Sui Wang

A pre-enrichment procedure using diethyldithiocarbamate-modified TiO2 nanoparticles for the analysis of biological and natural water samples by ICP-AES

In this article, a new method that utilizes a diethyldithiocarbamate-modified nanometre TiO2 (TiO2–DDTC) as solid-phase extractant has been developed for simultaneous preconcentration of trace Cu(II), Pb(II), Zn(II), and Cd(II) prior to measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The separation/preconcentration conditions of analytes, which include the effects of pH, sample flow rate and volume, elution conditions, and interfering ions on the recovery of the analytes, were investigated. At pH 5, the adsorption capacity of modified nanometre TiO2–DDTC was found to be 6.2, 19, 4.7, and 6.0 mg/g for Cu(II), Pb(II), Zn(II), and Cd(II), respectively. According to the definition of IUPAC, the detection limits (3σ) of this method for Cu(II), Pb(II), Zn(II), and Cd(II) were 0.41, 1.7, 0.39, and 0.52 ng/mL, respectively. The proposed method achieved satisfied results when applied to the determinations of trace Cu(II), Pb(II), Zn(II), and Cd(II) in biological and natural water samples.

Solid-phase spectrophotometric determination of nickel in water and vegetable samples at sub-μg l−1 level with o-carboxylphenyldiazoaminoazobenzene loaded XAD-4

A highly sensitive and selective solid-phase spectrophotometric method for the determination of sub-mugl(-1) level nickel(II) is described. Nickel(II) was sorbed on a styrene-divinylbenzene-type resin Amberlite XAD-4 as a Ni(II)-o-carboxylphenyldiazoaminoazobenzene (o-CDAA) complex. At pH 9.0, resin phase absorbances at 588 and 800nm were measured directly with an apparent molar absorptivity of 2.95x10(7)gmol(-1)cm(-1). The linear range of the determination was 1.2-41mugg(-1) resin. The detection limit and the quantification limit were found to be 0.24 and 0.76mugg(-1) resin, respectively. The relative standard deviation of 10 replicate determinations of 1.0mug nickel(II) in 100ml sample was of 1.5%. The tolerance limit of coexistent ions was also investigated. Most of them are in tolerable amount. For practical analyses, 1ml acetylacetone used can eliminate the interferences caused by Cu and Fe. The procedure was validated by analysis a certified water reference material (GBW 08618 Beijing, China) and a tomato leaf certified reference material (GBW 08402 Beijing, China) with the results in agreement with the certified values. The method was applied to the determination of nickel(II) in water and vegetable samples with satisfactory results.