Development and Validation of a Sensitive Method for Trace Nickel Determination by Slotted Quartz Tube Flame Atomic Absorption Spectrometry After Dispersive Liquid-Liquid Microextraction

Sensitive determination of nickel at trace levels in surface water samples by slotted quartz tube flame atomic absorption spectrometry after switchable solvent liquid-phase microextraction

In this study, switchable solvent (SS) for liquid-phase microextraction (LPME) was used as a tool to preconcentrate nickel from aqueous samples for determination by flame atomic absorption spectrometry. The SS-LPME method was optimized thoroughly to boost the absorbance signal of nickel for trace level determination. Parameters optimized included switchable solvent volume, sodium hydroxide concentration, sodium hydroxide volume, and eluent volume. The SS-LPME method enhanced the detection power by about 32-folds, and a slotted quartz tube (SQT) was used to obtain 2.6-folds increase in detection power. The combination of LPME and SQT-FAAS produced 104-folds enhancement, correlating to a limit of detection value of 1.8 μg/L. Low relative standard deviations calculated for the lowest calibration concentration indicated good repeatability for replicate measurements. Accuracy of the optimized method and its applicability to real samples was tested on two river samples. The results (85-103%) obtained from the spike recovery experiments were satisfactory.

Opportunities for green microextractions in comprehensive two-dimensional gas chromatography / mass spectrometry-based metabolomics - A review

Microextractions have become an attractive class of techniques for metabolomics. The most popular technique is solid-phase microextraction that revolutionized the field of modern sample preparation in the early nineties. Ever since this milestone, microextractions have taken on many principles and formats comprising droplets, fibers, membranes, needles, and blades. Sampling devices may be customized to impart exhaustive or equilibrium-based characteristics to the extraction method. Equilibrium-based approaches may rely on additional methods for calibration, such as diffusion-based or on-fiber kinetic calibration to improve bioanalysis. In addition, microextraction-based methods may enable minimally invasive sampling protocols and measure the average free concentration of analytes in heterogeneous multiphasic biological systems. On-fiber derivatization has evidenced new opportunities for targeted and untargeted analysis in metabolomics. All these advantages have highlighted the potential of microextraction techniques for in vivo and on-site sampling and sample preparation, while many opportunities are still available for laboratory protocols. In this review, we outline and discuss some of the most recent applications using microextractions techniques for comprehensive two-dimensional gas chromatography-based metabolomics, including potential research opportunities.