Detector array development

Two 256X256-pixel arsenic-doped-silicon (Si As) impurity band conduction (IBC) hybrid detector arrays developed by Hughes Technology Center have been evaluated for space-based astronomy applications. Potential applications include instrumentation on orbiting astronomy platforms such as the Space Infrared Telescope Facility (SIRTF). 

Haaland et al. [91] developed a so-called multi-window classical least-squares method for ICP-OES measurements [charge-couple device (CCD) detector arrays]. Essentially, it consisted in performing a classical least-squares regression in each of the spectral windows which were measured and combining the concentration predictions (for a given analyte). The methodology was compared with PLS and it proved superior and capable of handling interferences from several concomitants. 

The purpose of this chapter is to review the use of HPLC to determinate OPPs and OCPs. Primarily, the use of HPLC with UV and diode array detectors and developments in automation and HPLC-MS are reviewed. The use of HPLC to clean up and fractionate extracts from fatty samples prior to determination by GC is also reviewed. 

The NIR spectrometer used for method development and sample analysis was a Foss NIR Systems Model 6500 Forage Analyzer with a sample transport module and a standard reflectance detector array. The transport module moves the sample compartment up and down during data collection, thereby allowing a more representative spectrum to be obtained from bulky heterogeneous samples. The reflectance array uses two silicon detectors to monitor visible light from 400-850 nm and four lead-sulfide detectors to monitor NIR light from 850-2500 nm. Natural product sample compartment cells in 1/4-cup and 1-cup sizes were used as sample holders in the transport module. This instrument has a maximum resolution of 2 nm. 

Boxman et. al. suggest that more information can be obtained if the fluctuations in the signals from each detector are examined together with the mean values [150]. They note that this approach can identify whether the inaccuracy is due to insufficient sampling of the detector array or imperfections in the optical model. More recently Knight et. al. [151] developed an analytical inversion method that gave improved resolution and accuracy in size distribution measurement. 

We developed an ICP time-of-flight mass spectrometer, which is now a commercial instrument. We also have a new device, a double-focusing mass spectrometer with a detector array, to look at many different elements at the same time. The third new type of mass spectrometer geometry is a time-of-flight instrument that uses two ion sources at the same time. One third of proteins contain metal atoms, and we hope to separate the proteins by capillary electrophoresis, then use this spectrometer to characterize the proteins and measure their metal atoms at the same time. 

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