Journal of Analytical Chemistry最新文献

One of current areas of application of microfluidic paper-based analytical devices (μPADs) is the determination of biologically active substances in various samples, including pharmaceuticals. Such determination is often carried out as screening analysis to identify samples that should be examined in more detail by highly informative, but relatively expensive methods. In this paper, an original method for the colorimetric determination of quercetin is proposed using microfluidic analytical systems based on paper modified with gold and silver nanoparticles of various morphologies. It is based on the reduction of silver(I) ions to metallic silver under the action of quercetin with a contrasting change of the color of the μPADs detection zones. A possibility of using a monitor calibrator and a smartphone camera for recording the analytical signal is demonstrated. Optimal conditions for the analysis are selected. It is shown that the type of nanoparticles affects the sensitivity of quercetin determination, which offers promise for creating multisensor systems for discriminating complex samples. The limits of detection for quercetin under the selected conditions are 70–120 ng, depending on the nature of the analytical reagent and the method of recording the analytical signal. The analytical range is 2–10 μg. The sample volume sufficient for analysis does not exceed 25 μL. The selectivity of the proposed method for determining quercetin with respect to a number of common inorganic ions and organic substances is assessed. The applicability of the developed approach to determining quercetin in three pharmaceutical preparations is shown.

High-performance liquid chromatography-tandem triple quadrupole mass spectrometry was validated to analyze acrylamide in coffee samples. Under optimal conditions, the quantitative range for acrylamide was 50–1000 µg/L, and the method detection limit was 30 µg/L. The recovery ranged from 85.2 to 97.3%, with high repeatability and reproducibility. The measurement uncertainty of the method was calculated using a top-down approach and determined to be 12.3%. The validated method was then applied to analyze 68 samples of roasted coffee beans collected from markets in Ho Chi Minh City. The results showed that 51.5% of the samples contained acrylamide at concentrations ranging from 51 to 560 µg/kg, and 10.3% had acrylamide contamination exceeding the maximum acceptance level. The results also demonstrated that the acrylamide contamination level in medium-roast coffee was much higher than that in light-roast and dark-roast coffee. The observation indicates that the level of acrylamide contamination of roasted coffee sold in Ho Chi Minh City markets is an excellent concern for food safety and quality management.

The present review provides a comprehensive overview of the development of analytical methodologies that are well-developed and validated for the estimation of memantine. Memantine is an N-methyl-D-aspartate receptor and is widely used for dementia, Parkinson’s disease, pervasive developmental disorders, schizophrenia, and alcohol abuse disorder. However, the estimation of memantine continues to attract researchers' attention due to its unique chemical properties. Memantine is a saturated compound belonging to biopharmaceutics classification system Class I, due to its high solubility and permeability. However, its lack of unsaturation makes direct detection using ultraviolet-visible (UV-Vis) spectroscopy challenging. Consequently, various analytical approaches have been developed and validated for the detection of memantine, including UV-Vis spectroscopy, fluorescence spectroscopy, infrared spectroscopy, voltammetry, potentiometry, liquid chromatography, gas chromatography, nuclear magnetic resonance spectroscopy, and other hyphenated techniques. This paper provides comprehensive insights for analysts interested in developing analytical methods.

A procedure is developed for acid digestion of black shale samples weighing up to 1000 mg in an open system. The procedure involves the destruction of the mineral matrix with a fivefold excess of ammonium bifluoride at 230°C for 6 h, followed by the reagent removal through distillation and the subsequent treatment of the residue with a mixture of perchloric and nitric acids to achieve the complete dissolution. The resulting solution remains stable over time and serves as the basis for the direct determination of more than 60 elements using a combination of ICP–MS and ICP–AES techniques. The method enables the quantification of gold, silver, and rhodium directly in the post-decomposition solution with the computational correction of spectral interferences. The method was tested on certified reference black shale materials from the Baikal–Vitim province SLg-1 and SChS-1 (Sukhoi Log deposit, Irkutsk district, Russia). The study also presents analytical results for their updated counterparts, SLg-1A and SChS-1A.

In this study, a resonance Rayleigh scattering (RRS) technique and a spectrofluorimetric method were developed using a PbS quantum dot–glutathione nanocomposite sensor for the detection of 6-mercaptopurine in real samples. The sensor was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The scattering intensity (∆I_RRS) signal was detected using a fluorescence detector at an excitation wavelength of 345 nm. The analytical performance of the coupled system demonstrated a linear response to 6-mercaptopurine over a concentration range of 0.05–200.0 ng/mL. The method exhibited a relative standard deviation of ±1.1% and a detection limit (3 s/m) of 0.05 ng/mL, with a response time of 60 s in a Britton – Robinson buffer solution. Furthermore, the PbS quantum dot–glutathione nanocomposite sensor, based on the RRS technique, was successfully applied for the determination of 6-mercaptopurine in samples. The proposed method could be used for the analysis of pharmaceutical formulations, human biological fluids, and hospital samples for the detection of different drugs.

A voltammetric sensor for the determination of taxifolin is developed based on a glassy carbon electrode (GCE) modified with tin dioxide nanoparticles (SnO₂ NPs) dispersed in N-hexadecylpyridinium bromide. The modification of the electrode surface enhances the reversibility of the electrochemical reaction and significantly increases redox currents compared to an unmodified GCE, by factors of 2.3 and 3.3 for the anodic and cathodic peaks, respectively. Scanning electron microscopy reveals a uniformly distributed layer of spherical SnO₂ NPs on the electrode surface; their diameters range from 20 to 40 nm. This modification results in a 3.9-fold increase in the electrode’s effective surface area and a 143-fold enhancement in the heterogeneous electron transfer rate constant. It was found that the electrooxidation of taxifolin involves protons. The electrode reaction follows a mixed control mechanism including both diffusion and adsorption components. Under differential pulse voltammetry conditions, using Britton–Robinson buffer of pH 6.0, the sensor detects taxifolin over a concentration range of 0.075 to 25 μM, with a limit of detection of 70.7 nM. These analytical parameters are comparable to those achieved by other electrochemical techniques; however, the proposed method offers greater simplicity and higher speed, and does not require complex electrode modification. The sensor demonstrated successful application to the analysis of dietary supplements containing dihydroquercetin (taxifolin). The results aligned with those obtained by coulometric titration using electrochemically generated bromine.

A ratiometric electrochemical aptasensor for the sensitive detection of mucin 1 (MUC1) was designed based on a quadruped DNA walker driven by catalytic hairpin assembly (CHA). With the tetrahedral DNA nanostructure as the framework, the four legs that extend out acted as the walking chains. MUC1 bound specifically to the aptamer, activating the quadruped DNA walker and initiating the CHA reaction. The activated quadruped DNA walker hybridized with hairpin DNA1 labeled with methylene blue (MB-HP1) immobilized on the electrode surface, and the toehold area of the MB-HP1 probe was exposed to bind with hairpin DNA2 labeled with ferrocene (Fc-HP2), causing the quadruped DNA walker to be released. It continued to move on the electrode surface and bound with another MB-HP1. Eventually, a large number of electrochemical signal molecules were brought close to the electrode surface, while MB moved farther away. Under optimal conditions, the peak current ratio (I_Fc/I_MB) was linearly correlated with the logarithm of MUC1 concentration from 1 fg/mL to 1 ng/mL, with a detection limit as low as 0.56 fg/mL. In addition, the sensing platform demonstrated good performance in the analysis of serum samples.

A voltammetric sensor is developed based on a carbon fiber planar electrode modified with a nanocomposite for the simultaneous determination of synthetic food dyes Carmoisine (Car), Allura Red AC (AR), and Brilliant Blue FCF (BB). The nanocomposite includes nickel oxide nanoparticles, synthesized using a strawberry leaf extract; graphene nanoplatelets; and the cationic surfactant cetyltrimethylammonium bromide. The modified electrode exhibits enhanced responses for all three dyes at an improved resolution. Electrochemical oxidation proceeds irreversibly, governed by surface-controlled processes in the cases of Car and BB, and by diffusion-controlled processes in the case of AR. The proposed method enables the simultaneous voltammetric determination of Car, AR, and BB using the developed sensor. The limits of detection for Car, AR, and BB are 0.05, 0.08, and 0.15 µM, respectively. Under the selected conditions for recording differential pulse voltammetry signals, real samples—including soft drinks, syrup, and marshmallows—were successfully analyzed, recovery from 95 to 104%.

Lead ions in food can accumulate in the human body, leading to various diseases, so it is necessary to detect the content of lead ions in food. In this paper, a new Schiff base was prepared using derivatives of isophthalic acid and salicylaldehyde as a photoresponsive probe for Pb(II) ions. The Schiff base probe had an absorption peak at 505 nm after the addition of Pb(II) ions to an acetonitrile solution. However, other inorganic ions caused only slight absorbance changes at 505 nm. Based on this, a visible light analysis method for Pb(II) ions was established. The equilibrium time of the Schiff base probe with Pb(II) ions was 5 min, with a linear range of 2.5–25 ppm. The Schiff base probe was used to detect Pb(II) ion content in mustard samples, and the recoveries were over 90%. The detection results were not significantly different from those of the standard method, indicating that the Schiff base probe can be used for the rapid determination of Pb(II) ion content in real samples.

As a high-efficiency antibiotic, chlortetracycline hydrochloride (CTC) is widely used, and its environmental residues pose a threat to human health. Therefore, the detection of CTC is of great significance. In this study, gold nanoclusters (AuNCs) were synthesized under certain conditions with Nuclear Fast Red as a stabilizer, chloroauric acid as the raw material, and sodium borohydride as the reducing agent. The synthesized AuNCs exhibited an optimal excitation wavelength of 376 nm and an optimal emission wavelength of 513 nm. It was observed that CTC could effectively enhance the fluorescence of the synthesized AuNCs at an emission wavelength of 424 nm when excited at 352 nm. The fluorescence intensity of the AuNCs system in the absence (F₀) and presence (F) of CTC was measured. A good linear relationship was observed between the fluorescence intensity enhancement value (ΔF = F–F₀) and the concentration of CTC in the range of 10.0–90.0 μM. The linear equation was ΔF = 8.67c + 123.5, with a limit of detection of 2.0 μM (3σ/k). Thus, AuNCs could be used as fluorescent probes for the detection of CTC concentration. The applicability of the method was validated using a spiked recovery test with river water samples. The recovery rates ranged from 94.0 to 103.4%, demonstrating the potential of this method for detecting CTC concentrations in river water samples.