Immobilized Activated Carbon as Sorbent in Solid Phase Extraction with Cold Vapor Atomic Absorption Spectrometry for the Preconcentration and Determination of Mercury Species in Water and Freshwater Fish Samples.

A new preconcentration method using solid phase extraction (SPE) was developed by immobilizing dithizone (DZ) and 1,4-diphenylsemicarbazide (DPC) on oxidative activated carbon and then using this for the speciation and preconcentration of mercury species (Hg(II) and MeHg(I)) by flow injection cold vapor atomic absorption spectrometry (FI-CVAAS). The SPE experimental conditions were investigated including pH, amount of adsorbent and flow rate. The elution parameters and effect of foreign ions were also elucidated. Under the optimized conditions, the calibration graph was linear in the ranges of 0.015 - 3.0 µg L-1 of Hg(II), with a detection limit (LOD) of 0.0155 µg L-1, corresponding to three times the standard deviation (3SD, n = 20). The precision of the method, defined as percentage relative standard deviation (%RSD) for mercury was 1.25 - 3.79% at concentrations of 0.1 - 1.0 µg L-1, for which a preconcentration factor of 20 was obtained for Hg(II). The proposed method was validated by determining the mercury concentration in standard reference materials, and successfully applied to the speciation of mercury in several water and freshwater fish samples.

Speciation of mercury in water and biological samples by eco-friendly ultrasound-assisted deep eutectic solvent based on liquid phase microextraction with electrothermal atomic absorption spectrometry.

A simple, fast, sensitive and eco-friendly ultrasound-assisted deep eutectic solvent liquid phase microextraction (UA-DES-LPME) was developed for preconcentration and speciation of Hg2+ and CH3Hg+ combined with ETAAS. Choline-phenol based DES (1:3, molar ratio) was used as an extractant for the determination of species of mercury, Hg2+ formed hydrophobic complexes with dithizone and complexes were then extracted using DES. For CH3Hg+ determination, CH3Hg+ can be extracted directly into DES phase because of its hydrophobic property. Under optimized conditions, the detection limits of Hg2+ and CH3Hg+ were 0.073 and 0.091 ng mL-1, respectively. %RSD (n = 7) were less than 4.1% and the enrichment factor (10 mL sample volume) were 34 and 18.3 for Hg2+ and CH3Hg+, respectively. The accuracy of the developed method was verified by analysis of SRM-1566b oyster tissue. The proposed method was applied to the speciation of mercury in several water and fresh water fish samples.

Determination of cadmium in herbs by SFODME with ETAAS detection.

A method for the determination of cadmium in herb samples based on solidified floating organic drop microextraction (SFODME) using 1-(2-Pyridylazo)-2-naphthol (PAN) as a chelating reagent and detection by electrothermal atomic absorption spectrometry (ETAAS) was developed in the present work. The effects of pH, extraction solvent, extraction time, stirring rate, and extraction temperature were investigated. Under the optimized conditions, the calibration graph was linear in the range of 0.017-3.0µgL-1, with a detection limit (LOD) of 0.0052µgL-1. The relative standard deviation (%RSD) for 6 replicate measurements of 1.0µgL-1 cadmium was ±2.67%. The method was applied to the analysis of 10 types of Thai herb samples. Percentage recoveries were in the range 94.5-110.2%. It was found that cadmium concentrations in all Thai herb samples were less than the maximum residue level.