CS225790B1 - The metal electromagnetic atomizer - Google Patents

Description

The invention relates to metal electrothermal atomizers for atomic absorption spectrometry called AAS.

Metal electrothermal atomizers, for example according to A.O. 174 728 are usually constructed of metals having a melting point greater than 2000 ° C, whose mechanical properties make it possible to produce a suitable atomizer shape. The most commonly used are tungsten, molybdenum and tantalum. One of the basic conditions for their intensified analytical use is that the metal substrate of the atomizer with analyte, the so-called assay component, does not react to form thermostable compounds and is sufficiently chemically inert to the various matrices of the analyzed samples and to the plenum atmosphere in which it is operated. This condition is not always unequivocally met for the metals used. For example, in tungsten electrothermal atomizers, it is not possible to determine molybdenum, which forms an intermetallic alloy with tungsten and practically does not atomize from the tungsten surface. The analysis of samples containing organic matrix, whose thermal processing creates reactive carbon in atomizers, in turn results in a significant reduction in the service life of not only tungsten, but also molybdenum and tantalum atomizers. At high temperatures at which the atomizer is operated, the carbon formed reacts very rapidly with the metal to form the appropriate carbide; the result is a change in the physical and chemical properties of the atomizers and a loss of mechanical strength. The atomizer disintegrates completely after a short time. Similar problems occur, for example, when the tungsten electro-atomic atomizer is operated in a nitrogen atmosphere,

225 790

225 790, where tungsten nitride is formed. The tantalum electrothermal atomizer cannot be operated in a hydrogen atmosphere to produce hydrogen absorption and dissolution in the metal, as well as a rapid loss of mechanical strength, the presence of which in the vicinity of the metal electrothermal atomizer is often desirable from anylatic point of view.

The above-mentioned drawbacks are eliminated by the metal electronic atomizers by the treatment according to the invention, which consists in that a surface of the metal atomizer itself is preferably electrolytically coated or by vapor deposition of 0.1 to 100 .mu.m, preferably 5 .mu.m, of another high melting point metal and with suitable physical and chemical properties, such as rhenium or iridium, from whose surface it is possible to electrothermally atomize the relevant analyte in the matrix without difficulty, but whose use for the construction of the entire metal atomizer would be uneconomical or technically difficult to carry out.

The thickness of the applied layer must be chosen so that it has a sufficiently long life, but does not substantially change the physical properties of the atomizer as a whole, namely the power required to reach a certain temperature and its heating rate.

Example

The tungsten electrothermal atomizer of A.O. No. 174,728 was electrolytically coated with a 5 µm thick carbide-free rhenium layer. The lifetime of the treated atomizer was increased from 20 to 40 times the atomizer without surface treatment in the determination of vanadium and phosphorus nickel in samples of petroleum origin dissolved in an organic solvent. The atomizer treated in this way could also be used for the determination of molybdenum when it does not form an inthernetal rhodium alloy and has been operated in a nitrogen atmosphere for a long time. Its greater resistance to oxidation was also observed.

Claims (1)

Metallic electrothermal atomizer for atomic absorption spectrometry, characterized in that the surface of the metal atomizer itself is provided with a layer of 0.1 to 100 µm of other metal having a melting point of 2500 ° C to 3500 ° C, for example rhenium or iridium.