Analytical Chemistry Research最新文献

Pinot Noir red wines made by malolactic fermentation were studied for studying differences in their chemical profiles with help of a wide spectrum of grape-based and other chemical compounds used in winemaking. Determinations were made with capillary electrophoresis, liquid chromatography, and spectrometry to investigate carbohydrates, organic acids, aldehydes, anthocyanins, phenolic compounds, inorganic anions, and metals. In addition, tot-N, tot-S, and tot-P in the wines were examined.

The wine products showed different profiles of carbohydrates, organic acids, phenolic compounds, and minerals. Especially, saccharose (max. 0.21 g/L), rhamnose (max. 0.45 g/L), fructose (max. 1.9 g/L), and phosphate (max 1.4 g/L) quantities were extremely high in some wines. The results also showed that yeast fermentation in winemaking agitated high production of lactic (max 5.7 g/L) and tartaric (max 1.7 g/L) acids. The red wines processed by cold maceration and natural fermentation gave similar profiles. Only one of the Pinot Noir wines entirely differentiated from the others with comparison of carbohydrates and organic acids.

Heparin is a linear sulfated polysaccharide widely used therapeutically as an anticoagulant. It is also the starting material for manufacturing low-molecular-weight heparins (LMWH). Quality control of heparin and LMWH is critical to ensure the safety and therapeutic activity of the final product. However due to their complex and heterogeneous structure, orthogonal analytical techniques are needed to characterize the building blocks of heparin. One of the state-of-the-art methods for heparin analysis is based on complete enzymatic digestion using a mixture of heparinases I, II, and III, followed by the separation of the resulting oligosaccharides by liquid chromatography. The European Pharmacopoeia strong anion-exchange chromatographic method, used to quantify 1,6-anhydro derivatives in enoxaparin, is here applied to the analysis of the heparin building blocks. Their quantification, namely the determination of their average w/w percentage in the heparin chain, is obtained after identification of all components including glycoserine derivatives and 3-O sulfated di- and tetrasaccharides. This work therefore provides a comprehensive overview of the building blocks of unfractionated heparin, including those chemically modified by the manufacturing process, either within the polysaccharide chain or at its reducing end.

The electrochemical generation of arsenic volatile species (arsine) using an Au/Hg amalgam cathode in a 0.5 M H₂SO₄ solution, is described. Results were compared with those obtained with other cathodes commonly used for generation of arsine. The effects of the electrolytic conditions and interferent ions have been studied. Results show that the Au/Hg cathode has better tolerance to interference and higher repeatability than cathodes made out of platinum (Pt), gold (Au), reticulated glassy carbon (RGC), lead (Pb). Under optimized conditions, a 0.027 μg L⁻¹ (3σ) detection limit for As(III) in aqueous solutions and a 2.4% relative standard deviation for a 0.1 μg L⁻¹ As(III) were obtained. The accuracy of the method was verified by determination of As in a certified reference material. The proposed method was applied to the determination of As in spiked tap water samples.

This paper reports an RP-HPLC-UV-DAD study of the effects of four solvents and their mixtures on the extraction and antioxidant activities of three main catechins, epicatechin (EC), epigallocatechin gallate (EGCG) and epigallocatechin (EGC) of Camellia sinensis L. leaves for two harvests. The extraction efficiency solvent was measured by the chromatographic peak areas. The results showed that the relative abundance of the catechins in the second harvest is somewhat larger than in the first one, although there is no significant difference at the 95% level. The relative abundance found for EGCG is greater than for EGC which is greater than EC for all solvent mixtures. According to the mixture models, the maximum values of relative abundances of EGCG, EGC and EC can be obtained with a (70:30 v/v) ethanol:ethyl acetate binary mixture and the antioxidant activities with a (55:25:20 v/v/v) ethanol:ethyl acetate:dichloromethane ternary mixture.

PBDEs are widely used brominated flame retardant, which are increasingly reported in the environment. MeO-PBDEs are structural analogs to PBDEs, and reported as natural products and novel pollutants present in the environment. Concentrations of thirteen PBDEs and eight MeO-PBDEs in a large number of commercial sales of hen eggs representing 15 different regions and household productions of hen eggs representing 2 different regions collected from Hubei province of China were investigated in this study. An effective isotopic dilution GC–MS method was firstly developed to simultaneously determine thirteen PBDEs and eight MeO-PBDEs in hen eggs in this study. Liquid/liquid extraction, concentrated sulfuric acid and multi-layer silica gel column chromatography cleanup were used, some important steps and crucial parameters were modified and intensified compared with other literatures, and GC and MS conditions were optimized. The limits of quantitation values of 0.2–4, 0.8–4 μg kg⁻¹ wet weight in hen eggs were calculated for PBDEs and MeO-PBDEs, respectively. In addition, good repeatability and accuracy of the whole method were achieved. The established methods were therefore suitable for the simultaneous determinations of thirteen PBDEs and eight MeO-PBDEs in hen eggs at trace contamination levels. Using the established methods, PBDEs or MeO-PBDEs emerged in 4 of 40 household productions of hen eggs, and in low-μg kg⁻¹ wet weight for these samples.

A new ketamine coated silver electrode (KCSE) based on ketamine hydrochloride with sodium tetraphenylborate (KT-TPB) as electroactive material has been described. The influence of membrane composition, type of solvent mediators, kind of electroactive materials and interfering ions on the sensor was investigated. The sensor displays Nernstian response of 55.8 ± 0.3 mV/decade over the concentration range of 2.5 × 10⁻⁶ to 1.0 × 10⁻² M with limit of detection of 8.5 × 10⁻⁷ M. The coated wire electrode has short response time ∼8 s and it can be used in pH range of 2.6–6.4. The selective coefficients were determined in relation to several inorganic, organic ions, sugars and some common drug excipients. The KCSE electrode was successfully used for the determination of the ketamine content in ampoule and urine samples with satisfactory results. Statistical student’s t-test and F test showed insignificant systematic error between proposed and official methods.

Chemometric techniques such as partial least squares combined with discriminant analysis (PLS–DA) and artificial neural networks (ANN) analysis were used to enhance the detection, discrimination and quantification of chemical warfare agents simulants. Triethyl phosphate (TEP) mixed with commercial products in their original containers was analyzed through the container walls using fiber-optic-coupled Raman spectroscopy. Experiments were performed by employing a custom built optical fiber probe operating at 488 nm. Detection was accomplished using mixtures of the contents of the commercial bottles and water. The bottle materials included green plastic, green glass, clear plastic, clear glass, amber glass and white plastic. To account for the low scattering-peak intensities of some bottle materials, integration times were increased. Short integration times provided no information for amber glass and white plastic. The limits of detection were on the order of 1–5%, depending on bottle materials and contents. Good discrimination was achieved with PLS–DA when models were generated from a dataset originating from the same type of bottle material. ANN performed better when large sets of data were used, discriminating TEP from bottle materials and contents, as well as accurately classifying over 90% of the data.

To gain perspective on the use of tandem mass spectral libraries for identification of toxic cyclic peptides, the new library was built from 263 mass spectra (mainly MS² spectra) of 59 compounds of that group, such as microcystins, amatoxins, and some related compounds. Mass spectra were extracted from the literature or specially acquired on ESI-Q-ToF and MALDI-ToF/ToF tandem instruments. ESI-MS² product-ion mass spectra appeared to be rather close to MALDI-ToF/ToF fragment spectra which are uncommon for mass spectral libraries. Testing of the library was based on searches where reference spectra were in turn cross-compared. The percentage of 1st rank correct identifications (true positives) was 70% in a general case and 88–91% without including knowingly defective (‘one-dimension’) spectra as test ones. The percentage of 88–91% is the principal estimate for the overall performance of this library that can be used in a method of choice for identification of individual cyclopeptides and also for group recognition of individual classes of such peptides. The approach to identification of cyclopeptides based on mass spectral library matching proved to be the most effective for abundant toxins. That was confirmed by analysis of extracts from two cyanobacterial strains.