Supramolecular–based dispersive liquid–liquid microextraction: A novel sample preparation technique for determination of inorganic species

Vortex-assisted low density solvent and surfactant based dispersive liquid–liquid microextraction for sensitive spectrophotometric determination of cobalt

This study describes the development of vortex-assisted low density solvent and surfactant based dispersive liquid–liquid microextraction (VALS-DLLME) for Co(ii) prior to its spectrophotometric detection. The method consisted of the complexation of Co(ii) with pyrocatechol violet (PV) followed by the preconcentration of the Co(II)–PV complex using VALS-DLLME and then an absorption measurement at 600 nm. The optimum conditions for complex formation were a 1 : 3 mole ratio of Co(ii) and PV at pH 7.5, while the conditions for VALS-DLLME were 300 μL 1-dodecanol as extraction solvent, and 300 μL acetonitrile as dispersive solvent under a vortex for 20 s with the addition of cationic surfactant (0.02 mmol L⁻¹ CTAB). Under the optimum conditions, good linearity was in the range of 0.1–10 mg L⁻¹, the enrichment factor (EF) was 13.5 and the low limit of detection (LOD) was 0.04 mg L⁻¹. The method was applied to the analysis of Co(ii) in water, green leaf vegetable and vitamin B₁₂ samples. The proposed method provided good recoveries in the range of 86–104%, which were comparable to those obtained from flame atomic absorption spectrophotometry.

The formation of a Co(II)–PV complex and the VALS-DLLME procedure.

A new supramolecular based liquid solid microextraction method for preconcentration and determination of trace bismuth in human blood serum and hair samples by electrothermal atomic absorption spectrometry

A simple and reliable supramolecule-aggregated liquid solid microextraction method is described for preconcentration and determination of trace amounts of bismuth in water as well as human blood serum and hair samples. Catanionic microstructures of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants, dissolved in deionized water/propanol, are used as a green solvent to extract bismuth (III)-diethyldithiocarbamate complexes by dispersive microextraction methodology. The extracted solid phase is easily removed and dissolved in 50 μL propanol for subsequent measurement by electrothermal atomic absorption spectrometry (ET-AAS). The procedure benefits the merits of supramolecule aggregates' properties and dispersive microextraction technique using water as the main component of disperser solvent, leading to direct interaction with analyte. Phase separation behavior of extraction solvent and different parameters influencing the extraction efficiency of bismuth ion such as salt concentration, pH, centrifugation time, amount of chelating agent, SDS:CTAB mole ratio, and solvent amounts were thoroughly optimized. Under the optimal experimental conditions, the calibration curve was linear in the range of 0.3-6 μg L^-1 Bi (III) with a limit of detection (LOD) of 0.16 μg L^-1 (S/N = 3). The relative standard deviations (RSD) of determination were obtained to be 5.1 and 6.2 % for 1 and 3 μg L^-1 of Bi (III), respectively. The developed method was successfully applied as a sensitive and accurate technique for determination of bismuth ion in human blood serum, hair samples, and a certified reference material.

Supramolecular solvent-based microextraction method for cobalt traces in food samples with optimization Plackett–Burman and central composite experimental design

A new microextraction method based on formation of supramolecular solvent (Ss) was developed by using of chemometric optimization method for cobalt determination with microsampling flame atomic absorption spectrometry (MS-FAAS).

Dispersive liquid-liquid microextraction for the high performance liquid chromatographic determination of aldehydes in cigarette smoke and injectable formulations

A dispersive liquid-liquid microextraction method (DLLME) combined with high performance liquid chromatography (HPLC) was developed for the extraction and determination of some aldehydes, such as benzaldehyde (BzA), butyraldehyde (BuA) and furfural (Fur) in mainstream cigarette smoke as well as BzA in injectable formulations. After trapping of combustion smoke into sulfuric acid with a laboratory-made smoking machine, aldehydes were converted into their hydrazone derivatives by the reaction with 2,4-dinitrophenylhydrazine (DNPH), and then rapidly extracted by DLLME. The effects of various experimental parameters on the derivatization and extraction were studied and optimized. Under the optimum extraction conditions, linear calibration curves in the range 0.025 to 1.0 μg/mL with correlation coefficients of 0.9980-0.9996 were obtained for studied aldehydes. Limit of detections (LODs) for BzA, BuA and Fur were found to be 14.2, 21.3 and 7.92 μg/L, respectively. The relative standard deviations (RSDs) for inter-and intra-day assays were lower than 8.50%. Average recoveries for spiked samples were in the range 88.0-109%. The proposed method was successfully applied to the determination of aldehydes in different real samples.