Stabilized temperature platform

The stabilized temperature platform furnace (STPF) concept was first devised by Slavin et al. It is a collection of recommendations to be followed to enable determinations to be as free from interferences as possible. These recommendations include (i) isothermal operation (ii) the use of a matrix modifier (iii) an integrated absorbance signal rather than peak height measurements (iv) a rapid heating rate during atomization (v) fast electronic circuits to follow the transient signal and (vi) the use of a powerful background correction system such as the Zeeman effect. Most or all of these recommendations are incorporated into virtually all analytical protocols nowadays and this, in conjunction with the transversely heated tubes, has decreased the interference effects observed considerably. 

Andersen JR. 1988. Aluminum in peritoneal dialysis fluids as determined by stabilized temperature platform furnace atomic absorption spectrometry. J Pharm Biomed Anal 6 29-33. 

W. Slavin, D. C. Manning, G. R. Camrick, The stabilized temperature platform... 

Desaulniers JAH, Sturgeon RE, Berman SS (1985) Atomic absorption determination of trace metals in marine sediments and biological tissues using a stabilized temperature platform furnace. At Spectrosc 6 125-127... 

Slavin W, Carnrick G and Manning D (1982) Graphite-tube effects on perchloric acid interferences on aluminum and thallium in the stabilized-temperature platform furnace. Anal Chim Acta 138 103-110. 

In order to determine Bi by GF AAS under stabilized temperature platform furnace (STPF) conditions using the Pd-Mg modifier, a pyrolysis temperature of 1200 °C must be applied (Hiltenkamp and Werth 1988). The optimum atomization temperature under these conditions is 1900 °C the characteristic mass with Zeeman effect background correction (BC) is 28 pg, while in a non-Zeeman instrument it is about 20 pg. 

An investigation of two GF-AAS methods has been carried out in the authors laboratory (Brown et al., 1984). The first was a conventional approach using direct analysis of serum using a stabilized temperature platform in the graphite tube. The study demonstrated the necessity of using the method of standard additions as a means of standardization, since there were profound differences in the slopes of standard curves constructed from aqueous standards, sera from normal Individuals, and sera from uremic patients. Thus, considerable analytical errors would result from using aqueous standards or standards made up in normal sera as a means of standardizing assays for uremic patients. The standard additions method allows each serum sample matrix to serve as its own standard and, therefore, provide more accurate analyses. 

For urine analysis sample aliquots are diluted 1 1 with distilled water before application to the AAS stabilized temperature platform (Leung and Henderson, 1982). Fecal analysis require considerably more complicated preparation steps than serum or urine. The procedure developed in the author s laboratory (Brown et al., manuscript in preparation) is summarized as follows Frozen specimens are thawed and distilled water is added (1 mL per 2 g feces) and the sample is homogenized in a sealed container on a paint shaker. A 10 mL aliquot is ashed at 550°C in a muffle furnace, dissolved in dilute HNO3 snd analyzed by GF-AAS. 

Leung, F.Y. and Henderson, A.R. (1982). Improved determination of aluminium in serum and urine with use of a stabilized temperature platform furnace, Clin. Chem., 28, 2139-2143. 

Slavin, W., Carnrick, G.R., Manning, D.C. and Pruszkowska, E. (1983). Recent experience with the stabilized temperature platform furnace and Zeeman background correction. Atom. Spectrosc. 4. 69-86. 

Weighed tissue samples (kidney, liver, meat, bone and wool) of approximately 1 and 0.5 g CRM 185 bovine liver were placed in PTFE vessels, 5 ml of concentrated HNO3 and 5 ml of distilled H2O were added. A microwave oven program with temperature and pressure settings of 150°C and 130 p.s.i., respectively, was performed for all analyzed matrices. The digestion solutions were diluted to a final volume of 50 ml all dilution, excluding blood samples, were performed with 1% HNO3. Zinc analysis was performed on a Flame AAS 2100 (Perkin-Elmer), with an air-acetylene flame. Lead and cadmium analysis was performed on a GF-AAS 5100 ZL (Perkin-Elmer). Analysis on GF-AAS were carried out under stabilized temperature platform furnace (STPF) conditions. 

Stabilized Temperature Platform Furnace. The conditions in a Massmann furnace are by no means optimum during atomization. The sample is dispensed onto a cold wall of the tube which is then heated rapidly for atomization. After vaporization the sample is in an environment that is not in equilibrium with respect to volume or time. This can cause chemical interferences. Fewer interferences would occur in a continuously heated, isothermal furnace. It has been shown that about 60% of the atoms formed diffuse to the cooler cuvette ends and condense. In addition, at 2800 K a temperature gradient of 1000 K between the middle and the ends of a... 

Perkin Elmer introduced, in 1984, a Stabilized Temperature Platform Furnace (STPF) (Figure 49). There are two inert gas flows (internal and external). The heating rate of the furnace is high (about 2000 Ks ), which allows the use of lower atomization temperatures. After the thermal pretreatment a small temperature step (<1600 K) is used in order to prevent the atomization of the sample before the equilibrium has been reached. 

This concept should probably be referred to as the stabilized temperature platform atomizer, in line with recent International Union of Pure and Applied Chemists nomenclature recommendations, but will... 

Gas phase interferences due to compound formation of the analyte element with a concomitant should not be very significant in ETAAS because a much longer time is available for dissociation compared to FAAS. It was shown by high-temperature equilibrium calculations that gas phase interferences at the temperatures used in ETAAS should actually be rather insignificant [18], The reason why the literature is nevertheless full of reports on such interferences is largely due to an improper use of this technique. Slavin et al. [19], based on the systematic work of L vov [20], introduced a concept which they called stabilized temperature platform furnace (STPF). It is in essence a package of measures which eliminates most nonspectral interferences in ETAAS by atomization under local thermal equilibrium conditions. 

Graphite furnace atomic absorption spectrometry (GFAAS) is an excellent method to provide sub-ng/mL minimum detection limits [110]. Continuing advancements such as Zeeman correction, and stabilized temperature platform furnaces, have made GFAAS an effective analytical method for magnesium determination. Depending on the sample matrix, pretreatment can vary from direct analysis of fluids, to wet mineralization, dry ash, acid extraction, and by using PPRs (e.g., Triton X-100). 

The application of XRF to the determination of Se in very small blood [105] and blood serum samples [106] has been reported. Spectrofluorimetry and Zeeman-corrected, stabilized-temperature, platform-furnace AAS have been compared [107] for the determination of Se in milk. 

Interferences, such as background absorption, are reduced to a minimum in the AAS-HGA analytical technique by taking full advantage of the Stabilized Temperature Platform Furnace (STPF) concept. STPF includes all of the following parameters (5.2.) ... 

---