Cold-vapor atomic absorption

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, and inductively coupled plasma mass spectrometry (Lansens etal. 1991 Schintu etal. 1992 Porcella etal. 1995). Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10 pg Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry (Schintu et al. 1992). 

Atomic absorption spectroscopy is more suited to samples where the number of metals is small, because it is essentially a single-element technique. The conventional air—acetylene flame is used for most metals however, elements that form refractory compounds, eg, Al, Si, V, etc, require the hotter nitrous oxide—acetylene flame. The use of a graphite furnace provides detection limits much lower than either of the flames. A cold-vapor-generation technique combined with atomic absorption is considered the most suitable method for mercury analysis (34). 

The technique that has been widely apphed for analyzing total merctrry in aqttatic biota since the late 1960s (cold vapor atomic absorption spectrophotometry) lemains a vahd analytical method. Accordingly, we irtfer that most of the historical data for total merctrry in fish tissues are vahd. Moreover, the historical data on total merctrry concentrations in fish tissues provide defettsible estimates of prior MeHg concentrations. 

Compare atomic absorption (both flame and graphite furnace), ICP, flame photometry, cold vapor mercury, hydride generation, atomic fluorescence, and spark emission in terms of ... 

R02019 Method 1631, Revision E Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Eluorescence Spectrometry 821R96013 Method 1632 Determination of Inorganic Arsenic in Water by Hydride Generation Elame Atomic Absorption... 

Mercury is most accurately determined by the cold vapor atomic absorption spectroscopic method. The instrument is set at the wavelength 253.7 nm. The metal, its salts and organic derivatives in aqueous solution can be measured by this method. The solution or the solid compounds are digested with nitric acid to convert into water-soluble mercury(ll) nitrate, followed by treatment with potassium permanganate and potassium persulfate under careful heating. The excess oxidants in the solution are reduced with NaCl-hydroxylamine sulfate. The solution is treated with stannous chloride and aerated. The cold Hg vapor volatdizes into the absorption cell where absorbance is measured. 

Li, Z., Wei, Q., Yuan, R., Zhou, X., Liu, H., Shan, H., and Song, Q., A new room temperature ionic liquid l-butyl-3-trimethylsilylimidazolium hexafluoro-phosphate as a solvent for extraction and preconcentration of mercury with determination by cold vapor atomic absorption spectrometry, Talanta, 71,68-72, 2007. 

J. Moreda-Pineiro, P. Fopez-Mahia, S. Muniategui-Forenzo, E. Fernandez-Fernandez and D. Prada-Rodriguez, Direct As, Bi, Ge, Hg and Se(IV) cold vapor/hydride generation from coal fly ash slurry samples and determination by electrothermal atomic absorption spectrometry, Spectrochim. Acta, Part B, 57(5), 2002, 883-895. 

S. Rio Segade and J. F. Tyson, Determination of methylmercury and inorganic mercury in water samples by slurry sampling cold vapor atomic absorption spectrometry in a flow injection system after preconcentration on silica C18 modified, Talanta, 71(4), 2007, 1696-1702. 

C. Schickling and J. A. C. Broekaert, Determination of mercury species in gas condensates by online coupled high-performance liquid chromatography and cold-vapor atomic absorption spectrometry, Appl. Organo-met. Chem., 9(1), 1995, 29-36. 

Determination of Mercury, Fluorine, Boron, and Selenium. The Determination of Mercury. A coal sample is decomposed by igniting a combustion bomb containing a dilute nitric acid solution under 24 atm of oxygen. After combustion, the bomb washings are diluted to a known volume, and mercury is determined by atomic absorption spectrophotometry using a flameless cold vapor technique. 

ASTM D-6414. Standard Test Method for Total Mercury in Coal and Coal Combustion Residues by Acid Extraction or Wet Oxidation/Cold Vapor Atomic Absorption. 

Another test method for the determination of mercury in coal (ASTM D-6414) involves (method A) solubilizing of the mercury in the sample by heating the sample at a specified temperature in a mixture of nitric and hydrochloric acids. The acid solutions produced are transferred into a vessel in which the mercury is reduced to elemental mercury. The mercury vapor is determined by flameless cold-vapor atomic absorption spectroscopy. An alternative method (method B) involved solubilization of the mercury by heating the sample in a mixture of nitric acid and sulfuric acid with vanadium pentoxide. The acid solution is then transferred into a vessel in which the mercury is reduced to elemental mercury. The mercury content is determined by flameless cold-vapor atomic absorption spectroscopy. However, mercury and mercury salts can be volatilized at low temperatures, and precautions against inadvertent mercury loss should be taken when using this method. 

Cold vapor atomic absorption spectrophotometric method is applicable only for the mercury analysis. The principle of this method is described below. 

Cold vapor atomic absorption (CVAA) spectrophotometry for mercury analysis... 

Ahmed, R. and M. Stoeppler. 1986. Decomposition and stability studies of methylmercury in water using cold vapor atomic absorption spectrometry. Analyst 111 1371-1374. 

Notes DP-ASV, differential-pulse anodic stripping voltammetry RDE-Au, rotating gold electrode HG-AAS, /tydride generation atomic absorption spectrometry FA AS, /lame atomic absorption spectrometry FI-CV-AAS, /low-injection cold-vapor atomic absorption spectrometry and HMDE, /tanging mercury drop electrode. 

Notes ASV, anodic stripping voltammetry and CV-AAS, cold-vapor atomic absorption spectrometry. 

Notes HG-AAS, Aydride generation atomic absorption spectrometry HG-AFS, /tydride generation atomic fluorescence spectrometry FI-CV-AAS, flow-injection cold-vapor atomic absorption spectrometry FAAS,flame atomic absorption spectrometry GF-AAS, graphite furnace atomic absorption spectrometry and ET-AAS, electrothermal atomic absorption spectrometry. 

Fernandez, C., A.C.L. Conceicao, R. Rial-Otero, C. Vaz, and J.L. Capelo. 2006. Sequential flow injection analysis system on-line coupled to high intensity focused ultrasound Green methodology for trace analysis applications as demonstrated for the determination of inorganic and total mercury in waters and urine by cold vapor atomic absorption spectrometry. Anal. Chem. 78 2494-2499. 

Kagaya, S., Y. Kuroda, Y. Serikawa, and K. Hasegawa. 2004. Rapid determination of total mercury in treated waste water by cold vapor atomic absorption spectrometry in alkaline medium with sodium hypochlorite solution. Talanta 64 554-557. 

Ou, H., Y. Zhang, Q. Wu, J. Fang, and Y. Shu. 2004. Rapid determination of trace inorganic and total organic mercury in waste water by cold vapor atomic absorption spectrometry and pyrolysis atomic absorption spectrometry. Fenxi Ceshi Xuebao 23 68-70. 

Spectrometric techniques based on atomic absorption or the emission of radiation flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapor (CV)/hydride generation (HG), mainly for trace and ultratrace metal determinations. 

In EMEP, ICP-MS is dehned as the reference technique. The exception is mercury, where cold vapor atomic fluorescence spectroscopy (CV-AFS) is chosen. Other techniques may be used, if they are shown to yield results of a quality equivalent to that obtainable with the recommended method. These other methods include graphite furnace atomic absorption spectroscopy (GF-AAS), flame-atomic absorption spectroscopy (F-AAS), and CV-AFS. The choice of technique depends on the detection limits desired. ICP-MS has the lowest detection limit for most elements and is therefore suitable for remote areas. The techniques described in this manual are presented with minimum detection limits. Table 17.2 lists the detection limits for the different methods. 

Gil, S., I. Lavilla, and C. Bendicho. 2006. Ultrasound-promoted cold vapor generation in the presence of formic acid for determination of mercury by atomic absorption spectrometry. Anal. Chem. 78 6260-6264. 

Methods for several metals or metalloids involve conversion to a volatile form. Arsenic, antimony, and selenium can be reduced to their volatile hydrides, AsH3, SbH3, and H2Se, repectively, which can be determined by atomic absorption or other means. Mercury is reduced to volatile mercury metal, which is evolved from solution and measured by cold vapor atomic absorption. 

---