Cold vapour AAS

Mercury Comparision on different mercury chelating agents ad- Cold vapour AAS 0.016 ixg/1... 

Organomercury compounds Extraction with dithizone solution Gold trap cold vapour AAS - [537]... 

Steam distillation cold vapour aas Cold vapour aas... 

Sulphuric acid-perchloric acid digestion-spectrophotometry Toluene extraction, bromo derivitization, glc Cold vapour aas... 

A system for cold vapour AAS is shown in Fig. 7.3. The evolved mercury vapour is passed to a long path-length absorption cell, usually constructed of Pyrex glass tubing with silica end windows. A transient absorption peak is observed. In some systems, a recirculating pump is used to cycle the mercury vapour around the system and achieve a steady reading. 

Animal tissue Hg Cold-vapour AAS, Isotope dilution analysis 80)... 

O. Ertas and H. Tezel, A validated cold vapour-AAS method for determining mercury in human red blood cells, J. Pharm. Biomed. Anal., 36(4), 2004, 893-897. 

Flameless AAS methods have so far made little impact in applied geochemistry, except for methods for the element mercury, for which cold-vapour AAS is uniquely effective [2]. A plethora of methods are now in use ranging from simple attachments to standard instruments, to fully portable specific mercury meters of high sensitivity incorporating ingenious methods of background correction [3]. 

Bandy opadhyay S, Das AK. 1989. Determination of mercury in soil by cold vapour AAS after its separation with Aliquat-336. J Indian Chem Soc 66(6) 427-428. 

Vermeir G, Vandecasteele C, Temmerman E, et al. 1988. Determination of mercury in biological materials by CV (cold-vapour) AAS after wet digestion. Mikrochim Acta 3 305-313. 

Several experiments have been carried out on samples of natural waters and industrial wastewaters (12 for Cu, 9 for Hg and 14 for Fe), with standard addition for some samples [55]. The analysis of the samples was performed both by a reference method (graphite furnace AAS for copper and iron, cold vapour AAS for Hg), and by the proposed spectrophotometric method. 

Chemicai reduction of ionio mercury. In 1963 Poluektov and Vitkun reported an increase in the sensitivity by about one order of magnitude, when Sn(ll)-containing mercury solutions were analyzed according to Lindstrom (1959). They associated the increased sensitivity with the reduction and release of Hg(0) from the test solution, which was introduced through a spray chamber. Poluektov et al. (1964) presented a "cold vapour" AAS method with the spray chamber and the flame replaced by an aeration vessel, where Sn(ll) was added to a defined volume of sample solution, and the liberated Hg(0) was carried by an air stream to a gas cell. The principle of aeration was, in fact, the same as was utilized by Kimura and Miller (1962) for sample clean up prior to colorimetric determination. 

Hydride generation AAS (HGAAS) and cold vapour AAS (CVAAS) are special combinations of chemical separation and enrichment with AAS. In HGAAS the analyte is transformed to a volatile hydride, stripped off by an inert gas and atomized in a quartz tube, flame-in tube etc. About ten elements (As, Se, Bi, Sb etc.) can be determined by this technique. The accuracy and detection limits depend on the proper isolation of the hydride. CVAAS is the universally acknowledged most sensitive method for determination of Hg. The generation of elemental mercury vapour is similar to the hydride generation however the quartz cell may not be heated and this gives the name of the method. 

Zhang et al.[18] determined mercury at ultra-trace levels in sea water, lap water and waste waters using on-line ion-exchange preconcentration cold vapour AAS. Of three different ion-exchangers tested, CPG-8HQ produced the best sensitivity and selectivity. The sorbed analyte was eluted by 2 M hydrochloric acid in 0.5% thiourea. An EF of 40 and detection limit of 0.002 //g 1 with sampling frequency of 60 h was reported. 

For mercury, the borolydride technique is used to generate elemental mercury vapour from a mercury soluhoa This is then passed irrto the merenry hght beam without any need for a flame to decorrrpose mercury corrrporrrrds (so it is cahed cold vapour AAS). 

The determination of Cr, Ni and Pb require the addition of NH4H2PO4 to samples for matrix modification. Most elements in pulp effluent occur in pg L concentrations (As, Ba, Co, Li, Sr, Sn) while some, such as Na, Ca, Mg, Si and K (naturally present in wood or added to pulp during processing in various chemicals), occur in mg L concentrations. Mass spectrometry may be employed for certain elements that are present in very low concentrations < 1 pg L (Ag, Mo, Sb, Tl) and the combination of elements determined by this method offers a characterization of pulp and paper mill effluent in water. Mercury is determined by cold vapour AAS where the detection limit is 0.1 pg-Hg L L... 

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