Full set of Notes with Fill-Ins - San Jose State University

Chem 155 Unit 9 Atomic Emission Page 170 of 316Advantages of Emission MethodsOne of the main advantages of emission methods is:Simultaneous multielement determinationsWith the appropriate spectrometer design, it ispossible to measure many elements at once usingemission. This means:Simultaneous light detection at differentwavelengths – i.e. different points along the focalplane.With conventional spectrometers, this means manyphotomultiplier tubes (PMT’s) placed along the focalplane of the Czerny-Turner, or similarmonochromator. But, PMT’s are neither small, norcheap. So, PMT-based multi-channel spectrometersare both BIG, and EXPENSIVE.With the echelle design, there is a 2-dimensionalfocal plane that happens to be extremely well suitedto the lithographically designed semiconductorcharge-transfer array detector such as the CCD andCID.Page 170 of 316