Chromatographia最新文献

Elucidating the chemistry of wine would help defining its quality, chemical and sensory characteristics and optimise the wine-making processes. High-performance liquid chromatography coupled with UV–Vis spectroscopy (HPLC–UV–Vis) is a common analysis method used to obtain the molecular profile of wine samples. We propose a complete procedure for the analysis of wine chromatograms. Data are pre-processed using standard methods of down-sampling, smoothing and baseline subtraction. Multiple samples are then merged in a three-dimensional tensor, decomposed using parallel factor analysis (PARAFAC2) into three factors: (i) one reduced (rank-one) chromatogram per sample, (ii) an estimate of the samples’ spectral UV–Vis profile and (iii) an estimate of the samples’ concentrations. If the decomposition is performed on a single peak of the tensor, the second and third factors correspond to the representative wavelength spectrum and to the relative concentrations of the samples, respectively. Otherwise, when multiple peaks are analysed, further processing is required. In the latter case, the decomposed rank-one chromatograms are peak-detected and aligned, clustered and integrated. A table containing the concentration of the peaks at different retention times is obtained. The pipeline proposed in this study is a guideline for a quantitative and reproducible chemical analysis of wine, or other samples, via the HPLC–UV–Vis method.

Melatonin (MEL) and caffeine (CA) are mediated by cytochrome P450 1A2 (CYP1A2), and the plasma concentration of MEL is reportedly affected by CA intake and CYP1A2 activity. Because the plasma concentrations of MEL and CA or paraxanthine (PX) differ by approximately 10⁶, MEL, CA, and PX (a metabolite of CYP1A2) have not been quantified in a single-sample preparation. This study aimed to evaluate a liquid chromatography-tandem mass spectrometry method for quantification of MEL, CA, and PX in the same sample preparation. Initially, an injection volume of 10 µL produced a sharp peak for MEL, but the peaks for CA and PX were not suitable for quantification due to their asymmetric peaks. Therefore, CA and PX were separately quantified using 0.1 μL sample, which enabled measurement of both compounds with good peak symmetry. Under these conditions, the relative error for MEL, CA, and PX ranged from  − 9.62% to 1.01%, 0.96% to 9.39%, and − 2.77% to 5.67%, with relative standard deviations of 7.23%, 4.95%, and 8.54%, respectively. In conclusion, the developed method is suitable for use in future studies on the relationship among MEL, CA, and PX.

Worldwide polystyrene (PS) production in 2020 was approximately 27 million metric tons, distributed among many nations, making it one of the most heavily imported and exported chemicals. Commercially produced PS usually possesses a broad molar mass distribution, often with a substantial oligomeric component. The latter can significantly affect processing and end-use, in addition to having potentially hazardous health effects and to impacting the polymer’s export classification by regulatory agencies. Quantitation of the oligomeric region of polymers by size-exclusion chromatography with concentration-sensitive and/or static light scattering detection is complicated by the non-constancy of the specific refractive index increment (∂n/∂c) in this region, which affects the calculated amount (mass fraction) of oligomer in a polymer, molar mass averages, and related conclusions regarding macromolecular properties. Here, a multi-detector SEC approach including differential refractometry, multi-angle static light scattering, and differential viscometry has been applied to determining the ∂n/∂c of n-butyl terminated styrene oligomers at each degree of polymerization from monomer to hexamer, and also of a hexadecamer. Large changes in this parameter from one degree of polymerization to the next are observed, including but not restricted to the fact that the ∂n/∂c of the monomer is less than half that of PS polymer at identical experimental conditions. As part of this study, the individual effects of injection volume, flow rate, and temperature on chromatographic resolution were examined. Incorporation of the on-line viscometer allowed for accurate determination of the intrinsic viscosity and viscometric radius of the monomer and oligomers.

A simple, quick, and economical reverse-phase high-performance liquid chromatography (RP-HPLC) method for the quantitative determination of related substance in milrinone API was developed and validated. The method has shown adequate separation of milrinone and eight kinds of related substance. Chromatographic separation was achieved on an Agilent ZORBAX Rx-C8 (250 × 4.6 mm, 5 µm) column at wavelength of 220 nm, using a mobile phase acetonitrile: phosphate buffer (85:15) in an isocratic elution mode at a flow rate of 1.0 mL min⁻¹. The method was validated in terms of system suitability, specificity, linearity, range, accuracy, intermediate precision, and robustness. A linear relationship between peak area and concentration of milrinone and its related substances was observed in a level of 10–300% (determination coefficient, r² ≥ 0.998), respectively. The method showed acceptable levels of precision (%RSD ≤ 2), accuracy (> 96% recovery), robustness (< 10% content difference), and stability (> 96% recovery) over varied environment and laboratory conditions. The validation results suggested that the developed method is sensitive enough and repeatable and could be used for qualitative and quantitative assessment of eight kinds of related substance in milrinone. As a significant part of drug development process, stress testing is also performed to identify the degradation products and validate the stability-indicating power of our analytical methods, in which milrinone is subjected to acidic, base, oxidation, thermal and photolytic stress environment. To sum up, the proposed method is suitable for purpose in quality-control laboratories for quantitative analysis of the drugs individually, as it is simple and rapid with good precision and accuracy.

Calibration is a fundamental step in instrumental quantitative methods that produce an analytical signal proportional to the concentration of the analyte in the sample. Multi-wavelength calibration (MWC), a novel calibration strategy, has been proposed as a simple method for the determination of analytes in samples with complex matrices. It has minimal matrix effects and straightforward sample preparation. The objective of this work was to apply this calibration strategy to the determination of the synthetic dye Sunset Yellow in soft drinks by high-performance liquid chromatography with ultraviolet–visible analysis (HPLC/UV–Vis). Multi-wavelength calibration planning was performed as recommended in the literature. MWC results were statistically compared with conventional external calibration (limit of detection, limit of quantification, linearity, repeatability and recovery). The results obtained with both calibrations showed that the soft drinks complied with Brazilian legislation. The dye contents obtained with both calibration methods did not show significant statistical differences. MWC appears as an alternative or complement to external calibrations and ensures minimal matrix effects and straightforward sample preparation.

Short-chain fatty acids (SCFAs), such as acetic acid, propionic acid, lactic acid, β-hydroxybutyric acid, and crotonic acid, play key biological roles and are also strongly associated with the maintenance of health and the development of age-related diseases. However, an accurate method for SCFAs detection in human serum is lacking. Herein, we developed an UHPLC-QE-Orbitrap MS method based on 3-nitrophenylhydrazine derivatization in negative electrospray ionization through parallel reaction monitoring mode for the simultaneous detection of 11 SCFAs in the serum, and the analysis was performed on an Agilent Proshell 120 EC-C₁₈ column (2.1 mm × 100 mm, 2.7 μm). Three pairs of isomers—isobutyric and butyric acid, isovaleric and valeric acid, and isocaproic and caproic acid—were completely separated in 20 min in a single run. Our method exhibited satisfactory linearity (R > 0.99) for all analytes, and both intra-day and inter-day accuracies (73.74% to 127.9%) and precisions ( < 21%) were acceptable for most targeted compounds. The extraction recoveries ranged from 90.80% to 111.7%, and the internal standard-normalized matrix effects were 74.43%–116.9%. This method was successfully applied to a cohort of 1021 older Chinese individuals. Our results may further the understanding of the metabolic phenotypes associated with SCFAs in other populations.

A novel method for externally adjusting the column length during gas chromatography (GC) operation is introduced. The technique employs the controlled dehydration of a water stationary phase off a stainless-steel capillary column wall, which is then removed by the carrier gas. By halting the dehydration process (i.e. through adding water to the system) at specified times, partial column (i.e. coating) lengths are created as desired. For instance, since the phase is removed in a ‘peeling’ motion from inlet to outlet, then dehydrating 1/2 of the water coating away results in a 1/2 coated column remaining. This, in turn, acts analogous to a 1/2 column length in separations. In this way, direct and effective reduction in analyte retention time results from shortening column length. Adjustable lengths from 3/4 down to 1/10 of a full column are demonstrated. Good stability in maintaining new column lengths is realized, as analyte retention times vary by only about 1% RSD for most lengths and temperatures examined. Through calibration, column length can be predictably adjusted using system dehydration time, with changes being performed in a few minutes. Results indicate that this method could be useful for adjusting column length in-situ to accommodate various samples during GC operation.

A novel capillary electrophoresis method was developed for the determination of new 4-aryl-pyrido[1,2-c]pyrimidine derivatives, potential antidepressant agents, in serum. The derivatives have conformationally restricted tryptamine moiety in pharmacophore portion and exhibit high affinity to molecular targets: 5-HT_1A receptor and serotonin transporter protein. The separation process was conducted using an eCAP fused-silica capillary, detection wavelength 214 nm, 200 mM phosphate buffer adjusted to pH = 8.0, temperature 20 °C, voltage 5 kV. The proposed method was validated by determining its linearity in the concentration range of 200–1000 ng/mL. A satisfactory linearity was obtained for the method, with R² from 0.9978 to 0.9999 for all five derivatives and a limit of quantification level from 287.1 to 310.1 ng/mL. The recoveries for all derivatives were in the range from 94.7 to 100%. The speed of obtaining the result of the analysis was only 3 min. The developed method allows to determine all five derivatives both in water solutions and serum.