| Author | Message | ||
     Dilys |
i'm using NIR to measure TVBN in fish meal. how does the NIR differentiate between volatile and non volatile nitrogen? | ||
| David W. Hopkins (Dhopkins) |
Dylys, What do you know about the chemistry of volatile nitrogen? It has long been known that NIR can determine the molecular weight of hydrocarbons, and that is presumably done by a determination from the spectra of the ratio of the end groups CH3 to CH2 chain units NH. If volatile N is predominantly NH3, it should relatively easy to determine NH3 : NH2 ratios. In your case, I can only offer that there must be some chemical signatures in the samples that indicate differences in volatile and non-volatile N contents or their precursors. I suppose that some NH compounds may also be volatile, and these as a class should be distinguishable by NIR, as well as some compounds that might have -N= in ring structures. That is an interesting question, and I would be interested to know whether full spectrum techniques such as PCR or PLS would show any hints of the spectral differences in the principal components or B-vectors? Are you scanning complete spectra? What more can you tell us about the reference methods and what they measure? That would be a further hint at what the NIR is cueing on. Regards, Dave | ||
| David W. Hopkins (Dhopkins) |
Dylys, What do you know about the chemistry of volatile nitrogen? It has long been known that NIR can determine the molecular weight of hydrocarbons, and that is presumably done by a determination from the spectra of the ratio of the end groups CH3 to CH2 chain units NH. If volatile N is predominantly NH3, it should relatively easy to determine NH3 : NH2 ratios. In your case, I can only offer that there must be some chemical signatures in the samples that indicate differences in volatile and non-volatile N contents or their precursors. I suppose that some NH compounds may also be volatile, and these as a class should be distinguishable by NIR, as well as some compounds that might have -N= in ring structures. That is an interesting question, and I would be interested to know whether full spectrum techniques such as PCR or PLS would show any hints of the spectral differences in the principal components or B-vectors? Are you scanning complete spectra? What more can you tell us about the reference methods and what they measure? That would be a further hint at what the NIR is cueing on. Regards, Dave |