Current Analytical Chemistry - Current Issue

Introduction: Leaves of Salvia deserta Schang at seven harvesting times in the same year were collected as the materials. Method: The polyphenols were determined by the Folin–Ciocaileu method and High-Performance Liquid Chromatography (HPLC) to compare the quality of samples. The stability of polyphenols was studied under different conditions (light, temperature, pH, common additives). Results: The results showed that the established method is fast, simple and reliable, which is fully validated in terms of outstanding validation data. High Performance Liquid Chromatography (HPLC) for the determination of total polyphenol content can be quickly and accurately detected, reducing the error of manual determination of the content. The study of polyphenol stability was carried out using a UV spectrophotometer (UV) in order to explore the potential factors affecting polyphenol stability as much as possible and to make the study as scientific and rigorous as possible. The results of quantitative determination showed that there are obvious differences in the content of polyphenols in seven samples. The contents of total polyphenols, rosmarinic acid (RA) and caffeic acid (CA) in the samples harvested in July reached the highest level of 41.37, 26.73 and 1.05 mg/g. Conclusion: The results of the stability assay found that light could damage the stability of polyphenols in samples, especially UV light. Polyphenols are quite sensitive to high temperatures. While polyphenols are less stable when exposed to high alkali conditions and salt treatment, they are much more stable when subjected to low concentrations of redox agents, carbohydrates, and preservatives. The developed methods and stability evaluation provide valuable basis information for quality evaluation and the following use of polyphenols in S. deserta Schang leaves.

Background: Bacterial cellulose (BC) is a versatile biomaterial with numerous applications, and the identification of bacterial strains that produce it is of great importance. This study explores the effectiveness of a Stacked Autoencoder (SAE)-based deep learning method for the classification of bacterial cellulose-producing bacteria. Objective: The primary objective of this research is to assess the potential of SAE-based classification models in accurately identifying and classifying bacterial cellulose-producing bacteria, with a particular focus on strain GZ-01. Methods: Strain GZ-01 was isolated and subjected to a comprehensive characterization process, including morphological observations, physiological and biochemical analysis, and 16S rDNA sequencing. These methods were employed to determine the identity of strain GZ-01, ultimately recognized as Acetobacter Okinawa. The study compares the performance of SAE-based classification models to traditional methods like Principal Component Analysis (PCA). Results: The SAE-based classifier exhibits outstanding performance, achieving an impressive accuracy of 94.9% in the recognition and classification of bacterial cellulose-producing bacteria. This approach surpasses the efficacy of conventional PCA in handling the complexities of this classification task. Conclusion: The findings from this research highlight the immense potential of utilizing nanotechnology- driven data analysis methods, such as Stacked Autoencoders, in the realm of bacterial cellulose research. These advanced techniques offer a promising avenue for enhancing the efficiency and accuracy of bacterial cellulose-producing bacteria classification, which has significant implications for various applications in biotechnology and materials science.

Background: Terpenoids are essential aroma substances in teas, and their concentration brings various characteristics to different teas. Therefore, developing a simple and stable method is necessary for distinguishing tea categories. Objective: In previous studies, more attention was paid to non-chiral isomers of terpenes due to the challenges of separating chiral isomers. So, this paper aims to present a method for effectively separating seven terpenoid substances, including chiral isomers and non-chiral isomers, to facilitate the classification and identification of teas. Methods: A method utilizing headspace solid-phase microextraction coupled with gas chromatography- mass spectrometry was used to isolate and analyze 7 terpenoid compounds. After optimized conditions, the BGB-176 chiral column and the PDMS/DVB fiber were selected for subsequent analysis. Results: This method has a good linear range of 0.1-200 mg/L, and its linear correlation coefficients are between 0.9974 and 0.9994, and the limit of detection and the limit of quantification is 0.02–0.03 and 0.06–0.09 mg/L, respectively. Only five terpenoid substances were detected in a total of 15 tea samples. Furthermore, In the detection of carvon and α-ionone optical isomers, the S isomer was mainly detected. Conclusions: An effective approach was developed to separate and analyze 7 terpenoid compounds in natural and synthetic teas. Meanwhile, 15 tea samples can be identified and classified using principal component analysis.

Background: Bronze knives, which have been excavated in large quantities and acquired hierarchical significance, are essential artifacts in Shu State in Southwest China. Building upon previous typological analyses of bronze knives, it is hypothesized that Shu culture may have imported foreign-style bronze knives. However, further demonstration of the provenance of metal materials, the types of knives, and the cultural exchange necessitates a comprehensive examination through the lens of scientific analysis. The purpose of this study is to investigate the differences in the manufacturing processes and metal resources of Shu bronze knives with various cultural styles and whether bronze knives in the foreign styles were imported or locally imitated. Methods: In this study, the typology, portable X-ray fluorescence spectrometry and multi-collector inductively coupled plasma mass spectrometry were used to analyze twenty-four bronze knives unearthed from Shuangyuan Cemetery, a cemetery of the Eastern Zhou Dynasty in Chengdu City, Sichuan Province, Southwest China. Results: The results of the study show that the knives of Shuangyuan Cemetery can be classified typologically into five types, encompassing both local and foreign styles. The predominant alloy composition of these knives is lead-tin bronze, characterized by a notably high tin content. Lead isotope ratios indicate that metal materials from the South China geochemical province and the Yangtze geochemical province were mainly used to manufacture the bronze knives unearthed from the Shu state. Conclusion: While the majority of foreign-style knives with ring-shaped heads were likely imported from neighboring regions like Chu state, distinctively styled type D and type E bronze knives appear to have been locally imitated by the Shu, showcasing a blend of external influences and indigenous innovation. The combination of typology and scientific analysis of the bronze knife may shed new light on the study of the Shu culture of the Eastern Zhou period.

Background and Objective: This study presents a novel potentiometric method for the precise, accurate, selective, and rapid determination of Cr(III) ion concentration in different samples. Methods: A new ionophore, namely macrocyclic tetramide ionophore (MCTA), was synthesized through an inexpensive and straightforward approach, yielding a high-quality product. The (MCTA) ionophore was utilized as the active center in the preparation of modified carbon paste electrodes (MCPEs) to quantify the Cr(III) ion. The paste was made by adding graphite, MCTA, and plasticizer and mixing them in varying weight percent ratios. Results: The proposed electrodes, I and II, exhibited a trivalent Nernstian response of 20.029 ±0.57 and 20.3±0.56 mV decade-1, respectively, with linearity of 1.0x10^-7 – 1.0x10^-2 and 1.0x10^-5 – 1.0x10^-2 mol L^-1. Electrodes I and II were examined for their pH, response time, and thermal stability. In comparison to other mono-, bi-, and trivalent cations, starch, and sugars, the electrodes demonstrated a high degree of selectivity for Cr(III). The modified electrodes were used to determine the concentration of Cr(III) in various real samples, including drug tablets, juice extractions, and tap water, with acceptable recovery values. Conclusion: The results were compared with those obtained using the previously reported method, with no significant difference observed between them, as indicated by the F and t-test values. The data showed good accuracy and precision, as well as a high percentage of recovery. The adsorption capacity of the MCTA ionophore towards Cr(III) ions was also examined.

Background: Non-enzymatic direct glucose biofuel cell is a promising technology to harness sustainable renewable energy. Furthermore, monitoring glucose levels is essential for human lives with age. Thus, there is an increasing need to develop highly efficient and stable modified electrodes. Methods: This study reported the manufacture of gold nanoparticles/polyaniline/modified gold electrodes (Au NPs/PANI/Au electrode) based on the electrochemical polymerization method followed by the deposition of gold nanoparticles. The shapes and chemical constitution of the electrodes were examined by using different techniques including SEM, FTIR, XRD, EDS, and Raman spectroscopy techniques. The electrocatalytic efficiency of the present electrodes toward direct glucose oxidation was evaluated by applying cyclic voltammetry, linear sweep voltammetry, and square wave voltammetry techniques. Results: The results exhibited high electrocatalytic performance for direct glucose electrooxidation in alkaline media. The modified electrodes show the ability to electrooxidation of various glucose concentrations (1 μM 100 μM) with a limit of detection and limit of quantitation of 140 nM and 424 nM, respectively. Furthermore, the Au NPs/PANI/Au electrode showed higher durability, sensitivity, and selectivity toward glucose oxidation than the Au NPs/ Au electrode, which confirmed the role of the PANI layer in enhancing the stability of the modified electrode. Conclusion: Moreover, the molar fraction of glucose to KOH has a crucial role in the output current. Hence, the modified electrodes are great candidates for direct glucose biofuel cell application.

Background: The pharmaceutical industry is constantly looking for a better way to ensure and improve its products' safety, quality, and effectiveness. Since there are many attributes of the drug substance and excipients that could potentially affect the Critical Quality Attributes (CQAs) of the intermediates and the final product, the evaluation of the raw material's physicochemical characteristics is crucial as they directly affect the quality, safety, efficacy, and lot-to-lot consistency. Scientists rely on methods, like HPLC, HPTLC, LC-MS, GC-MS, and NMR, to analyze these substances. The advantage of NMR is that it is considered a primary analytical method compared to other analytical techniques. Objective: This work aimed to present a simple, rapid, specific, and accurate method by proton Nuclear Magnetic Resonance spectroscopy (¹H-NMR) developed to determine the activity of the antiretroviral Efavirenz’s (EFZ) Active Pharmaceutical Ingredient (API). The method was based on quantitative NMR spectroscopy (qNMR). Methods: A Bruker Avance spectrometer (11.7 Tesla, 500 MHz for ¹H) with a 5mm probe was used. The ¹H-NMR signal at 7.54 ppm corresponding to the analyte of interest was employed to quantify the drug. The method was validated for specificity, selectivity, intermediate precision, linearity, range of work, accuracy, and robustness. Results: The method developed was specific and linear (r² = 0.9998) with a value between 4.30 mg/mL and 12.40 mg/mL. The relative standard deviation for accuracy and precision was 0.4% or less. The method's robustness was demonstrated by changing four different parameters, and the difference among each was 1.2% or less. The results of this work have been found to be in agreement with those obtained from High-performance Liquid Chromatography (HPLC) analysis. Conclusion: The proposed method has been found to be a valuable and practical tool for quality control. Its applicability to determining many APIs and saving solvent use and time is highlighted.

Background: As one of the most important economic crops, tobacco products have a long history and dominate the development of the world economy. Pectin, as a complex colloidal substance widely present in plant cell walls, its content is an important factor affecting the safety of tobacco smoking. Objective: This study aimed to analyze the content and structure of pectin in tobacco samples. Methods: In this study, tobacco pectin was extracted by ultrasonic-assisted ionic liquid extraction, and the ¹³C MultiCP/MAS NMR spectral analysis of pectin was conducted. Results: The type of extractant, duration of ultrasonication, extraction temperature, and solid-liquid ratio were optimized. Under the conditions of using 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) as the extractant, the solid-liquid ratio of 1:20 g/mL, and the ultrasonic power of 600 w for 30 min at 30°C, the yield of 23.7% of tobacco stem pectin and the purity of 54.2% could be obtained. The optimized MultiCP sequence parameters, with 10 CP cycles of 1.0 ms and the repolarization time of 50 ms could obtain high-resolution spectra within a time of 1.0 h. The C-6 peaks of the pectin in spectra were fitted using the spectral deconvolution technique and calculated the methylesterification (DM) of the tobacco pectin, which was generally less than 50% and belonged to the low methyl esterification pectin. The pectin content of the tobacco sample was calculated using the standard curve method with the addition of dimethyl sulfone (DMS) as an internal reference. The results of this method were consistent with the colorimetric method. Conclusion: The ¹³C MultiCP/MAS NMR method has the advantages of being green, fast, and accurate and provides a new technical tool for quantitative and qualitative studies of cell wall substances in tobacco samples.