Charged coupled device methods

Fig. 8 PossibUities for on-line coupling of thin-layer chromatography with physical measurement and determination methods. CCD = Charge Coupled Device Detection.

Westbrook, E. M. and Naday, 1. (1997). Charge-couple device-based area detectors. Method Enzymol. 276, 244-268. 

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. 

A photodiode array or charge coupled device can measure an entire spectrum at once. The spectrum is spread into its component wavelengths, and each wavelength is directed onto one detector element. For the infrared region, the most important method for observing the entire spectrum at once is Fourier transform spectroscopy. 

The method uses a silver hydrosol active substrate. A charge-coupled device was used as the detector. All measurements were made with a 180° scattering geometry. The 507.1 nm line of an Ar-ion in laser (Spectra-Physics Model 2020) was used for excitation with a laser power of 6-8 mW at a resolution of 2 cm-1. Prior to inducing the SERRS effect, the nitrite was transformed into a colored azo dye. 

Fluorescence spectroscopy offers several inherent advantages for the characterization of molecular interactions and reactions. Firstly, it is 100-1000 times more sensitive than other spectrophotometric techniques. Secondly, fluorescent compounds are extremely sensitive to their environment. For example, vitamin A that is buried in the hydrophobic interior of a fat globule has fluorescent properties different from molecules that are in an aqueous solution. This environmental sensitivity enables characterization of viscosity changes such as those attributable to the thermal modifications of triglyceride structure, as well as the interactions of vitamin A with proteins. Third, most fluorescence methods are relatively rapid (less than 1 s with a Charge Coupled Device detector). One particularly advantageous property of fluorescence is that one can actually see it since it involves the emission of photons. The technique is suitable for at-line and on/in-line process control. 

Deev, a. a. (2002). Direct detection of isotopically labeled metabolites bound to a protein microarray using a charge-coupled device. J. Biochem. Biophys. Methods 51, 57-67. 

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