Use of tetraethylenepentamine-functional Fe3O4 magnetic polymers for matrix solid phase dispersion extraction and preconcentration of Cr(VI) in water samples at ultratrace levels.

A new method that utilizes tetraethylenepentamine-functional Fe(3)O(4) magnetic polymers (TEPA-NMPs) as a solid-phase extractant for matrix solid phase dispersion extraction (MSPD) has been developed for preconcentration of Cr(VI) at ultratrace levels prior to the measurement by flame atomic absorption spectroscopy (FAAS). The separation/preconcentration conditions of Cr(VI) was investigated, including the pH value, shaking time, adsorption temperature, sample volume, desorption conditions and interfering ions. The results showed the adsorption properties of the TEPA-NMPs were highly pH dependent. The data of adsorption kinetics obeyed pseudo-second-order rate mechanism well. Adsorption thermodynamic studies suggested that the adsorption processes of Cr(VI) onto the TEPA-NMPs was endothermic and entropy favored in nature. Under the best experimental conditions, the enhancement factor was 125 times, the detection limit of the method was 0.16 µg L(-1) and the relative standard deviation was 1.9% (n=7). Furthermore, the developed method was validated by comparing with Graphite Furnace atomic absorption spectrometry (GF-AAS) method, and has been applied for the determination of ultratrace Cr(VI) ions in the river and tap water samples with satisfactory results, which revealed the sensitivity of the proposed TEPA-NMPs MSPD-FAAS method was comparable with that of GF-AAS method.

[Improvement on flame atomic absorption spectrometry for determining Tin concentration in air of workplaces].

OBJECTIVE: To explore the influence factors on determining Tin concentration in air of workplaces with flame atomic absorption spectrometry and to establish an accurate, sensitive and high-efficient method. METHODS: The different reagents were used to digest the sampling filter membranes and the determining conditions of flame atomic absorption spectrometry were adjusted, then the determining results were compared. RESULTS: When 3 ml hydrochloric acid and 0.5 ml nitric acid served as the digesting reagents and the determining conditions of flame atomic absorption spectrometry were adjusted to the best conditions, there was the good linearity in the tested concentration range of Tin, the correlation coefficient was larger than 0.9990. The limit of quantification was 1.0 p.g/ml. The extraction recovery was between 99.6%-102.6%, and the RSD were all less than 5.0%. CONCLUSION: The proper kinds and quantity of digestive reagents in pretreatment of the samples should be chosen for the accuracy and precision of the determination according to the influence factors of determination.