

Electrophoretic determination of taurine

An electrophoretic method (on-line coupled capillary isotachophoresis and capillary zone electrophoresis) with conductometric detection for the determination of free taurine in selected food and feed is described. Taurine is converted to isethionic acid by van Slyke method. Under optimized conditions (leading electrolyte: 5 mM HCl, 10 mM glycylglycine, and 0.05% 2-hydroxyethyl cellulose solution, pH 3.2; terminating electrolyte: 10 mM citric acid; background electrolyte: 50 mM acetic acid, 20 mM glycylglycine, and 0.1% 2-hydroxyethyl cellulose solution, pH 3.7), isethionic acid is separated from other sample components in anionic mode and detected using a conductimeter within 15 minutes. The performance method characteristics, such as linearity (25 - 1250 ng/mL), accuracy (99 ± 9%), repeatability (3.9%), reproducibility (4.3%), limits of detection (3 ng/mL) and quantification (10 ng/mL) were evaluated. By analysing 20 food and pet food samples the method was proved suitable for routine analysis. High sensitivity and selectivity, short analysis time and low costs are significant features of the presented method.