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Photodiode arrays in UV-Visible spectroscopy provide fast and reliable results
By Grant Drenkow
Agilent UV-VIS Marketing Manager
In today’s fast-paced world, getting a reliable answer quickly has become the benchmark for success. The ultraviolet-visible (UV-Vis) spectrophotometer is a tool used in many research labs and quality assurance (QA) departments to characterize and verify the appropriate chemical mixtures. Getting a reliable answer every time is important. Getting that answer in seconds is an extra advantage. The Agilent 8453A UV-Visible spectrophotometer allows you to do both.
Conventional UV-Vis spectrophotometers rely on mechanical movements of gratings to take measurements at multiple wavelengths. These mechanical movements reduce reproducibility, slow the acquisition of data, and increase the need for instrument maintenance. In contrast, the Agilent 8453A UV-Visible spectrophotometer incorporates well-proven photodiode array technology, which has no moving parts and ensures reliable results every time. The 8453A spectrophotometer can measure the complete UV-Visible spectrum in less than one second, making it possible to characterize chemical activities like drug dissolution.
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Figure 1. The Agilent 8453A UV-Visible spectrophotometer has no moving parts, making it highly reliable and repeatable from one cycle to the next.
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Figure 2. The Agilent photodiode array measures many wavelengths in parallel, which allows you to acquire a complete UV-Visible spectrum in less than a second.
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Robust design, for ruggedness and speed
The 8453A spectrophotometer uses two light sources – deuterium and tungsten-halogen lamps – for complete coverage of the UV and visible spectra. The light is focused by a lens through the sample onto a grating. The grating disperses the UV light into a spectrum of individual frequencies that is directed to the photodiode array.
The photodiode array (Figure 2) is a solid-state electronic device consisting of capacitors in a fully charged state. Photons from the grating that strike the silicon in the array cause the diodes to turn on and the capacitors to discharge. The amount of charge needed to recharge the capacitors is proportional to the number of photons that strike the silicon, which is proportional to the intensity of the light across the wavelengths in the spectra. The readout cycle on the photodiode array is typically 100 ms.
Reliable results for many applications
UV-Vis spectroscopy is an excellent technique for the direct quantification of single, known components. Organic compounds with double bonds, as well as some transition metals, have known spectra and work well with UV-Vis. When compounds fail to absorb in the UV-Vis range, they can often be derivatized with a chromophore and then quantified. UV-Vis spectroscopy is applied in a number of industries, such as organic chemicals, inorganic chemicals, agriculture/food, environmental, and polymers/plastics.
Biotech and pharmaceutical companies use UV-Vis spectroscopy for drug development and QA. Analysts can determine equilibrium constants (pKa) and “melting” temperatures of proteins and nucleic acids using this technique. Time-based applications like enzyme reactions and dissolution tests require the speed and reliability of a photodiode-based UV-Vis system. The Agilent 8453A spectrophotometer is a good match for these applications, and is certified for requirements of both US and European pharmacopoeias.
Given the versatility of UV-Vis spectrophotometers, the instruments are quite popular in academic and government labs. A photodiode-based system with no moving parts is attractive because other than changing a lamp, maintenance is rarely needed.
An Agilent software solution sure to fit your lab
The Agilent 8453A UV-Visible spectrophotometer is available with a variety of software choices. The Agilent UV-Visible ChemStation general purpose software is ideal for many analysts who want to simply operate the instrument and collect data. Agilent UV-Visible ChemStation advanced software makes it possible to do more sophisticated analysis and data collection, such as measurement of multiple sample components. Specialized software is also available for biochemical analysis and dissolution testing.
If you need rapid spectral acquisition with a rugged instrument that gives highly reproducible results, consider the Agilent 8453A UV-Vis spectrophotometer with its photodiode array technology. For more information on this proven tool for fast and reliable results, talk with your Agilent Representative today.
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