Pick ‘n’ Mix

Choice – a mantra of politicians and an expectation in our every purchasing decision – whether we’re buying a sugar rush, a new gadget or the latest analytical equipment. Having a choice is great but it brings with it the responsibility of getting the decision right. How irritating to find that you’d have made a different decision if you’d simply had the right information in front of you at the time.

When choosing was easy….

In the early days of gel permeation chromatography / size exclusion chromatography (GPC/SEC) life used to be simpler. You might be able to choose where you bought your refractive index (RI) detector but you weren’t likely to be offered any other technology. RI detection delivered concentration measurement and concentration measurement alone was the only thing available.

Those days are now long gone. Today, many detectors, employing any number of different analytical techniques can be configured to operate with a GPC/SEC column. Detector choice has become a more complex matter. And getting the right array is crucial since it directly influences the productivity of the instrument, and hence its value.

A diversity of detectors

GPC/SEC systems are usefully thought of in  two parts – the separation system and the detector array. The separation system simply provides the harware to achieve the separation and separates on the basis of molecular size. The type and quantity of information you gather about the resulting size fractions depends on what detectors you use.
While many remain wedded to RI detection only – because it suits their needs – those looking for more information may choose to add in some or all of the following detectors:
•    UV – to measure the concentration where a chromaphore is present – usually protein applications
•    Light scattering – to measure absolute molecular weight in the absence of relevant calibration standards and for the direct measurement of molecular size.
•    Viscometry – to reduce the calibration burden and probe molecular structure

In subsequent blogs we’re going to introduce to each of the detection methods in turn and explain why you might want to use them.

Choose your favourite

In the mean time we’re canvassing opinion – what detectors do you use, which wouldn’t you like to live without and why? Please tell us or ask us for help if you’re currently trying to choose. Simply type a comment below.