Journal of Analytical Chemistry最新文献

In this research, density functional theory and molecular docking calculations were utilized to select appropriate molecularly imprinted polymers (MIPs) for malathion (MAL). The MIP was synthesized with MAL as the template molecule, ethylene glycol dimethacrylate as the cross-linker, and methacrylic acid as the functional monomer on the surface of graphene quantum dots (GQDs). The MIPs were coated on GQDs to fabricate the GQDs@MIP sensor. The electrochemical sensor was characterized by Fourier-transform infrared spectroscopy, X-ray scattering spectroscopy, and field-emission scanning electron microscopy. Parameters affecting the electrochemical response of MAL, including the GQDs@MIP percentage amount, pH of the rebinding solution, pH of the analysis solution, and incubation time, were optimized. Differential pulse voltammetry revealed a linear calibration curve in the concentration range of 0.01 to 55.00 µM with a limit of detection of 1.5 nM. The relative standard deviation for five consecutive tests of 1.00 μM MAL was 2.2%. The GQDs@MIP sensor was successfully applied to determine MAL in various fruit samples.

A procedure is developed for the simultaneous determination of organophosphorus pesticides (OPP) diazinon, dimethoate, omethoate, pirimiphos-methyl, pirimiphos-ethyl, malathion, malaoxon, chlorpyrifos-methyl, and fosalone in medicinal plant raw materials using high-resolution liquid chromatography–mass spectrometry. The procedure uses a rapid method of sample preparation by the extraction of crushed plant materials with acetonitrile. The analysis conditions in the reversed-phase chromatography version are optimized. Determination is carried out by the internal standard method using deuterated standards malathion-d6 and dichlorvos-d6 based on the two most intense ionic reactions specific for each individual OPP. The procedure was tested on an example of plant raw materials—valerian (Rhizomata cum radicibus Valerianae officinalis) rhizomes and roots and validated according to the specificity, linearity, accuracy, analytical range, limit of quantification, precision, and matrix effect parameters. The proposed procedure can be used to determine the indicated OPP in a wide range of concentrations from 0.01 to 10 000 ng/g of raw materials in medicinal and agricultural plant growing.

Abstract

Analytical methods used in mineral analysis laboratories are susceptible to significant sources of random error that define the level of intralaboratory precision. This requires a good quality control system to ensure that analytical performance is within statistical criteria established by institutional, national, or international bodies. The Horwitz equation and the Horwitz ratio (HorRat) are two related parameters derived from the historical reproducibility analysis that allow for predicting interlaboratory precision and establishing control criteria. The Horwitz ratio can be used not only to establish precision control methodologies between laboratories but also within them. This paper presents the development of a methodology based on the Horwitz ratio to enhance the existing precision quality system based on minimum difference tolerances through volumetric analysis. Data obtained from the quantification of iron, nickel, and cobalt by inductively coupled plasma optical emission spectrometry were analyzed for precision control verification. The HorRat values for iron ranged from 0.48 to 1.25 across concentrations ranging from 3.5 to 48.95%. For nickel, it ranged from 0.20 to 0.36 within the concentration interval of 0.2 to 4.99%. For cobalt, the HorRat ranged from 0.56 to 2.05 across concentrations from 0.01 to 0.499%. An acceptance criterion of HorRat < 1 was established, revealing problems in the established system resulting from the assumption of volumetric tolerances for a spectrometric method. The main deficiencies in the existing methodology were detected in the quantification of iron. The Horwitz-based methodology presented allowed for the improvement of intralaboratory precision and maintained better control over the process.

Abstract

The control of oxygen and carbon dioxide concentrations in an airflow released from a reactor, in which a sample is heated, can be used to investigate the thermal stability of polymer materials. This approach, known as oxithermography, involves analyzing experimental data (oxithermograms), representing the variation in oxygen concentration decrease and carbon dioxide appearance in an airflow with changing temperature conditions. This method allows for monitoring the effect of fillers introduced into polymer compositions on their thermal stability. The application of oxithermography to studying oxidative thermostability is demonstrated using pure polypropylene and polypropylene with titanium dioxide admixtures as examples.

Abstract

The effect of the sweat and grease deposits (SGD) from fingerprints on the detection efficiency of trace amounts of explosive substances—triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD), and ammonium nitrate (AN) by ion mobility spectrometry in air at atmospheric pressure was investigated. Among the main components of SGD, urea is identified as a positive mode influencer, while lactic acid (LA) affects in a negative mode. The presence of urea or SGD in the sample does not significantly affect the detection of TATP in the positive mode but decreases the efficiency of HMTD ion formation and leads to the appearance of adduct cations of HMTD and urea. The presence of lactic acid or SGD slightly decreases the efficiency of ammonium nitrate ion formation in the negative mode and significantly alters the qualitative composition of HMTD ions, leading to the appearance of HMTD and LA adduct anions. In the absence of any impurities in the sample, the best reduced limit of detection (signal-to-noise ratio = 3σ), estimated at 30–50 pg, was observed for HMTD. The lifetime of HMTD, TATP, and AN traces on aluminum foil under laboratory conditions was determined to be 1, 3, and 12 h for samples with masses of m_HMTD 1 × 10^–9, 2 × 10^–9, and 1 × 10^–8 g and surface densities d_s of 0.008, 0.016, and 0.08 μg/cm², respectively; 10² and 10³ s for m_TATP 1 × 10^–5 and 1 × 10^–4 g and d_s of 80 and 800 μg/cm², respectively; 12 and 25 h for m_AN 3 × 10^–8 and 5 × 10^–8 g and d_s of 0.24 and 0.4 μg/cm², respectively.

Abstract

The extraction of nandrolone as a steroid hormone using fast methods is of high importance. This was done by dispersive micro-solid phase extraction in the presence of two widely used organometallic frameworks (MIL-53(Al) and ZIF-8). The extraction steps were optimized by an extensive study on the main factors affecting the absorption/desorption efficiency. The optimum conditions were obtained by design of experiments for the extraction and determination of nandrolone in a blank human plasma matrix. Maximum extraction of nandrolone was achieved in 8.5 min by 2.5 mg of MIL-53(Al) in the solution with 0.89% (w/v) salt concentration, while the maximum extraction by ZIF-8 as another sorbent required 10 min, 4.5 mg of sorbent, and 0.60% (w/v) of salt concentration. Batch experiments were carried out to find appropriate kinetic and isotherm models. Finally, the analytical validation of the proposed method was investigated. The dynamic range of the method was from 0.05 to 1 µg/mL. The precision (expressed as the relative standard deviation, RSD) and accuracy (expressed as the percentage error) of extraction by MIL-53(Al) were found 3.90 and 3.39%, respectively, while those by ZIF-8 were calculated as 4.59 and 4.50%, respectively. The proposed method was successfully applied for the determination of nandrolone in spiked samples, achieving high recovery rates of approximately 96% and 94% using MIL-53(Al) and ZIF-8.

Abstract

The gas-chromatographic retention indices (RIs) of trimethylsilyl (TMS) derivatives of the simplest amino acids on standard nonpolar polydimethylsiloxane stationary phases were systematized. This processing of data included combining them for derivatives of the same amino acids depending on the number of TMS groups (from one to four) and calculating average RI values together with their standard deviations based on data from various sources of information. This form of presenting the results made it possible to identify the best characterized derivatives and evaluate the reliability of the retention indices known for them. The simplest additive scheme for calculating retention indices based on even limited data for the most common amino acids was formed to estimate their unknown values, control previously determined values, and identify erroneous data. The increment ΔRI = RI(bis) – RI(mono) for the transformation −CO₂Si(CH₃)₃ + −NH₂ → −CO₂Si(CH₃)₃ + −NHSi(CH₃)₃ was well reproducible (118 ± 9). The other increments ΔRI = RI(tris) – RI(bis) were different for the transformations −NHSi(CH₃)₃ + XH → −N[Si(CH₃)₃]₂ + XH (238 ± 35) and −NHSi(CH₃)₃ + XH → −NHSi(CH₃)₃ + −XSi(CH₃)₃ (111 ± 16). A method for monitoring the correctness of the obtained values of ΔRI was proposed.

Abstract

The review describes the fundamental electrochemical properties of nucleic acids manifested on solid electrodes, with an emphasis on the spatial structure of macromolecules. The formation of the double helix impedes the contact of the electroactive groups of the nitrogenous bases with the electrode surface, resulting in the disappearance of the analytical signal of deoxyribonucleic acid (DNA). The insufficient electroactivity of the double-stranded DNA is overcome by introducing electrochemically active fragments into the nucleic acid sequence through the polymerase incorporation of chemically modified nucleotides. Currently, an extensive range of artificial nucleotides has been synthesized, which contain various electroactive groups capable of both oxidation and reduction on electrode surfaces at different potentials. Artificial modified nucleotides must exhibit high electrochemical activity while also serving as good substrates for enzymes (polymerases) involved in nucleic acid amplification reactions. Introducing modified nucleotides instead of natural ones into polymerase reactions represents a compromise between the number of labels inserted in one amplicon and the length and quantity of the resulting products. Modified nucleotides find application in the detection of gene mutations and single-nucleotide polymorphisms, nucleic acid sequencing, determination of protein and peptide concentrations, and the detection of pathogenic viruses and bacteria. With the advancement of isothermal amplification methods, the development, synthesis, and investigation of artificial nucleotides have become highly relevant for creating new off-laboratory electrochemical nucleic acid analyzers.

Abstract

Pharmaceutical manufacturers are globally forced to follow international guidelines on cleaning validation. Cleaning validation is related to the concept of the worst-case product; however, the worst-case product is a function of the manufacturer and the product portfolio. Consequently, manufacturers are faced repeatedly by cycles of worst-case product alteration, and repeated cycles of worst-case oriented analytical method development. Generally, this problem is hardly controlled due to the various products manufactured by the same facility. However, Analytical Quality by Design (AQbD) offers a possible solution through the development of robust and sensitive multicomponent analytical methods that span a wide spectrum of possible products. Cephalosporin antibiotics are a broadly manufactured class of antibiotics that can lead to anaphylaxis in extremely small quantities; therefore, an ultra-level of cleanness is required for facilities involved in such products. A group of the highest market share cephalosporin products was used to present the application of AQbD to introduce a reliable solution to cleaning validation that can be employed in pharmaceutical facilities. A multivariate optimization approach was utilized for the development of a sensitive multicomponent HPLC method; in addition to the proposal of a novel chemometric approach to troubleshoot the developed method.

Abstract

The high catalytic activity of arenediazonium, along with the ability of gold ions to form specific bonds with amikacin, has been used in the fabrication of an electrochemical sensor based on a glassy carbon electrode modified with a gold solution and arenediazonium tosylate (Ar/GGCE) for the detection and quantification of amikacin upon its release from implants. Atomic force microscopy, cyclic voltammetry, and square-wave voltammetry were used to demonstrate that the use of a gold solution and arenediazonium tosylate for the surface modification of a glassy carbon electrode significantly enhances the electrode characteristics. The determination of amikacin was achieved using square wave voltammetry, which enabled the detection of amikacin at the Ar/GGCE in the concentration range 0.2–60 μM and ensured a limit of detection of 0.058 μM for amikacin released from implants.