Analytical and Bioanalytical Chemistry Research
Volume:8 Issue: 1, Winter 2021

In this study, the efficiency of packed needle trap with hydroxyapatite/polyaniline (NTD-HAP/PA) nanocomposite was assessed in air sampling and analysis of a hazardous group of VOCs such as benzene, toluene, ethylbenzene and xylenes. The effects of main parameters, including desorption temperature and time, were evaluated on the performance and carryover of prepared NTDs. Moreover, the repeatability, reproducibility and stability of the developed sampler were investigated for the sampling and determination of the interest analytes. The results of experiments indicated that the highest peak area was obtained at desorption temperature and time of 250˚C and 3 min, respectively. The reproducibility of the proposed method was investigated with three distinct NTDs with similar structure. The weight of the adsorbent also was obtained results showed that the relative standard deviation (RSD) of experiments was in the range of 0.2-9.7%. The RSD of repeatability was obtained at four different concentrations, with three times replications less than 15%. The Limit of Detection and Quantitation (LOD and LOQ) for the studied VOCs ranged from 0.01 to 0.14 ng/mL and 0.04 to 0.48 ng / mL, respectively. Also, the storage stability of the analytes of interest in the NTD-HAP/PA after 3 and 7 days at 4 °C was above 95 and 93%, respectively. It can be concluded that the proposed method could be applied as a desirable and powerful tool for air sampling and microextraction of volatile organic compounds

The surface of a fused silica fiber was activated and coated with graphene oxide (GO) film, using a facile layer-by-layer coating strategy. PTES, (3-aminopropyl) triethoxysilane, was used as a covalent cross-linker for tight-binding of the GO layers. By the combination of GO sorption capacity and APTES cross-linking ability, the developed solid-phase microextraction (SPME) fibers exhibited a very good chemical/mechanical stability and high extraction efficiency. The developed fibers were used for headspace sampling of nicotine from the hair of smokers, without any sample preparation step. The determination of the analyte was done using GC-FID technique. Despite the thin thickness of GO multilayer, it was very robust and durable and its performance was higher than traditional GO coatings and polyacrylate commercial fibers. The most important experimental variables were studied. Under the optimal conditions, the limit of detection and relative standard deviation (RSD%, n=3) was 0.02 μg/g 5.6-8.9%, respectively. The calibration graph was linear over the range of 0.1-100 μg/g. The fiber was successfully applied for the determination of nicotine in hair samples of active and passive smokers.

A simple, inexpensive, nearly solvent-free headspace single-drop microextraction (HS-SDME) followed by gas chromatography and flame ionization detection (GC-FID) was developed for determining methanol and ethanol in samples of transformer insulation oils. Five effective parameters in HS-SDME process, including extraction solvent volume, sample content, extraction time, extraction temperature, and agitation speed were screened and subsequently optimized using fractional factorial screening methodology (FFSM) and response surface methodology using Box-Behnken design (BBD). The extraction was carried out with dimethyl sulfoxide (DMSO) as micro drop, with 1µl of extraction phase injected into the GC-FID system. The calibration curve for the analytes was found to be linear within the range of 0.05 µg/g to 10.00 µg/g, and the limits of detection for methanol and ethanol were 0.02 µg/g and 0.03 µg/g, respectively. The relative standard deviation obtained within 1.8 - 5.2% and a good recovery achieved within the range of 95.0 to 102.6% in the analysis of oil samples revealed that methanol and ethanol could be determined as a chemical marker of the transformer life using this method.

In the present work, an on-line solid-phase extraction system is proposed for the preconcentration and accurate determination of trace amounts of cadmium(II) ions by flame atomic absorption spectrometry. The preconcentration of cadmium(II) ions was performed using polyvinyl chloride functionalized with 3-(2-thiazolylazo)-2,6-diaminopyridine in a minicolumn system. The adsorbed cadmium(II) ions were then eluted from the sorbent by the eluent. The important influencing parameters such as the sample solution pH, type and concentration of the eluent used for stripping cadmium(II) ions from the sorbent, flow rate of the sample and the eluent, and amount of adsorbent were investigated in detail. Under the optimum experimental conditions, the linear dynamic range of the method was found to be in the range of 2.0–40.0 µg L−1 (with the determination coefficient equal to 0.9987). The limit of detection and improvement factor were 0.7 µg L−1 and 52.4, respectively. The inter assay precession (RSD%, n=7) was in the range of 0.8-4.1% at the concentration levels of 5.00, 9.00, and 25.0 µg L−1. The validated method was successfully employed for determination of cadmium(II) ions at trace levels in the spiked water and soil samples with satisfactory results.

This study presents hollow fibers in liquid-phase micro extraction (LPME) method as a technique, in order to pre-concentrate Metoprolol Succinate drugs from tap water and urine samples. The extracted analyte with hallow fiber was detected with high performance liquid chromatography equipped with ultraviolet detector (HPLC-UV). The effect of several parameters on extraction efficiency such as organic solvent type, receiving phase, pH of receiving and extractant phase, the extraction time and mixing speed were investigated and optimized. After extracting the Metoprolol Succinate drug under the optimum conditions such as types of extraction solvents, stirring speed, extraction time and solvent pH, the pre-concentration factor was obtained 192 for tap water and 169 for urine samples. The obtained detection limit was 3.90 μg/L for urine and 1.5 μg/L for tap water in which R2 > 0.995. The extraction recovery for real samples was 94% for urine sample and 98 % for tap water.

The present study quantitative structure-property relationship (QSPR) model developed for the adsorption efficiency (AE) of 70 pesticides in water sample on MWCNT/PbO2 solid phase extraction cartridge. Stepwise-multiple linear regression (SW-MLR) method employed for selection of descriptors. The selected descriptors are MATS7v, MATS6c, GATS3s, ATSC6i, C040, SpMin8_Bhi, E2v, JGI1 and Mor08u. Curiosity at the effective descriptors indicates electronic, topological and geometrical characteristics of studied pesticides are the most effective parameters on their AE on MWCNT/PbO2 nanocomposite adsorbent. Symbolic regression via genetic programming (SR-GP) utilized to offer the symbolic regression QSPR model. The accuracy and predictive power of the SR-GP model compared with traditional linear and nonlinear regression models contain multiple linear regression (MLR) and support vector regression (SVR). Inspection the fitness parameters confirmed the superiority of SR-GP model over MLR, and SVR models. In SR-GP model, the correlation coefficient (R) was 0.930 and 0.890, and the root mean square errors (RMSE) were 0.04 and 0.05 for the training and test sets, respectively. These results can be used to predict the AE for other pesticides by MWCNT/PbO2 adsorbent and designing a more efficient nano cartridge for SPE.

In this study, aggregated silver nanoparticles were prepared using sulphanilic acid and catechol as a collection of stabilizing-reducing system. Preliminary studies showed that catechol (CAT) is readily oxidized by silver ions followed by sulphanilic acid (SA) nucleophilic attack. The resulting catechol derivative aggregates silver nanoparticles (Ag-NPs). The resulting product was characterized by different characterization techniques including UV–VIS spectrometry and transmission electron microscope (TEM). The SA-CAT induced aggregated Ag-NPs were used to develop a fast and ready to use colorimetric detection method for fluoride ion in water. In the presence of fluoride ions, the color of aggregated Ag-NPs solution change from brown to yellow with an absorbance decrease at 508 nm and an increase at 397 nm. Under the optimized conditions, the ratio of the absorbance intensity at 508 nm and 397 nm (A397/A508) was proportional to the fluoride ion concentration in the range of 1-40 µM with a detection limit of 0.2 µM. The proposed new method was successfully used for the determination of fluoride concentration in the local spring water samples.

Facile hydrothermal synthetic technique was employed for the fabrication of SALEN grafted multifunctional nanocomposite biochar with the main aim of efficient and effective removal of cadmium (Cd). The elemental composition and structure of the composite and the cadmium loaded sorbent were characterized using EDX, FTIR and SEM. Variables affecting cadmium removal such as initial metal ion concentration, contact time and pH were investigated by batch experiment. Maximum adsorption capacity of 8220 mg/kg was obtained at optimal pH 10 with percentage removal efficiency of 99.30 % for 4480 ppm initial metal ion dosage. Data simulated into the adsorption and kinetic models fitted well the Freundlich isotherm implicating multilayer adsorption – chemisorption process and pseudo-second –order kinetics as the rate limiting step. Critical examination of the adsorption mechanism showed that inner-sphere complexation, ion exchange, co-precipitation and electrostatic attraction are the main driving force in the mechanistic interaction of the SALEN Schiff base N2O2 surface functionalized nanocomposite biochar with cadmium. The new nanocomposite is of low cost, benign, effective and efficient for the removal of cadmium in comparison with industrial sorbents and other functionalized biomaterials and highly recommended for decontamination of cadmium polluted sites.