Current Analytical Chemistry - Volume 16, Issue 8, 2020

Background: Selenium’s popularity in a wide variety of products and industries means that it has, unfortunately, become a common environmental pollutant, particularly from sources such as industrial wastewater discharge and agricultural runoff. Objective: Quantification of the selenium (IV) ion content of natural water sources via atomic fluorescence spectrophotometry (AFS) was performed using hollow ZnO microflowers as the enriched materials. The hollow ZnO microflowers were prepared via a hydrothermal method with polystyrene (PS) microspheres as the template. Methods: Since the pH of the selenium (IV) solution is known to influence the degree of adsorption onto the sorbent, both the acidity of adsorption and elution were studied at various pH values to obtain the adsorption isotherm and adsorption capacity of the sorbent. AFS was used to quantify the amount of selenium ion that was present in the samples. The structure of the hollow ZnO microflowers was characterized using XRD, SEM, and TEM characterization methodologies. Results: When the pH was between 6.0 and 7.0, the percentage of Se (IV) adsorption was as high as 93%. It was found that the amount of Se (IV) that was eluted from the sorbent exceeded 96% with 5.0 mL of a 0.01 mol L−1 NaOH solution over the course of 10 minutes. The maximum adsorption capacity was 31.5, 31.8, and 32.0 mg·g−1 at 273, 333, and 353 K, respectively. Conclusion: The LOD for Se (IV) detection via enrichment was achieved at 0.006 μg L−1 with a linear range between 0.1 and 200 μg L−1. Thus, this method is applicable to the analysis of natural water samples and GBW(E)080394.

Background: A lack of regulation about the chemical composition of essential oils and the growing popularity of these oils among consumers presents an urgent need for the accurate characterization of various oil types from a variety of manufacturers. The aim of this paper was to characterize the composition of essential oils bought from a popular retail location, with the goal of understanding the chemical composition and presence of adulterants with potential toxicity. Methods: Reported herein is an investigation into the components of a variety of essential oils using gas chromatography-mass spectrometry (GC-MS). The investigation initially focused on two popular oils, tea tree and lavender oil, and then moved to investigate four additional essential oils from the same brand (sandalwood, rose, eucalyptus, and lemongrass). Results: Results of this analysis indicated that all six store brand essential oils contained Carbitol (in concentrations from 23% to 35%), and four of the six oils had diethyl phthalate (in concentrations ranging from 0.33% to 16%). These toxicants are particularly concerning because they are known inhalation hazards, and the intended usage of these oils is for aromatherapy (i.e. inhalation). Conclusion: These results highlight a potentially significant and under-reported health concern from inhalation of toxic contaminants in the store brand oils, and showcase the need for more regulation and transparency about the composition of these commercial products.

Background and Objectives: Contamination of aquatic sediments by trace metals is one of the global problems. This is because trace metals in sediments are persistent and nonbiodegradable. They may pose danger to flora and fauna since they can be released into freshwater systems. This study aimed at the development of microwave-assisted extraction using diluted hydrogen peroxide and nitric acid for extraction of trace elements from sediment samples prior to inductively coupled plasma optical emission spectrometry (ICP OES) determination. Methods: Response surface methodology (RSM) based on the Box-Behnken design was used for the optimization of factors affecting the microwave-assisted extraction process. The optimum conditions, for quantitative extraction of trace metals such as Cd2+, Cu2+, Cr2+, Pb2+ and Zn2+ were 16 min, 1.5 mol L-1 and 15% for extraction time, nitric acid concentration and H2O2 concentration, respectively. Results and Discussion: Under optimized conditions, the accuracy of the method was evaluated by analyzing loamy clay certified reference materials (CRM052) and the recoveries were above 92%, suggesting that the obtained results were in good agreement with the certified values. The developed method has shown reproducibility (RSD < 5%), as well as relative low limits of detection (0.02-0.09 μg g-1) and limit of quantitation (0.07-0.3 μg g-1). The developed analytical method was applied for extraction and the determination of trace metals in freshwater sediment samples. Conclusion: The method displayed advantages such as simplicity, rapidity, environmentally friendly and safe compared to classical methods that are based on concentrated acids.

Background: Losartan, one of the most frequently used drugs in Heart Failure (HF) treatment, could be modified for its bioavailability (BA) by generic formulations and other factors. Hence, the importance of therapeutic drug monitoring. Objective: Development and validation of a simplified analytical method using HPLC for simultaneous quantification of losartan and E-3174 in human plasma samples. The method was tested for determining the pharmacokinetics parameters of HF patients. Methods: Analytical conditions were optimized using a C18 column (4.6 X 50 mm, 3 μm. Thermo Scientific) at 25ºC. Conditions of mobile phase: a phosphate buffer (0.01M), adjusted to pH 2.5 with phosphoric acid (1M) and Acetonitrile (60:40 v/v). The flow rate was maintained at 1.2 mL/min, on a running time of 5 min and a sample injection volume of 50 μL. Absorbance for measurement of losartan and E-3174 was 200 nm. Pharmacokinetics profiles were determined with Phoenix Win- Nonlin 8.1 software in a non-compartmental model. Results: Analytical method developed and validated in this work is precise and accurate for simultaneous determination of losartan and E-3174 in human plasma samples in a range of 0.02 -10 μg/mL. In HF subjects, lower Tmax and higher Cmax for losartan and E-3174 patent than generic formulation were observed, which can be translated into less biological effect and more time to present it by the generic drug. Conclusion: The pharmacokinetic profile is dependent on the type of formulation studied (generic/ patent) hence the importance of conducting evaluations in our patients to ensure that the expected therapeutic effect is achieved with treatment administered.

Background: Simple, sensitive, and economic colorimetric device based on a smartphone digital image coupled with Color Grab™ application was developed for DCH drug determination. The method is based on the diazotization reaction of benzocaine with DCH drug to get an orange azo dye. Methods: Variable parameters such as volumes of reagents, the internal walls and ambient light have been analyzed and optimized. From the optimized conditions, a calibration curve was created by the effective intensity (IG) of an orange azo dye, a correlation of determination is 0.999 and limit of detection 0.808 mg/L. Results: The results of the Smartphone method were statistically compared with the reference method using a t-test and found to be a good agreement. Conclusion: This method requires neither solvent extraction and temperature control, also it has achieved an extensive linear range and low limit of detection compared with different methods reported in the literature.

Background: Hypertension is a major risk for morbidity and mortality, while hypertension is associated with cardiovascular disease and organ damage. Recent research efforts have focused on the development of highly selective angiotensin receptor blockers. In which losartan (LOS) is considered as a new generation of an effective oral drug product against arterial hypertension. Therefore, the determination of drugs in biological fluids, pharmaceuticals (tablets), and wastewater is of critical importance for clinical applications, forensics, quality control, and environmental protection that call for the development of analytical methods. Many ranges of methods such as spectroscopic methods and chromatographic techniques have been developed to determine LOS in pharmaceutical formulations and biological fluids. However, there are crucial interference problems in these methods. For these reasons, more sensitive, desirable, portable, low-cost, simple, and selective nanocomposite-based sensors are needed in terms of health safety. Nanomaterials such as reduced graphene oxide, chitosan, and metal nanoparticles are used to improve the sensitivity in the development of electrochemical sensors. Objective: In this study, a novel reduced graphene oxide (RGO), chitosan (Chit), gold (Au), and zinc oxide (ZnO) nanocomposite (RGO/Chitosan/Au/ZnO) was synthesized and used to develop a sensitive and efficient electrochemical sensor for LOS detection. Methods: Modification of electrode by RGO/Chit/Au/ZnO nanocomposite was performed in four stages with GO (at -2.0 V for 150 s), Chitosan (at -3.0 V for 300 s), Au nanoparticles (at -0.4 V for 400 s), and Zn nanoflowers like (at -0.7 V for 1200 s). The RGO/Chitosan/Au/ZnO nanocomposite was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR). Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) were used to detect LOS, and the influence of pH value, scan rate, accumulation potential, and time also losartan concentration on the performance of ZnO/Au/Chitosan/RGO/GCE were investigated. In order to investigate the selectivity of the modified electrode for the determination of LOS, the effect of possible interfering species was evaluated and showed that these species are not interferences. Also, the reproducibility of the modified electrode was investigated and implying that the RGO/Chit/Au/ZnO nanocomposite was highly reproducible. Results: The modified electrode was used as a sensor for the selective and sensitive determination of LOS with a detection limit of 0.073 μM over the dynamic linear range of 0.5μM to 18.0 μM. In addition, electrochemical oxidation of LOS was well recovered in pharmaceutical formulations. Conclusion: LOS is used to treat high blood pressure, taking into account the oxidation of this compound, the use of electrochemical based sensors, ideally suited to a specific chemical species, can be fully selectable and High-sensitivity answer is very important. In this study, the electrodes with RGO/Chit/Au/ZnO nanocomposite were modified by the electrochemical method. Nanocomposites were characterized by various methods such as FE-SEM, FT-IR, XRD, Raman, and XPS. The electrocatalytic activity of the modified electrode was then investigated for measuring LOS. According to the results of the modified electrode, high sensitivity, reproducibility, and selectivity have been shown to oxidize this composition.

Background: Lamotrigine (LTG), topiramate (TPM), and oxcarbazepine (OXC) are commonly used antiepileptic drugs. The bioactivity and toxicity of these drugs were related to their blood concentrations which varied greatly among individuals and required to be monitored for dose adjustment. However, the commercial method for monitoring of these drugs is not available in China. Methods: A UHPLC-MS/MS method for simultaneous determination of LTG, TPM, OXC, and OXC active metabolite (10,11-dihydro-10-hydroxycarbazepine, MHD) was developed and validated according to the guidelines and applied in clinical practice. Results: The separation was achieved by using methanol and water (both contain 0.1% formic acid) at 0.4 mL/min under gradient elution within 3 min. For all analytes, the isotope internal standard was used; the selectivity was good without significant carry over; LTG and TPM were linear between 0.06 to 12 mg/L while OXC and MHD were linear between 0.03 to 6 mg/L, the upper limit could be 10-fold higher because 10-fold dilution with water did not affect the results; the intra-day and interday bias and imprecision were -13.11% to 5.42% and < 13.32%; the internal standard normalized recovery and matrix factor were 90.95% to 111.94% and 95.57% to 109.91%; and all analytes were stable under tested conditions. LTG and OXC-D4 shared two ion pairs m/z 257.1 > 212.0 and 257.1 > 184.0, and m/z 257.1 > 240.0 was suggested for OXC-D4 quantitation. Lamotrigine and lamotrigine- 13C3 shared three ion pairs m/z 259.0 > 214.0, 259.0 > 168.0 and 259.0 > 159.0, and m/z 259.0 > 144.9 was suggested for LTG-13C3 quantitation. CBZ had a slight influence on OXC analysis only at 0.225 mg/L (bias, 20.24%) but did not affect MHD analysis. Optimization of chromatography conditions was useful to avoid the influence of isobaric mass transitions on analysis. This method has been successfully applied in 208 patients with epilepsy for dose adjustment. Conclusion: An accurate, robust, rapid, and simple method for simultaneous determination of LTG, TPM, OXC, and MHD by UHPLC-MS/MS was developed, validated, and successfully applied in patients with epilepsy for dose adjustment. The experiences during method development, validation, and application might be helpful for other researchers.

Background: Cadmium (Cd2+) is considered to be one of the most important hazardous heavy metals due to its toxicity for living organisms at low concentration levels. Therefore, the estimation of trace Cd2+ in different types of various samples is a very important objective for chemists using effective methods. In the present work, a novel, green, easy and fast ultrasoundassisted ionic liquid-dispersive liquid phase microextraction technique (UA-IL-DLPME) was developed to preconcentrate and determine trace quantities of cadmium (Cd2+) ions from real samples, prior to detection by FAAS. Methods: The proposed technique is based on utilization of ionic liquid (IL) (1-hexyl-3- methylimidazolium tris(pentafluoroethyl)trifluorophosphate [HMIM][FAP]) as an extraction solvent for Cd2+ ions after complexation with 2-(6-methylbenzothiazolylazo)-6-nitrophenol (MBTANP) at pH 7.0. The impact of different analytical parameters on the microextraction efficiency was investigated. The validation of the proposed procedure was verified by the test of two certified reference materials (TMDA-51.3 fortified water, SRM spinach leaves 1570A) applying the standard addition method. Results: In the range of 2.0-200 μg L−1, the calibration graph was linear. Limit of detection, preconcentration factor and the relative standard deviation (RSD %, 100 μg L-1, n=5) as precision was 0.1 μg L-1, 100 and 3.1%, respectively. Conclusion: Green UA-IL-DLPME method was developed and applied to preconcentrate and determine trace quantities of Cd2+ in real water, vegetables and hair samples with satisfactory results.

Background: Analysis of drug concentrations in biological fluids is required in clinical sciences for various purposes. Among other biological samples, exhaled breath condensate (EBC) is a potential sample for follow up of drug concentrations. Methods: A dispersive liquid-liquid microextraction (DLLME) procedure followed by a validated liquid chromatography method was employed for the determination of budesonide (BDS) in EBC samples collected using a homemade setup. EBC is a non-invasive biological sample with possible applications for monitoring drug concentrations. The proposed analytical method is validated according to the FDA guidelines using EBC-spiked samples. Its applicability is tested on EBC samples collected from healthy volunteers receiving a single puff of BDS. Results: The best DLLME conditions involved the use of methanol (1 mL) as a disperser solvent, chloroform (200 μL) as an extraction solvent, and centrifugation rate of 3500 rpm for 5 minutes. The method was validated over a concentration range of 21-210 μg·L-1 in EBC. Inter- and intra-day precisions were less than 10% where the acceptable levels are less than 20%. The validated method was successfully applied for the determination of BDS in EBC samples. Conclusion: The findings of this study indicate that the developed method can be used for the extraction and quantification of BDS in EBC samples using a low cost method.

Background: The determination of mancozeb, a fungicide extensively used in agriculture, is a challenge, due to the nature of the compound, a manganese and zinc complex of ethylenebis dithiocarbamate and because of the general instability of the dithiocarbamates. Methods: Mancozeb was analyzed in a GC-EI-MS system after derivatization by CE-UV with detection at 280 nm and in LC-ESI-MS-MS in MRM mode. Results: A comparative study of the performance of three different techniques for the detection of mancozeb was explored, highlighting the advantages and drawbacks of them. The limits of detection and quantification of the techniques were determined; the repeatability was assessed, showing values of relative standard deviation. Gas chromatography, although very sensitive, was not reproducible enough due to fast degradation of the derivatization product, whereas capillary electrophoresis-UV showed problems in run-to-run reproducibility which had the worst limit of detection. LC coupled with tandem mass spectrometry was the most reliable and precise technique and was able to determine the main degradation product of Mancozeb, at the same time. The proposed LC procedure was verified by applying it to a commercial formulation, a fungicide of known concentration, and to Italian white grapes treated with the formulation sprayed during cultivation. Conclusion: Thanks to the simplified sample handling, the proposed method resulted to be simple, fast, green, economic, and suitable for residue analysis in grapes and other fruits. Finally, the method was compared with other similar investigations.

Background: Catalase is a vital antioxidant enzyme that dismutates H2O2 into water and molecular oxygen. Many protocols have been developed to measure catalase enzyme activity. Spectrophotometric methods are the most common assays that used to assess catalase enzyme activity. Methods: Because the rate-limiting step during catalase enzyme activity depends upon the dissociation of hydrogen peroxide, the developed assay measures the reaction between a hydroquinone/ anilinium sulfate/ammonium molybdate reagent and Unreacted Hydrogen Peroxide, which results in the production of a purple, disubstituted quinone compound with a maximum absorbance value at 550 nm. Results: To clarify the precision of the developed method, the coefficients of variation were determined to be 2.6% and 4.7% within run measurements and between run measurements, respectively. This method returned results that correlated well (r = 0.9982) with the results returned using the peroxovanadate method to assess catalase enzyme activity. Additionally, we examined the use of the newly developed hydroquinone assay to measure catalase enzyme activity in liver and bacterial homogenate samples. Conclusion: These results demonstrated that this assay can be used for scientific research and routine health applications because it is inexpensive, simple, accurate, and rapid. This method is suitable for use in clinical pathology laboratories because it is simple and produces precise and reproducible results.

Background: Paracetamol is a common antipyretic and analgesic drug, but its excessive intake can accumulate toxic metabolites and cause kidney and liver damage, so it is critical to determine the content of paracetamol for clinical diagnosis and dose use. Methods: Au-reduced graphene oxide (Au-rGO) nanocomposite decorated with poly(L-cysteine) on carbon paste electrode was fabricated for the determination of paracetamol. Au-rGO was first coelectrodeposited on the carbon paste electrode surface. Afterwards, L-cysteine was electropolymerized to fabricate the Au-rGO/poly(L-cysteine) modified carbon paste electrode. Scanning electron microscope was used to characterize the morphology of Au-rGO and poly(L-cysteine)/Au-rGO. The electrochemical properties of the sensor were studied by cyclic voltammetry and differential pulse voltammetry. Results: After exploring the optimal conditions, the sensor showed a wide linear response for paracetamol detection in the range of 1-200 μM with a detection limit of 0.5 μM (S/N = 3). Conclusion: The fabricated sensor demonstrated good sensitivity with rapid detection capacity in real samples.

Background: Multivariate analysis is a chemometric tool that has been little explored to determine physiological status under heavy metal stress. Nevertheless, PCA has an unexplored potential to determine the plant physiologic status and its modification under stress factors like heavy metals. Objectives: This work aims to assess the physiological and biochemical effects and responses of wheat plants under the different exposition of As and Cd using multivariate models. Material and Methods: Wheat plants growing in a greenhouse were exposed to 0, 10 and 50 mg kg-1 soil of As and 0, 10 and 33 50 mg kg-1 soil of Cd until growth stage 5. After 56 days, wheat leaves and roots were collected to determine dry weight, lipid peroxidation and the activity of three enzymes: catalase, ascorbate peroxidase and guaiacol peroxidase. These measures were considered as the variables of three performed multivariate models to determine physiological status. Results: Through the interpretation of score plot and loading plot in combination, it was possible to determine that both As and Cd affect chlorophyll content and antioxidant response. However, a chlorophyll decrease and a lipid peroxidation increase were observed together with an inhibition of antioxidant response more accentuated in wheat plants exposed to As than those exposed to Cd. Conclusion: Multivariate analysis allows us to determine the differences between the physiological behavior of both stressors, which turn this chemometric tools useful for the characterization of a physiological response.

Background: The elemental composition of maize grains depends on the soil, land and environment characteristics where the crop grows. These effects are important to evaluate the availability of nutrients with complex dynamics, such as the concentration of macro and micronutrients in soils, which can vary according to different topographies. There is available scarce information about the influence of topographic characteristics (upland and lowland) where culture is developed with the mineral composition of crop products, in the present case, maize seeds. On the other hand, the study of the topographic effect on crops using multivariate analysis tools has not been reported. Objective: This paper assesses the effect of topographic conditions on plants, analyzing the mineral profiles in maize seeds obtained in two land conditions: uplands and lowlands. Material and Methods: The mineral profile was studied by microwave plasma atomic emission spectrometry. Samples were collected from lowlands and uplands of cultivable lands of the north-east of La Pampa province, Argentina. Results: Differentiation of maize seeds collected from both topographical areas was achieved by principal components analysis (PCA), cluster analysis (CA) and linear discriminant analysis (LDA). PCA model based on mineral profile allowed to differentiate seeds from upland and lowlands by the influence of Cr and Mg variables. A significant accumulation of Cr and Mg in seeds from lowlands was observed. Cluster analysis confirmed such grouping but also, linear discriminant analysis achieved a correct classification of both the crops, showing the effect of topography on elemental profile. Conclusion: Multi-elemental analysis combined with chemometric tools proved useful to assess the effect of topographic characteristics on crops.

Background: The poly(ADP-ribose) polymerases (PARP) is a nuclear enzyme superfamily present in eukaryotes. Methods: In the present report, some efficient linear and non-linear methods including multiple linear regression (MLR), support vector machine (SVM) and artificial neural networks (ANN) were successfully used to develop and establish quantitative structure-activity relationship (QSAR) models capable of predicting pEC50 values of tetrahydropyridopyridazinone derivatives as effective PARP inhibitors. Principal component analysis (PCA) was used to a rational division of the whole data set and selection of the training and test sets. A genetic algorithm (GA) variable selection method was employed to select the optimal subset of descriptors that have the most significant contributions to the overall inhibitory activity from the large pool of calculated descriptors. Results: The accuracy and predictability of the proposed models were further confirmed using crossvalidation, validation through an external test set and Y-randomization (chance correlations) approaches. Moreover, an exhaustive statistical comparison was performed on the outputs of the proposed models. The results revealed that non-linear modeling approaches, including SVM and ANN could provide much more prediction capabilities. Conclusion: Among the constructed models and in terms of root mean square error of predictions (RMSEP), cross-validation coefficients (Q2 LOO and Q2 LGO), as well as R2 and F-statistical value for the training set, the predictive power of the GA-SVM approach was better. However, compared with MLR and SVM, the statistical parameters for the test set were more proper using the GA-ANN model.

Background: Axitinib (AXT) is a member of the new generation of the kinase inhibitor indicated for the treatment of advanced renal cell carcinoma. Its therapeutic benefits depend on assuring the good-quality of its dosage forms in terms of content and stability of the pharmaceutically active ingredient. Objective: This study was devoted to the development of a simple, sensitive and accurate stabilityindicating high-performance liquid chromatographic method with ultraviolet detection (HPLC-UV) for the determination of AXT in its bulk and dosage forms. Methods: Waters HPLC system was used. The chromatographic separation of AXT, internal standard (olaparib), and degradation products were performed on the Nucleosil CN column (250 x 4.6 mm, 5 μm). The mobile phase consisted of water:acetonitrile:methanol (40:40:20, v/v/v) with a flow rate of 1 ml/min, and the UV detector was set at 225 nm. AXT was subjected to different accelerated stress conditions and the degradation products, when any, were completely resolved from the intact AXT. Results: The method was linear (r = 0.9998) in the concentration range of 5-50 μg/ml. The limits of detection and quantitation were 0.85 and 2.57 μg/ml, respectively. The accuracy of the method, measured as recovery, was in the range of 98.0-103.6% with relative standard deviations in the range of 0.06-3.43%. The results of stability testing revealed that AXT was mostly stable in neutral and oxidative conditions; however, it was unstable in alkaline and acidic conditions. The kinetics of degradation were studied, and the kinetic rate constants were determined. The proposed method was successfully applied for the determination of AXT in bulk drug and dosage forms. Conclusion: A stability-indicating HPLC-UV method was developed and validated for assessing AXT stability in its bulk and dosage forms. The method met the regulatory requirements of the International Conference on Harmonization (ICH) and the Food and Drug Administration (FDA). The results demonstrated that the method would have great value when applied in quality control and stability studies for AXT.