Trace determination of cobalt in biological fluids based on preconcentration with a new competitive ligand using dispersive liquid-liquid microextraction combined with slotted quartz tube-flame atomic absorption spectrophotometry

Microextraction techniques for occupational biological monitoring: Basic principles, current applications and future perspectives

The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers' exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.

Surface-Active Ionic Liquid-Assisted Cloud Point Extraction for Pre-Concentration and Determination of Cobalt Ions in Pharmaceutical Preparations

: Herein we describe an efficient, simple, and precise micelle-mediated microextraction strategy based on the aggregation behavior of surface-active ionic liquids (SAILs) for the preconcentration and determination of cobalt ions in pharmaceutical preparations. Unlike the commonly used hydrophobic ionic liquids in IL-based microextraction methods, a water-soluble surface-active ionic liquid [1-hexadecyl 3-methylimidazolium chloride (C16MeImCl)] was used. A modified cloud point extraction (CPE) procedure based on the C16MeImCl-Triton X-114 mixed micellar system was proposed as an efficient extracting phase. A comparison of the analytical features of the extraction process with and without SAILs revealed the benefits of the proposed method. Advantages such as a wider linear range, lower detection limit, higher reproducibility, and improved extraction efficiency highlighted the proposed method over the conventional CPE method. These attractive specifications are due to the higher extraction efficiencies achieved in the presence of the SAIL and its favorable effects at the phase separation stage. Various parameters affecting the extraction efficiency were optimized by univariate and multivariate (Box-Behnken design) approaches. The calibration curve was obtained in the optimal experimental conditions with a linear range from 0.01 to 5.5 mg L-1 of cobalt ion concentration (R = 0.9992) and a detection limit of about 0.005 mg L-1. The RSD% for 10 replicate determinations of 1.0 mg L-1 Co was 0.9%. The proposed method was successfully applied to determine cobalt ions in vitamin B12 ampoules and tablets.

Efficiency enhancement of the spectrophotometric estimation of cobalt in waters and pharmaceutical preparations using dispersive liquid-liquid microextraction and microcells with long optical paths

In this paper, dispersive liquid-liquid microextraction (DLLME), long optical path microcells, and a selective chromogenic reagent were employed to improve the analytical efficiency of cobalt determination by spectrophotometry. The methodology proposed in the present study is based upon the microextraction of a cobalt(II) complex with 1-[4-[(2-hydroxynaphthalen-1-yl)methylideneamino] phenyl]ethanone (HNE) by DLLME and measurement of the absorbance of the sedimented phase using a microcell with an optical path length of 50 mm (Microcell-50). DLLME was performed using a binary mixture containing 900 μL of methanol as a dispersing solvent and 400 μL of CHCl₃ (extraction solvent) at pH 6-8 adjusted by a mixture of HCl and NaOH. The electronic spectrum of the dark brown complex recorded in the sedimented phase using Microcell-50 shows a well-defined peak at λ_max 324 ± 3 nm with a molar absorptivity of 1.08 × 10⁶ M^-1 cm^-1. Cobalt was monitored at a detection limit (LOD) of 0.08 μg L^-1 and in the linear concentration range of 0.45-10 μg L^-1, while the limit of quantitation (LOQ), relative standard deviation (RSD), and the enhancement factor (EF) were 0.264, 1.6 μgL^-1, and 223, respectively. Our method was evaluated by determining cobalt in certified reference materials and experimental samples, and the results were compared with ICP-MS measurements. Moreover, the chemical structure of the [Co(C₃₈H₂₈O₂N)₂] complex was suggested through using different characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermal analysis, and powder X-ray diffraction.

Recent applications of microextraction sample preparation techniques in biological samples analysis

Analysis of biological samples is affected by interfering substances with chemical properties similar to those of the target analytes, such as drugs. Biological samples such as whole blood, plasma, serum, urine and saliva must be properly processed for separation, purification, enrichment and chemical modification to meet the requirements of the analytical instruments. This causes the sample preparation stage to be of undeniable importance in the analysis of such samples through methods such as microextraction techniques. The scope of this review will cover a comprehensive summary of available literature data on microextraction techniques playing a key role for analytical purposes, methods of their implementation in common biological samples, and finally, the most recent examples of application of microextraction techniques in preconcentration of analytes from urine, blood and saliva samples. The objectives and merits of each microextration technique are carefully described in detail with respect to the nature of the biological samples. This review presents the most recent and innovative work published on microextraction application in common biological samples, mostly focused on original studies reported from 2017 to date. The main sections of this review comprise an introduction to the microextraction techniques supported by recent application studies involving quantitative and qualitative results and summaries of the most significant, recently published applications of microextracion methods in biological samples. This article considers recent applications of several microextraction techniques in the field of sample preparation for biological samples including urine, blood and saliva, with consideration for extraction techniques, sample preparation and instrumental detection systems.

Ionic hydrophobic deep eutectic solvents in developing air-assisted liquid-phase microextraction based on experimental design: Application to flame atomic absorption spectrometry determination of cobalt in liquid and solid samples

This paper reports a new and simple microextraction procedure for cobalt determination using green ionic hydrophobic deep eutectic solvent in developing air-assisted liquid-phase microextraction and flame atomic absorption spectrometry. Thecomplexationof Co(II) ions was carried out by using dithizone solution as complexing agent at pH5.The key variables affecting microextraction steps were optimized by response surface methodology (RSM) based on central composite design. Under the optimum microextraction conditions, calibration graph was linear in the range of 0.1-500 µg L^-1 Co(II) with correlation coefficient of 0.9985. Additionally, detection limit, quantitation limit and enrichment factor were found to be 0.04 µg L^-1, 0.1 µg L^-1 and 175, respectively. The reproducibility and repeatability were ≤ 2.9% and ≤ 3.6%, respectively. Based on the results obtained, the proposed methodology has been successfully employed for Co analysis in liquid and solid samples with recovery range of 94.2-105%.