The seasonal changes in the concentration of polycyclic aromatic hydrocarbons in precipitation and aerosol near Lake Balaton, Hungary.

The concentration of polycyclic aromatic hydrocarbons (PAHs) in atmospheric precipitation and aerosol samples was monitored in a rural site by Lake Balaton, Hungary to examine the seasonal variation. The seasonal mean concentration of individual 3-6-ring PAHs in precipitation varied from 1 to 54 ng l-1 and from 3 to 350 ng l-1 in summer and winter, respectively. In the atmospheric aerosol samples the seasonal mean concentration of PAHs varied from 4 to 880 pg m-3, from 4 to 300 pg m-3, from 11 to 1050 pg m-3 and from 36 to 5000 pg m-3 in spring, summer, autumn and winter, respectively. Wet (412 micrograms m-2 year-1) and aerosol (190-300 micrograms m2 year-1) deposition rates were also estimated indicating that the two processes are of comparable importance in the removal of 3-6-ring PAHs from the atmosphere.

Isolation of water-soluble organic matter from atmospheric aerosol.

The development of a solid phase extraction (SPE) method is presented, which is capable of isolating approx. 60% of the water-soluble organic compounds from aerosol samples. The aqueous extracts of the filter samples were acidified then passed through an SPE column. Four silica-based and two polymeric reversed phase columns were tested and similar recoveries of the organic carbon were found. The isolated organic matter was nearly free from inorganic ions, which are major constituents of atmospheric aerosol. This fraction accounted for a major part of the UV absorption above 250 nm and fluorescence activity of the aerosol extract. The precision of the method was tested by performing three parallel sample preparations with Oasis HLB columns. It was found that the relative standard deviation of the carbon content of the isolated organic matter was better than 7%, which indicated the reliability of the method. In the atmospheric aerosol research the newly developed sample preparation method facilitates the physical and chemical characterisation of water-soluble organic compounds without the interference of inorganic constituents.

Electrokinetic injection in capillary electrophoresis and its application to the analysis of inorganic compounds.

In capillary electrophoresis, electrokinetic injection is a highly controversial sampling technique. It is a simple mode of sample introduction which is suitable for on-line preconcentration of the analytes, but its precision and accuracy are more strongly affected by experimental conditions compared to hydrodynamic injection. In the first part of this paper the features of electrokinetic and hydrodynamic injections are compared, followed by a detailed discussion on the different biases of electrokinetic injection and on how to reduce them. Finally, applications of the electrokinetic injection are reviewed with special emphasis on the analysis of inorganic compounds.

Sample preparation of atmospheric aerosol for the determination of carbonyl compounds.

Sample preparation including sonication and solid phase extraction has been developed for the determination of carbonyl compounds in atmospheric aerosol. Aerosol samples were sonicated in acidified acetonitrile containing 2,4-dinitrophenylhydrazine (DNPH) to form hydrazone derivatives of aldehydes and ketones. Water was added to the extract to increase its polarity. Then the solution was passed through an octadecyl or phenyl solid phase extraction cartridge. The concentrated hydrazone derivatives were eluted with tetrahydrofuran, the eluate was evaporated to dryness then dissolved in acetonitrile/water mixture and finally analysed by RP-HPLC with UV detection at 360 nm. The absolute detection limits of the individual carbonyl compounds range from 0.4 to 5.8 ng.

Comparison of calibration methods in quantitative diffuse reflectance infrared spectroscopy.

Four different calibration methods were used for quantitative analysis of quartz and calcite in atmospheric aerosols by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS): (A) conventional calibration with one measurement on each standard (single calibration); (B) calibration with an internal standard; (C) calibration with parallel (n = 4) measurements on each standard (multiple calibration); (D) multiple calibration followed by reference reflectance correction. The accuracy and the precision of the methods were compared and it was found that by using method D the reliability of the conventional pellet preparation transmission technique can be achieved.

Effect of sample packing on the scattering properties of the reference material in diffuse reflectance infrared spectrometry.

Effect of the sample packing on the scattering properties of KBr, one of the most conventional matrix used in diffuse reflectance Fourier transform infrared (IR) spectrometry (DRIFTS), has been studied. The particle size of KBr ranged between 2 and 15 mum with a mean of 9.9 mum. The average particle size of quartz and calcite used as analytes were 2 mum and 6 mum, respectively. The scattering coefficient of KBr has been found to increase with increasing pressure applied during sample packing. 1 MPa pressure was necessary for reproducible scattering properties and quantitative results. The scattering coefficient of KBr using 1 MPa pressure for 1 min during sample packing has been determined from calibration curves and found to be as s = 107 +/- 11 cm(-1). It has been experimentally demonstrated that using 2 mm deep sample cups, the criteria of infinite sample thickness is practically fulfilled. It has been also shown that band intensities of reflectance spectra were strongly influenced by the change of the reflectance of the reference material and the less the sample concentration (c) the greater the effect. If c < 0.1 w/w%, that often occurs in practice, the RSD of band intensities can vary upto +/- 10-60%. Therefore, in quantitative analysis all spectra should be measured against one and same sample of reference material.