Wood's Corner - The Colorimeter
MeasureNet Spectrum Quarterly; November, 2005
I thought that I’d deviate from our normal discussion of probe care to answer some of the questions about our newest device, the colorimeter.
“What is a colorimeter and how is it different from a spectrometer?”
Colorimeters are generally simple photoelectric devices used to measure light over selected, relatively wide, frequency ranges in the visible region of the electromagnetic spectrum. A spectrometer is a more complex device designed to first disperse the light into the wavelengths present and then measure narrow regions anywhere along the electromagnetic spectrum. Our colorimeter, for example, produces three separate colored bands of light-red, green, and blue-using a three-color light emitting diode (LED). Our standard spectrometer, on the other hand, covers all frequencies in the visible and near infrared spectrum. It employs a monochromator and a diode array detector to provide one nanometer resolution over the entire range.
“Why would I need a colorimeter in my lab if I have a MeasureNet spectrometer?”
This is a very good question. Let me answer it this way. Let’s say you want to do a simple kinetics experiment in your laboratory. Since the spectrometer is designed to be a shared device, it would be inconvenient to use by multiple groups of students for the large number of repeated measurements required to follow the course of the reaction. The colorimeter, on the other hand, is a much simpler, less expensive device, and each student group (i.e., each workstation) has its own. They are not shared. The colorimeter determines the absorbance of the reaction mixture twice per second, allowing your students to easily follow reactions occurring over times ranging from one or two minutes up to many minutes.
Another reason for getting colorimeters for your students is that the unit also functions as both a fluorimeter and a turbidimeter. Yes! We’ve combined these two features along with the colorimeter into one single unit. This means a new group of optical experiments can easily be incorporated into your laboratory at no extra cost.
“Is the colorimeter difficult to install and use?”
Those of you who have known us for a while know that we at MeasureNet attempt to make the instrumentation as simple as possible to use. We don’t want your students spending valuable laboratory time trying to figure out how to use instrumentation. We want them spending their time learning chemistry! Adding our colorimeter to your existing MeasureNet equipment only requires you to install new software in your controller and on your PC. If you need help with this, you can always contact us and we’ll guide you through this process. For our new customers who buy computers from us, your networks will be set up for you at the factory.
You use the colorimeter like any other MeasureNet probe. Simply plug it into the station and follow the usual simple menus to choose the LED color, calibrate (set 0% and 100% T), and begin measuring. The spectrometer can come in handy here for determining which of the LED colors is most strongly absorbed by the substance to be studied, and will therefore be the easiest to measure.
“Is your colorimeter different from other brands?”
Yes! We all use LEDs, but one of the problems with using LEDs for light sources is that they drift with time as they warm up. That makes it difficult to get accurate results for kinetic experiments in some systems. Some vendors pulse the LED to keep it cooler to help decrease the drift. We made a fundamentally different choice. The MeasureNet colorimeter incorporates a double beam design, and our testing shows that this configuration almost completely eliminates the problem of drift. Absorbance readings on simple samples are very stable over long time periods.
“I really like the MeasureNet concept but I have some other probe brands. Will these other probes, like a colorimeter, interface with MeasureNet?”
No! MeasureNet probes are designed specifically to work on our system. That allows us to provide the best data collection system possible for the cost. Probes designed for other systems are not compatible with MeasureNet and cannot be used. This does not include, however, various standard devices such as pH electrodes and ion-selective electrodes, which are available from numerous suppliers in addition to MeasureNet.
Keep your questions coming!
Elwood Brooks, Ph.D. is a MeasureNet Senior Applications Specialist, motorcycle enthusiast, and Cincinnati Bengals fan. He can be reached at brooks@measurenet-tech.com