Peltier cooling element

Figure 5.15 Experimental arrangement of microconcentric PFA nebulizer with heated cyclonic spray chamber and Peltier cooled multipass condenser APEX. (Reproduced by permission of Element Scientific Inc., Omaha).

The frequency and amplitude of an oscillating quartz crystal are influenced by even a minimal mass load. A sensitive dew sensor was developed by using a Peltier-cooled quartz plate [54]. This sensor is capable of measuring relative humidity with an accuracy better than l.St o of the measured relative humidity in automatic dew-point hygrometry. Since the frequency but not the amplitude of specially cut quartz crystals depends strongly on the temperature, the dew-point temperature can be determined simultaneously with the same sensor element. Compared with optical dew-point hydrometers, this quartz sensor combines dewpoint detection and temperature measurement in a single element. 

The Ettingshausen cooler consists of only a single cooling element of one type of material while each Peltier junction requires an w-type and a p-type leg with metal-to-semiconductor contacts between them. 

The effect of infinite cascading can be achieved by appropriately shaping the cooling element, while cascaded Peltier coolers are very complicated structures requiring a large number of elements. 

Spray chambers can be cooled via a water jacket or Peltier cooling to reduce the amount of solvent vapor introduced into the ICP [31, 32). A further reduction in the amount of solvent introduced can be realized via a desolvation system. Traditionally, such a desolvation system consisted of a sequence of a heated and a cooled tube. In the heated tube, the solvent is vaporized, after which it condenses on the inner wall of the cooled tube and is thus removed. Nowadays, desolvation systems equipped with a membrane desolvator are often used [33, 34). These basically consist of a tube manufactured from a semipermeable porous material, around which heated Ar gas is flowing in the opposite direction to the sample aerosol flow. The solvent is vaporized, and the gaseous solvent molecules leave the central tube via the pores and are carried off by the heated Ar flow. Desolvation of the sample aerosol can lead to an 10-fold increase in signal intensity. For rather volatile analyte elements, (partial) analyte loss needs to be taken into account [35]. 

Silicon drift detectors (SDD, Figs 4.8 and 4.9) now also provide sufficient resolution (FWHM = 0.175 keV) above a sample spot sized 2 x 2 to 100 x 100 mm, and enable high-speed operation (> 10 counts s ). SDD can be combined with microelectronics and applied in portable TXRF models for microanalytical applications [4.30]. They must be cooled by a Peltier element. 

The dewpoint hygrometer detects the dewpoint temperature of air by cooling a surface in contact with the air to the dewpoint temperature. There are several ways to achieve cooling and to observe the formation of condensate on the surface. The early dewpoint hygirometers were cooled simply by applying the vaporization of ether or some other suitable liquid. Condensate formation on the surface was determined visually. Other cooling methods are to use a refrigerant flow in direct or indirect contact with the back of the surface, or to use electricity with a (thermoelectric) Peltier element. 

The APEX system (Element Scientific Inc., Omaha) as an improved Aridus nebulizer was introduced for ICP-MS in 2004 for more effective solution introduction at flow rates from 20-400 p,lmin-1.88 In this solution introduction system (see Figure 5.15), a microflow PFA nebulizer is combined with a heated cyclonic spray chamber followed by cooling of the nebulized aerosol in a condenser loop and using a multipass condenser cooled by a Peltier element. The APEX solution introduction system results in a significant increase of sensitivity (by a factor of ten in comparison to a standard nebulizer spray chamber arrangement) and a decreasing polyatomic formation rate.89... 

The experimental arrangement of LA-ICP-MS using a powerful laser ablation system coupled to a double-focusing sector field ICP-MS (Element, Thermo Fisher Scientific, Bremen) is shown in Figure 5.22. A cooled laser ablation chamber using two Peltier elements in serial connection... 

Figure 5.22 Schematic of laser ablation inductively coupled plasma mass spectrometer a laser ablation system (wa velength 213 nm) is coupled to a double-focusing sector field ICP-MS (Element, Thermo Fisher Scientific, Bremen). The cooled laser ablation chamber using two Peltier elements was developed in the author s laboratoryJ26 (M. V. Zoriy, M. Kayser, A. Izmer, C. Pickhardt and J. S. Becker, Int. J. Mass Spectrom., 242, 297 (2005). Reproduced by permission of Elsevier.)...

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