Direct atmospheric sampling

Finally, a general and promising approach has been very recently described by Kovacs et al. [51]. This paper reports on the direct ablation of samples without the use of any ablation chamber, in what is called direct atmospheric sampling. The authors explain that the laser-... 

From an instrumental point of view, the research in years to come will be most likely linked to the new femtosecond lasers, which can offer a significantly improved performance for metallic materials, such as coins and metallic artifacts, as confirmed by the first results presented [26]. The development of the so-called direct atmospheric sampling (ablation of sample without the need to use a closed ablation cell) by Kovacs et al. is another significant development that can help in the analysis of large and precious objects [51]. 

Kovacs, R., Nishiguchi, K., Utani, K., Gtinther, D. (2010) Development of direct atmospheric sampling for laser ablation-inductively coupled plasma-mass spectrometry. Journal of Analytical Atomic Spectrometry, 25,142-147. 

The data in Table 31.1 represent the concentrations of the trace elements Na, Cl and Si (columns) in atmospheric samples that have been collected at the prevailing wind directions of 0, 90, 180 and 270 degrees (rows). 

Concentrations of trace elements in atmospheric samples at prevailing wind directions... 

In the case of a = 1 we compute the scores S for the wind directions in the current example of concentrations of trace elements in atmospheric samples as follows ... 

As microwave sample preparation has evolved, standard microwave procedures have been developed and approved by numerous standard methods organisations (ASTM, AOAC International, EPA, etc.), see ref. [64]. Examples are standard test methods for carbon black/ash content (ASTM Method D 1506-97), lead analysis in direct paint samples (ASTM Method E 1645-94), etc. Table 8.15 shows some microwave ashing references (detection weight). A French AFNOR method utilises the atmospheric pressure single-mode microwave method as an alternative sample preparation procedure for Kjeldahl nitrogen determination [84], The performance of a microwave-assisted decomposition for rapid determination of glass fibre content in plastics for QC has been described [85]. 

Figure 8.4 Positive ion direct atmospheric pressure LD mass spectrum of in vitro grown P. falciparum parasites. Protocol C is used for sample preparation estimated number of parasites deposited is approximately 103. A commercially available AP LD quadrupole ion trap (LCQ) system is used.19,20 Typical laser beam spot diameter is 0.5 mm acquisition time is approximately 20 s LCQ inlet capillary temperature -200°C.

Shows effects of atmosphere, sample history, purity, etc. Measures sample temperature directly. 

Over the stretch of Prut River the StSica Coste ti reservoir represents a major part of the total water surface (Figure 2a). Therefore the estimation was limited to the direct atmospheric contribution to the surface of this reservoir, which is about 60 km The values of heavy metal concentrations in Hypnum cupressiforme (mg-kg ) moss samples from Stefanesti (the site closed to the St ica reservoir) were selected. The yearly deposition values (mg m y ) were calculated. Assuming the mean depth of the reservoir to be 12.5 m, the total volume is of the order of 7,5x10 m. The annual atmospheric addition of metals to the reservoir were calculated from the estimated deposition rates. If diluted over the whole volume, and given that the residence time of water in the reservoir is about 4 month, the increments to the metal concentrations in water are estimated... 

PAHs are measured directly from emission sources or indirectly as deposition from the atmosphere. Because of the comphcated nature of particulate and aerosol analysis, and the sheer number of PAH, OP AH, and NPAH compounds present in atmospheric samples, sample analysis is commonly... 

Determination of the concentrations of a hydrochloricInitric acid in a mixture. Prepare an external standard mixture for gas chromatographic analysis as follows. Add nitric acid (0.5 g) and hydrochloric acid (0.1 g) to dichloromethane (10 ml) followed by scrubber solution (10 ml). Stir for 15 min then dilute to 50 ml with dichloromethane. Generate a mixed acid vapour environment by placing a small beaker containing the acids in equal volume on a hot-plate stirrer inside a fume cupboard and heat gently. Sample the atmosphere as detailed in (a) but for 10 min. Note the volume sampled. Make 0.5 pi duplicate injections of standard and sample and hence determine the concentrations of the acids in the sample by direct comparison with peak areas of the standard (external standardisation). From this data and the volume of atmosphere sampled determine the short term exposure limit. By comparison with HSE recommended limits would this atmosphere pose a hazard (See Figures 9.15-9.17.)... 

Most published applications of microwave spectrometry have taken data from samples at Pa pressures. It is widely recognised, however, that the technique would be far more useful if it could deal directly with samples at atmospheric pressure and some recent work has been directed to this end and is discussed in Chapters 5 and 6. Linewidths at atmospheric pressure are 6 GHz making it essential for frequency scanning spectrometers to employ wideband MMW sources, but at the same time the requirement for source frequency stability is much reduced. 

McCarry et al. [19-25] performed a similar series of HPLC fractionations to determine the PAHs in sediment samples. They observed C24H14 LPAHs similar to those found by Wise and co-workers in a coal-tar SRM. In later work, LPAHs of 26, 28, 30, and 32 carbons were found. Both a DAD and direct atmospheric-pressure chemical-ionization mass spectrometry were used for detection. To make the DAD less specific and more universal, the average response from 250 nm to 370 nm was collected as a total-absorbance chromatogram. 

Direct in-situ atmospheric observations of humidity-induced restructuring are difficult to obtain and remain sparse. Most evidence for humidity processing has come from laboratory and ground-based measurements. Trials on the humidity processing of atmospheric samples attributed a decrease in size to the restructuring of freshly emitted smoke [69]. In the same trials, laboratory experiments indicated that aggregate... 

Chen H, Zheng J, Zhang X, Luo M, Wang Z, Qiao X (2007) Surface desorption atmospheric pressure chemical ionization mass spectrometry for direct ambient sample analysis without toxic chemical contamination. J Mass Spectrom 42 1045-1056... 

Few applications based on flow analysis can be found for the automated and direct determination of gaseous sulfur dioxide [8,9] or hydrogen sulfide [10] in atmospheric samples. This is mainly due to the difficulty encountered in the online sampling of gases, which has been partially overcome with the use of chromatomembrane cells or tubular and planar permeation denuders and diffusion cells for the collection of the analyte from air into an absorbing solution and its introduction into the flow manifold, followed by conductivity, potentiometric, piezoelectric, or spectrophotometric detection. 

The newly developed instrument has several important features. It accepts high capacity direct introduction of samples, operates with the atmospheric sampling device, and allows easy coupling of varions sample introduction sonrces to the mass spectrometer. It permits real-time detection of chemical species, possibly in-clnding radical intermediates and easy identification of compounds via the generation of ions that do not fragment. In addition, the capillary leak inlet system is simple and adaptable. In the near future, a large increase is expected in the use of lAMS for environmental and food chemistry research, especially in cases where... 

When a sample was injected into the gas chromatograph, the valve was turned to the "valve closed" (v.c.) position, venting the portion of the effluent split to the MED to the atmosphere. After the bulk of the solvent had passed through (as indicated by the FID), the valve was turned to the "valve open" (v.o.) position directing the sample... 

Chen, H. Zheng, J. Zhang, X. Luo, M. Wang, Z. Qiao, X. Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry for Direct Ambient Sample Analysis Without Toxic Chemical Contamination. J. Mass Spec-trom. 2007,42, 1045-1056. 

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