Analytical Letters

Zhu, Qiyong; Tian, Dong; Guo, Wei; He, Jiahao

doi: 10.1080/00032719.2021.1991365pmid: N/A

Abstract G-quadruplex/hemin (GQH) is a mimicking enzyme, which has good catalytic performance and high stability for hydrogen peroxide decomposition. A new chemiluminescence (CL) method has been developed for H2O2 and Ag+ based on the GQH catalyzed CL reaction between luminol and H2O2. The silver ions react with GQH, causing the decomposition of GQH and the loss of catalytic activity. The catalytic system has been characterized by CL, absorption spectroscopy, and circular dichroism (CD). Under the optimal conditions, there were wide linear ranges between the CL intensity and the concentrations of H2O2/Ag+. The CL increases linearly from 0.1 μM to 3 mM for H2O2 and decreases linearly from 10 nM to 2 μM for Ag+. The limits of detection are 0.03 μM and 3.33 nM for H2O2 and Ag+, respectively. This method has been used for real sample analysis with satisfactory results.

Silva, Arlene Santos; Brandão, Geovani Cardoso; Ferreira, Sergio Luis Costa; dos Santos, Ana Maria Pinto

doi: 10.1080/00032719.2021.1991941pmid: N/A

Abstract Here is reported an analytical method for the multielemental determination of Cd, Fe and Ni in toothpaste employing slurry sampling high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ET AAS). Using a single sample aliquot, Cd was determined at 228.802 nm, and, sequentially, Fe (232.036 nm) and Ni (232.003 nm) were simultaneously determined. Pyrolysis and atomization temperatures were 800 and 1500 °C for Cd, respectively. An atomization temperature of 2600 °C was used for Fe and Ni. A Pd and Mg mixture was used as the chemical modifier for standards and samples. The procedure for the slurry preparation was optimized using multivariate methodology with a multiple response function while employing a sample mass of about 250 mg. The optimized conditions were: 0.8 mol L−1 HNO3, 0.5% (m/v) Triton X-100 and a sonication time of 15 min. Using aqueous standards for the calibration, limits of detection and quantification were of 3.2 and 10.8 ng g−1 for Cd, 2.2 and 7.4 µg g−1 for Fe, and 0.044 and 0.148 µg g−1 for Ni. The precision estimated as relative standard deviation (n = 5) was 6.1% for Cd, 3.5% for Fe and 4.4% for Ni. The method accuracy was evaluated by standard addition and recovery tests and the recoveries varied from 93 to 114%. The method was applied for the analysis of five toothpaste samples of different brands. The concentrations ranged from 52.0 to 73.6 µg g−1 for Fe, and < 0.148 to 0.227 µg g−1 for Ni. For Cd, the concentrations were below the limit of detection.

Zhang, Bing; Qu, Cuilan; Pang, Liyan; Chen, Weijian; Tan, Lei; Zhang, Yang; Qian, Cheng; Dai, Jianxiong

doi: 10.1080/00032719.2021.1992416pmid: N/A

Abstract The rapid determination of cadmium in solid rice and wheat samples was carried out using plasma jet spectroscopy. This technology is based on the atomic emission spectrometry (AES) with a plasma jet (PJ-AES). The performance of PJ-AES for the determination of Cd in rice and wheat samples was systematically investigated, including the linear range and sensitivity. The linear regression relationships for Cd in rice and wheat were y = 7659.496x + 4933.642 with R 2 = 0.987 and y = 10844.734x + 7815.255 with R2 = 0.984, respectively. The linear range was from 0.03 to 1.28 mg/kg. The detection limits were 0.0071 and 0.0078 mg/kg. This method has the advantages of speed, which is reflected in its sample preparation time of only 7.5 min, while the preparation times for AAS and ICP-MS are 3 and 2 h. The developed method offers simple sample processing, small size, low cost, and accurate analysis, while being economical and efficient.

Chen, Hui; Feng, Meiqin; Li, Jing; Lu, Jie; Gu, Haiyang; Chen, Junhong; He, Shihang; Qi, Xingpu; Chen, Wenjun; Chen, Tong

doi: 10.1080/00032719.2021.1992417pmid: N/A

Abstract A priori knowledge-incorporating method based on time resolved fluorescence was successfully developed for the determination of polycyclic aromatic hydrocarbons in edible vegetable oils. Specifically, fluorescence decay functions of polycyclic aromatic hydrocarbons at characteristic emission wavelengths were used as the priori models and incorporated into the deep-autoencoder. The priori model-incorporating deep-autoencoder models were shown to be effective for the determination of polycyclic aromatic hydrocarbons in edible vegetable oils and root-mean-square errors of prediction lower than 2% were achieved. The influence of analyte, matrix and proportion of priori model were characterized. Increasing the proportion of priori model appropriately was beneficial to the performance of models and 16% was shown to be the best incorporated proportion.

He, Sile; Tang, Weiyang; Row, Kyung Ho

doi: 10.1080/00032719.2021.1993237pmid: N/A

Abstract A hydrophobic deep eutectic solvent (DES) based vortex-assisted liquid-liquid microextraction (LLME) procedure was developed for the effective and rapid determination of thiophanate-methyl (TM) and carbendazim (CA) in lake water and tap water samples, with an excellence extraction efficiency (recovery: 87.2% to 97.4%, enrichment factor: 87.2 to 97.4). Twelve hydrophobic DESs based on terpenoids and fatty acids/alcohols were prepared, and those with the highest recovery for TM and CA were selected. The main parameters, including assisting methods, molar ratio of DES components, volume of DES, and NaCl content that may affect vortex-assisted LLME, were optimized. The intra-day and inter-day relative standard deviation (RSD) of this method were from 1.7% to 3.8% and 1.8% to 4.1%, showing excellent precision. The proposed method exhibited suitable limits of detection (TM: 0.053 µg/mL; CA: 0.007 µg/mL) and limits of quantification (TM: 0.177 µg/mL; CA: 0.024 µg/mL).

Al-Hinaai, Mohammad; Khudaish, Emad A.

doi: 10.1080/00032719.2021.1993878pmid: N/A

Abstract A surface base polymeric film was fabricated onto a glassy carbon electrode (GCE) via reversible voltammetric scanning in acidic electrolyte containing a (2,4,6-triaminopyrmidine) monomer (TP). The assembled poly(2,4,6-triaminopyrmidine) (PTP) surface material was further modified by electrochemical attachment of tris(2,2'-bipyridine) ruthenium(II) described as Ru(II)-complex. The structure and electrochemical properties of the resulting (Ru-PTP-GCE) surface network were characterized using X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The apparent estimated value of electron transfer rate constant (k app) of the prepared sensor was three times greater than the virgin PTP. The cooperative effects of the (PTP) and Ru(II)-complex composite increased the efficiency and the stability of the proposed sensor for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). The detection limit (DL3σ) of DA in this environment was 0.021 μM. The fabricated sensor was successfully applied for DA detection in a blood serum sample with satisfactory recovery.

Harrington, James M.; Poitras, Eric P.; Weber, Frank X.; Fernando, Reshan A.; Liyanapatirana, Chamindu; Robinson, Veronica G.; Levine, Keith E.; Waidyanatha, Suramya

doi: 10.1080/00032719.2021.1993876pmid: 35571259

Abstract Thallium (Tl) can be released as a byproduct of smelting, mining, and other industries, causing human exposure. There are knowledge gaps on the toxicity of thallium compounds, so the National Toxicology Program is investigating the toxicity of thallium (I) sulfate in rodents. We developed and validated a method to quantitate Tl in rodent plasma and secondary matrices. Primary matrix standards and validation samples were digested with nitric acid and analyzed for Tl by inductively-coupled plasma – mass spectrometry (ICP-MS). Method performance was validated for linearity, accuracy, precision, and other criteria. Calibration was linear from 1.25 to 500 ng Tl/mL plasma; accuracy (RE) was −5.9 to 2.6% for all calibration standards. The lower limit of quantitation (LLOQ) was 1.25 ng Tl/mL plasma, and the limit of detection was 0.0370 ng Tl/mL plasma. Intra- and interday RE and precision (RSD) were −5.6 to −1.7% and ≤0.8% (intraday) and −4.8 to −1.3% and ≤4.3% (interday), respectively, at three sample concentration levels. Standards up to 10.0 x 103 ng/mL could be analyzed by dilution with digested blank matrix, with −6.4% RE and 5.4% RSD. Method was also evaluated in post-natal day 4 (PND4) Hsd:Sprague Dawley SD (HSD) dam and pup plasma, gestation day 18 (GD 18) HSD rat fetal homogenate, HSD rat urine, female HSD rat brain homogenate, female B6C3F1 mouse plasma. Background Tl was detected in control fetal and brain homogenates and urine at < 30% of LLOQ response. Results demonstrate that the method is suitable for determination of Tl in rodent matrices for toxicology studies.

Stoikov, Dmitrii; Ivanov, Alexey; Shurpik, Dmitriy; Stoikov, Ivan; Evtugyn, Gennady

doi: 10.1080/00032719.2021.2000621pmid: N/A

Abstract A flow-through biosensor has been developed and manufactured by 3D printing from poly(lactic acid). Uricase or tyrosinase were immobilized on the inner walls of the reactor cell and the concentrations of the reaction products, i.e., hydrogen peroxide in the case of uricase and quinone product of the tyrosine oxidation in the case of tyrosinase, were monitored in the amperometric mode. The screen-printed electrode modified with carbon black, pillar[5]arene and electropolymerized thionine and methylene blue was separated from the enzyme layer by 0.1 mm gap and used as a biosensor transducer. The components of the modifier layer exerted a synergetic effect and increased the cathodic current up to seven times compared to electrodes modified with individual components, increasing the sensitivity of the analysis. In the optimal conditions, biosensor allowed the determination of 1 × 10−7 to 1 × 10−5 M uric acid and 2 × 10−7 to 1 × 10−5 M tyrosine. The biosensors analyzed spiked samples of blood serum and urine and provided recoveries from 95 to 110%. Easy mounting of the flow-through cell and low cost of the replaceable parts make promising future application of the biosensor for routine clinical assays.

Rihana-Abdallah, Alexa; Li, Zhe; Lanigan, Katherine C.

doi: 10.1080/00032719.2021.2002349pmid: N/A

Abstract The determination of heavy metals in drinking water is an important assessment for quality as well as for the detection of pipeline corrosion. The aim of this research was to develop a simple, low cost, and accurate method based on cloud point extraction for the preconcentration and determination of iron, lead, and cadmium by flame atomic absorption spectrometry (FAAS) when the metal concentration in the sample is below the limit of detection without enrichment. By utilizing both 2,4-diamino-6-phenyl-1,3,5-triazine (DPT) and 3-amino-7-dimethylamino-2-methylphenazine (Neutral Red, NR) as chelating agents, and using Triton X-114 as the surfactant, lead, cadmium, and iron were concentrated in water samples prior to determination. The preconcentration was optimized by varying experimental factors, including the temperature, pH, and the concentrations of the chelating agents and surfactant. Using the optimized conditions, this novel procedure allows the determination of these trace elements with a 20-fold reduction in the detection limit with recoveries as high as 99%. The good reproducibility of the results demonstrates that this method was successfully applied to the determination of iron, lead, and cadmium in water samples by FAAS.

Wei, Cheng; Xiao, Jun; Liu, Sheng; Wang, Zhiwei; Chen, Luchuan; Teng, Wenhao

doi: 10.1080/00032719.2021.2002887pmid: N/A

Abstract Developing simple and effective method for carbohydrate antigen 72-4 (CA72-4) detection is important to achieve the early diagnosis and treat of gastric cancer. In this work, multiwalled carbon nanotubes (MWCNT) were treated with a simple wet-chemistry method to form MWCNT/graphene oxide (MWCNT/GO) core/shell nanohybrids that provide high electron transfer, high dispersibility, and a large surface area to immobilize CA72-4 antibodies (Ab) due to the carboxyl groups on the GO shell. Using ferrocyanide/ferricyanide ([Fe(CN)6]3−/4−) as the signaling probe, a simple, label-free and effective electrochemical immunosensing platform was constructed for CA72-4. Upon optimizing the experimental conditions, the simple MWCNT/GO hybrids-based immunosensor showed desirable sensing including a wide linear range and low detection limit. Furthermore, the reproducibility, selectivity and practical applications demonstrated potential value to determine CA72-4 in clinical applications for diagnosing gastric cancer.