Spray chambers Peltier-cooled

Such is the added capability and widespread use of these nebulizers across all application areas that manufacturers are developing application-specific integrated systems that include the spray chamber and a choice of different desolvation techniques to reduce the amount of solvent aerosol entering the plasma. Depending on the types of samples being analyzed, some of these systems include a low-flow nebulizer, Peltier-cooled spray chambers, heated spray chambers, Peltier-cooled condensers, and membrane desolvation technology. Some of the commercially available equipment include the following ... 

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... 

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).

It must be noted that increasing the amount of solvent in the ICP produces a higher load on the plasma and an increase in reflected powers, causing plasma instability. Desolvation of the sample aerosol may overcome this hurdle and is achieved by the use of a cooled spray chamber. In addition, Peltier coolers and membrane dryers [23] have been used for desolvating liquid aerosols and eliminate approximately 90% of the aerosol (Fig. 10.3). Spray chambers may also im-... 

In some recent ICP-MS systems the spray chamber is Peltier cooled to reduce solvent loading on the plasma. Further information about organotin speciation can be found in (Drickx etal. 1995) and for LC techniques in (Ebdon etal. 1995). 

An ICP-Q-MS (Varian 820-MS, Darmstadt, Germany) with a concentric nebulizer (MicroMist) and a double-pass Scott-type spray chamber cooled by a Peltier system was used for analysis of Pd. Table 1 details the ICP-Q-MS operating conditions. Maximal intensity was optimized for In" and minimal values for CeOVCe and Ba QBa. For ID calculations three isotope ratios ( ° Pd/ °" Pd, 105pd/106pd, lOSpjj/lOSpj 2). 

The capability to obtain accurate isotope ratio results at very low concentrations as presented here is dependent on the system used. MS-ICP-MS is a more sensitive instrumentation than is a Q-ICP-MS.The use of a desol-vating introduction system permits greater sensitivity than does use of a standard double-pass, cyclonic, or conical spray chamber, even if Peltier cooled. The use of desolvation also permits lower polyatomic ion formation as demonstrated by very low uranium oxides during optimization. Thus, instrumental setups that differ from those utilized here will have to be evaluated for limitations of their capabilities. The results obtained using SPE, a desolvating introduction system with nitrogen addition, and an MS-ICP-MS instrument will differ dramatically from those obtained at the same concentration using dilution only with a Q-ICP-MS and a standard introduction system. One should not expect to use QC samples spiked with only 20 ng/L total uranium with the latter system. 

Protocol 2 is not instrument specific but, for the purpose of this discussion, will assume the use of a PerkinEImer Sciex Q-ICP-MS instrument, preferably with a PC3 or equivalent Peltier-cooled cyclonic spray chamber or dualspray chamber as the introduction system. In Protocol 2, elution of uranium from 1-mL TRU SPE cartridges is accomplished with 1% v/v (0.18 M) sulfuric add. 

Table 23.4 contains the results of analysis of a urine sample spiked with 50 ng/L natural uranium with an Elan DRC2 optimized as described with a PC3 Peltier-cooled SSI spray chamber. Acquisition included 0.010 s dwell times and five replicates of 1000 scans. Note that simple division of cps by cps by the Elan software gives an erroneously high ratio because of the lack of internal standard corrected background subtraction (see Figure 23.6), whereas taking these into account in Excel gives the correct natural uranium isotope... 

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]. 

Water-Cooled and Peltier-Cooled Spray Chambers... 

Microflow nebulizer coupled with a Peltier-cooled spray chamber An... 

Microflow nebulizer with heated spray chamber and Peltier-cooled condenser An example of this design is the Apex inlet system from ESI. This unit includes a microflow nebulizer, heated cyclonic spray chamber (up to 140°C), and a Peltier multipass condenser/cooler (down to -5°C). A number of different spray chamber and nebulizer options and materials are available, depending on the application requirements. Also, the system is available with Teflon or Nafion microporous membrane desolvation, depending on the types of samples being analyzed. Figure 17.12 shows a schematic of the Apex sample inlet system with the ctoss-Aow nebulizer. 

Microflow nebulizer with heated spray chamber and Peltier-cooled condenser An example of this design is the Apex inlet system from ESI. This unit includes a microflow nebulizer, heated cyclonic spray chamber (up to 140°C), and a Peltier multipass condenser/cooler (down to -5°C). 

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