Atomic Absorption in the Study of the Thermal Properties of Compounds

The accurate determination of metals in minute quantities is of great importance. Gas chromatographic determinations of various materials are routinely performed in many areas of chemical analysis. In the case of metals this must be preceded by a conversion to an easily vaporized compound. Metal chelates provide a suitable means of quantitative determination of such metals. However, volatilization without accompanying thermal decomposition is necessary and in many cases this is found to be very difficult. The main objective of this investigation is to determine the applicability of the graphite furnace to the study of thermal properties of metal chelates. Copper(II) acetylacetonate hereinafter abbreviated as (Cu(AcAc)2) was used as the representative chelate. The knowledge of the thermal behaviour of copper(II) acetylacetonate could then be utilized to predict the potential of determining it by gas liquid chromatography. Several attempts have been made to utilize gas liquid chromatography for determination of metal chelates with varying degrees of success. It has been found that while metal chelates can be adapted to gas chromatographic determination, the actual detection levels and ease of volatilization depend on the thermal properties of individual chelates and the nature of the metal atom. Examples of such attempts have been cited and discussed elsewhere in this thesis. Although ease of volatilization and thermal stability alone do not exclusively determine a compound\u27s suitability for gas chromatographic estimation, they do provide a basis for further investigations into its use for such analyses. Copper(II) acetylacetonate and many of its derivatives have found use in such diverse areas from the curing of urethane polymers to the use of acetylacetone in extracting metallic copper from sea water. The devising and development of an accurate, reproducible and extremely sensitive method becomes even more essential. It is hoped that the findings of this investigation would logically lead to the development of such a method. The choice of the ligand forming the chelate has also been investigated quite extensively by different researchers (19, 26). Their findings have uniformly shown that volat1lization without decomposition is difficult to achieve, more particularly so in the case of copper chelates. The literature search provided no instance where these thermal properties of (Cu(AcAc)2) have been systematically studied to a satisfactory extent. Therefore a thorough investigation of the thermal properties of Cu(AcAc)2 is a necessary first step in achieving the practical goal of this investigation. This study does not include any attempt to determine the suitability of Cu(AcAc)2 for gas chromatographic estimation from a practical standpoint. Further studies are needed 3 which would include not only the stability of these chelates at the high temperatures used for gas chromatographic analysis but also their stability in the injection port, on the column itself and their interaction with the stationary/mobile phases and the support material of the column