Journal of Analytical Chemistry最新文献

The study examines the impact of chemically active fluorine-containing additives, namely AlF₃, ZnF₂, and SrF₂, on the evaporation behavior of low- and medium-volatile impurity elements from a crater in a direct current arc electrode in the analysis of graphite powder. The results demonstrate that the use of AlF₃ and ZnF₂ significantly increases the intensity of spectral lines for the analyzed elements and shortens the time required for their complete evaporation from the electrode crater. Among the additives tested, zinc fluoride in a concentration of 5 wt % proved to be the most effective. The greatest increase in intensity was observed for low-volatile elements prone to carbide formation. The use of ZnF₂ lowered the limits of detection for low- and medium-volatile elements in the graphite powder by direct arc atomic emission spectrometry by 2–3 orders of magnitude, reaching concentrations of n × 10^–7 to n × 10^–5 wt %. This approach improved the reproducibility of the results by a factor of 2 compared to the analysis of graphite powder without additives.

Soils on forest lands are likely characterized by high organic matter content and a diversity of nutrients. Thus, differentiating forest soils from different sites of origin is a challenging task. This study aims to assess the variability of 163 forest soils based on two easily measured physiochemical properties: soil color and pH. The soil samples were collected from 11 different sites across six states in Malaysia. Soil color was recorded under both air-dry and moistened conditions based on the Munsell Soil Color Chart. Meanwhile, soil pH was determined using a soil-to-water ratio of 1 : 20 (w/v). The association between the source origins and the physiochemical properties of the soils was assessed using simple correspondence analysis. Classification of the soils by the type of anthropogenic activities, according to pH, was further modeled using the classification and regression tree algorithm. The results showed that soils from ecotourism sites tended to be less acidic than those from reserved forest sites. Meanwhile, soils from forest lands used for hiking showed acidity levels between the two types of sites. On the other hand, variability in soil color by the source origin was found to be insignificant. In conclusion, forest soils could be further classified according to the type of anthropogenic activities, which are partly governed by the type and magnitude of human activities.

A novel naphthalene-based Schiff base ligand (SBL) was synthesized by the condensation of naphthalene-1-8-diamine with 4-dimethylaminobenzaldehyde as a colorimetric probe for the selective detection of Fe³⁺ ions in ethanol solution. The UV-Vis spectroscopic technique was employed to study the sensing ability of the probe SBL for Fe³⁺ ions, which was monitored in ethanol solution (pH 4). The Job’s plot confirmed a 1 : 1 molar complex formation between SBL and Fe³⁺. Density functional theory computations also supported the binding framework between SBL and Fe³⁺. The limit of detection for Fe³⁺ is 6 × 10^–6 M, and the limit of quantification is 2 × 10^–5 M. The binding constant, evaluated using the Benesi–Hildebrand method, is 6.9 × 10⁴ M. Cyclic voltammetry study shows that there is no change in the electrochemical structure of SBL after complex formation with Fe³⁺.

The principal aim of this investigation is to improve the precision and accuracy of quantifying sugars, such as glucose, sucrose, and fructose, through the utilization of hydrophilic interaction liquid chromatography (HILIC) with charged aerosol detection (CAD) in Pueraria tuberosa, a plant renowned for its pharmacological properties. Refractive index detectors are commonly employed to determine sugars in plant extracts. However, it is important to note that these detectors suffer from poor sensitivity and are prone to interference from co-eluting components. Therefore, alternative methods need to be explored to overcome these limitations. HPLC-CAD offers a promising solution by providing improved sensitivity, enhanced precision, and reduced interference from co-eluting sample components. Optimal separation of substances was achieved by implementing an Inertsil HILIC column (250 × 4.6 mm, 5 μm). The mobile phase consisted of 0.1% trifluoroacetic acid in acetonitrile and 0.1% trifluoroacetic acid in water. The flow rate was set at 0.8 mL/min. By employing a systematic approach to modify the chromatographic conditions, this study has successfully improved the sensitivity, resolution, and reliability of sugar determination.

The non-destructive control of levofloxacin, non-steroidal anti-inflammatory drugs, acetylsalicylic acid, and vinpocetine in medicines by their intrinsic fluorescence and diffuse reflectance of near-IR radiation using a smartphone and a 3D-printed device is proposed. Blister packs and tablet shells slightly reduce the intensity of the diffuse reflectance signal at a wavelength of 850 nm and fluorescence due to UV irradiation (390 nm), which is confirmed by a comparative analysis of the results of colorimetric measurement in samples of medicines in blister packs, without packs, and on a tablet split. A correlation is observed between the analytical signal and the mass of the active substance regardless of the study version. The data array was processed using principal component analysis (PCA), hierarchical cluster analysis (HCA), and partial least squares (PLS) regression methods using the PhotoMetrix PRO^® smartphone software. It was shown that these algorithms can be used to identify drugs by their manufacturer and to determine the mass of active substances in tablets. Colorimetric signals from tablets from one manufacturer form separate clusters on dendrograms created using the HCA algorithm. The data obtained using PCA indicate the location of signals from tablets from different manufacturers in separate quadrants, which facilitates the identification of a pharmaceutical company. The use of chemometric analysis methods for determining the mass of the active substance in tablets is considered. The relative standard deviation of the analysis results does not exceed 0.04. The relative error of the analysis results does not exceed the recommended values for the preparation of medicines according to the Order of the Ministry of Health of the Russian Federation dated October 26, 2015 No. 751n.

Determination of the total content (с_Σ) of similar analytes recalculated to a standard substance X_st is a commonly used but a metrologically incorrect measuring procedure, leading to significant systematic errors (B-type uncertainty). Interval estimate с_Σ (Vershinin et al., 2016) is an alternative method that does not require recalculation to X_st and, in contrast to calculating total indices, slightly depends on the nature and ratio of the sought-for group components present in the sample. Such estimates are used for evaluating the total content of antioxidants (AOs) of foodstuffs. However, the dependence of these estimates on the choice of the group reagent and the signal measuring procedure is uncertain. To address this question, model mixtures of AOs with known с_Σ values, ranging from 10^–5 to 10^–4 mol/L, were prepared and tested. Generalized signals were measured by spectrophotometry using Folin–Ciocâlteu (F–C) and FRAP assays, and traditional and interval estimates of с_Σ were calculated and compared. The true values of с_Σ were within the respective intervals for all model mixtures; in the case of the F–C assay, the intervals were wider and shifted towards higher с_Σ values. The FRAP assay was modified using AO concentrations in mol-eq/L, reducing reaction time, and substituting the auxiliary reagent. This modification successfully brought the sensitivity coefficients of individual AOs closer to one another and made the relative widths of intervals three times narrower. Modified FRAP assay was used for the group analysis of wines, black tea infusions, and juices. Corresponding interval estimates of с_Σ were obtained and compared. The unresolved issues and future research directions related to interval estimates are discussed.

The following versions of the electrophoretic determination of carbohydrates after derivatization are considered: reductive amination with p-aminobenzoic acid ethyl ester and condensation with 1-phenyl-3-methyl-5-pyrazolone. The derivatization products were separated by capillary zone electrophoresis and in the micellar mode and their characteristics were compared. Reductive amination followed by determination by micellar electrokinetic chromatography demonstrated the best values of separation efficiency (400 000–650 000 theoretical plates), selectivity (2.1–2.4), and limit of detection (LOD) (0.8–2.9 μg/mL). Derivatization conditions for reductive amination were optimized using a central composite experimental design. In-capillary sample preconcentration samples through sweeping significantly improved the LOD and enhancement factors of 13–19 were achieved. A proof-of-concept possibility of in-capillary reductive amination using detergent micelles as carriers for the derivatization agent was demonstrated. Both derivatization techniques were successfully applied to the analysis of baby food, showcasing their practical applicability.

Ionic liquids based on quaternary ammonium cations—tetrahexylammonium dioctyl sulfosuccinate (THADOSS) and tetrabutylammonium dioctyl sulfosuccinate—were synthesized in situ by mixing aqueous solutions of salts yielding the cation and anion components of the ionic liquid. The ionic liquids were tested for the extraction of heavy metal ions from aqueous solutions. The Cd(II), Co(II), Cu(II), Ni(II), Pb(II), and Zn(II) ions were quantitatively extracted into the in situ formed THADOSS in the presence of 4-(2-pyridylazo)resorcinol (1 × 10^–3 M) at pH 4.9 within 1 min. The study demonstrated the feasibility of determining metals by microwave plasma atomic emission spectrometry after extraction into ionic liquids. The limits of detection ranged from 2 to 25 µg/L.