The rapid and non-destructive determination of sodium chloride (NaCl) in aqueous solutions is critical to food-process monitoring, pharmaceutical manufacturing, and the chlor-alkali and desalination industries. This study presents a method based on Raman spectroscopy (785 nm; 350–2000 cm−1) combined with partial least squares regression (PLS-R) for estimating NaCl in simple aqueous solutions at concentrations between 0.02 and 4.0 mol·L−1. Since Na+ and Cl− ions lack intrinsic Raman modes, the quantification was based on the modifications that ionic solvation induces on the hydrogen-bond network of water, mainly affecting the librational (450–780 cm−1) and H-O-H bending modes (~1640 cm−1). Four preprocessing strategies were systematically evaluated. The model with the combination of asymmetric least squares baseline correction and Savitzky–Golay smoothing (ALS-SG) provided the lowest root mean square error of cross-validation (RMSECV = 0.0608 mol·L−1), requiring only two latent variables (calibration coefficient of determination, R2cal = 0.9990 and cross-validated coefficient of determination, Q2CV = 0.9979). The holdout prediction set (n = 5) yielded a coefficient of determination (R2ext) of 0.9946 and a root mean square error of prediction (RMSEP) of 0.0681 mol·L−1, with an empirical lower limit of reliable prediction of ~0.18 mol·L−1. The holdout samples span 0.04–2.50 mol·L−1, so predictive performance between 2.50 and 4.00 mol·L−1 is supported by calibration and cross-validation only. Given the small size of this set, these figures are reported as a proof-of-concept indication and support the potential of the approach for NaCl monitoring in simple aqueous matrices.
This study evaluates a miniaturized Near-infrared spectroscopy MicroNIR/Chemometrics platform as a rapid tool for monitoring chloroform, a representative disinfection by-product from the trihalomethanes class. Two MicroNIR devices were tested in three configurations: reflectance measurements in glass vials and transmittance measurements in static and flow modes. Experiments were conducted with spiked distilled water over the 1–200 µg/L range relevant to regulations. Principal Component Analysis provided clear separation between blanks and chloroform-containing samples in all configurations. Partial Least Squares Discriminant Analysis achieved 100% specificity and non-error rate, with a root mean square error in prediction (RMSEP) of approximately 0.06–0.08 for static and flow measurements and 0.09–0.10 for vial mode. In the 1–20 µg/L range, Partial Least Squares Regression demonstrated comparable performance for static and flow measurements (R2 = 0.91; RMSEP = 2.3 µg/L), while flow provided the lowest estimated limits of detection and quantification (2.6 µg/L and 7.9 µg/L, respectively). In the 20–200 µg/L range, flow showed the highest quantitative performance. The results support the feasibility of MicroNIR/Chemometrics as a rapid screening tool for chloroform in water, complementary to reference methods. Future work will focus on improving inter-campaign transferability, extending the approach to all regulated trihalomethanes, and validating it in real matrices.
Molecularly imprinted polymers (MIPs) are synthetic receptors in which a template-shaped cavity, formed by polymerising functional monomers around the target and then removing it, confers preferential rebinding of that target. Their chemical and thermal robustness, low unit cost, straightforward preparation and reusability make them attractive recognition elements for psychoactive substance analysis, a field constrained by sample throughput, cost and the need for field-deployable measurement. This review is restricted to small-molecule targets and distinguishes four groups whose forensic and regulatory contexts differ: classical controlled drugs, novel psychoactive substances (NPSs), psychoactive medicinal products, and performance-enhancing agents encountered in the same laboratory workflows. We summarise (i) the imprinting formats and computational pre-screening strategies relevant to these targets and (ii) their implementation in electrochemical, optical and piezoelectric sensors, in chromatographic and spectroscopic sample preparation, and in microfluidic platforms. Reported figures of merit are compiled on a common molar basis to permit direct comparison across platforms. We then assess the factors that currently govern forensic and clinical deployment: cross-reactivity towards close structural analogues, which for imprinted receptors typically remains well above the one-to-two per cent level and makes them class-selective rather than compound-specific; residual template bleeding; electrode fouling in undiluted biological fluids; and the reproducibility and scale-up of imprinting. On this evidence, the productive role of MIPs in clinical and forensic toxicology is as class-selective extraction sorbents and rapid presumptive screening devices upstream of chromatographic confirmation, rather than as replacements for it.
DNA methylation is a central epigenetic regulator of genome stability, developmental plasticity, and stress adaptation in plant tissue culture systems. During dedifferentiation, callus formation, organogenesis, somatic embryogenesis, transformation, and prolonged subculture, DNA methylation patterns can be extensively remodeled, thereby contributing to regeneration competence and somaclonal variation. To detect such changes, traditional methylation-detection methods, including bisulfite-based sequencing and methylation-sensitive polymerase chain reaction, provide high analytical output but remain labor-intensive (2–3 days), destructive (requiring microgram amounts of DNA), and difficult to deploy as rapid screening tools across large tissue-culture plantlets. Surface-enhanced Raman scattering (SERS) offers a complementary route by coupling molecular fingerprinting with plasmonic signal amplification. Controlled systems have demonstrated highly sensitive detection of methylation-associated molecular signatures, with reported detection limits reaching the nanomolar-to-submicromolar range depending on analyte type, substrate architecture, and measurement conditions. However, these quantitative values primarily come from synthetic DNA or model systems and should be interpreted cautiously when applied to complex plant tissue culture samples. This review critically examines current SERS-based strategies for DNA methylation analysis, emphasizing substrate selection, signal-enhancement mechanisms, SERS enhancement mechanisms, surface functionalization, and computational spectral analysis. SERS has emerged as a promising complementary technology for DNA methylation analysis due to its molecular fingerprinting capability and high sensitivity. However, direct demonstrations of SERS-based DNA methylation detection in plant tissue culture systems remain limited. Current evidence largely originates from synthetic DNA models, purified nucleic acid systems, and non-plant biological applications, providing methodological foundations rather than complete plant validation. Future studies are required to establish plant-specific substrates, calibration strategies, and biological validation workflows.
Reliable determination of heavy rare earth elements (HREEs) in ores with multiple components through ICP-OES analysis is limited by their complex spectral signatures and dependency on the chemical matrix of each sample. A double gate-line selection method was developed that utilizes both correlation between candidate ICP-OES line intensity values and ICP-MS reference concentration values for 24 geological samples and standard addition recovery screening. The multi acid decomposition of all samples utilized HNO3, HCl, HF, HClO4, and H2O2. The eight selected lines were Gd at 335.048 nm, Tb at 350.914 nm, Dy at 353.171 nm, Ho at 345.600 nm, Er at 369.265 nm, Tm at 313.125 nm, Yb at 369.419 nm, and Lu at 291.139 nm. Limits of detection for the blank-derived data range from 0.02 to 0.10 mg/kg; the limit of quantification ranges from 0.07 to 0.32 mg/kg. However, the lower bound of calibration standards represents 2.00 mg/kg in the solid phase. Therefore, any results that fall below this threshold will be represented as estimated (extrapolated) rather than measured (quantitatively determined). CRM recoveries for the eight target analytes fell within the range of 91.67 to 105.78 percent; however, the two CRM comparisons where the analytical result for one or more target analytes exceeded the two-sided critical T-value (two tailed) of 2.31 were Tb in OREAS 465 and Er in OREAS 461. Due to the fact that the 24 samples analyzed for ICP-OES/ICP-MS correlation analysis were also used for the initial selection of candidate ICP-OES lines, the demonstrated correlations represent internal validity versus independent prediction. Single interferent controlled experiments and matrix-matched calibration experiments were not completed.
