Quartz cell, heated

Concerning AFS, the atomiser can be a flame, plasma, electrothermal device or a special-purpose atomiser e.g. a heated quartz cell). Nowadays, commercially available equipment in AFS is simple and compact, specifically configured for particular applications e.g. determination of mercury, arsenic, selenium, tellurium, antimony and bismuth). Therefore, particular details about the components of the instrumentation used in AFS will not be given in this chapter. 

Haring et al. [31] determined arsenic and antimony by a combination of hydride generation and atomic absorption spectrometry. These workers found that, compared to the spectrophotometric technique, the atomic absorption spectrophotometric technique with a heated quartz cell suffered from interferences by other hydride-forming elements. 

The recommended procedure for the determination of arsenic and antimony involves the addition of 1 g of potassium iodide and 1 g of ascorbic acid to a sample of 20 ml of concentrated hydrochloric acid. This solution should be kept at room temperature for at least five hours before initiation of the programmed MH 5-1 hydride generation system, i.e., before addition of ice-cold 10% sodium borohydride and 5% sodium hydroxide. In the hydride generation technique the evolved metal hydrides are decomposed in a heated quartz cell prior to determination by atomic absorption spectrometry. The hydride method offers improved sensitivity and lower detection limits compared to graphite furnace atomic absorption spectrometry. However, the most important advantage of hydride-generating techniques is the prevention of matrix interference, which is usually very important in the 200 nm area. 

Figure 1 Apparatus of Oxford experiment [6]. LI, L2 tunable dye lasers. UV ultra violet radiation (243 nm). RF radiofrequency dissociation of flowing molecular hydrogen. PI signal photomultiplier (Lyman-a detector). P2 photomultiplier for cavity locking and signal normalisation. SI cavity length servo-control. C conrouter. AOM acousto-optic modulator. T heated quartz cell containing tellurium. S2 laser frequency servo-control. D fast photodiode...

Inorganic, methyl, and n-butyl tin compounds may be converted to volatile hydrides, and the latter separated on a chromatographic column prior to detection of tin by AAS.58 In this particular study, an electrically heated absorption cell was used, although a flame-heated quartz cell could have been employed equally well. Balls59 used on-line cryogenic trapping on a silanized glass-wool column to separate dibutyl tin and tributyl tin in sea water prior to transport to a quartz-tube atomizer for determination by AAS. 

Boron, Li, Mo, Pb, and Sb were determined in the standard mode, while Al, Cd, Co, Ni, Mn, Rb, Sb, Sn, and V were determined in the DRC mode. The determination of Ni was done with a gas flow of 0.15 ml min-1 of CH4, while for the other elements NH3 was used as cell gas at 0.4 ml min-1. The determination of Se by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) was carried out by means of the Perkin-Elmer FLAS 200 system, equipped with the Perkin-Elmer autosampler AS-90, and connected to an electrically heated quartz cell installed on a PerkinElmer absorption spectrometer AAS 4100. The analytical conditions are given in Table 10.3. 

Peter et al. [15] used an electrically heated quartz cell for the determination of arsenic in urine. Urine, 2 ml, was digested with 2 ml of nitric and perchloric acids (1 1). Aliquots of this solution were used for the subsequent arsine generation by sodium borohydride. The normal level of arsenic in urine was found to be less than lOppb. 

The ability to monitor trace levels of a number of heavy metals in a variety of samples is an important feature of modern environmental chemistry. Hence, sensitive analytical methods are required. When faced with the task of analyzing very low concentrations of antimony, bismuth and tin the hydride generation method is the first choice because of the improved sensitivity and lower detection limits as compared to many other techniques. The hydride generation technique includes the use of a reductant, such as a NaBH4 solution, to separate the volatile metal hydrides from the sample solution and the subsequent determination with atomic absorption after decomposition of the hydrides in a heated quartz cell. 

In principle, the devices used for hydride removal can also be employed with cold vapour — which in addition requires a non-heated quartz-cell atomizer. In any case, research interests have focused on systems for specific use with mercury vapour. 

The physico-chemical properties of the analytes and the way they reach the detector have made atomic spectroscopy the detection technique of choice in most instances. A heated quartz cell or a similar device is connected directly to the gas outlet of the separation cell [26]. The use of an atomic fluorescence detector has provided methods for selenium [25,27] and mercury [28,29] that possess excellent analytical features and use inexpensive instruments. On a less affordable level are ICP emission [30] and atomic emission cavity spectrometers [31]. 

Welz B. and Melcher M. (1983) Investigations on atomisation mechanisms of volatile hydrideforming elements in a heated quartz cell, Analyst 108 213-224. 

A recent innovation in processing of CPs has been direct vapor deposition of films. This is illustrated by the work of Plank et al. [291] who deposited P(ANi) films on substrates such as Cu(110) and Au in ultrahigh vacuiun (10 to 10 " Torr). The source was a resistively heated quartz cell filled with emeraldine base powder. Thicknesses were controlled via control of pressure. Thin films, ca. 10 nm thick, doped with HCl were said to exhibit plasma frequencies in the ar-IR, suggesting a high degree of ordering and associated high conductivity, whilst thicker films, ca. 100 nm thick, showed apparently lower conductivity. 

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