Abdulnaser Alsharaa

Evaluation of layered double hydroxide/graphene hybrid as a sorbent in membrane-protected stir-bar supported micro-solid-phase extraction for determination of organochlorine pesticides in urine samples

In this work, the potential of layered double hydroxide/graphene (LDH-G) hybrid as a sorbent for extraction and preconcentration of fifteen organochlorine pesticides (OCPs) in urine samples was evaluated. The LDH-G hybrid was synthesized by co-precipitation method and it was then characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The sorbent was then employed in membrane-protected stir-bar supported micro-solid-phase extraction (SB-μ-SPE) of OCPs in urine samples. This extraction approach is highly suitable for the samples representing matrix complexity such as urine because the sorbent is effectively protected inside the membrane. The extracted samples were analyzed by gas chromatography mass spectrometry. The factors that affect the performance of SB-μ-SPE were suitably optimized. This method demonstrated good linearity with coefficients of determination up to 0.9996. The limits of detection ranged between 0.22 and 1.38ngmL-1. The RSD values for intra and inter-day precision were also in a satisfactory range (2.7-9.5%).

Single-step microwave assisted headspace liquid-phase microextraction of trihalomethanes and haloketones in biological samples.

A single-step microwave assisted headspace liquid-phase microextraction (MA-HS-LPME) method was developed for determination of trihalomethanes (THMs) and haloketones (HKs) in biological samples. In this method, a porous membrane envelope was filled with few microliters of extraction solvent and then placed inside the microwave extraction vial. A PTFE ring was designed to support the membrane envelope over a certain height inside the vial. An optimum amount of biological sample was placed in the vial equipped with magnetic stirrer. After that nitric acid was added to the vial for digestion of biological sample. The sample was digested and the volatile THMs and HKs were extracted at headspace in the solvent containing porous membrane. After simultaneous digestion and extraction, the extract was injected to gas chromatography/mass spectrometry for analysis. Factors affecting the extraction efficiency were optimized to achieve higher extraction performance. Quantification was carried out over a concentration range of 0.3-100ngg(-1) for brominated compounds while for the chlorinated ones linear range was between 0.5-100ngg(-1). Limit of detections (LODs) were ranged from 0.051 to 0.110ngg(-1) while limit of quantification (LOQ) were in the range of 0.175-0.351ngg(-1). The relative standard deviations (RSDs) of the calibrations were ranged between 1.1 and 6.8%. The MA-HS-LPME was applied for the determination of trace level THMs and HKs in fish tissue and green alga samples.

Determination of haloacetic acids in water using layered double hydroxides as a sorbent in dispersive solid-phase extraction followed by liquid chromatography with tandem mass spectrometry.

In the present study, highly efficient and simple dispersive solid-phase extraction procedure for the determination of haloacetic acids in water samples has been established. Three different types of layered double hydroxides were synthesized and used as a sorbent in dispersive solid-phase extraction. Due to the interesting behavior of layered double hydroxides in an acidic medium (pH˂4), the analyte elution step was not needed; the layered double hydroxides are simply dissolved in acid immediately after extraction to release the analytes which are then directly introduced into a liquid chromatography with tandem mass spectrometry system for analysis. Several dispersive solid-phase extraction parameters were optimized to increase the extraction efficiency of haloacetic acids such as temperature, extraction time and pH. Under optimum conditions, good linearity was achieved over the concentration range of 0.05-100 μg/L with detection limits in the range of 0.006-0.05 μg/L. The relative standard deviations were 0.33-3.64% (n = 6). The proposed method was applied to different water samples collected from a drinking water plant to determine the concentrations of haloacetic acids.

Biogenic synthesis of silver nanoparticles; study of the effect of physicochemical parameters and application as nanosensor in the colorimetric detection of Hg2+ in water

ABSTRACT This research demonstrates the ability of biogenic synthesised silver nanoparticles (AgNPs) to sensitively and selectively detect the presence of mercury (Hg2+) in water. To achieve this, the following study investigated the synthesis of AgNPs using plant extract from basil and characterised the synthesised AgNPs using scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-visible spectrophotometry, X-ray diffractometry and Fourier transform infrared spectroscopy. We studied the effect of various factors, such as broth concentration, precursor concentration, temperature, contact time and pH, on the synthesis of the nanoparticles. The synthesised AgNPs were then used in the colorimetric detection of Hg2+ in water. The as-prepared AgNPs showed high selectivity to detect Hg2+ alone compared to other cations and high sensitivity at different concentration of Hg2+. The limit of detection for Hg2+ was 6.25 × 10–8 mol/L (12 µg/L) indicating that these biogenic synthesised AgNPs represent a highly sensitive Hg2+ detection tool.