#### Analytical Letters

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ISSN / EISSN : 0003-2719 / 1532-236X
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Magadima Mary Thosago, , Abayneh Ataro Ambushe, Taddese Wondimu Godeto
Published: 16 May 2022
Analytical Letters pp 1-16; https://doi.org/10.1080/00032719.2022.2075883

Abstract:
A method was developed for arsenic speciation of South African wheat flour by microwave-assisted extraction with ion chromatography (IC) separation and detection with high resolution inductively coupled plasma–mass spectrometry (IC-HR-ICP-MS). Method optimization included development of the extraction and elution methods for baseline separation of the As-species in the samples. The As-species were successfully extracted using deionized water and baseline separation was attained using a gradient elution method with 0.5 mM HNO3 (pH 3.4) and 50 mM HNO3 (pH 1.4). Method validation parameters, including trueness (bias), precision, linearity, limit of detection (LOD), limit of quantification (LOQ) and selectivity were evaluated to assess the quality of the results. Three certified reference materials (CRMs), NIST SRM 1568b (rice flour), NMIJ CRM 7533-a (brown rice flour), and ERM BC211 (brown rice flour) were used to evaluate the trueness of the developed method. Low limits of detection and quantification were achieved (0.3 to 2.6 pg g−1 and 1.1 to 8.6 pg g−1, respectively) for the As-species. The dominant peaks in the wheat flour were arsenite (As(III)), dimethyl arsenic acid (DMA), and arsenate (As(V)). The concentrations of the inorganic (iAs), i.e., As(III) and As(V) in the wheat flour were very low from 6.8 to 17.8 ng g−1, with a relative expanded uncertainty ( $U$) of <6.9% ( $k$=2), which is below the permissible level of iAs in food and food products proposed by the World Health Organization (WHO).
Chang Liu, Ruyuan Wang, Peihua Wang, Yifan Yu,
Published: 14 May 2022
Analytical Letters pp 1-14; https://doi.org/10.1080/00032719.2022.2075374

Abstract:
A chemiluminescence (CL) nanosensing platform was constructed by using reduced graphene oxide (rGO) as the carrier, which was loaded with N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as the signaling molecule, hemin as the catalyst, and glucose oxidase (GOx) as the enzyme. The loading efficiency of GOx was determined to be 0.64 mg GOx/mg rGO. The nanosensing platform achieved one-step determination of glucose without pre-incubation steps. When glucose is added to the CL nanosensing platform, the GOx on the nanocomposite catalyzes the reaction between glucose and O2 to produce H2O2 which oxidizes ABEI to emit light with the catalysis of hemin. When glucose was mixed with the nanocomposite, a growth-type CL profile was observed and the maximum signal was obtained approximately 6 min after the addition of glucose to the nanocomposite. The CL nanosensing platform exhibited a linear enhanced response for glucose from 10 μM to 1 mM. The detection limit for glucose was 2.6 μM. The proposed glucose CL sensing platform also exhibited good selectivity and specificity. Furthermore, it was successfully applied in the determination of glucose in serum, and satisfactory recoveries were obtained, signifying its potential in clinical diagnosis.
Qin Luo, Zhenping Gao, Qinni Xiao,
Published: 13 May 2022
Analytical Letters pp 1-10; https://doi.org/10.1080/00032719.2022.2076108

Abstract:
Alkaline phosphatase (ALP) is a significant biomarker of diseases, such as osteoblastic bone cancer, hepatitis, and myeloma, and hence its determination is essential and important. MnO2/Mn2+ conversion-based magnetic relaxation sensing was developed to directly determine ALP in blood. In the presence of ALP, 2-phospho-L-ascorbic acid trisodium salt was catalyzed to produce ascorbic acid (AA), which reduced MnO2 to Mn2+, causing transverse relaxation time (T2) decay. A linear relationship of ALP from 5 mU·L−1 to 500 mU·L−1 with T2 signal and a low limit of detection (LOD) of 3.32 mU·L−1 were obtained using the optimized conditions of 200 µM of ascorbic acid-phosphate (AAP), 10 µg·mL−1 of MnO2, 37 °C, pH 7.4, and a 30 min reaction time. When directly measuring ALP in serum with the proposed method, the recoveries were from 99.2% to 101.3%, in accordance with values obtained by a commercial assay. In conclusion, a sensitive one-step method for ALP in complex samples was established which has potential for clinical applications.
Mihai M. Rusu, Cristian Vilau, Cristian Dudescu, Petru Pascuta, ,
Published: 13 May 2022
Abstract:
Designing of new cement-based materials, suitable for three-dimensional printing applications, requires accurate control of the porosity and strength development. This goal may be achieved by introducing the so-called accelerators in the cement mixture. One such accelerator, used in many commercial products, is calcium nitrate. In the present work, the effect of calcium nitrate on the kinetics of pore evolution and strength development was investigated using low-field nuclear magnetic resonance relaxometry and compressive tests. The presence of calcium nitrate in cement paste accelerates the hydration dynamics immediately after mixing but does not significantly affect the pore structure. Moreover, the presence of calcium nitrate increases the compressive strength at 7 days compared with the simple cement paste but the same compressive strength was reached following 28 days of hydration.
Published: 13 May 2022
Analytical Letters pp 1-18; https://doi.org/10.1080/00032719.2022.2067863

Abstract:
A fast, selective and sensitive magnetic dispersive solid-phase extraction (SPE) method is presented for the first time for simultaneous preconcentration of ultra-trace levels of cobalt (II) and chromium (III) before their quantification by flame atomic absorption spectrometry (FAAS). Urea-formaldehyde polymer/magnetite nanoparticles (UFP/MNPs) were used as adsorbents. The prepared nano-adsorbent was assessed by x-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The excellent magnetic properties of the prepared adsorbent promote rapid isolation of the analytes. A comprehensive study was performed on the extraction conditions and optimal levels of effective parameters were determined. Using the optimum conditions, linear dynamic ranges of 0.8–150 and 0.3-80 μg L−1 were obtained for cobalt (II) and chromium (III), respectively. The limits of detection were 0.2 and 0.09 µg L−1 for cobalt (II) and chromium (III). Intra-day and inter-day relative standard deviations (RSDs) were 3.8% and 5.7%, respectively. Adsorption isotherms were investigated and high adsorption capacities were obtained for the metal ions. The developed method managed to extract and quantify the analytes from unspiked and spiked environmental water samples from the Caspian Sea, Ardabil Balighli Chay River, and Ardabil tap water. The recoveries and relative standard deviations for the samples were from 98.2 to 103% and 0.2 to 5.7%, respectively. The results were validated by comparison with inductively coupled plasma – optical emission spectroscopy (ICP-OES) measurements.
Ekrem Güllüce, Taha Yasin Koç, Medine Güllüce,
Published: 13 May 2022
Analytical Letters pp 1-11; https://doi.org/10.1080/00032719.2022.2073365

Abstract:
Biosorption was carried out using Fraxinus excelsior L. (Oleaceae) (FEO) as a natural waste to remove methylene blue from aqueous solutions. Based on the results of the study carried out under optimum conditions (pH: 6, initial dye concentration: 5 mg/L, biosorbent dose: 1 g, contact time: 30 min, stirring speed: 150 rpm, and temperature: 298 K), the FEO biosorbent removed 89% of methylene blue from aqueous solutions. In addition, parameters affecting biosorption (pH, initial dye concentration, biosorbent dose, temperature, and stirring speed) were examined, and isotherm, kinetic, and thermodynamic studies were performed. Freundlich, Langmuir, Elovich, Temkin, and Dubinin–Radushkevich isotherms were calculated in the isotherm studies, and the Freundlich isotherm was higher than the others. The correlation coefficient of pseudo-second-order kinetic model was higher than for the pseudo-first-order kinetic model. The ΔG values from the thermodynamic studies showed that the process occurred spontaneously. Consequently, the FEO biosorbent is suitable in removing synthetic dyes from aqueous solutions due to its effectiveness, low cost, and eco-friendly characteristics.
Shuangmin Wu, Wei Shen, Yushuang Chen, Yongli Zhu, Ren Hou, Menghong Dai,
Published: 11 May 2022
Analytical Letters pp 1-14; https://doi.org/10.1080/00032719.2022.2072857

Abstract:
Cephalexin (CFE) residues in animal-derived food and its deleterious effects on human health has attracted extensive attention. In this study, a specific anti-cephalexin monoclonal antibody (mAb) was used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) with a half-maximal inhibitory concentration (IC50) of 1.83 µg/L that was suitable for the determination of cephalexin in animal-derived foods. The limit of detection (LOD) and limit of quantitation (LOQ) for cephalexin were from 0.44 to 0.58 µg/kg and 0.57 to 0.67 µg/kg, respectively. The recovery was from 90.1 to 103.6% with coefficients of variation (CV) less than 10.0%. In addition, the established ELISA method and high-performance liquid chromatography – mass spectrometry (HPLC-MS/MS) were used to analyze the samples with good correlation between the results. The results show that the established ic-ELISA is suitable for the determination of cephalexin in animal-derived food.
Jaber Adam, Maria Rosaria Del Sorbo, Jasneet Kaur, Rocco Romano, Manjot Singh, ,
Published: 11 May 2022
Analytical Letters pp 1-15; https://doi.org/10.1080/00032719.2022.2070186

Abstract:
The interaction between two-dimensional nanoflakes and bacteria in water-based physiological liquids is a hot topic that unveils new types of phenomena and is fundamental to bioscience applications. In this work, we extend Derjaguin, Landau, Verwey, and Overbeek theory (DLVO theory) that describes the properties of nano-objects in solutions, to the case of two-dimensional nanoflakes interacting with bacteria cell membranes, both for Gram-positive and Gram-negative bacteria. We have studied the role of the bacterial shape, membrane potential, and two-dimensional nanomaterials nature showing the interplay of these parameters in determining whether the interactions are attractive or repulsive and whether electrostatic or van der Waals forces are dominant. We calculated the interaction distances at equilibrium for different bacterial species and hydrophobic nanomaterials such as $MoS2$ in two environmentally friendly solvents, water and cyrene.
Quanfang Lu, Yan Feng, Hui Luo, , Yuejing Kang
Published: 8 May 2022
Analytical Letters pp 1-14; https://doi.org/10.1080/00032719.2022.2072856

Abstract:
A miniature atomic emission spectrometry (AES) was developed using a liquid cathode glow discharge (LCGD) as an excitation source and optical fiber spectrometer as the detection system. The instrument was employed for the sensitive determination of lithium (Li). The addition of 0.15% cetyltrimethylammonium chloride (CTAC), 0.15% cetyltrimethylammonium bromide (CTAB) and 3 critical micelle concentration (CMC) Triton X-405 enhanced the Li emission by 3.7-, 3.2-, and 1.8-fold, respectively. The presence of 50 mg L−1 Al3+ and SO42− inhibited the recovery of 0.5 mg L−1 Li about 73% and 75%, respectively. After adding CTAB, CTAC, and Triton X-405, the recovery of Li was from 98% to 108%, suggesting that the addition of surfactant eliminated the Al3+ and SO42− interferences. The sensitivity of Li was improved by adding the surfactants by factors of 2.3 for 0.15% CTAB, 2.0 for 0.15% CTAC, and 1.9 for 3 CMC Triton X-405. The limit of detection (LOD) with 0.15% CTAB for Li was 0.55 μg L−1 which was improved by 5.6-fold. In addition, the energy consumption was below 60 W and good precision was obtained. The accuracy, reliability, and repeatability of the proposed method were verified by analysis of water samples and satisfactory recoveries between 91% and 115% were obtained. The results demonstrate that LCGD-AES with surfactants can be used for highly sensitive determination of Li in complex samples because of its low cost, small size, and low power consumption.
Zeyi Yue, Zifang Peng, Yun Guo,
Published: 5 May 2022
Analytical Letters pp 1-12; https://doi.org/10.1080/00032719.2022.2071433

Abstract:
A covalent triazine-triphenyl polymer (CTPCC-TP) was examined as a novel column packing material for high-performance liquid chromatography (HPLC). The separation performance of CTPCC-TP was characterized using anilines as the analytes in reverse-phase (RP) and normal-phase (NP) modes. Various retention mechanisms, such as hydrogen-bonding, π-π, and hydrophobic-hydrophobic interactions, endowed CTPCC-TP with a hydrophilic-hydrophobic balance performance, demonstrating promise for applications as a stationary phase for HPLC in normal-phase and reversed-phase. The CTPCC-TP column showed good reproducibility with relative standard deviations from 0.28 to 0.93%, 1.73 to 3.12%, 1.57 to 3.69%, and 1.36 to 2.54% for retention time, peak height, peak area, and peak width at half maximum, respectively. In the normal and reverse phase modes, a thermodynamically spontaneous transfer process is demonstrated through negative ΔG values controlled by negative ΔH and ΔS values during the chromatographic separation. Excellent chemical and solvent stabilities, and the hydrophilic-hydrophobic balance performance make CTPCC-TP a good candidate for use in HPLC.