Liquid samples atomic absorption spectrometry

Micro-pipetting instruments such as the "Eppendorf or "Oxford pipettors with disposable plastic cone tips are customarily employed to dispense the liquid samples into electrothermal atomizers. Sampling problems which are associated with the use of these pipettors are among the troublesome aspects of electrothermal atomic absorption spectrometry (67,75). The plastic cone-tips are frequently contaminated with metals, and they should invariably be cleaned before use by soaking in dilute "ultra pure nitric acid, followed by multiple rinses with demineralized water which has been distilled in a quartz still. 

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). 

Nebulization is inefficient and therefore not appropriate for very small liquid samples. Introducing samples into the plasma in liquid form reduces the potential sensitivity because the analyte flux is limited by the amount of solvent that the plasma will tolerate. To circumvent these problems a variety of thermal and electrothermal vaporization devices have been investigated. Two basic approaches are in use. The first involves indirect vaporization of the sample in an electrothermal vaporizer, e.g. a carbon rod or tube furnace or heated metal filament as commonly used in atomic absorption spectrometry [7-9], The second involves inserting the sample into the base of the... 

Metal ions such Cu, Cd, and Pb can be preconcentrated from water samples using liquid membranes containing 40% w/w of di-2-ethylhexylphosphoric acid in kerosene diluent in a PTFE support. The liquid membrane can be coupled on-line to an atomic absorption spectrometer and has been shown to be stable for at least 200 h with extraction efficiencies over 80%, and enrichment factors of 15 can be obtained. A liquid membrane has also been used for sample cleanup and enrichment of lead in urine samples prior to determination by atomic absorption spectrometry [100]. The experimental setup for metal enrichment is shown in Fig. 13.4. Lead was enriched 200 times from urine [80] and several metals were enriched 200 times from natural waters [88]. Using hollow fiber... 

Investigations of lead speciation in various environmental samples have relied upon gas and liquid chromatographic separations coupled to mass spectrometric and atomic absorption spectrometric detectors. The combination of atomic absorption spectrometry with gas chromatography (GC-AAS) has proved to be the most widely applied technique. Sample types have included air, surface water, air particulates, sediments, grass, and clinical materials such as blood. A review of speciation analyses of organolead compounds by GC-AAS, with emphasis on environmental materials, was published (Lobinski et al., 1994). 

High, K.A., Azani, R., Fazekas, A.F., Chee, Z.A. and Blais, J.-S. (1992) Thermospray-microatomizer interface for the determination of trace cadmium and cadmium-metallothioneins in biological samples with flow injection- and high-performance liquid chromatography-atomic absorption spectrometry. Anal. Chem., 64, 3197-3201. 

Jiang, H., Y. Qin, and B. Hu. 2008. Dispersive liquid phase microextraction (DLPME) combined with graphite furnace atomic absorption spectrometry (GFAAS) for determination of trace Co and Ni in environmental water and rice samples. Talanta 74 1160-1165. 

Farajzadeh, M.A., M. Bahram, B.G. Mehr, and J.A. Jonsson. 2008. Optimization of dispersive liquid-liquid microextraction of copper (II) by atomic absorption spectrometry as its oxinate chelate Application to determination of copper in different water samples. Talanta 75 832-840. 

High performance liquid chromatography coupled with hydride generation-atomic absorption spectrometry has been used for the determination of arsenic species in non saline water samples [265],... 

Since some form of liquid sample presentation is common to most atomic spectrometric techniques, these may be considered as the method of choice for the identification and quantification of trace metals in liquid foods. In spectrometric techniques, after conversion of the sample into microspray, chemical flames as in flame atomic absorption spectrometry (FAAS) and atomic... 

K. J. Lamble, S. J. Hill, Arsenic speciation in biological samples by on-line high performance liquid chromatograph microwave digestion hydride generation atomic absorption spectrometry, Anal. Chim. Acta, 334 (1996), 261-270. 

Sarica, D.Y., Turker, A.R., and Erol, E. Onhne speciation and determination of Cr(III) and CrfVt) in drinking and waste water samples by reversed-phase high performance liquid chromatography coupled with atomic absorption spectrometry. J. Sep. Sci. 2006, 29,1600-1606. 

In some situations, an apparent decrease in the detection limit can occur when the analytical procedure includes a preliminary preconcentration (e.g., by extraction or evaporation of a liquid sample). For example, if direct determination by atomic absorption spectrometry allows detection of 0.1 ng/mL metal in solution, then an increase in concentration after separation/preconcentration in the ratio 1 20 lowers the detection limit for the whole procedure to 0.005 ng/mL. Both values are useful and have real meaning when they are correctly described. 

Mercury, the only metallic element with significant volatility at room temperature, has been conventionally determined for many years by atomic absorption spectrometry, as the mercury vapor detector (W20) is based on this principle. Lindstrom (L7) used a flame to volatilize the mercury in the liquid sample, but determined its concentration in the exhaust gases with the mercury vapor meter after cooling and purification in a filter that removed particulate matter. The method is said to be capable of detecting 0.1 pg % of mercury in the original liquid sample... 

Atomic absorption spectrometry with flame (AA-F) or electrothermal atomization furnace (AA-ETA), inductively coupled plasma-emission spectroscopy (ICP-ES), inductively coupled plasma-mass spectrometry (ICP-MS), and high-performance liquid chromatography-mass spectrometry (LC-MS) are state-of-the-art analytical techniques used to measure metals in biological fluids. They are specific and sensitive and provide the cfinical laboratory with the capability to measure a broad array of metals at clinically significant concentrations. For example, ICP-MS is used to measure several metals simultaneously. Photometric assays are also available but require large volumes of sample and have limited analytical performance. Spot tests are also... 

Flame atomic absorption spectrometry (FAAS) is used primarily for liquids. The sample is converted into an aerosol by the nebuliser, atomised to free atoms, mixed with the combustible gases and ignited in the flame, which can rise to a temperature of 2600 °C. A long burner is used to increase the pathlength. The most commonly used flames are air-acetylene and nitrous oxide-acetylene mixtures. 

---