Coupling of Gas Chromatography with ICP-OES or Atomic Emission Detector

5 Coupling of Gas Chromatography with ICP-OES or Atomic Emission Detector 

Approximately 10 in a million carbon atoms are converted to ions in the FID. The ions produced in the FID carry an electric current from the anode flame to the cathode detector. This electrical charge is the detector signal and response to individual organic compounds is directly proportional to the solute mass and is extremely sensitive. In the absence of CHO+ the current is zero. The FID is widely used as a GC detector and responds to most hydrocarbons that eluate from a GC column. Unfortunately, it is insensitive to hydrocarbons, H2, He, N2, 02, CO, C02, H20, NH3, NO, S, H2S, SiF4 and a host of volatile metallic compounds in gasoline, diesel, distillates, crude oils, natural gas, environmental pollutants and volatile organics in water samples. 

The photodiode array detector is connected to a computer fitted with a suitable package to control the method, calculate and report the results. The photodiode array detector consists of 1000 or more silicon photodiodes arranged side by side on a single small silicon chip and absorption of electromagnetic radiation by a pn-junction causes promotion of electrons from the valence bands to the conduction bands and thus the 

6 Metal Analysis Using ICP-OES Coupled with Electro-Thermal Vaporisation 

Samples for trace metal analysis by A AS or ICP-OES must be presented to these instruments in liquid form. However, in some cases, samples are submitted as powders or solids (chippings, residues, etc.) requiring chemical decomposition prior to metal analysis that can lead to systematic errors in accuracy and precision of measurements. There have been many attempts to introduce samples as a slurry suspension and these were found to be successful for a limited number of samples provided that the particle sizes are suitably small. In most cases the nebulisation of the majority of samples analysed this way has shown that very low sample-introduction efficiency caused by variable particle sizes is in some cases difficult to dissociate, owing to the short residence times in the plasma. The availability of standards for this type of analysis is non-existent or difficult to obtain. 

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