Journal of Analytical Chemistry最新文献

A novel reagent derived from salicylaldehyde has been synthesized and characterized by determining its crystalline structure through X-ray diffraction analysis. The complex formation of this reagent with iron(III) has been investigated by spectrophotometric methods. The dissociation constant of the reagent was determined by potentiometry in an aqueous–ethanolic medium, yielding pK = 9.66 ± 0.02. The interaction of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol in the presence and absence of diantipyrylmethane (DAM), diantipyrylphenylmethane (DAPhM), and diantipyrylpropylmethane (DAPrM) has been thoroughly studied. Optimal conditions for complex formation (λ_opt, pH_opt) were found. Iron(III) forms colored mixed-ligand complexes with the reagent in the presence of the third component—DAM, DAPhM, or DAPrM,—resulting in a hypsochromic shift in the absorption spectrum. The maximum yield of complexes was achieved in a more acidic medium compared to the binary complex. Molar absorption coefficients of the complexes and the ranges of compliance with Beer’s law were determined. Component ratios in the homogeneous and mixed-ligand complexes were established using isomolar series methods, as well as the relative yield of the Starik–Barbanel and equilibrium shift methods. These analyses revealed that the component ratio of Fe(III)–R in the binary complex is 1 : 2, while in the mixed-ligand complexes Fe(III)–R–DAM, Fe(III)–R–DAPhM, and Fe(III)–R–DAPrM, the ratios are 1 : 2 : 1, 1 : 1 : 1, and 1 : 1 : 2, respectively. The mixed-ligand complexes of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol exhibit favorable chemical-analytical characteristics. The developed procedure was successfully applied to the determination of trace amounts of iron(III) in oil sludge.

Lysimachia foenum-graecum Hance (LF) has a special fragrance due to its volatile components (VCs). However, this fragrance, which might be related to the changes in VCs and contents, is obviously disparate across LF samples from different storage times and regions. In order to investigate the differences in VCs of LF from different storage times and regions, a headspace-gas chromatography-ion mobility spectrometry technique was proposed and applied. The Gallery plots of different samples showed significant differences. According to the fingerprints, a total of 29 compounds with significant differences were identified. Furthermore, 1,8-cineole, 2-octanone, heptanal monomer, and 2-methylpropa might be the key components for origin identification, while phenylacetaldehyde, 2-ethylfuran, 2-pentyl furan monomer, gamma-butyrolactone monomer, and maltol might be the key components that make LF more fragrant after storage. Besides, the principal component analysis initial solution to original variables demonstrated that the two principal components accounted for 51 and 22% of the total variance, respectively. Similarity analysis showed the similarity within the individual groups was above 90% excluding 1A and 2E, while it was only 60 to 70% between the groups. The research results provide a non-destructive method without pretreatment for LF from different origins and different storage times and also provide a scientific basis for the application of LF.

The review primarily considers the scientific progress in the identification of impurities, molecular compounds, and heterophase inclusions in high-purity sulfur. Methods for their determination, established by the present time, based on atomic emission spectrometry, mass spectrometry, colorimetry, gravimetry, titrimetry, turbidimetry, conductometry, gas chromatography, infrared spectrometry, chromatography–mass spectrometry, and laser ultramicroscopy are thoroughly characterized.

An ultra-performance liquid chromatography-tandem mass spectrometry method for estimating nitrofurantoin in K₂EDTA human plasma has been developed using the liquid-liquid extraction technique. This method used electrospray ionization in negative mode for nitrofurantoin using triple quadruple mass spectrometry, with nitrofurantoin-¹³C₃ employed as an internal standard. Nitrofurantoin was extracted via the liquid-liquid extraction method and separated on an analytical column Xbridge C18 (4.6 × 100 mm, 3.5 μm). Nitrofurantoin and nitrofurantoin-¹³C₃ were performed using multiple-reaction monitoring acquisition modes with the transition of m/z from 237.06 to 152.05 (nitrofurantoin) and from 240.04 to 152.04 (nitrofurantoin-¹³C₃). The linearity range for nitrofurantoin was optimized from 5 to 800 ng/mL, respectively. The average recovery of nitrofurantoin and nitrofurantoin-¹³C₃ was 82.9 and 93.8%, respectively. The inter-precision ranged from 2.5 to 5.5%, and the inter-run accuracy range (deviation) ranged from –0.5 to 3.6% across quality control levels. The method was validated following USFDA guidelines and was determined to be straightforward, highly sensitive, precise, robust, and accurate. Therefore, it is suitable for routine quantification of nitrofurantoin in bulk drug and formulation.

With the use of the products of free-radical chlorination of indane as an example (data for tetralin are mentioned for comparison), it was shown that only their molecular formulas can be determined as a result of gas chromatography–mass spectrometry analysis, and the reaction mechanism was detailed on this basis. The structure refinement of the components requires an interpretation of their gas-chromatographic retention indices in the form of local additive schemes created for solving a specific problem under consideration. These schemes are sufficiently reliable if they are formed on the basis of data for objects containing all the structural elements of the molecules of characterized compounds. If this condition is not met (as in the case under consideration), the possibility of interpreting retention indices is fundamentally preserved; however, the accuracy of their estimates is significantly reduced and the volume of preliminary calculations increases considerably. The key fragment of the structure of chlorinated indane derivatives, which was almost not represented among the compounds characterized to date, is the chlorine atom in the alicyclic structural fragment in the α-position to the aromatic system. Secondary chlorine derivatives are formed as a result of dehydrochlorination of the primary reaction products with the subsequent addition of chlorine at the C=C double bonds.

Herein, an eco-friendly, simple, and inexpensive electrochemical sensor for the determination of the antibiotic metronidazole (MET) was developed based on a carbon paste electrode (CPE) modified by a CaO-Chitosan nanocomposite (CaO-Chi-NC/CPE). Eggshell waste was utilized to prepare CaO nanoparticles, which were then combined with chitosan to obtain CaO-Chi-NC/CPE. The prepared CaO-Chi-NC/CPE was characterized using different techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The produced sensor showed higher electrocatalytic activity toward MET in the Britton–Robinson buffer (pH 7.0) compared to the unmodified CPE. The influence of pH and scanning rate on the reduction peak of MET implies that the reduction process of MET at CaO-Chi-NC/CPE surface was a diffusion-controlled reaction with four electrons and four protons. Additionally, under ideal conditions, differential pulse voltammetry revealed that the cathodic current was directly proportional to MET concentrations within two various detection ranges of 0.003–0.35 and 0.35–3.0 μM. The limit of quantification and the limit of detection were 2.88 and 0.86 nM, respectively. Moreover, the fabricated sensor provided acceptable selectivity towards MET, good stability, and repeatable response, with recoveries ranging from 94.6 to 100.4%. This electrode was also successful in detecting MET in commercial tablets and milk samples.

The study considers a possibility of studying the manifestation of the major background ions derived from the main elements (H, N, O, and Ar) of inductively coupled plasma under low-temperature (“cold”) plasma conditions through thermodynamic simulation. These ions, known to induce significant spectral interferences, are always observed when aqueous samples are injected into inductively coupled plasma mass spectrometers (ICP–MS). Using thermodynamic simulation in the temperature range from 2000 to 5000 K, the quantitative composition of the major background ions in ICP–MS was determined as a function of plasma temperature. A comparison of the theoretical calculations and experimental data from mass spectral measurements of the major background ions was conducted, revealing a high degree of correlation between the two sets of the results. This agreement between the calculations and experiments confirms the validity of the thermodynamic model used for thermochemical processes in ICP–MS and its applicability to subsequent calculations in addressing analytical challenges. Additionally, a method is proposed for the unambiguous evaluation of the gas kinetic temperature of the plasma, while simultaneously considering practically all major background ions.

4-[(S)-2-Methyl-3-hydroxypropyloxy]-4'-formylazobenzene, 4-(3-hydroxypropyloxy)-4'-formylazobenzene and µ-oxodimer of iron 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine were synthesized using known methods. A mixture with a certain concentration of components was prepared from the synthesized compounds. The resulting mixture was used as an impregnation of the wide-porous adsorbent Chromaton N-AW. The degree of impregnation was 10%. The prepared adsorbent was used as a stationary phase for inverse gas-mesophase chromatography. In this work, the sorption redistribution of a number of volatile organic compounds—isomers of methyl and dimethylpyridines, weakly polar xylenes and enantiomers from the gas phase on the prepared adsorbent was studied using inverse gas chromatography. During the experiment, the specific retention volumes of sorbates, characterizing the sorption activity of the prepared stationary phase were calculated. For structural isomers, activity coefficients for the distribution of sorbates in the liquid layer of the liquid crystal were obtained. To confirm the data on the sorption activity of sorbates, the thermodynamic parameters of the dissolution of specific isomers were found. Conclusions were drawn about the influence of enthalpy and entropy factors on the retention ability of sorbates. The influence of structure, isomerism, intermolecular interactions, and the addition of a macrocycle on the sorption properties of sorbates is discussed. Data on the analytical features of sorption were obtained, namely, the maximum values of separation factors for structural and optical isomers and compounds of different structures, but with similar boiling points, were calculated. It was experimentally established that the prepared adsorbent exhibits a fairly high ability to separate close-boiling structural isomers and a moderate ability to separate enantiomers. Emphasis is placed on the maximum value of the separation factor of 3,4- and 3,5-lutidines, which is the highest in value among the previously developed stationary phases of similar structure. In conclusion, the use of the resulting adsorbent in a unified system of chemical analysis is justified.

Modified electrodes based on gold particles, mixed-valence ruthenium oxides, and a binary system combining these components were developed for the voltammetric determination of ceftriaxone, cefotaxime, and cefoperazone. The electrode with the binary system of gold particles and mixed-valence ruthenium oxides, which exhibited the best performance, was used for the detection of cephalosporins in flow-injection analysis. Optimal conditions for the detection of cephalosporins in a flow-injection system were selected. The dependence of the analytical signal on the concentration of the compounds under consideration is linear on logarithmic coordinates over the range from 5 × 10^–7 to 5 × 10^–3 M. The proposed procedure was tested in the determination of cephalosporins in pharmaceuticals.