The resolution of an array spectrophotometer is determined by slit width, dispersion, and pixel binning. Because wavelength dispersion lacks an exit slit, order-sorting filters are required in linear C.C.D. array UV-VIS spectrophotometers. In C.C.D. array systems, temperature control of the spectrograph optics improves long-term precision and wavelength accuracy. The spectrograph is more miniature and more temperature stable because it has fewer optical components. The sizeable visual footprint of typical scanning instruments makes temperature control of optical components difficult.
A quartz tungsten lamp is used for visible wavelengths between 350 and 1000 nm, while deuterium lamps are used for U.V.U.V. wavelengths below 350 nm. Low-cost systems employ Xenon lamps, which lack the light output, stability, and flexibility of dedicated deuterium and tungsten sources. Users should look for instruments with actual light sources, regardless of scanning or C.C.D. arrays.
Many early critics pointed to photo-oxidation of samples and polarization of optical fibers as potential flaws of array spectrographs due to the use of solarization-resistant threads and short sample analysis times.
These effects are virtually eliminated in high-quality optical designs with optical shutters. Optical shutters are used in the 400 Series spectrophotometers (S.I.S.I. Photonics) to precisely control light exposure to fiber-optic devices. As a result, the polarization that usually occurs within the first 10 hours of use would necessitate over 35,000 analyses. Photo-oxidation is eliminated when the optical shutter is placed before the sample.
The modern UV-VIS system has a plethora of applications. The versatility of numerous fiber-optic sampling accessories is frequently discovered and implemented. Traditional UV-VIS spectroscopy, for example, used 1-cm cuvettes for liquid matrices. Aglient UV-Vis & UV-Vis-NIR spectroscopy is now accessible to a wider audience thanks to today’s flexible fiber-optic systems. Dip probes, rather than cuvettes, now account for more than half of all sales. Solids, powders, and aqueous matrices can all be sampled using fiber-optic reflectance probes. It is simple to use integrating spheres to calculate actual diffuse reflectance. Pharmaceuticals, radiometry, and colorimetry, as well as criminal investigations, are now using agri-technical systems.
C.C.D. array spectrophotometers have built-in software flexibility. These data can be evaluated multiple times because the entire spectrum is instantly available and stored in memory. Timed acquisition and peak location quantification are also public.
Captured in real-time
C.C.D. Spectrophotometers outperform scanning systems in both of these cases. Concurrent full-spectrum data acquisition outperforms monochromatic systems in many ways. Most C.C.D. Spectrophotometers include software for displaying spectra over time. As a result, users can study the entire wavelength range or just a subset of wavelengths. It is essential for chromatographic applications and fraction collection. In real-time, full-spectrum acquisition not only confirms parent compounds but also identifies contaminating artifacts.
The C.C.D. array spectrophotometer of today exemplifies the evolution of UV-VIS spectroscopy. Now more versatile, dependable, and compact than ever before. Because of the versatility of fiber optics and C.C.D. Detection, UV-VIS spectroscopy is now accessible to a broader range of users and applications. New systems with Peltier-cooled C.C.D.s and dual-beam designs are almost certainly on the way.