| Author | Message | ||
     Sheelagh Halsey (shalsey) Intermediate Member Username: shalsey Post Number: 17 Registered: 12-2006 |
Hi Limor I agree with previous postings on checking sample presentation, repeating measurements and checking for moisture changes. The most likely reason for change over a short time period is moisture in the samples. I would overlay the old and new spectra to check the water peaks. If the changes are due to water, you can then update your calibration sets with the new samples. Checking you instrument is always a good thing to do. You might want to consider setting up a sealed check cell. If you run this every day and get a similar result, it will give you some confidence that the instrument is performing properly. I don't know if you have ValPro intalled, but this will also give you good diagnostics. Regards Sheelagh | ||
| Tony Ainscough (tony_ainscough) New member Username: tony_ainscough Post Number: 2 Registered: 5-2009 |
Hi Limor, assuming that the positioning of the seed is good then may be the poor fit to your method (assuming calibration) is due to insufficient repeat measurements of your sample in the calibration. Typically i would scan each sample at least 3 times. Remove sample and reposition then scan 3 times again. Check your variabillity if it appears poor you may have to collect the same sample several times to account for this variation. It would also be reasonable to consider instrumental variation as a possibillity if this variation only occurs after a few days. The Antaris is typically a very stable instrument as it employs a sophisticated method of dynamic alignment for the interferometer but as with all things sophisticated they can go wrong. You may want to try a long term stabillity test to confirm the instrument performance if you exaust possibilities associated with the sample. regards Tony | ||
| Limor Baruch (baruch) New member Username: baruch Post Number: 2 Registered: 5-2009 |
Dear Tony, I'm working with an Antaris II FT-NIR analyzer in reflectance mode. I scan the exact same seeds, which are clean. I've also tried to keep the seeds in a controlled environment (for a non-destructive, however not immidiate method) or to dry them (for a destructive but immidiate method). I can discriminate seeds of different varieties or even hybrids from their parent lines, but when I scan them after few days they don't fit to the method. Thanks a lot for your help Limor | ||
| Peter Tillmann (tillmann) Intermediate Member Username: tillmann Post Number: 16 Registered: 11-2001 |
Dear Limor, to determine varieties by NIR: I had the same approach back in the mid 90s for gene bank (?) material of Brassica species. We had at that time a dispute inside the institute regarding the usefulness. It culminated in the following arguments: - NIR is detecting chemical composition in form of molecules of mainly macro ingredients - species are determined by its genetics - the same genetics will and do result in different phenological composition under varying growing conditions You will easily be able to distinguish wheat from barley from rice from Brassica, because genetics will have a markedly effect on phenotype. Whether you can distinguish varieties inside one specie is mainly dependent on the heretability (percentage of phenotypic variation being explained by genotypic variation). Single seed: We have developed a single seed analyser for rapeseed together with the university of Goettingen, Germany. There was no way to get reproducible spectra from single seeds by hand. Which was mainly due to the distance of the seed to the fiber optics. Rapeseed is a favorable specie because of the lack of the specific storage compartment in the seed. This is very different from e.g. rice or maize, where the seed differenciates into starch storage compartment and germ, resulting in a heavy influence of the positioning of the seed onto the spectra. We use the single seed analyser for C18:1, oil and GSL determintation. Yours Peter | ||
| Gabi Levin (gabiruth) New member Username: gabiruth Post Number: 1 Registered: 5-2009 |
Hi Limor, I think I can help. Gabi Please call 050-7733911 or mail to [email protected] In general Seeds only appear to be stable chemically. Besides mositure as well pointed out - there are chemical processes. This is why vigor and germination rates decline with storage, even under best conditions. Even freezing will not solve problem totally, because microcrystalline changes due to freezing and thawing can also affect the spectrum. Looking forward to hear from you Gabi | ||
| thomas ricour (tricour) Intermediate Member Username: tricour Post Number: 16 Registered: 2-2006 |
Dear Limor, now for many years, we are analysing in transmission and reflexion seeds (corn, rape, sunflowers...) by AOTF to determine and sort seeds and parameters. If you want some help or advice, please contact me : [email protected] Kind regards Thomas Ricour | ||
| Tony Ainscough (tony_ainscough) New member Username: tony_ainscough Post Number: 1 Registered: 5-2009 |
Hi Limor, it would be useful to know a little more about exactly how you are presenting and scanning your samples. When you say you are scanning the same seeds do you mean seeds from the same batch or exactly the same seeds. Are the seeds clean? (free from any other debris) The most likely parameter to change in your samples is moisture. Either keep them in a controled humidity environment or if this is not possible store them in a sealed bag in an air tight container. It would also be useful to see the spectra to give a better idea of exactly what is changing. Please could you also give some information as to the equipment you are using and its operating parameter setup. regards Tony | ||
| Limor Baruch (baruch) New member Username: baruch Post Number: 1 Registered: 5-2009 |
Hello all, I'm new in this great forum and I'm interested in seed classification to their varieties for quality control. In particularly castor seeds, canola, and rice. I'm trying to develop a non-destructive method for single seed scans. My main problem so far is that I scan the same seeds after few days and get significant changes. I'll be glad to get any helpful information or advices. Limor |