Analytical Letters

Shi, Shengyang; Wen, Luhong; Hu, Shundi; Chen, La; Qiao, Juanjuan; Hong, Huanhuan

doi: 10.1080/00032719.2023.2180016pmid: N/A

Abstract Ambient ionization mass spectrometry (AIMS) is an emerging onsite rapid detection technique that has been applied in the area of public security. AIMS measurements of samples with complex matrices are characterized by poor reproducibility and complexity. Low reproducibility and complex background cause imprecise screening for trace drugs in hair. In this work, a rapid screening method of methamphetamine in hair is proposed. Firstly, the generalized weighted robust principal component analysis (GWRPCA) algorithm is used to remove background and extract the analytical signals. The similarity scores between the analytical signals and standard mass spectrum of methamphetamine were calculated based upon an improved Pearson’s correlation coefficient combined with the preset matching threshold to achieve rapid screening of methamphetamine in hair. The results show that this method accurately screens for this drug hair and identifies actual false positives with 100% accuracy when the analyte threshold was 0.1 ng/mg and the matching threshold was 0.6. This study provides technical support for the rapid screening for drug abuse by AIMS.

Nakhostin-Allaf, Farhad; Eskandari, Habibollah; Shamkhali, Amir Nasser; Heydari, Amir

doi: 10.1080/00032719.2023.2180014pmid: N/A

Abstract Two new methods were developed for sub-nanomolar electrochemical detection of orange II and sulfasalazine. A hydrated Ni(OH)2/Fe3O4 phase was prepared in situ and used for enrichment of orange II and sulfasalazine. Thereafter, the nanosorbent phase was washed with the acidic solutions to release orange II and sulfasalazine before detection by adsorptive differential pulse voltammetry on a Pt electrode modified by carboxyl functionalized multi-walled carbon nanotubes and adsorptive square wave voltammetry on a glassy carbon electrode modified by freshly prepared gold nanoparticles/carboxyl functionalized multiwalled carbon nanotubes composite, respectively. The enrichment-detection methods provided limits of detection of 0.29 and 0.49 nmol L−1 for orange II and sulfasalazine, respectively. The linear working ranges for orange II and sulfasalazine were 0.5–10 and 5–80 nmol L−1. Also, the selectivity of the methods was investigated. No significant interferences were observed. The methods were successfully applied on the determination of orange II and sulfasalazine in food, tablets, urine, soil, and water samples. Furthermore, density functional theory was used to predict the most stable structures of the orange II and sulfasalazine complexes with the hydrated nickel hydroxide. In addition, experiments showed that the Sips isotherm was the most suitable for describing the adsorption of sulfasalazine by the nanosorbent.

Svalova, Tatiana S.; Malysheva, Natalia N.; Zaidullina, Regina A.; Medvedeva, Margarita V.; Mazur, Alena V.; Morshchinin, Ivan V.; Kozitsina, Alisa N.

doi: 10.1080/00032719.2023.2180015pmid: N/A

Abstract A novel electrochemical sensing platform based on Fe3O4-antibody conjugate was developed for the rapid and sensitive determination of Salmonella typhimurium antigen in model suspensions. The conjugates Fe3O4-antibody were synthesized via carbodiimide cross-linking and characterized by infrared spectroscopy and cyclic voltammetry. The electrochemical properties of Fe3O4 magnetic nanoparticles in water were investigated; the possible mechanism of direct electrochemical reduction was proposed and justified as an analytical signal. The design of an electrochemical sensing platform with magnetically controlled flows has been proposed. Under the most appropriate conditions, the developed portable device was provided the linear response as I (µA) = (7.20 ± 0.35) × (–lg CAg) − (23.77 ± 1.95) in the concentration range 1 × 10−7–1 × 10−4 mg/mL. The detection limit was 390 ng/mL and was comparable to other works.

Al Rashed, Nasser; Gerlach, Christoph; Guenther, Klaus

doi: 10.1080/00032719.2023.2180018pmid: N/A

Abstract Nonylphenols (NPs) are a degradation product of nonylphenol ethoxylate surfactants, which occur in many samples from the environment, food, and human organism. NPs are persistent and toxic and exhibit estrogenic activity. One of the challenges in understanding the estrogenic effects of NPs is the large number of isomers that may exist in different samples. After analyzing selected foods from different countries by high-performance liquid chromatography coupled with tandem mass spectrometry, NPs were detected in 8 of the 12 food samples. The concentration of NPs, based on fresh weight, ranged from 0.5 to 18.9 μg kg−1. The highest NP contents were found in coffee samples, and therefore an isomer-specific analysis was carried out by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS). Fourteen pure isomers of NP were used as standards for cross-referencing the NP isomers. We identified the two main NP isomers in the coffee samples as 4-[3-ethyl-1,1-dimethylpentyl]-phenol and 4-[1-ethyl-1,3-dimethylpentyl]-phenol or NP128 and NP111 (Juelich nomenclature), respectively. The GCxGC-TOF-MS system with a liquid nitrogen cryogenic modulator used in this study is suitable for the isomer-specific analysis of NP and can be applied and further optimized for future routine analysis in food control.

Yu, Banglin; Hu, Jun; Yang, Lin; Ye, Changwen; Zhu, Beibei; Li, Dong; Jiang, Chenxi; Xue, Fang; Huang, Kuo

doi: 10.1080/00032719.2023.2180017pmid: N/A

Abstract This study isolated two dominant molds (Penicillium chrysogenum and Aspergillus sydowii) from cigar tobacco leaves. Gas chromatography–ion mobility spectrometry (GC–IMS) was used for rapid qualitative and semi-quantitative analysis of mold growing from 0 to 7 days on potato dextrose agar (PDA). GC–IMS fingerprint, galleryplot, one-way analysis of variance (ANOVA), and partial least squares – discriminant analysis (PLS-DA) were used to assess different periods of cigar tobacco mildew. ANOVA and PLS-DA were compared to identify possible mildew markers in PDA. The potential mildew markers were verified using 0–7 days of artificial mildew samples. The results showed that 1-octene-3-alcohol, 1-pentanol, and pentanal were characteristic markers of early mildew in cigar tobacco. In conclusion, GC–IMS and chemometrics enables early warning of cigar tobacco mold, which is of great significance for storage and quality control.

Jiao, Long; Sun, Chengyu; Yan, Naying; Yan, Chunhua; Qu, Le; Wang, Qin; Zhang, Shengrui; Ma, Ling

doi: 10.1080/00032719.2023.2180515pmid: N/A

Abstract A method for discriminating Salvia miltiorrhiza from different geographical origins was developed using laser-induced breakdown spectroscopy (LIBS) with convolutional neural network (CNN). The LIBS spectra of Salvia miltiorrhiza samples from six geographical locations were preprocessed with the maximum minimum normalization method. The classification model for discriminating these samples was developed by using a one-dimensional convolutional neural network. The discrimination accuracy of the developed CNN model reached 97.09%. Compared with support vector machine and k-nearest neighbor methods, the CNN model showed higher discrimination accuracy. The results demonstrate that the combination of LIBS and CNN is suitable for discriminating Salvia miltiorrhiza from different geographical locations.

Nasereddin, Jehad; Shakib, Mohammad

doi: 10.1080/00032719.2023.2180516pmid: N/A

Abstract Fourier transform infrared spectroscopy (FTIR) is one of the techniques most commonly employed in material characterization and identification. However, software licensing and proprietary file format limitations are commonly encountered hindrances when analyzing FTIR data. Spectrometers are generally provided with a license for a single copy of the operation/analysis software to run the machine, with additional copies requiring the purchase of software licenses. Furthermore, incompatibility between file formats across different spectrometers and spectral analysis software dictates additional limitations on analysts wishing to characterize spectra generated by devices incompatible with their software. This communication reports on the development of a free and open-source FTIR peak detection software, at the center of which is an in-house developed peak detection algorithm implemented in JavaScript (JS).

Zhang, Jie; Fu, Yulin; Li, Lin; Yan, Liqiang; Wu, Xiongzhi; Lei, Chenghong

doi: 10.1080/00032719.2023.2180644pmid: N/A

Abstract Ascorbic acid (AA) determination is of high importance in the diagnosis and treatment of diseases. Herein, we report a new ratiometric electrochemical sensor for ascorbic acid using a glassy carbon electrode (GCE) modified with a copper nanoparticle@resin nanosphere nanocomposite (CuNPs@RNS). The ratiometric strategy was established by immobilizing an internal reference (thionine) on the modified electrode using cyclic voltammetry (CV). The performance of the modified electrodes as well as the newly established ratiometric strategy was explored. The sensing platform had good electrocatalytic ability, reproducibility, and stability. In addition, the ratiometric strategy significantly improved the performance of electrochemical sensing with a wide linear range (0.0837 to 15.5 μM) and a low detection limit of 0.0279 μM under the optimal conditions. The original ratiometric electrochemical sensor was successfully applied to monitor ascorbic acid in tablets and urine. These results showed that the sensor provides a new strategy and broad prospects for biomolecular sensing with reliability and high sensitivity.

Guan, Yanan; Zu, Yueyue; Ma, Pengyi; Li, Shutao; Ma, Qi; Song, Jinping; Guo, Yong

doi: 10.1080/00032719.2023.2180802pmid: N/A

Abstract Tungsten and nitrogen co-doped carbon dots (W, N-CDs) with a high quantum yield of 51.08% were synthesized by a facile hydrothermal process. Doping of tungsten effectively enhanced luminescent properties of the carbon dots, and the quantum yield was increased by 10.3%. The surface composition and morphology of the synthesized W, N-CDs were characterized. W, N-CDs were employed as nanoprobes to develop a sensor for the selective and sensitive determination of Hg2+ and captopril. Under the optimal conditions, the linear response range for Hg2+ and captopril were 0.125 to 9.0 μM and 0.5 to 10 μM with detection limits of 40 nM and 300 nM, respectively. The developed sensor was successfully applied for the determination of Hg2+ in water and captopril in urine with recoveries from 95.50 to 105.50% and 96.33 to 105.13%, which demonstrates suitable accuracy and reliability. The fluorescence mechanisms of W, N-CDs toward Hg2+ and captopril were also evaluated.

Zhao, Yimeng; Lv, Xuefei; Peng, Zhao; Zhao, Kexin; Zhou, Di; Deng, Yulin

doi: 10.1080/00032719.2023.2180803pmid: N/A

Abstract Abnormally expressed miRNAs have been employed as crucial indicators for the diagnosis and prognosis of disease. It is essential to develop quick, affordable, accurate, and multiplexed methods for miRNA detection. In this study, polyethylene glycol (PEG) hydrogel microparticles were used as solid-phase carriers for the hybridization chain reaction (HCR) in combination with cation-exchange fluorescence amplification, thus enabling the development of a new method for miRNA determination. The assay was sensitive with the detection limit for miRNA let7a equal to 46 pM. The assay was specific, the base-mismatched sequences of miRNA let7a were distinguished, and the serum matrix did not cause any interference. Moreover, by integration with a microfluidic chip, the throughput was significantly enhanced and the process was noticeably simplified. With further development, the developed method may be suitable for practical clinical analysis.