Cross-flow nebulisers

The most widely used nebuliser system in ICP is the crossed-flow nebuliser shown in Fig. 20.12. The sample is forced into the mixing chamber at a flow rate of 1 mL min 1 by the peristaltic pump and nebulised by the stream of argon flowing at about 1 Lmin-1. 

Carey and Caruso [126] also summarised the two main approaches to interfacing the SFC restrictor with the ICP torch. The first method, used with packed SFC columns, introduces the restrictor into a heated cross-flow nebuliser and the nebulised sample is subsequently swept into the torch by the nebuliser gas flow. Where capillary SFC systems are used, a second interface design is commonly employed where the restrictor is directly introduced into the central channel of the torch. This interface is more widely used with SFC-ICP-MS coupling [20]. The restrictor is passed through a heated transfer line which connects the SFC oven with the ICP torch. The restrictor is positioned so that it is flush with the inner tube of the ICP torch. This position may, however, be optimised to yield improved resolution. The connection between the transfer line and the torch connection must be heated to prevent freezing of the mobile phase eluent after decompression when exiting the restrictor. A make-up gas flow is introduced to transport the analyte to the plasma. This... 

SFC has received attention as an alternative separation technique to liquid and gas chromatography. The coupling of SFC to plasma detectors has been studied because plasma source spectrometry meets a number of requirements for suitable detection. There have been two main approaches in designing interfaces. The first is the use of a restrictor tube in a heated cross-flow nebuliser. This was designed for packed columns. For a capillary system, a restrictor was introduced into the central channel of the ICP torch. The restrictor was heated to overcome the eluent freezing upon decompression as it left the restrictor. The interface and transfer lines were also heated to maintain supercritical conditions. Several speciation applications have been reported in which SFC-ICP-MS was used. These include alkyl tin compounds (Oudsema and Poole, 1992), chromium (Carey et al., 1994), lead and mercury (Carey et al., 1992), and arsenic (Kumar et al., 1995). Detection limits for trimethylarsine, triphenylarsine and triphenyl arsenic oxide were in the range of 0.4-5 pg. 

Cross Flow Nebulisers [6], The cross flow nebuliser design is based on a V-groove principle (Figure 2.13). This type of nebuliser is less sensitive to high salt content and can be used for aqueous and non-aqueous samples. It needs a peristaltic pump to transport the sample that must contain a sufficient number of precision rollers that do not... 

Figure 2.73 Diagram of V-groove cross flow nebuliser suitable for high solids content. (Reproduced with kind permission from E-PONDS. A., C.P. 389, CH-1800 Vevey, Switzerland)...

Fuishiro, M., Kubota, M. and Ishida, R. (1984) A study of designs of cross flow nebulisers for ICP atomic emission spectrometry, Spectrochimica Acta, Part B, 39, pp617-620. 

The development of the Babington [10] cross flow nebuliser allowed samples containing high salt content and slurries (max. 20 pm) to be analysed with considerable ease. 

A pneumatic cross-flow micronebuliser has been described for use in ICP-MS. The high efficiency cross-flow micronebuliser (HECFMN) has a narrow capillary placed inside the conventional sample capillary. The inner diameter of the nebuliser gas nozzle is reduced with respect to the conventional cross-flow design. Due to the characteristics of this device, the free liquid uptake rate (i.e. about 9 p-L/min) is lower than that found for either a conventional cross-flow nebuliser (i.e. 1900 pL/min) or concentric pneumatic micronebulisers (i.e. from about 30 to 100 pL/min). This fact makes the HECFMN attractive for CE ICP-MS interfaces. ... 

The on-line interface of flow manifolds to continuous atomic spectrometric detectors for direct analysis of samples in liquid form typically requires a nebuliser and a spray chamber to produce a well-defined reproducible aerosol, whose small droplets are sent to the atomisation/ionisation system. A variety of nebulisers have been described for FAAS or ICP experiments, including conventional cross-flow, microconcentric or Babington-type pneumatic nebulisers, direct injection nebuliser and ultrasonic nebulisers. As expected, limits of detection have been reported to be generally poorer for the FIA mode than for the continuous mode. 

There are several types of nebulisers, for example the concentric quartz system (Fig. 3.9) or cross-flow system (Fig. 3.10) the tips of which are made from synthetic material or precious stones. The first system can be subject to blockage with solutions containing as little as 0.1% of dissolved salts due to its small capillary inlet. The second system is less fragile and is resistant to corrosion from solutions containing hydrofluoric acid. 

Figure 2.9 Overview of sample introduction methods and hyphenated techniques used in ICP-AES. (A) Pneumatic concentric (sometimes called the Meinhard nebuliser) (B) Babington (C) fritted disc (D) Hildebrand nebuliser (E) cross flow (G) standard ultrasonic nebuliser for aqueous and non-aqueous solvents (H) electro-thermal graphite ( ) electro-thermal carbon cup (K) graphite tip filament (L) laser ablation (M) hydride generation (P) flow injection...

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