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Results in Analytical Letters: 10,965

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, , Yahui Yue, Shouqian Zhao,
Published: 23 February 2018
Analytical Letters, Volume 51, pp 1122-1146; https://doi.org/10.1080/00032719.2017.1371727

Abstract:
A method was developed to determine rhenium contents in geological samples using multicollector–inductively coupled plasma-mass spectrometry (MC–ICP-MS) and extraction with an ion-exchange resin. Samples were digested in Carius tubes and osmium was converted into volatile OsO4, which was purified by distillation and microdistillation. The purified Os contents and isotopic ratios were determined using negative thermal ionization mass spectrometry. After the distillation of Os, the samples were treated with HF, then 1.2 M HCl, and loaded on ion-exchange resin columns. Re was eluted using 0.75 M HNO3 and directly determined by MC–ICP-MS. This method was validated using a series of reference materials and the analytical Re data are consistent with the literature values. This method precision (relative standard deviation) ranged from 0.8 to 6%. The procedural blank and detection limit (3σ) of Re were 1.1 pg and 0.5 pg/g (for a sample size of 2g), respectively. These results indicate that the proposed method can be applied to determine trace Re in geological samples. Using Carius tube digestion combined with HF desilicification and redissolution, the Re and Os contents found in the soluble and insoluble phases of several reference materials indicated that the distributions of Re and Os were homogeneous and heterogeneous, respectively.
Ungkhana Atikarnsakul, ,
Published: 18 January 2018
Analytical Letters, Volume 51, pp 983-997; https://doi.org/10.1080/00032719.2017.1370596

Abstract:
Electromembrane extraction (EME) is a powerful extraction and preconcentration technique for ionizable species. However, the ionic contents in the sample can influence the extraction efficiency and system stability due to electrolysis. In this work, the electromembrane extraction of chromium(VI) was developed using various levels of ionic samples. 2-Nitrophenyl octyl ether was the most suitable supported liquid membrane that delayed the electrolytic occurrence of air bubbles at the electrodes due to its high viscosity and high dielectric constant properties. The electromembrane extraction method was optimized using 5 mM NaCl (630 µS cm−1); the applied potential was 100 V and the extraction time was 15 min. The enrichment factor of 80 was obtained over a linear working range of 10.0–80.0 µg L−1. The method performance was tested using mineral water, drinking water, tap water, and surface water. The method recoveries based on matrix-matched calibration were 95–125% with standard deviations within 15%.
Published: 23 February 2018
Analytical Letters, Volume 51, pp 1194-1207; https://doi.org/10.1080/00032719.2017.1373117

Abstract:
A new calibration methodology based on the combination of integrated calibration method (ICM) and the H-point standard addition method (HPSAM) is presented. It allows the diagnosis and correction of errors caused in an analytical system by different kinds of interference effects. Six calibration solutions consisting of mixtures of sample, diluent, and one standard are prepared in accordance with the ICM principle to integrate the external calibration method with the standard addition method and thereby to detect and eliminate proportional interferences. Absorbance increments chosen according to the HPSAM principle are proposed to correct the errors caused by additive interferences. A set of as many as six apparent estimations of analyte concentration in a single calibration procedure is calculated for validating accuracy. As a consequence, doing calibration by the ICM-HPSAM method, it is possible to obtain the final analytical results with considerably improved accuracy. The determination of calcium in several different water samples (containing amounts between 4.9 and 127 mg L−1) with Arsenazo III has been chosen as an example because it is biased if the errors are not diagnosed and corrected. The results are characterized by small (not higher than 8%) relative error (RE), and good precision (RSD values smaller than 6%).
Published: 23 February 2018
Analytical Letters, Volume 51, pp 1208-1218; https://doi.org/10.1080/00032719.2017.1373285

Abstract:
A method for the determination of lead is described using thiol-functionalized gold nanoparticle. The detection method is based on the prevention of thiol-induced aggregation of gold nanoparticles by lead. Among six thiols, e.g., 4-mercapto-1-butanol, meso-2, 3-dimercaptosuccinic acid, mercaptosuccinic acid, 6-mercapto-1-hexanol, 4-(methylthio)-1-butanol, 1-propanethiol, four (4-mercapto-1-butanol, 6-mercapto-1-hexanol, 4-(methylthio)-1-butanol and 1-propanethiol) induced the aggregation of the gold nanoparticles which was measured by the change in absorbance at 520 and 650 nm. Prior incubation of the gold nanoparticles with lead decreased the 4-(methylthio)-1-butanol-induced aggregation of gold nanoparticles in a dose-dependent manner. A linear inverse relationship between the logarithmic concentration of lead and the ratio of absorbance at 650 to 520 was noted. The method has a dynamic range from 10 nM to 100 µM. However, metals such as mercury and chromium were more effective in comparison with lead in preventing the 4-methylthio-1-butanol-induced aggregation of gold nanoparticles. The method can be used for assessing the heavy metal load in water samples.
, Rida Khalid, Zaib Hussain
Published: 14 December 2017
Analytical Letters, Volume 51, pp 892-907; https://doi.org/10.1080/00032719.2017.1363770

Abstract:
The catalytic oxidation of organic dyes using various systems has been widely reported during the past decade. Photocatalytic methods, heterogeneous processes for the degradation of dyes, are one of the best and efficient oxidation processes to treat industrial wastewater with minimal residual waste. This review describes the improvement in catalytic activity of silver-doped titanium dioxide and silver-doped zinc oxide. The degradation of dyes provides information about the catalytic performance of silver-doped metal oxide. The effects of pH, catalyst concentration, dye concentration, hydrogen peroxide, dissolved oxygen, temperature, irradiation time, and light source have been reviewed along with the degradation mechanism and reaction methodology of organic dyes.
Ghazala Riaz, , , Adeel Mahmood, Mehvish Mumtaz, Abdul Qadir, ,
Published: 23 February 2018
Analytical Letters, Volume 51, pp 1245-1263; https://doi.org/10.1080/00032719.2017.1372467

Abstract:
The current study assessed the spatiotemporal variations and human health surveillance associated with organochlorine pesticide (OCP) contamination in water, sediments, and fish from Chenab River, Pakistan. The OCP determinations were performed using high-performance liquid chromatography with a reverse-phase C18 column. The total OCP levels ranged from 13.33 to 274.59 ng/L in water, 4.63 to 239.11 ng/g in sediments, and 23.79 to 387.12 ng/g in fish species. The overall pattern of mean OCP concentrations followed the order as ΣDDTs > Σendosulfan > aldrin and OCP pollution pattern among the headworks were Khanki Barrage > Qadirabad Barrage > Trimmu Barrage > Marala Barrage in all three environmental matrixes during both seasons. The estimated daily intake (EDI) for ∑OCPs was found to be 22.44 ng/kg/day. The hazard ratios calculated to assess the carcinogenic risk indicated that the values for ∑DDT and aldrin at the 95th percentile concentrations were greater than one, indicating the probability of carcinogenic risk occurrence of one in million populations due to fish consumption. Therefore, these high levels of OCPs and carcinogenic risk through fish consumption highlight the needs of immediate elimination of OCPs from riverine environment of Chenab River and we recommend long-term monitoring-based freshwater ecological studies to be conducted in the study area.
Weifeng Du, Ying Yang, Dongjing Jiang, Weihong Ge,
Published: 25 September 2017
Analytical Letters, Volume 50, pp 2634-2648; https://doi.org/10.1080/00032719.2017.1307384

Abstract:
A new method was developed using Fourier transform near-infrared spectroscopy and high-performance liquid chromatography with diode array detection for the identification and determination of eight major compounds in crude and sweated Radix Dipsaci. Partial least square regression was selected for the analysis. Multiplicative scatter correction, first derivative, and a Savitzky–Golay filter were used for the spectral pretreatment of the crude material, while standard normal variation, first derivative, and the Savitzky–Golay filter were used for the sweated samples. The correlation coefficients of the calibration models were above 0.99 and the root mean square error of calibration, the root mean square error of prediction, and root mean square error of cross-validation were under 0.63. The developed models were used to analyze unknown crude and sweated Radix Dipsaci with satisfactory results. The established methods were rapid, simple, nondestructive, and useful for quality control of Radix Dipsaci.
Fan Yi, Lin-Zhen Liu, Mei-Jiang Zhang, Ting-Ting Wang, , ,
Published: 7 March 2018
Analytical Letters, Volume 51, pp 1358-1372; https://doi.org/10.1080/00032719.2017.1378661

Abstract:
The primary clinical diagnosis of Alzheimer’s disease is mainly based on medical history and neuropsychiatric inventory. It is urgent to seek biological indicators with better sensitivity and higher specificity to clinically diagnose and evaluate Alzheimer’s disease. In this work, an electrophoretic method based on 2-thiobarbituric acid derivatization and amperometric detection was developed to determine formaldehyde as a urinary biomarker of Alzheimer’s disease. Under the optimum conditions, the formaldehyde derivative was well separated from the coexisting interferences in urine sample. The limit of detection for formaldehyde was 80.0 nM (2.4 ng/ mL) based on an electrophoretic stacking technology. The average recovery values were in the range of 91.7–110%, and the relative standard deviation values were less than 4.1%. This method has been applied to analyze human urine samples from healthy volunteers and patients with different degrees of Alzheimer’s disease. The assay results showed that the content of urinary formaldehyde in patients suffering Alzheimer’s disease was significantly higher than that in healthy subjects (P< 0.01), suggesting that urinary formaldehyde may be speculated to be an auxiliary noninvasive biomarker for the preliminary diagnosis of Alzheimer’s disease. High separation efficiency, simple sample preparation, environmental friendliness, and low cost are the main advantages of this proposed method.
Cuiyan Wu, Xue Peng, Qiujun Lu, , , Shouzhuo Yao
Published: 18 January 2018
Analytical Letters, Volume 51, pp 1013-1028; https://doi.org/10.1080/00032719.2017.1370595

Abstract:
A novel ratiometric fluorescence sensing system for the ultrasensitive detection of Hg2+ was developed. It used aminofunctionalized silicon nanoparticles and rhodamine B, which exhibit two distinct fluorescence emission peaks at 449 and 581 nm, respectively, under a single excitation wavelength (350 nm). The fluorescence of the amino-functionalized silicon nanoparticles was selectively quenched by Hg2+, while that of rhodamine B was insensitive to Hg2+. The ratio of fluorescence intensities at 449–581 nm linearly decreased with increasing concentrations of Hg2+ from 0.005–0.1 and 0.1–7 µM within 0.5 min, and a detection limit as low as 3.3 nM was achieved. Moreover, the ratiometric fluorescence sensing system exhibited good selectivity toward Hg2+ over other metal ions with relatively low background interference, even in a complex matrix such as lake water. Most importantly, the practical use of this sensing system for Hg2+ detection in real water samples was also demonstrated.
, , Ayşem Arda
Published: 3 November 2017
Analytical Letters, Volume 51, pp 1-6; https://doi.org/10.1080/00032719.2017.1372465

Abstract:
This special issue of ‘Analytical Letters’ is devoted to selected papers based on contributions from the 10th Aegean Analytical Chemistry Days (AACD 2016) International Meeting. The first AACD Meeting was held in Izmir-Turkey in 1998 for enhancing the scientific collaboration of analytical chemists from Aegean countries primarily comprising Turkey and Greece, but these series of conferences later evolved into a successful international event covering the entire field of analytical chemistry practiced in almost all countries. Selected papers from most of these conferences were published in the special issues of reputable journals. Specifically in this special edition, the authors have extended their conference proceedings papers and added their latest experimental results. The papers have undergone the standard review process. The AACD 2016 Conference, providing a forum among analytical chemistry researchers from many different countries, was held in Çanakkale, jointly hosted by Çanakkale Onsekiz Mart University (ÇOMU) and Istanbul University (IU). AACD 2016 combined invited lectures, parallel oral sessions and poster presentations, altogether comprising 14 invited lectures, 45 contributed oral presentations and 343 posters, and three company presentations. The selected best 40 posters were orally presented for 5 min at the ‘flash poster presentation’ session. The Conference Organizers are thankful to the AACD Continuation Committee, invited speakers and all presenters, authors and reviewers who were willing to share their expertise with us by submitting/reviewing the valuable contributions to this special issue, and finally to the Chief Editor of ‘Analytical Letters’ and Taylor & Francis who handled the complete review process.
Li Li, Yanyan Zhao, Ruqin Yu, Tingting Chen,
Published: 18 January 2018
Analytical Letters, Volume 51, pp 998-1012; https://doi.org/10.1080/00032719.2017.1368530

Abstract:
A novel fluorescence sensing platform based on polydopamine nanospheres and 6′-carboxyfluorescein labeled single-stranded DNA has been developed for monitoring the concentration of exonuclease I. Due to the interaction between single-stranded DNA and polydopamine nanospheres, the single-stranded DNA may be adsorbed on the surface of polydopamine nanospheres. The fluorescence of 6′-carboxyfluorescein was subsequently quenched by the polydopamine nanospheres through energy transfer or electron transfer. However, the 6′-carboxyfluorescein-labeled single-stranded DNA was specifically degraded by exonuclease I, producing mono or oligonucleotide fragments, which were not adsorbed by the polydopamine nanospheres, and thus the fluorescence signal was retained. The retained fluorescence of the sensing platform was found to be linear with the concentration of exonuclease I in the range of 0.15–10 U mL−1 with a detection limit of 0.05 U mL−1. In addition, the sensing platform was highly selective toward exonuclease I. Benefiting from the high efficiency and the simple design process, satisfactory performance has been successfully demonstrated for the determination of exonuclease I in complex samples.
Published: 18 January 2018
Analytical Letters, Volume 51, pp 1087-1107; https://doi.org/10.1080/00032719.2017.1367007

Abstract:
Polycyclic aromatic hydrocarbons (PAHs) represent priority contaminants, and the development of fast, reliable and accurate methods for their determination is of essential importance. The soil is a part of the environment which easily accumulates PAHs, making them available for transport to the air and water over long time periods and by plants through the food chain to humans. The aim of present study was to introduce a novel sorbent to the quick, easy, cheap, effective, rugged, and safe technique for soil sample preparation for the determination of 16 European Union priority PAHs by gas chromatography–mass spectrometry. Two solvent systems, 2:1 (v/v) hexane:acetone and ethyl acetate, were investigated in combination with five clean-up sorbents [Primary secondary amine (PSA), C18, florisil, clinoptilolite, and diatomaceous earth] in this study. The highest overall recovery of the method was achieved by the combination of hexane:acetone with clinoptilolite (recoveries of 70–110%) with limits of detection in the range of 0.60–1.53 µg kg−1. The analysis of 20 soil samples from Niš, Serbia resulted in the identification of 11 samples with concentration greater than the values prescribed by law. The ratios of phenanthrene/anthracene and fluoranthene/pyrene were used to elucidate the origin of the PAHs as pyrolytic.
Nan Zhan, Feng Guo, Qin Tian, Zhi Peng Yang,
Published: 4 January 2018
Analytical Letters, Volume 51, pp 955-970; https://doi.org/10.1080/00032719.2017.1367798

Abstract:
The identification and quantification of organic compounds in leaching basin soil is important for the evaluation of soil pollution. In this study, a non-target screening strategy and a quantitative analytical method were developed based on the accelerated solvent extraction method followed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry. First, a screening method for potential risk compounds in soil samples was established, and the major compounds were screened under the conditions such as matching similarity, signal-to-noise ratio, and relative area ratio. Second, a quantitative method was further developed by internal calibration curves for 50 main organic pollutants in the soil samples, including 27 polycyclic aromatic hydrocarbons and their derivatives (PAHs), 10 phthalic acid esters, eight phenolic compounds, and five benzene derivatives. The quantitative procedure exhibited good selectivity, accuracy, precision, low limits of detection (0.03–1.02 ng/g), and quantification (0.1–3.0 ng/g) for all target compounds. Finally, the proposed strategy was applied to the soil samples that were collected from a leaching basin and polluted by electroplating wastewater. Abundant PAHs and phenolic compounds were detected in the topsoil sample, which were mainly released from the electroplating wastewater. The application of this multi-dimensional strategy in leaching basin soil samples can also be used for the assessment of organic pollution in other complex soil samples.
Wahid Ben Mefteh, Yves Chevalier, ,
Published: 14 December 2017
Analytical Letters, Volume 51, pp 971-982; https://doi.org/10.1080/00032719.2017.1368531

Abstract:
A voltammetric sensor based on a methyl-naphthyl cyclam (1,4,8,11-tetraazacyclotetradecane) film deposited through dip coating on gold electrodes allowed the sensitive detection of copper (II). The obtained film was characterized in terms of the composition and morphology using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy. In the presence of divalent metallic ions (copper and nickel) and trivalent metallic ions (iron), at pH 7 and 7.7, the current density of the ionic oxidation peak maximum was determined using square wave voltammetry. The relative variation of this current density varies linearly with the base-ten logarithm of the ion concentration. From this calibration curve, a detection limit of 7 × 10−12 M was obtained for copper (II) at pH 7. At this pH value, the sensitivity of detection of copper (II) was 2.5 times higher than for nickel (II) and 5.8 times higher than for iron (III). The methyl-naphthyl cyclam film-modified gold sensor was validated for the detection of copper in spiked urine samples.
Lavinia Claudia Buruleanu, , Andreea Antonia Georgescu, Florin Andrei Danet, , Cristina Mihaela Nicolescu,
Published: 18 January 2018
Analytical Letters, Volume 51, pp 1039-1059; https://doi.org/10.1080/00032719.2017.1366499

, Shiyu Li, Jinmei Wang
Published: 14 December 2017
Analytical Letters, Volume 51, pp 860-869; https://doi.org/10.1080/00032719.2017.1365266

Abstract:
In sample measurements, matrix effects are unavoidable. The matrix effects are one of the main factors affecting the accuracy of the pulsed electrolyte cathode atmospheric pressure discharge detection system. The stability of sodium, potassium, and magnesium, under optimized parameters is measured; the relative standard deviation of spectral intensity is found to be no more than 2%; and the relative standard deviation of background intensity is less than 2%. The matrix effects on the elements potassium, sodium, and magnesium were studied, and the experiments showed that high concentrations of sodium and potassium interfere with each other. A concentration of 200 mg L−1 K+ affected the sodium signal with an enhancement of more than 120%; and the K+ intensity increased 20% in the presence of a high concentration of 200 mL−1 Na+. In high concentrations of sodium or potassium, the elemental signal for magnesium enhancement was approximately 8%. Sodium, potassium, and magnesium were quantitatively determined using a mixed calibration sample. When sodium, potassium, and magnesium are present at low concentrations in solution, there were no obvious matrix effects. The sodium, potassium, and magnesium in the calibration samples are quantitatively determined. The relative error and precision are less than 3%, and the recoveries are less than 105%. The detection limits for sodium, potassium, and magnesium were found to be 2.1, 3.4, and 92.6 µg L−1, respectively.
Jianqiang Zhang, , Ying Hou, Changgui Qiu, Shuangyan Yang, Changyu Li, Linru Nie
Published: 14 December 2017
Analytical Letters, Volume 51, pp 1029-1038; https://doi.org/10.1080/00032719.2017.1365882

Abstract:
A spare representation classification method for tobacco leaves based on near-infrared spectroscopy and deep learning algorithm is reported in this paper. All training samples were used to make up a data dictionary of the sparse representation and the test samples were represented by the sparsest linear combinations of the dictionary by sparse coding. The regression residual of the test sample to each class was computed and finally assigned to the class with the minimum residual. The effectiveness of spare representation classification method was compared with K-nearest neighbor and particle swarm optimization–support vector machine algorithms. The results show that the classification accuracy of the proposed method is higher and it is more efficient. The results suggest that near-infrared spectroscopy with spare representation classification algorithm may be an alternative method to traditional methods for discriminating classes of tobacco leaves.
Chan Seo, Youngbae Kim, Hyeon-Seong Lee, Sook Za Kim,
Published: 14 December 2017
Analytical Letters, Volume 51, pp 793-806; https://doi.org/10.1080/00032719.2017.1363769

Abstract:
An efficient method for the simultaneous profiling analysis of 44 fatty acids including 24 aliphatic, 12 hydroxyl, and eight methyl-branched fatty acids as tert-butyldimethylsilyl (TBDMS) derivatives was developed by gas chromatography–mass spectrometry. In this study, new mass spectral databases of isolauric, 11-methyllauric, isomyristic, isopentadecylic, isopalmitic, isostearic, 17-methylstearic, and 19-methylarachidic acids were constructed as TBDMS derivatives. Under the optimal conditions, linearity in the range of 0.1–10.0 µg/mL (24 aliphatic fatty acids) and 0.01–1.0 µg/mL (eight methyl-branched and 12 hydroxy fatty acids) showed good correlation coefficients (r ≥ 0.997). The repeatability showed relative standard deviation of less than 11.2% and accuracy (percent relative error) varied from −11.0 to 7.8 for the 44 fatty acids studied. The recoveries ranged from 61.7 to 90.1% with good repeatability. When applied to human plasma sample, 18 aliphatic, three 2-hydroxy, three 3-hydroxy, and five methyl-branched fatty acids were positively identified and quantified. Therefore, the present method will be useful for profiling analysis of various fatty acids in biological samples including plasma.
Published: 19 December 2017
Analytical Letters, Volume 51, pp 935-954; https://doi.org/10.1080/00032719.2017.1365368

Abstract:
This work focuses on the synthesis and characterization of porous silica monolith-based adsorbent materials. Materials with bimodal porosity (macro and meso) were prepared through a sol–gel process. The capacity of adsorption of organic molecules was ensured by grafting of hydrophobic organic coating on the silica surface. Alkylsilane chains or lauryl acrylate polymer were used for this purpose. The adsorption kinetic behavior of the produced materials was assessed through benzophenone adsorption studies in aqueous media. The results have shown that the macropore size of the monoliths had no effect on the adsorption capacity. The thicker organic layer prepared by polymerization of lauryl acrylate has decreased the adsorption kinetics without affecting the total adsorption capacity. The over-coating with additional external layer of hydrogel further slowed the diffusion of benzophenone thus better matches the passive-sampler requirements.
Hong Zhang, Pingmei Wang, Qiang Zhou,
Published: 19 December 2017
Analytical Letters, Volume 51, pp 921-934; https://doi.org/10.1080/00032719.2017.1364744

Abstract:
Uniform-sized fluorescent molecularly imprinted polymers were prepared by one-step swelling and suspension polymerization, while chlorpyrifos, methacrylic acid, ethylene glycol dimethacrylate, and oil-soluble CdSe/ZnS quantum dots were used as the carrier, template molecule, functional monomer, cross-linker, and fluorophor, respectively. The morphology, adsorption dynamics, binding ability, and selectivity of quantum dot-labeled molecularly imprinted polymers were evaluated. The dosage of quantum dots for labeling the molecularly imprinted polymers was optimized. The results showed that the optimized dose of quantum dots was 200 µL using a concentration of 8.0 µM. The microsphere size was approximately 10 µm with a honeycombed surface. The quantum dot-labeled molecularly imprinted polymers had an even brightness and a high selectivity. In the presence of different concentrations of chlorpyrifos, a decrease in the fluorescence intensity of the quantum dot-labeled molecularly imprinted polymer was clearly identified by flow cytometry. The whole detection process was accomplished within 2 h including pretreatment. This method was used for the determination of chlorpyrifos in tap water samples.
Published: 31 May 2007
Analytical Letters, Volume 40, pp 1333-1346; https://doi.org/10.1080/00032710701326692

Abstract:
In this work are presented methods for detection of aflatoxin B1 and type‐A trichothecenes, based on the use of indirect competitive ELISA format coupled with a 96‐well screen‐printed microplate. Electrochemical immunoassays for AFB1, T‐2, and HT‐2 were performed and the activity of the alkaline phosphatase or horseradish peroxidase labeled enzymes were measured using intermittent pulse amperometry (IPA) as electrochemical technique. Using standard solutions of the target analyte the LOD of the assays were 0.3 and 0.2 ng ml−1 for T‐2 and AFB1 respectively, while the sensitivity was 1.2 ng ml−1 for both. For Aflatoxin B1, a stability study of electrochemical plate was also performed. Moreover, the matrix effect was evaluated using two different extraction treatments from corn.
Huawei Li, Yanyang Jin,
Published: 8 February 2022
Analytical Letters, Volume 55, pp 841-856; https://doi.org/10.1080/00032719.2017.1360901

Abstract:
Selective and efficient electrochemical analytical methods for the characterization of the corrosion behavior of beryllium bronze alloys are significant and necessary. These electrochemical methods are based on open-circuit chronopotentiometry curves, potentiodynamic polarization, and electrochemical impedance spectroscopy. From the electrochemical analysis, the results show that the corrosion reaction of the untreated samples became more severe as the NaCl concentration was increased. However, the corrosion reaction was not obvious when the alloy was treated by commercial latex paint and laboratory-produced latex paint. Furthermore, the corrosion potential has the same variation tendencies and the value of the corrosion potential was more positive when the alloy surface was treated by the laboratory-produced latex paint. The maximum and minimum of the corrosion potential were found for conditions using the untreated samples and samples treated with the laboratory-produced latex paint. The corrosion current, the charge transfer resistance, and the radius of capacitive resistance all decreased with increasing NaCl concentration. The above results suggest that the corrosion rate increased as the NaCl concentration was increased. Better anti-corrosion technology was found through various experimental analyses. The innovative electrochemical methods applied in the electrochemical corrosion behavior of beryllium bronze alloy are accurate, efficient, and reliable.
Wen-Xuan Zhang, Jun-Tao Cao, Yu-Ling Wang, Shu-Hui Ma, Yan-Ming Liu
Published: 14 December 2017
Analytical Letters, Volume 51, pp 820-833; https://doi.org/10.1080/00032719.2017.1360900

Abstract:
A label-free photoelectrochemical aptasensor for the sensitive and selective determination of carcinoembryonic antigen was constructed based on a CdS quantum dot sensitized TiO2 nanotube electrode. TiO2 nanotubes with highly ordered structure and more active sites than bulk TiO2 were prepared with an electrochemical anodic oxidation process. The CdS quantum dots were immobilized on the TiO2 nanotubes using poly(diallyldimethylammonium chloride) as a bridge. Due to the energy level match between TiO2 and CdS, the CdS quantum dots/TiO2 nanotubes electrode exhibits excellent photoelectrochemical performance. The large surface area of the electrode also allows for capturing large numbers of aptamers. The fine photoelectrochemical performance and the large surface area of the electrode greatly enhanced the detection sensitivity. Under the optimal conditions, the prepared photoelectrochemical aptasensor presents desirable analytical properties for the determination of carcinoembryonic antigen in the range of 0.05 to 10 ng mL−1 with a detection limit of 0.014 ng mL−1. The application of the designed protocol was investigated by analyzing carcinoembryonic antigen in human serum samples with recoveries from 80.0 to 115.0%. This simple and sensitive method provides an alternative tool to standard biochemical assays.
Ren Mu, , Xiaoguang Gao, Jian Jia, Jianping Li
Published: 14 December 2017
Analytical Letters, Volume 51, pp 807-819; https://doi.org/10.1080/00032719.2017.1362645

Abstract:
A corona discharge (CD) ion mobility spectrometer combined with solid-phase microextraction was constructed. The detection limit and stability of the system for malathion detection were improved using a novel sample introduction port through which the sample desorption was performed in high-temperature drift tube and the sample was introduced directly to the ionization area. The working parameters of the distance between CD needle tip and carrier gas outlet, the drift tube and carrier gas temperature, the carrier gas flow, and the voltage on CD needle were selected. When the extraction time for standard malathion was set to 5 min, the detection limit was 0.96 µg L−1 based on thrice the baseline noise, the linear range was 50–500 µg L−1, the correlation coefficient was approximately 0.9941, and the relative standard deviation was below 10%. Malathion-spiked lake water samples were analyzed using the developed system and the recovery was 92–102%. This method is suitable for the rapid detection of organophosphorus pesticide residues.
, Elizaveta S. Vakhranyova, , Sergei G. Kazarian, Tatyana N. Shekhovtsova
Published: 19 December 2017
Analytical Letters, Volume 51, pp 870-891; https://doi.org/10.1080/00032719.2017.1361434

Abstract:
In this work, the first use of a cellulose hydrogel film reconstituted from ionic liquid (IL) 1-butyl-3-methylimidazolium chloride for the fluorescent determination of a plant antimalarial endoperoxide artemisinin is reported. The sensing material was fabricated by noncovalent co-immobilization of the fluorescent cationic dye pyronin B and complex of Mn(II) with anionic surfactant sodium dodecyl sulfate into the film prepared by dissolution and regeneration of microcrystalline cellulose in ionic liquid. Artemisinin determination in a concentration range of 0.25–8 µM is based on the dynamic quenching of pyronin B fluorescence (emission wavelength/excitation wavelength of 581/355 nm) that is accelerated by the above-indicated complex. The developed disposable cellulose film exhibits a high sensitivity toward artemisinin (limit of detection of 30 nM), sufficient selectivity for pharmaceutical analysis, a rapid response time (30 s), and a strong stable fluorescent signal for over a month. The applicability of the cellulose film was demonstrated by analyzing a dietary supplement with an extract from the traditional Chinese herb Artemisia annua. The accuracy of the fluorescent determination of artemisinin in the dietary supplement was supported by a liquid chromatography–mass spectrometry technique. The developed fluorescent cellulose film is a biocompatible and easy to handle sensing material that makes it suitable for wide variety applications in pharmaceutical analysis.
Ramona Georgescu-State,
Published: 14 December 2017
Analytical Letters, Volume 51, pp 849-859; https://doi.org/10.1080/00032719.2017.1362420

Abstract:
Tryptophan is an important amino acid for humans with a significant role in cell metabolism. Depletion of tryptophan in the human body may contribute to diseases and development of disorders among the human population. It is, therefore, very important to have a reliable, stable, sustainable, and cost-effective analytical method for the determination of tryptophan. Tryptophan was determined using sequential injection–zone fluidics analysis with luminol–hydrogen peroxide and the Firefly with its unique liquid core waveguide flow-cell design as chemiluminescence tubular reactor with a high-sensitivity photomultiplier tube. This was based on an intense chemiluminescence formation of tryptophan in luminol–hydrogen peroxide inside the tubular reactor for measurement. The chemiluminescence intensity was linear with tryptophan in the range of 1.0 × 10−6 to 1.0 × 10−3 mol/L, and the limit of detection was 7.5 × 10−7 mol/L. The precision for the method was 3.6% (relative standard deviation) for six measurements of 1.0 × 10−4 mol/L tryptophan. The proposed method has been used to determine tryptophan in pharmaceutical formulations. The system is relatively fast for online assays. Eighty seconds are required to complete one cycle providing a throughput of 45 samples/h. The proposed sequential injection analysis–zone fluidics–chemiluminescence system for the assay of tryptophan in certain specific pharmaceutical capsules is simple, reliable, sustainable, and convenient with relatively low-cost consumption of reagents.
Violeta D. Mitic, , Jovana Pavlovic, Jelena Nikolic, Strahinja R. Simonovic, Vesna P. Jovanovic Stankov,
Published: 19 December 2017
Analytical Letters, Volume 51, pp 908-920; https://doi.org/10.1080/00032719.2017.1362646

Abstract:
Currant fruit extracts were characterized by (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, 2,2-azinobis-3 ethyl benzothiazoline-6-sulfonic acid cation decolorization activity, total reducing power, cupric ion reducing antioxidant power, and ferric ion reducing antioxidant power (FRAP) assays to evaluate their antioxidant activity. All five antioxidant assays revealed the highest antioxidant activity to be present for the black currants. The highest concentrations of phenolics were present in the black currants (1690 ± 10 mg gallic acid equivalents (GAE)/100 g fresh weight), while the lowest value was obtained in the white currants (579 ± 5 mg GAE/100 g fresh weight). The correlation between the total phenolic content and antioxidant activity assays was evaluated using regression analysis. A significant positive correlation was obtained between the total phenols and the cupric ion reducing antioxidant power (r = 0.97, p < 0.05), followed by that between the total phenols and FRAP (r = 0.93, p < 0.05). Hierarchical cluster analysis separated these selected fruit species into two statistically significant clusters with black currants as a distinctive cluster.
Fang Ye, Jianzhi Huang, Yongqun Xu, Qiang Zeng, ,
Published: 15 November 2017
Analytical Letters, Volume 51, pp 728-741; https://doi.org/10.1080/00032719.2017.1360898

Abstract:
An electrochemical sensor based on a polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode has been developed for the sensitive and rapid determination of nitrofurazone. The morphologies and properties of the sensor were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). In pH 7.0 Britton–Robinson buffer solution, the as-prepared polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode shows excellent electrocatalytic performance for the electrochemical reduction of nitrofurazone, and the reduction peak current is about 9.45, 1.31, and 1.25 times higher than that of the bare glassy carbon electrode, polyfurfural modified glassy carbon electrode, and electrochemically reduced graphene oxide modified glassy carbon electrode, respectively. The DPV determination of nitrofurazone indicates that the linear range and detection limit of nitrofurazone are 1–50 and 0.25 µmol/dm3, respectively. In addition, this sensor exhibits high selectivity, reproducibility, stability, and also was successfully used to directly determine nitrofurazone in the commercial antibacterial lotion with comparative sensitivity to high-performance liquid chromatography, showing its promising application prospects.
Published: 27 November 2017
Analytical Letters, Volume 51, pp 773-791; https://doi.org/10.1080/00032719.2017.1360897

Abstract:
In this study, a novel sorbent material bearing a bis(aldimine) group was designed and successfully synthesized by covalently bonding a 2-[N,N′-bis(salicylaldimine)]aminoethyl amine ligand to the silica gel surface that was characterized by carbon, hydrogen, and nitrogen elemental analysis, thermogravimetric analysis, and the Fourier transform infrared spectroscopy technique. The sorbent was used for the online solid-phase extraction (SPE) of Cd(II), Cu(II), and Co(II) ions for their determination at trace concentration levels by flame atomic absorption spectrometry. The effective factors for the online SPE such as the pH and the flow rate of the sample solution, and type, volume, and flow rate of eluent were investigated. The concentration levels of Cd(II), Cu(II), and Co(II) were measured in certified reference materials including Virginia tobacco leaves (CTA-VTL-2) and water-trace elements (NWTM-15.2) to validate this method. The metal levels in environmental water were determined by this method, and the values were checked by spiking and recovery experiments and independent analysis by inductively coupled plasma-mass spectrometry. The adsorption capacities of the sorbent were found to be 41.2, 31.6, and 25.6 mg/g for Cd(II), Cu(II), and Co(II), respectively. This method was also successfully used for the determination of Cd(II), Cu(II), and Co(II) concentrations in rice and molasses.
Eun Yeong Nho, Nargis Jamila, Naeem Khan, Yun Mi Dang, Ga Hyun Lee, Yu Min Park, Ji Yeon Choi,
Published: 15 November 2017
Analytical Letters, Volume 51, pp 686-701; https://doi.org/10.1080/00032719.2017.1360896

Abstract:
Recent research studies have confirmed that the dietary intake of vegetables and fruits has a positive and profound impact on human health, performance, and disease. This research was designed to determine the concentrations of essential trace elements; cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), selenium (Se), vanadium (V), and zinc (Zn), toxic metals; cadmium (Cd), mercury (Hg), and lead (Pb); and a metalloid; arsenic (As) in fruits of seven species of Cucurbitaceae family including gourd, zucchini, pumpkin, sweet pumpkin, melon, watermelon, and oriental melon commonly consumed in South Korea. The concentrations of As, Cd, Co, Cr, Cu, Pb, Se, and Zn were determined using inductively coupled plasma mass spectrometry, and Hg by a mercury analyzer. To analyze the samples after microwave digestion for the validation of analytical techniques, satisfactory values of all quality parameters of linearity, detection limits, precision, accuracy, and recovery experiments were obtained in all cases. On the whole, all analyzed elements were found in accordance to the published literature around the world and well within the critical recommended standards by CODEX and Ministry of Food and Drug Safety, Korea. The estimated daily intake values, and hazard quotients and indices of the analyzed samples were all below the World Health Organization, Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives, and European Food Safety Authority limits.
, Eda Büker, Zehra Ceren Ertekin
Published: 15 November 2017
Analytical Letters, Volume 51, pp 742-759; https://doi.org/10.1080/00032719.2017.1360895

Abstract:
This paper presents a new application of three-way parallel factor analysis (3W-PARAFAC) model to the coeluting spectrochromatograms for the quantitative resolution of a quaternary mixture system consisting of paracetamol, propyphenazone, and caffeine with aspirin as an internal standard. Spectrochromatograms of calibration standards, validation sets, and unknown samples were recorded as a function of retention time and wavelength in the range of 0.0–2.5 min and 200–400 nm, respectively, using ultra-performance liquid chromatography with photodiode array detection (UPLC-PDA). Three-way UPLC-PDA data array X (retention time × wavelength × sample) was obtained from the data matrices of the spectrochromatograms. 3W-PARAFAC decomposition of three-way UPLC-PDA data array provided three loading matrices corresponding to chromatographic mode, spectral mode, and relative concentration mode. Quantitative estimation of paracetamol, propyphenazone, and caffeine in analyzed samples was accomplished using the relative concentration mode obtained by the deconvolution of the UPLC-PDA data set. The validity and ability of 3W-PARAFAC model were checked by analyzing independent test samples. It was observed from analyses that 3W-PARAFAC method has potential to uniquely resolve strongly overlapping peaks of analyzed compounds in a spectrochromatogram, which was obtained under experimental conditions consisting of the lower flow rate, short run time, and simple mobile phase composition. The proposed three-way chemometric approach was successfully applied to the simultaneous quantification of paracetamol, propyphenazone, and caffeine in tablets. Experiments showed that the determination results were in good agreement with label amount in commercial pharmaceutical preparation.
Cheng Jun Sun, Xian Xiang Sun, Hassan Y. Aboul‐Enein
Published: 27 December 2004
Analytical Letters, Volume 37, pp 2259-2266; https://doi.org/10.1081/al-200028059

Abstract:
Potentiometric, enantioselective electrodes responsive to R(+)‐ and S(−)‐propranolol were constructed, based on a lipophilic cyclodextrin, 2‐hydroxy‐3‐trimethylammoniopropyl‐β‐cyclodextrin as an ionophore. Different plasticizers, ortho‐nitrophenyl octyl ether (o‐NPOE) and bis(t‐butylphntyl) adipate (BBPA), and inner filling solutions were studied. Electrode A, prepared with O‐NPOE as a plasticizer, and 1.0 × 10−3 M R‐enantiomer solution as an inner filling solution, has a sensitivity of 59.1 mV decade−1, with a limit of detection, −log a = 4.92. Electrode B, prepared with BBPA as a plasticizer and 1.0 × 10−3 M NH4Cl as an inner filling solution, shows a sensitivity of 60.0 mV decade−1, with a limit of detection, −log a = 5.28. Inorganic cations (Na+, K+, Ca2+, Zn2+) and racemic and R‐sabutamol did not interfere with the measurement. The enantioselectivity coefficient (K±pot), determined in 1.0 × 10−3 M appropriate enantiomer solutions, was 0.20.
Noman Khan, , Hasan Imran Afridi, Muhammad Balal Arain
Published: 15 November 2017
Analytical Letters, Volume 51, pp 673-685; https://doi.org/10.1080/00032719.2017.1354868

Abstract:
Task-specific ionic liquid dispersive liquid–liquid microextraction (TSIL-DLLME) is a simple and rapid preconcentration approach for the measurement of cadmium in serum and blood samples of human subjects. In this method a novel task-specific ionic liquid, trioctylmethyl ammonium thiosalicylate (TOMATS), which has dual characteristics as a chelating agent and extractive solvent, was investigated. TOMATS complexes with Cd due to the chelating effect of the ortho-positioned carboxylate relative to the thiol functionality. The assessment of the optimum values of variables including the pH, amount of reagents (TOMATS, diluents, Triton X114, and back extracting acid solution), temperature, and incubation time, which affect the recoveries of analyte by TSIL-DLLME method were studied. After enrichment experiments, acidic solution was used to back extract the metal ions from the ionic liquid rich phase and with determination by electrothermal atomic absorption spectrometry. Using the optimal experimental conditions, the limit of detection (3 s), precision (relative standard deviation), preconcentration, and enhancement factors of developed method for Cd were found to be 0.05 µg/L, greater than 5%, 62.5, and 52.8, respectively. To check the accuracy of the developed method, certified reference material of serum and blood were analyzed by the developed method, and the measured values of Cd were in good agreement with the certified values. The developed method was applied successfully to determine Cd in blood and serum samples of lymphatic cancer patients relative to healthy controls.
, Ömür Çelikbıçak,
Published: 15 November 2017
Analytical Letters, Volume 51, pp 760-772; https://doi.org/10.1080/00032719.2017.1355376

Abstract:
In general, phosphopeptides are specifically adsorbed to the surface of the material at the initial step of phosphopeptide enrichment methods. Thus, nonphosphopeptides can be removed from the media by following the appropriate washing steps. After sufficient washing, the phosphopeptides are eluted from the surface of the material completely for further analysis. Performing the elution of phosphopeptides fully in the enrichment step is very important in terms of determining the whole phosphoproteome profile of a sample by subsequent mass spectrometric analysis. Materials containing anion exchanger groups such as amines on the surface can be used as a selective stationary phase in phosphopeptide enrichment methods. Positively charged groups on the surface of this type of material interact with the phosphate groups of phosphopeptides through electrostatic interactions. Such interactions can be basically manipulated by changing the pH of the medium or replacing the salts present in the solution. Phosphopeptides attached to the surface of anion-exchange materials may be displaced with the addition of highly acidic compounds such as sulfonates to the enrichment medium. Here, we used various sulfonates as desorption agents for the elution of retained phosphopeptides from the surface of an anion-exchange material. We found that differences in the chemical structures and properties of the sulfonates remarkably affected phosphopeptide retrieval from the anion-exchange material.
Yuqin Wu, Hong Zheng, Jinlong Chen, , Lun Wang, ,
Published: 1 January 2004
Analytical Letters, Volume 37, pp 711-723; https://doi.org/10.1081/al-120029747

Abstract:
A new hydrophobic near‐infrared (NIR) cationic cyanine dye was synthesized and evaluated as a new reagent for the determination of anionic surfactant sodium dodecyl benzenesulfonate (SDBS). The cyanine dye with an absorption maximum at 770 nm reacted with SDBS, causing significant hypochromism. Under the optimal conditions, the decreased absorption is proportional to the concentration of SDBS over the range 2.9 × 10−7–1 × 10−5 mol/L. The detection limit was 1.9 × 10−7 mol/L. The relative standard deviation for 1.43 × 10−6 mol/L SDBS was 1.3% (n = 9). The proposed method was applied to determination of anionic surfactant in the river with 93–106% recovery levels. Preliminary research shows that the hypochromism is due to the formation of dye aggregate facilitated by SDBS.
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