UV-VIS SPECTROPHOTOMETERS continued


Spectral bandwidth Spectral bandwidth is a measure of how narrow- ly the chosen wavelength is being measured. For example, setting a monochromator with a 2-nm bandwidth slit to 450 nm will allow light between 449 and 451 nm through. A narrower bandwidth enables close or overlapping peaks to be better resolved. The tradeoff is that less energy gets through the smaller slit, thus reducing the signal-to-noise ratio and increasing the effective


amount of noise, points out Derek Hodgeman, Production Manager at Buck Scientific (www. bucksci.com). Higher-end instruments may compensate by using higher-energy light sources and more sensitive detectors. Some manufacturers offer interchangeable slits, or a wheel with multiple slit sizes.


Cuvette holder


A typical UV-VIS spec will come with a single cuvette holder. An automated multicuvette


changer, standard on the Thermo Fisher GENESYS™ 10S, is often available as an option. Similarly, throughput can be boosted with a sip- per accessory that allows the user to spend less time filling and rinsing cuvettes.


User interface The user interface is another consideration. Most specs come with a touchpad, with the software to run the instrument built in. More sophisticated operations and applications can generally be run from a PC. “Some vendors include software with the instrument, and some sell it as an option,” warns Bain. “The level of sophistication of what you can do on a local [built-in] control also varies.”


Advanced Instrumentation


Density Meters | Refractometers | Polarimeters | Viscometers Color Determination | Oxygen Meters | Turbidity Meters pH Measurement | CO2


Meters


Applications and accessories Of course, there are varied applications for which a UV-VIS spec will be used, and a host of acces- sories are available to cater to them, depending on the instrument. These include shakers, heat- ers, and coolers, as well as specific measurement tools like different relative specular reflectance accessories for different degrees of incident light.


So think about what you will need from a UV- VIS spectrophotometer, both now and in the foreseeable future:


• What will you be measuring, and what will you need to measure it?


• How accurate and precise do you need to be, and over what range of wavelengths and absorbance?


• Will you be processing just a few, or many, samples at a time?


• How much bench space are you willing to dedicate?


• What is your budget?


Then you can determine which spectrophotom- eter can best meet those needs.


For more information on UV-VIS spectropho- tometers, visit www.labcompare.com


www.anton-paar.com | 800.722.7556 AmericanLabMay1.indd 1 AMERICAN LABORATORY • 10 • MAY 2014 4/22/14 12:50 PM


Josh P. Roberts has been a full-time biomedical sci- ence writer for more than a decade. After earning an M.A. in the history and philosophy of science, he went through the Ph.D. program in molecular, cel- lular, developmental biology, and genetics at the University of Minnesota, with dissertation research in ocular immunology; e-mail: tcwriter@msn.com.


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