| Author | Message | ||
     lucy liu |
Hi NIR Fellows Our next NIR project is determination of Insulin in water and other placebo, such as cresol and glycerol. If you know some good references or some good starting points on that I'll be happy. My initial plan is to go for a transmission measurement, with a 4 cm-1 resolution. comments are welcomed. Thanks for a good forum Lucy Liu | ||
| hlmark |
Lucy - what's a big movie star doing on OUR little forum?? :-) But for your question: as long as you're dealing with clear solutions, you should be fine. Glycerol should be soluble, but I'm not so sure what the solubility limit is for the cresol - if the concentration is too high then it might precipitate out and cause optical scattering. Other considerations are whether there are any other constituents in the solution that might scatter, and what the concentration of insulin is that you want to measure. Howard \o/ /_\ | ||
| Lucy Liu |
Hi, Howard, The concentration of cresol is about 3 mg/ml. Based on the MSDS, it is water souble. The concentration of insulin for the study will be 2 mg/ml. Any suggestion and common is welcome. Lucy | ||
| hlmark |
Well, that makes the insulin concentration about 2 parts per thousand, or 0.2%. This is normally considered to be roughly the lower end for sensitivity for NIR, but those considerations are based on the measurement of powdered solids. It would be interesting to learn how well analysis at that level can be done in a clear liquid. At that level, though, you'll have to watch out for the effect of temperature, especially the effect of temperature on the water, since the water spectrum is very sensitive to temperature, and also since water is the major component. Also, there's a distinct possibility that you might wind up measuring the insulin indirectly, by it's effect on the water spectrum - that sort of stuff is known to happen. And when it does, that exacerbates the temperature effect, too. Howard \o/ /_\ |