Analyte introduction efficiency

Secondly, the thermal evaporation process can be performed with a conversion efficiency of 100%, by which the analyte introduction efficiency into the source may be increased from a few percent in pneumatic nebulization, through around 10-20% in ultrasonic nebulization to nearly 100%. 

It should be kept in mind that both thermospray nebulization and high-pressure nebulization [143] successfully allow the analyte introduction efficiency to be increased and thus also the power of detection, however, again only when aerosol desolvation is applied. They are especially interesting for speciation by on-line coupling of ICP-AES and HPLC, as shown later. 

In spite of all the advantages mentioned above, ETV-ICPMS, the introduction of which 25 years ago was received with great enthusiasm by the analytical community, has failed to become a standard introduction system for ICPMS. Nowadays, its use is mainly restricted to research centers and academia, not only in the field of polymer analysis, but also in every other field. The reason is perhaps related to the more recent introduction of microflow nebulizers that also show some of the advantages displayed by ETV (low sample consumption, higher analyte introduction efficiency). Moreover, the lack of the general success of ETV can also in part... 

Ultrasonic nebulization has two advantages over pneumatic nebulization. The aerosol particles have a lower diameter and a narrower particle size distribution compared with pneumatic nebulization (< 5 compared with 10-25 pm). Therefore, aerosol production efficiency may be up to 30%, and analyte introduction efficiency is high. No gas flow is required for aerosol production, the trans-... 

Optimization. For the optimization of ICP-MS with respect to maximum power of detection. minimal spectral interference, signal enhancement or depression, and maximum precision, the most important parameters are the power of the ICP, its gas flows (especially the nebulizer gas), the burner geometry, the position of the sampler, and the ion optical parameters. These parameters determine the ion yield and the transmission, and thus the intensities of analyte and interferenee signals. At increasing nebulizer gas flow, the droplet size decreases (Section 21.4.1) and thus the analyte introduction efficiency goes up, but at the expense of the residence time in the plasma, the plasma temperature, and the ionization [304]. However, changes of the nebulizer gas flow also... 

Figure 2.17 provides a schematic overview of a quadrupole-based ICP-MS instrument. Typically, the sample solution is pumped to a nebulizer by means of a peristaltic pump. The nebulizer converts the sample solution into an aerosol. This primary aerosol is introduced into a spray chamber that filters out the droplets with diameter > 10 pm. Although this process is highly inefficient - it reduces the analyte introduction efficiency by 1-2 orders of magnitude, depending on the actual type of nebulizer and spray chamber used - it is necessary to obtain a stable plasma... 

Here, the laser generated aerosol is continuously mixed with a nebulizer-generated aerosol of a spike solution in the ablation chamber [51, 52]. In addition to the potential occurrence of matrix and fractionation effects, this approach also requires the determination of a homogeneously distributed element in the sample and its subsequent use as an internal standard to correct for the different analyte introduction efficiencies of LA and solution nebulization. Real IDMS analyses of trace elements should only use the spike as an internal standard and no additional internal standard(s). In addition, one major advantage of LA-ICP-IDMS for the analysis of powdered samples is lost, namely the elimination of matrix and fractionation effects. 

With the standard sample introduction system, consisting of a pneumatic nebuliser and spray chamber, only droplets < 10 xm in diameter are permitted to reach the ICP. This selection results in an analyte introduction efficiency of only 1-2%, but is required to maintain plasma stability and ensure efficient desolvation, atomisation and ionisation in the ICP. Additionally, the total concentration of dissolved solids is usually limited to a maximum of 2 g/L only, to prevent clogging of the nebuliser, torch injector tube and/or sampling cone and skimmer orifices, and also to limit signal suppression and long-lasting memory effects. Of course, when using ETV for sample... 

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