International Journal of Analytical Chemistry最新文献

Natural gas (NG), primarily composed of methane, is colorless and odorless, thus necessitating odorization to enable leak detection and accident prevention. Precise monitoring of odorants is critical to meet safety standards while preventing excessive dosing. This study introduces a real-time gas chromatography system integrating gas chromatography and photoionization detection for the real-time, online odorant analysis in gas pipelines. This system effectively isolates tetrahydrothiophene (THT) and sulfur-free odorants from NG, enabling accurate concentration quantification. It achieves THT detection within 2∼150 mg/m³, with a relative standard deviation (RSD) of less than 1.5% and maximum deviation of less than 3 mg/m³. Additionally, this system exhibits good field applicability. When combined with a cloud-based warning platform, it can achieve monitoring, warning, and self-optimization of odorant concentration. This study demonstrates the reliability of this system for NG odorant monitoring, providing a robust solution for pipeline safety management and regulatory compliance, while offering a new approach for NG safety testing.

With the advancement of multiomics technologies and cohort study designs, integrative omics research is increasingly applied to human health and nutrition. However, optimal storage and preprocessing of labile biological samples, particularly feces, remain challenging. In this study, we systematically evaluated three normalization methods-wet weight, dry weight, and protein quantification-for quantitative metabolomic profiling of fecal samples, using 41 metabolites. Fresh fecal samples from three healthy individuals showed high reproducibility, with 24 metabolites exhibiting a coefficient of variation (CV) below 30 for both wet and dry weight normalization. Fecal samples from 20 obese patients collected using the OMNIgene·GUT kit demonstrated improved reproducibility with wet weight normalization (20 metabolites, CV < 30) and protein quantification normalization (19 metabolites, CV < 30), whereas dry weight normalization yielded no metabolites meeting the CV < 30 criterion. Direct analysis of the kit solution without a drying step further enhanced chromatographic clarity, highlighting practical considerations for large-scale studies. Overall, wet weight normalization consistently minimized variation across sample types, providing a robust and standardized framework for fecal metabolite profiling. These findings demonstrate that the OMNIgene·GUT kit is compatible with broad-spectrum metabolomic analyses and support its integration into multiomics workflows. By establishing reproducible normalization protocols, this study provides the foundation for accurate, comparable, and scalable fecal metabolomics in both clinical and nutritional research settings.

A current problem in analytical chemistry is to match the uncertainty of several independent sample replicates with the measurement uncertainty associated with first-order models. According to contemporary guidelines, calibration lines for method validations should be prepared with few standards, frequently without any blanks. These suggestions weaken the validity of the statistics, which are meant to address truth and accuracy rather than precision. As was previously shown when looking at the pooled calibration (PoPC) paradigm for method validation, excellent precision does not imply good accuracy. A novel technique known as combinatorial regression (CR) was created to estimate slopes, intercepts, and standard deviations to reduce disagreements regarding the computation of measurement uncertainty in accordance with the calibration line. The related standard deviations of several replicates were discovered to be too large to be applied to uncertainty. Concurrently, the idea of employing the numerical values of concentration residuals as promising estimates of measurement uncertainty arose from the fact that the standard deviations of the IUPAC equations are too small to be used in the computation of uncertainties. High-resolution continuous-source flame atomic absorption spectrometry (HR-CR FAAS), which has been demonstrated to produce inconsistent findings for the analysis of elements Na, Mg, and Ni, was used to evaluate the CR method on the determination of copper. The CR provided coefficients of variations (CVs) that rose with concentrations and number of replicates, favoring analyzing low concentrations in contrast to the IUPAC equations.

This research mainly focused on developing and validating the ultraperformance liquid chromatography photodiode array (UPLC-PDA) method to analyze 4-oxo-2-nonenal (4-ONE) in fully cooked meat products. The UPLC-PDA method developed has advantages such as sensitivity, excellent resolution, and fast separation through chromatography. To ensure its reliability and accuracy, the method underwent validation processes for linearity, precision, accuracy, robustness, and limit of detection (LOD) and quantification (LOQ). The results demonstrated a linear relationship between concentration and response within the 0.0032-10 ng/mL range with a correlation coefficient of R ² ≥ 0.9993. The method also exhibited precision with relative standard deviations (RSDs) below 2% for both intraday and interday analyses. Moreover, recovery studies confirmed the method's accuracy, with percent recoveries ranging from 97.16% to 105.9%. Furthermore, the results for LOD and LOQ were 0.03 and 0.091 ng/mL, respectively. Lastly, it was concluded that the developed method remains reliable under certain conditions by varying parameters such as the flow rate, mobile phase composition, and detection wavelength in robustness evaluations. This developed UPLC-PDA technique offers a reliable and effective means of identifying and measuring 4-ONE in cooked meat. It plays a role in ensuring food safety and addressing health issues associated with its consumption.

This study was carried out to assess the health hazards associated with the amount of the heavy metal lead (Pb), which is one of them, and samples of chromium (Cr) and cadmium (Cd) of dried fruits sold in Iraqi marketplaces. We gathered and used atomic absorption spectrometry (AAS) to assess 15 different samples of dried fruits that were imported from Iran. The average metal concentrations were as follows: (Pb = 0.6416 mg/kg), (Cd = 0.1910 mg/kg), and (Cr = 0.3544 mg/kg), according to the data. A number of samples were found to be above the FAO/WHO maximum allowable levels, which are 0.12 mg/kg for chromium and 0.05 mg/kg for cadmium. Apple (Cd = 0.897 mg/kg), peach (Cr = 1.289 mg/kg), and quince (Pb = 1.951 mg/kg) had the greatest values. Pb, Cd, and Cr had average estimated daily intakes (EDIs) of 0.4584, 0.1502, and 0.2532 mg/kg/day, respectively, according to the health hazard indices that were also constructed. Cd = 0.1364, Cr = 0.084, and Pb = 0.131 were the average target hazard quotient (THQ) index. The average hazard index (HI) for all metals was less than 1, at 0.351, showing no direct noncarcinogenic health harm associated with regular use. The possibility of long-term cumulative hazards, however, is indicated by samples that exceed the allowable levels, necessitating stricter food control of imported goods. The TCR (carcinogenic risk) values for lead (Pb), chromium (Cr), and cadmium (Cd) levels were assessed in dried fruit samples. The average overall TCR value was 5.106 ± 1.10, with a range of 0.002 × 10^-6 to 16.90 × 10^-6. Every one of these values falls below the acceptable ranges (10^-6 and 10^-4) established by the US Environmental Protection Agency (USEPA), suggesting that eating these fruits did not significantly increase a person's chance of developing cancer. This is one of the rare studies to focus on dried fruits in Iraq, despite the fact that there have been earlier international studies on heavy metals in fruits. In accordance with the international standards, such as THQ, HI, and TCR, it integrates chemical assessment with health analysis to produce reliable data that back up the nation's food control initiatives.

The purpose of this study is to develop and validate a simple and rapid analytical method using ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous quantification of two commonly used contrast agents, iopromide and iodixanol, in human plasma. The separation of two compounds was analyzed utilizing an Agilent ZORBAX SB-C₁₈ column (2.1 × 100 mm, 3.5 μm) with an isocratic elution procedure. The mobile phase consisted of acetonitrile and 0.2% formic acid aqueous solution (14:86, V:V). A simple protein precipitation method was used to pretreat plasma samples. The iopromide and iodixanol exhibited excellent linearity between 2.0 and 400.0 μg/mL, with both R values exceeding 0.99. Recovery of iopromide ranged from 91.39% to 102.69%, and matrix effect varied between 87.88% and 104.08%; the relative standard deviation (RSD%) of intra- and interday precisions fell within the range of 1.29%-4.7%. For iodixanol, recovery ranged from 97.68% to 100.14%, and the matrix effect was between 87.88% and 96.64%, and RSD% values of intra- and interday precisions ranged from 1.58% to 8.2%. Method validation results all met methodological criteria. The UHPLC-MS/MS method was successfully developed and validated and then applied to determine two common contrast agents, iopromide and iodixanol, in human plasma.

N-nitroso-dimethylamine (NDMA, acceptable daily intake limit 96 ng/day), a probable human carcinogenic impurity, has been reported in metformin formulations. In some cases, it is difficult to accurately detect its presence due to suboptimal extraction technique(s), coelution of other probable human carcinogenic impurities such as dimethyl formamide (DMF) and/or ionization suppression in mass spectroscopic measurements. In this study, we provided a simple method to address DMF artifact using an affordable high-performance liquid chromatography coupled with a single-stage mass spectrometer. The results were further confirmed by dual-stage mass spectrometry. The two developed methods can simultaneously identify NDMA in the presence of DMF with good linear range from 10 to 100 ng/mL (r ² = 0.971) and 1 to 10 ng/mL (r ² = 0.994), respectively. The accuracy, expressed as % recovery, was close to 100% with overall precision (%RSD) < 8. The two methods were linear in the presence of 100 ng/mL DMF with r ² = 0.996 and 0.98, respectively. Five commercial formulations of metformin tablets showed traces of NDMA below the regulatory limit (0-12 ± 0.2 ng/tablet) but appreciable amounts of DMF (50-653.5 ng/tablet), still lower than the permissible daily exposure limit (8.8 mg/day) based on the maximum daily dose of metformin (5 tablets, 2500 mg). Both methods proved reliable and informative in the quality control of the NDMA content in metformin tablets and provided reciprocal verification of results.

Near-infrared (NIR) spectroscopy data encounter challenges in data processing such as peak overlapping, information redundancy, and background or noise, which complicate the evaluation of weak differences among similar samples. Therefore, accurately identifying these differences and assessing similarities are essential in practical applications for sample classification and further replacement of raw materials in the product formulation. In this work, 32 data preprocessing strategies of NIR data were systematically combined for comprehensive comparison, and 11 methods for similarity analysis were evaluated to attain optimal performance. Using the rationality of similarity evaluation as the assessment criterion, the combination of NIR data pretreatment methods of "standard normal variate (SNV) + first-order derivative by Savitzky-Golay (1D/SG) + maximum-minimum scaling (MMS) + spectral similarity by combinatorial strategy (SS/CS)" is ultimately preferred as the most effective combination for similarity evaluation. It uses SNV transformation, 1D/SG, MMS, and scattering correction to eliminate the scattering effect, enhance the signal-to-noise ratio (SNR) of the distinction of overlapping peaks, and improve data comparability. After this, the widely used methods for similarity evaluation were employed for comprehensive analysis and comparison of the rationality, such as Euclidean distance, correlation coefficient, and divergence information. The evaluation strategy proposed in this work can effectively distinguish the difference among the tobacco samples existing in 10 different categories. The similarity among typical samples in the same class is above 0.9, while the values in different classes are below 0.7. In real applications for method validation, recognition precision of tobacco samples with blending of interfering mixtures reaches 5%, which is conducted using complex tobacco materials for formulation replacement and optimization. The satisfactory results introduce robust and CS that outperforms traditional single-method approaches to resolve weak spectral differences through real-world tobacco formulation replacement applications. It can be widely used in the areas related to NIR for similarity evaluation, such as pharmaceuticals, food quality control, and environmental monitoring.

Background: Reliable determination of calcium in pharmaceuticals is crucial for quality control, yet conventional methods often rely on synthetic chelating agents such as EDTA, which raise environmental and safety concerns. Curcumin, the principal polyphenolic compound in Curcuma longa (turmeric), exhibits strong metal-chelating properties through its β-diketone structure. This study explores the use of curcumin as a natural and sustainable chelating agent for the spectrophotometric determination of calcium in pharmaceutical formulations.

Method: Curcumin was extracted from turmeric rhizomes collected from different altitudes in Nepal using ethanol and was allowed to form a stable color complex with various calcium-containing drugs, such as calcium gluconate, calcium lactate, and calcium docusate. The method was optimized by adjusting reagent volume, pH, and buffer volume. Validation was carried out according to ICH guidelines, evaluating linearity, precision, accuracy, and robustness. The environmental impact was assessed using Green Analytical Procedure Index, Analytical Eco-Scale, and AGREES tools. The Click Analytical Chemistry Index was used to analyze overall sustainability, while the Carbon Footprint Reduction Index was applied to evaluate the prime environmental impact of the already developed analytical laboratory procedures.

Results: The highest curcumin yield was from the Kaski region. The optimized method produced a stable yellow-orange complex with maximum absorbance at 430 nm. It demonstrated high precision (%RSD < 2%), accuracy (recovery: 101.63% and 102.01%), and robustness with a stable reaction lasting up to 4 h. The environmental assessment confirmed its sustainability and eco-friendliness, with a very good score reflecting minimal solvent use and no hazardous waste.

Conclusions: This study successfully developed a green, cost-effective, and reliable method for calcium analysis in pharmaceutical products using curcumin as a natural reagent. Its simplicity and environmental sustainability make it a promising alternative to conventional techniques for calcium analysis.

Nirmatrelvir, a key antiviral agent in the treatment of COVID-19, requires accurate and reliable monitoring of drug levels to optimize therapeutic efficacy. In this study, we developed and validated a sensitive and specific LC-MS/MS method for the quantification of nirmatrelvir in human plasma. The method includes nirmatrelvir-D9 as an internal standard, with quantification achieved using selected reaction monitoring in positive electrospray ionization mode, targeting m/z 500.3 ⟶ 110.1 for nirmatrelvir and m/z 509.3 ⟶ 110.1 for nirmatrelvir-D9. Sample preparation involved a simple phospholipid removal step using 96-well plate and automated liquid handler, which improved efficiency in a high-throughput process. The validated method, following international bioanalytical guidelines, demonstrated a linear range from 10.9 to 3013 ng/mL. Intra- and interassay precisions were both below 15%. All validation tests meet the criteria for matrix effect, carryover, dilution integrity, and stability. The method offers a rapid analysis time of 2 min per sample and provides highly accurate, reproducible results, making it a valuable tool for evaluating the pharmacokinetics of nirmatrelvir in clinical settings.

Trial registration: ClinicalTrials.gov identifier: NCT05041907.