The Practical Spectrometer

November 07, 2017

Since 2007 BMG LABTECH has used UV/vis spectrometers in their microplate readers for absorbance measurements. In fact, BMG LABTECH was the first company to incorporate a UV/vis absorbance spectrometer into a multifunction microplate reader. But, what is an absorbance spectrometer and what makes it unique?

Dr Carl Peters | BMG LABTECH
Dr Carl Peters
PhD, Senior Applications Scientist

A vital clue to the functionality of a spectrometer exists in the name itself. Spectro, from spectrum, and meter, as in a scientific instrument used for measuring or detection. Therefore, the spectrometer is a device that is used for measuring a spectrum. More specifically in this case, it is an instrument that is used to measure a spectrum in the visible and ultraviolet wavelengths, hence UV/vis spectrometer. The spectrometer is an instrument capable of measuring an entire spectral range, from 220nm to 1000nm and a spectrum out to 700nm is shown below.

The BMG LABTECH absorbance spectrometer measures the complete UV/vis spectrum with 1nm resolution in less than a second. Put another way, in less than one second you are able to capture the individual absorbance value of over 700 wavelengths. That’s powerful, and it has important implications for your research.


One of the most common applications for absorbance in a life science laboratory is the quantitation of DNA. Traditionally this measurement involves using the absorbance at 260nm to determine the DNA concentration, however, five other absorbance wavelengths are also used to greatly improve the accuracy of the measurement: 230nm for contamination by phenolate, 280nm correction for protein contamination, 340nm corrects for light scattering, and the pathlength can be corrected or normalized to 1cm by using the absorbance values at 900nm and 977nm. Therefore the best results are produced by measuring six discrete wavelengths; 230nm, 260nm, 280nm, 340nm, 900nm, and 977nm.

Older generation microplate readers that employ filters or a monochromator will take a long time to read the microplate, or even a single well, because the instrument will have to essentially read the plate six times, once for each wavelength. The BMG LABTECH microplate readers with a UV/vis spectrometer suffer no reduction in speed no matter how many wavelengths you need to read because the spectrometer can capture all wavelengths in the same amount of time it takes other readers to read a single wavelength. All wavelengths, all the data, all of the time.


The UV/vis spectrometer can be used for low volume DNA quantitation as well using the BMG LABTECH LVis Plate.


This accessory is compatible with all current BMG LABTECH microplate readers and allows DNA quantitation of sixteen samples down to 2 µL. The software includes calibration routines, cleanliness check to ensure data quality, and is very easy to use.

The UV/vis spectrometer can also be used for life science related applications such as the scanning of filers and dichroics. Many specialized applications require high performance filters and/or dichroics to function properly. Some of these optical components can degrade over time or with heavy use. The BMG LABTECH spectrometer can be used to measure the transmission profile of a filter or dichroic to help ascertain filter quality, lifetime, or to compare filters of the same type using a special accessory plate that holds the filters.

The filter plate is available in a variety of configurations to accommodate filters ranging in size from 13mm to 40mm. Once loaded the filter plate can be read in under 30 seconds allowing rapid and precise determinations of transmission spectra of the filters. Shown below are 24 filters from various production lots that are being sorted for quality control purposes.

Optical plate are also available that can be used to scan dichroics as well as filters. Dichroics are carefully selected with filters to improve the overall performance of an optical system. Dichroics must be held at a 45 degree angle to the light path and the dichroic optical plate will accommodate a variety of dichroic sizes.

Dichroics are typically used in optical systems to discriminate light of differing wavelengths into discrete optical paths, such as in the PHERAstar FSX optical detection system that can simultaneously detect two emission wavelengths. The example below shows a transmission scan of a dichroic and two luminescence filters for the PHERAstar FSX that is being used to construct a custom optical module for R&D purposes.

BMG LABTECH and other optical companies use BMG LABTECH spectrometer equipped microplate readers in their filter production and quality control facilities. If you have a novel use of a BMG LABTECH UV/vis spectrometer in your laboratory please contact us. We’re always interested in hearing about new uses of our technologies and would love to feature you or your company on our blog.