Direct reader ICP

ICP is used for the determination of ppm levels of metals in liquid samples. It is not suitable for the noble gases, halogens, or light elements such as H, C, N, and 0. Sulfur requires a vacuum monochromator. A direct reader ICP excels at the rapid analysis of multi-element samples. 

A direct reader ICP excels at the rapid analysis of multi-element samples. Common sample types analyzed by ICP include trace elements in polymers, wear metals in oils, and numerous one-of-a-kind catalysts. ICP instruments are limited to the analysis of liquids only. Solid samples require some sort of dissolution procedure prior to analysis. The final volume of solution should be at least 25 mL. The solvent can be either water, usually containing 10% acid, or a suitable organic solvent such as xylene. ICP offers good detection limits and a wide linear range for most elements. With a direct reading instrument multi-element analysis is extremely fast. 

The advantage of ICP is that the emissions are of such intensity that it is usually more sensitive than flame AA (but less sensitive than graphite furnace AA). In addition, the concentration range over which the emission intensity is linear is broader. These two advantages, coupled with the possibility of simultaneous multielement analysis offered by the direct reader polychromator design, make ICP a very powerful technique. The only real disadvantage is that the instruments are more expensive. See Workplace Scene 9.3. 

Simple, low-dispersion monochromators or even interference filters are used for most flame emission applications since few atomic line spectral interferences are expected as a result of the limited population of the higher-lying excited states. For high-temperature sources such as ICPs, higher-dispersion spectrometers are typically used. Instruments set up to do simultaneous multielemental analysis can use direct readers with PMT detection. However, most modern detections systems for this type of source for simultaneous multielemental analysis employ a high-dispersion eschelle grating spectrometer and an array detector such as a CCD or CID. 

A wide variety of different methods of analysis have been applied to different trace metals in seawater. All these documents are beyond the scope of this article and the reader is referred to Fmrher Reading. In general, the methods fall into two groups those that can be used without preconcentration and those that do require such a procedme. In the first group are spectrophotometric, chemilmninescence, and fluorimetric procedures, electrochemical methods, and some ICP-AES and inductively coupled plasma mass spectrometry (ICP-MS) methods. In the latter group, involving preconcentration, a variety of concentration methods have been used followed by AAS, gas chromatography, mass spectrometry, and neutron activation methods, or indeed any of the direct analysis procedures. These methods will now be briefly discussed. 

Several detectors are used for VOCs analysis by GC flame ionization detector (FID), photo ionization detector (PID), electron capture detector (BCD), electrolytic conductivity detector (ELCD), mass spectrometer detector (MSD or MS), and Fourier-transform infrared detector (FTIRD). For the in-depth reviews of the detectors, readers are directed to Refs. [52-54]. Examples of ICP-MS or microwave-induced plasma atomic emission spectrometry (atomic emission detector, AED) have been reported as detection technique after chromatographic separation [55,56]. Current trends and developments in GC analysis of VOCs have been recently reviewed by the group of Dewulf [16,57]. Mass spectrometer detectors allow low detection limits in single/selected ion monitoring (SIM) and a qualitative confirmation by full scan mode or by means of other ion selected as qualifier. 

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