Cold vapour flame atomic absorption

Maintaining the quality of food is a far more complex problem than the quality assurance of non-food products. Analytical methods are an indispensable monitoring tool for controlling levels of substances essential for health and also of toxic substances, including heavy metals. The usual techniques for detecting elements in food are flame atomic absorption spectroscopy (FAAS), graphite furnace atomic absorption spectrometry (GF AAS), hydride generation atomic absorption spectrometry (HG AAS), cold vapour atomic absorption spectrometry (CV AAS), inductively coupled plasma atomic emission spectrometry (ICP AES), inductively coupled plasma mass spectrometry (ICP MS) and neutron activation analysis (NAA). 

CV-AAS, Cold Vapour Atomic Absorption Spectrometry ETA-AAS, Electrothermal Atomization Atomic Absorption Spectrometry FAAS, Flame Atomic Absorption Spectrometry FIG-AAS, Flydride Generation Atomic Absorption Spectrometry ICP-AES. Inductively Coupled Plasma Atomic Emission Spectrometry ID-MS, Isotopic Dilution Mass Spectrometry HR-ICP-MS, Magnetic Sector High Resolution Inductively Coupled Plasma Mass Spectrometry NAA, Neutron Activation Analysis Q-ICP-MS, Quadrupole Inductively Coupled Plasma Mass Spectrometry Z-ETA-AAS, Zeeman Electrothermal Atomization Atomic Absorption Spectrometry... 

To summarise, FAAS is very easy to use. Interferences are known and can be controlled. Extensive application information is also readily available. Its precision makes it an excellent technique for the determination of a number of commonly analysed elements at higher concentration in polluted soil samples. Its main drawback is its speed in relation to multi-element techniques such as ICP-AES and ICP-MS. Where direct-aspiration flame atomic absorption technique does not provide adequate sensitivity, reference is made to specialised techniques (in addition to graphite furnace procedure) such as the gaseous-hydride method for arsenic, antimony and selenium and the cold-vapour technique for mercury. 

In AAS, FIA has been applied to hydride generation and cold vapour techniques, microsampling for flame atomic absorption, analysis of concentrated solutions, addition of buffers and matrix modifiers, dilution by mixing or dispersion, calibration methods, online separation of the matrix and analyte enrichment, and indirect AAS determinations. 

Flame atomisation is not necessary for the atomic absorption spectrophotomehy of mercury. The cold vapour technique described here employs a reduction vessel (which may be purchased) to produce mercury vapour the vapour is led to a quartz absorption cell within the atomic absorption inshument. The method is applicable to inorganic and organic mercurial compounds in urine. 

The technique can be used with or without a flame. In the flameless technique several variations are possible, including a graphite furnace or cold vapour, all of which are more sensitive than flame photometry. Further details on atomic absorption spectroscopy are given in Chapter 27. 

Metals Hg, Pb, Cd, Ca, Mg Fe, Mn, Al Flame and cold-vapour atomic absorption. ICP atomic emission spectrometry. Graphite furnace. Zeeman effect. Anodic stripping voltammetry. X-ray fluorescence. ISEs. Colorimetry... 

The mercury vapour may be entrained in a stream of an inert gas or in air and measured by the atomic absorption of the cold vapour without the need of either flame or flame atomizers. 

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