Needle-Trap Device (NTD) Packed with Reduced Graphene Oxide (rGO) for Sample Preparation Prior to the Determination of Polycyclic Aromatic Hydrocarbons (PAHs) from Aqueous Samples by Gas Chromatography–Mass spectrometry (GC-MS)Kędziora-Koch, Kamila; Rykowska, Iwona; Wasiak, Wiesław
doi: 10.1080/00032719.2018.1563792pmid: N/A
AbstractA needle trap device (NTD) was developed for the extraction of polycyclic aromatic hydrocarbons (PAHs) from liquid samples followed by determination by gas chromatography–mass spectrometry (GC-MS). The extraction was performed using the dynamic sampling approach, in which a liquid sample was pumped through the system. Due to the flexibility and softness of graphene, its application in NTD may be difficult. Herein, the effectiveness of reduced graphene oxide (rGO) packed in NTD in dynamic extraction of PAHs was evaluated. Several experimental parameters, such as the adsorbent mass, eluent type and its volume, as well as the sample volume were optimized to achieve satisfactory performance for dynamic extraction. Comparative studies showed that the extraction performance of rGO-NTD was better than using NTDs packed with other sorbents such as activated carbon. The recovery rate for reduced graphene oxide exceeded 92%. Comparison of dynamic and headspace sampling showed comparable results but the dynamic mode is more suitable for field measurements. The recovery rates of PAHs spiked in water samples were from 76.5 to 100.2% and the relative standard deviation values were from 2.7 to 7.5% under the optimal conditions. This work reveals the potential of NTD with a graphene-based material for sample preparation before chromatographic analysis of liquid samples.
Determination of Ultra-Trace Platinum, Palladium, Ruthenium, Rhodium, and Iridium in Rocks and Minerals by Inductively Coupled–Plasma Mass Spectrometry Following Nickel Sulfide Fire Assay Preconcentration and Open Mixed Acid DigestionNi, Wenshan; Mao, Xiangju; Zhang, Hongli
doi: 10.1080/00032719.2019.1566348pmid: N/A
AbstractPlatinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), and osmiun (Os) are platinum-group elements with similar physic-chemical properties, and have important applications in geochemistry and environmental chemistry. However, due to their low abundance and inhomogeneous distribution in natural ores as well as the nugget effect, the accurate determination of the platinum-group elements has been a challenge for geological analysis. In this work, self-prepared and purified sodium carbonate (NiCO3) instead of commercial nickel oxide (NiO) was used as the fire assay collector in order to greatly reduce the reagent blank and method detection limits. In addition, the fuming time of HClO4 was strictly controlled at 10 min and a high sensitive method was developed for the simultaneous determination of ultra-trace Pt, Pd, Ru, Rh, and Ir in minerals by inductively coupled plasma-mass spectrometry (ICP-MS) following preconcentration with the nickel sulfide fire assay. Under the optimized conditions, the linear ranges of Pt, Pd, Ru, Rh, and Ir were between 0 and 100 ng mL−1, with correlation coefficients exceeding 0.9997. The detection limits were 0.015, 0.056, 0.014, 0.004, 0.012 ng mL−1 (for 10 g sample) for Pt, Pd, Ru, Rh and Ir, respectively. The developed method was successfully applied to analyze Chinese Certified Reference Materials (CRMs) GBW07288, GBW07289, GBW07290, GBW07291, GBW07292, GBW07293, GBW07294, GBW07101, GBW07102 and GBW07201 and the determined values were in good agreement with the certified values. The relative standard deviations (n = 5) of Pt, Pd, Ru, Rh and Ir were between 3.42% and 6.87% for the determination of GBW07291.
N, S Co-Doped Carbon Quantum Dots for the Selective and Sensitive Fluorescent Determination of N-Acetyl-l-Cysteine in Pharmaceutical Products and UrineLi, Yingping; Hu, Yue; Jia, Yong; Jiang, Xiaohui; Cheng, Zhengjun
doi: 10.1080/00032719.2019.1566349pmid: N/A
AbstractTo design a probe with “turn-on” sensing, nitrogen and sulfur co-doped carbon quantum dots (N, S-CQDs) were prepared and screened against some metallic cations to first induce “turn-off” fluorescence. The ferric iron (Fe3+) was shown to be the most responsive and effective in the fluorescence quenching of the N, S-CQDs based on a proposed photo-induced electron transfer mechanism. In addition, the fluorescence of N, S-CQDs-Fe3+ system was well recovered using N-acetyl-l-cysteine (NAC) (turn-on) due to a redox reaction, suggesting that the N, S-CQDs-Fe3+ system acts as a highly sensitive and selective sensor for the determination of N-acetyl-l-cysteine with a low limit of detection equal to 65.0 nmol/L and wide linear ranges from 0.67 to 25.56 and 25.56 to 193.55 μmol/L. The “turn-off/on” fluorescence method was successfully employed to monitor N-acetyl-l-cysteine in pharmaceutical products and human urine samples with a recovery range from 99.2 to 101.3%. In addition, the fluorescence switch properties of the nitrogen and sulfur co-doped carbon quantum dots were also investigated by alternate additions of Fe3+ and N-acetyl-l-cysteine.
Near-Infrared Spectroscopy Analytical Model Using Ensemble Partial Least Squares RegressionLuo, Na; Han, Ping; Wang, Shifang; Wang, Dong; Zhao, Chunjiang
doi: 10.1080/00032719.2019.1568447pmid: N/A
AbstractA novel ensemble-based feature selection method was developed which is designated as ensemble partial least squares regression coeffientents (EPRC). It was composed of two steps: generating a series of different single feature selectors and aggregating them to reach a consensus. Specifically, the bootstrap resampling approach was used to generate a diversity of single feature selectors, and the absolute values of the regression coefficients of the partial least squares (PLS) model were used to rank the features. Next, these feature rankings out of single feature selectors were aggregated by the weighted-sum approach. Finally, coupled with the regression model, the features selected by EPRC were evaluated through cross validation and an independent test set. By experiments of constructing the spectroscopy analysis model on three near infrared spectroscopy (NIRS) datasets, it was shown that the EPRC located key wavelengths, gave a promotion to regression performance, and was more stable and interpretable to the domain experts.
Electrochemical Determination of Lead(II) in Environmental Waters Using a Sulfydryl Modified Covalent Organic Framework by Square Wave Anodic Stripping Voltammetry (SWASV)Wang, Rongyu; Ji, Wenhua; Huang, Luqi; Guo, Lanping; Wang, Xiao
doi: 10.1080/00032719.2019.1568448pmid: N/A
AbstractA novel sulfhydryl-modified covalent organic framework was designed for the selective determination of lead(II) using square wave anodic stripping voltammetry. The introduction of sulfhydryl groups enhanced the selectivity and sensitivity of the covalent organic framework for analytes. The sulfhydryl-modified covalent organic framework was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Under the optimized conditions, a sulfhydryl-modified covalent organic framework/gold electrode was successfully used for the determination of lead(II) in water samples. The newly developed square wave anodic stripping voltammetry method exhibited wide linearity (0.05 to 20 ng mL−1, r = 0.991), a low limit of detection (0.015 ng mL−1) and good precision, with a relative standard deviation values <5.1%. The limit of detection was lower than 10 ng mL−1, the level of lead(II) in drinking water permitted by the World Health Organization. The recoveries of three spiked samples ranged from 90.0% to 104.0%, with relative standard deviations <4.9%. Satisfactory reproducibility and good repeatability demonstrated that the newly developed method is very suitable for the detection of lead(II) in real water samples, with significant advantages over existing methods.
Determination of β-Agonists in Porcine Urine by Molecularly Imprinted Polymer Based ChemiluminescenceXu, Ming Xin; Li Zhao, Wei; Liu, Jing; He, Tong; Huang, Jing Jie; Ping Wang, Jian
doi: 10.1080/00032719.2019.1569019pmid: N/A
AbstractIsoprenaline was used as the template to synthesize a molecularly imprinted polymer that was able to simultaneously recognize ten β-agonists. The simulation showed that the three-dimensional conformation of the template was the main factor responsible for the polymer’s recognition. The polymer particles were coated in the wells of a conventional microplate as the recognition reagent to prepare a chemiluminescence sensor. The light signal was initiated with a highly effective bis(2,4,6-trichlorophenyl) oxalate-H2O2-imidazole system. The assay contained only one sample-loading step followed by immediate data acquisition, so one measurement was complete within 12 min. The sensor was used to determine the ten analytes in porcine urine. The results showed that the senor achieved ultrahigh sensitivity, with limits of detection from 2.0 to 7.0 pg/mL, high recoveries from 78.6% to 99.4%, and satisfactory recycle performance up to seven times. This is the first study reporting a molecularly imprinted polymer based microtiter chemiluminescence sensor for the determination of β-agonists.
Isolation and Determination of Beta-Carotene in Carrots by Magnetic Chitosan Beta-Cyclodextrin Extraction and High-Performance Liquid Chromatography (HPLC)Dai, Yunliang; Row, Kyung Ho
doi: 10.1080/00032719.2019.1570245pmid: N/A
AbstractBeta-carotene is a carotenoid with strong antioxidant activity that has been used in many areas and attracted significant attention. Among the articles reported, however, there are few examples of the convenient and eco-friendly use of magnetic chitosan biopolymers to extract beta-carotene. This paper reports the ultrasonic-assisted solid phase extraction of beta-carotene. The beta-carotene in carrot samples was extracted using synthesized magnetic chitosan beta-cyclodextrin biopolymers prior to high-performance liquid chromatography (HPLC) detection. Under the optimal conditions, the beta-carotene content of carrot was found to be 41.06 ± 0.02 μg/g. This newly developed method using magnetic chitosan cyclodextrin biopolymers is a promising method for the ultrasonic-assisted solid phase extraction of carotenoids from vegetables because the procedure is facile and rapid and the magnetic biopolymers can be removed using simple process.