Dotse Selali Chormey

Determination of Lead in Drinking and Wastewater by Hydride Generation Atomic Absorption Spectrometry

ABSTRACT This work describes the optimization of hydride generation atomic absorption spectrometry for the determination of lead at trace concentrations. The parameters affecting the production, transport, and atomization of plumbane in a closed vessel were optimized. The concentrations of reagents affecting the generation of the lead hydride were also optimized to obtain high hydride generation efficiency. The atomization temperature, reaction period, pump speed, pump period, and flow rates of reducing agent and carrier gas were varied to maximize the sensitivity for lead. The accuracy of the method was evaluated by the analysis of certified reference materials. The method provided a linear dynamic range for lead from 2.0 to 40 µg/L with a limit of detection of 0.56 µg/L.

Development of a sensitive liquid–liquid extraction method for the determination of N-butyryl-L-homoserine lactone produced in a submerged membrane bioreactor by gas chromatography mass spectrometry and deuterated anthracene as the internal standard

Quorum sensing is defined as the bacterial communication through sending and receiving chemical signals such as N-acyl homoserine lactone (AHL) and oligopeptide for Gram negative bacteria and Gram positive bacteria, respectively. This mysterious bacterial interaction regulates a wide range of activities affecting the environment, agriculture, and therefore, humans. In the last century, quorum sensing investigations trying to follow and measure these chemical signals have accelerated. In this study, an analytical method was developed and optimized in order to extract and measure one of the AHLs: N-butyryl-L-homoserine lactone (C4-HSL) by gas chromatography-mass spectrometry (GC-MS). The aim of the study was to develop a method that increases the sensitivity and precision of AHL detection by GC-MS due to the problem in the determination of analytes in wastewater which have a complex matrix. The limits of detection and quantification obtained for C4-HSL were 12.9 ng mL−1 and 43.3 ng mL−1, respectively. The precision of the method was improved upon using deuterated anthracene as the internal standard, which gave a lower relative standard deviation compared to that without the internal standard.

Arsenic speciation in water and biota samples at trace levels by ion chromatography inductively coupled plasma-mass spectrometry

ABSTRACT A sensitive, reliable, simple and rapid analytical method was developed for the determination of arsenite [As(III)], arsenate [As(V)] and arsenobetaine (AsB) species using ion chromatography combined with inductively coupled plasma-mass spectrometry (IC-ICP-MS). Inorganic and organic arsenic species were separated with an anion exchange column (Dionex AS9) and a 50 mM sodium bicarbonate mobile phase (pH 10) at a flow rate of 1.0 mL min−1. %RSD values were found to be lower than 5.1% for all arsenic species. The limits of detection (LOD) obtained for As(III), As(V) and AsB were 16.5 ng L−1, 14.1 ng L−1 and 6.2 ng L−1, respectively. The developed analytical method was tested using AsB certified reference material (NMIJ CRM 7901-a), and spring water certified reference material (UME CRM 1201) for accuracy check. This method was applied for the quantitative determination of arsenic species in different water samples and chicken samples as a solid matrix.

Accurate determination of pesticides, hormones and endocrine disruptor compounds in complex environmental samples using matrix dilution and matrix matching with dispersive liquid–liquid microextraction

Abstract Quantitative determination of contaminants in environmental samples is usually hampered by low analyte recovery which results from the complex nature of the sample matrix. This study presents the application of a developed dispersive liquid–liquid microextraction method for the determination of 12 analytes in environmental samples including sea water, fresh water (lake, well and tap water), brackish water and soil samples. Matrix matched standards were used to compensate for the low analyte recovery recorded by the conventional calibration method. The effect of matrix dilution on analyte recovery was also tested. All matrix matched and matrix diluted spiked recoveries were done concurrently with calibration standards prepared in deionized water. Percent recoveries recorded for the analytes according to deionized water calibration standards ranged between 66 and 137%. Matrix matching and matrix dilution yielded close to 100% recovery results, but the later lowered the detection limit according to the dilution factor.

Development of a sensitive closed batch vessel hydride generation atomic absorption spectrometry method for the determination of cadmium in aqueous samples

ABSTRACT Hydride generation atomic absorption spectrometry was used as a simple, sensitive, and economical method for the determination of cadmium at trace levels. This study includes a stepwise optimization of all parameters that have an impact on the production, transport, and atomization of cadmium hydride for rapid determination due to the unstable nature of the hydride produced. The cell temperature for atomization, pump period, and flow rate of carrier gas were varied, and the best conditions were defined to obtain lower detection limits. In addition, the acid and sodium borohydride concentrations were optimized since they directly affect the production of the cadmium hydride. Under optimum experimental conditions, the hydride generation efficiency was greatly enhanced to record optimized analytical signals. The accuracy of the method was determined by the analysis of a certified reference material, and the results were in good agreement with the certified value. A linear dynamic range for cadmium was observed from 0.10 to 2.0 µg/L. High sensitivity was obtained with a limit of detection of 0.029 µg/L.

Determination of Bismuth in Bottled and Mineral Water Samples at Trace Levels by T-Shaped Slotted Quartz Tube – Atom Trapping – Flame Atomic Absorption Spectrometry

Abstract An accurate and reliable analytical method for the determination of bismuth at trace levels in bottled and mineral water samples has been developed based on hydrogen assisted T-shape slotted quartz tube-atom trap-flame atomic absorption spectrometry (T-SQT-AT-FAAS). Conventional FAAS is not sufficiently sensitive to measure trace and ultra-trace levels of metals due to the low nebulization efficiency and short residence time of atoms in the light path. To overcome this problem, atom trapping with a T-shaped slotted quartz tube was coupled to the FAAS system. Bismuth atoms were trapped on the surface of T-SQT and released by hydrogen gas, which provided a reducing environment. All of the system parameters such as flame type, hydrogen flow rate, the height of T-SQT from the burner head, and trapping period were optimized to enhance the analytical signal to attain low detection limits. After obtaining the optimum conditions, the limit of detection and limit of quantitation of the developed method were found to be 0.95 and 3.2 µg L−1, respectively. Recovery values were obtained between 90% and 104% that showed good accuracy and applicability of the proposed method to the analysis of bottled and mineral water samples.