A simple, comprehensive, and miniaturized solvent extraction method for determination of particulate-phase polycyclic aromatic compounds in air.

The method allowed simultaneous characterization of PAHs, nitro-PAHs and quinones in atmospheric particulate matter. This method employs a miniaturized micro-extraction step that uses 500 µL of an acetonitrile-dichloromethane mix and instrumental analysis by means of a high-resolution GC-MS. The method was validated using the SRM1649b NIST standard reference material as well as deuterated internal standards. The results are in good agreement with the certified values and show recoveries between 75% and 145%. Limit of detection (LOD) values for PAHs were found to be between 0.5 pg (benzo[a]pyrene) to 2.1 pg (dibenzo[a,h]anthracene), for nitro-PAHs ranged between 3.2 pg (1-nitrobenzo[e]pyrene) and 22.2 pg (3-nitrophenanthrene), and for quinones ranged between 11.5 pg (1,4-naphthoquinone) and 458 pg (9,10-phenanthraquinone). The validated method was applied to real PM10 samples collected on quartz fiber filters. Concentrations in the PM10 samples ranged from 0.06 to 15 ng m(-3) for PAHs, from

Doehlert matrix for optimisation of procedure for determination of nickel in saline oil-refinery effluents by use of flame atomic absorption spectrometry after preconcentration by cloud-point extraction.

This paper proposes a preconcentration procedure for determination of nickel in saline aqueous waste samples by flame atomic absorption spectrometry (FAAS). It is based on cloud-point extraction of nickel(II) ions as 2-(5-bromo-2-pyridylazo)-5-diethilaminophenol (Br-PADAP) complexes using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The optimisation step was performed using a four-variable Doehlert design, involving the factors centrifugation time (CT) of system after addition of surfactant, solution pH, methanol volume (MV) added at micellar phase, and buffer concentration (BC). The analytical response used was absorbance, after volume correction. Using the established experimental conditions in the optimisation step the procedure enables nickel determination with a detection limit (3 delta/ S) of 0.2 microg L(-1), quantification limit (10 delta/ S) of 0.7 microg L(-1), and precision, calculated as relative standard deviation ( RSD) of 4.7 ( n=8) and 3.5% ( n=8) for nickel concentration of 1 and 5 microg L(-1), respectively. The preconcentration factor, determined from the ratio of the slopes of the analytical curves with and without preconcentration, is 74. The recovery achieved for nickel determination in the presence of several cations demonstrated that this procedure could be applied for analysis of water samples. The robustness was checked by using saturated fractional factorial designs, centred on the established experimental conditions in the optimisation step. The results of these tests demonstrated that the variables centrifugation time and buffer concentration are robust for modification by 10% and that solution pH and methanol volume are robust for 5%. Accuracy was evaluated by using the certified material reference SLEW-3 estuarine water for trace metals. The procedure was used for determination of nickel in saline effluents from oil refinery samples. Recovery results (95-104%) indicate that the procedure has satisfactory accuracy for nickel determination in these samples.