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Gavriel Levin (levin)
Senior Member
Username: levin

Post Number: 50
Registered: 1-2006
Posted on Friday, August 03, 2007 - 2:38 am:   

Hi Guys,

Well, it seems we have many issues mixed here.

To the issus of falling powder (Micahel Mound) - from my experience in various powders it is definitely possible to get good signal with diffuse reflectance probes that have sufficient number of fibers. In many cases (if the powder is fine enough, like flour or so)even mini-bundles (37 launch, 37 collect) are sufficient, if powders are coarse you will be better off with full bundle, (144 launch, 144 collect) it is only a question of money. These probes have a sapphire 1/2 ball at the end that help to collect light from as wide an angle as the fibers can accept (aperture issues)

If there is an issue, then one needs to go to a set-up where there is direct illumination and collection through a sapphire window that will be installed somewhere in the powder conduit where powder always come in contact with the window, but does not stick to it.

If you wish to conatct me directly for more specific information you are welcome, my address is posted.

The second issue was about measuring virus in blood, or deterioration of fruits - well very narrow topic to be covered here within 5 minutes - virus is at concentration levels that can not be detected by NIR.
Fruit deterioration is another subject - in the deterioration process there are chemicals consumed (sugar, starch) and chemicals produced, many times deterioration is associated also with softening, and the NIR has a good chance of detecting these conditions. In fact, some people use NIR to determine firmness in apples, and other fruits. However, it can not be viewed as a very general method, and a good deal of testing needs to be done to determine the limits of applicability for each fruit type.

I hope it helps some.

Gabi Levin
Brimrose
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Michael C Mound (mike)
New member
Username: mike

Post Number: 5
Registered: 7-2007
Posted on Friday, August 03, 2007 - 1:11 am:   

Hi, everybody. Any takers on the use of fiber probes for quantitative analysis NIRS in falling powders???...see above...

Thanks.
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rahimi (malirahimi)
New member
Username: malirahimi

Post Number: 1
Registered: 7-2007
Posted on Wednesday, August 01, 2007 - 12:21 am:   

hello every body
i'm interested in NIR as a new method having vast capabilities but just know a little about it's mechanism of work.can any body help me in this regard?what's the machanism of detecting a virus in blood or assaying a deterioration in fruits.
thanks and best wishes
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Michael C Mound (mike)
New member
Username: mike

Post Number: 1
Registered: 7-2007
Posted on Wednesday, July 11, 2007 - 2:21 am:   

Hello, out there...not to confuse things, but I wonder if anyone has an idea as to how to gain sufficient illumination while using a (non-contact)NIR probe(recommendations?)for characterization of PCA of falling powders? By "falling", I mean to insert probe(s)into a conduit where the materials are transferred to a downstream processing point via gravity fall.

Thanks
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Weyer
Posted on Thursday, November 08, 2001 - 7:53 am:   

I would like to hear comments about how well fiber bundle probes perform quantitative analyses. The probe I'm trying does not reject the specular component of light and I am having trouble getting a good calibration with it. This is a contact measurement, with the probe inserted into a white powder. I'm looking for a minor component. I can get a good calibration with another instrument, using a cup arrangement. Are such probes being used for quantitative analyses, or are they designed mainly for qual?
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David Hopkins (Hopkins)
Posted on Thursday, November 08, 2001 - 8:28 am:   

Lois,

I have no experience with fiber measurements that I am free to discuss, but I have some observations. I think that a probe design with bundles with random fibers carrying the input light and collected reflected light have the problem of poor depth of penetration due to the close spacing of the input/collection. In addition, they may be subject to higher stray light collection, which may be a problem you lump under the term specular component. It seems to me that the concentric ring arrangement might be better suited to your requirements. This concept was pioneered in Karl Norris' early work on "interactance" and measurements of fat in the human body.

I think the principle has been used very well in the fruit measurement instrument made by Kubota. I don't know whether they make an instrument with a fiber optic wand with probe that you could insert into a powder. I recommend you ask Susumu Morimoto about that. His email is: [email protected]
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David Russell (Russell)
Posted on Thursday, November 08, 2001 - 8:36 am:   

I'm confused by Dave Hopkins' reply.
I thought all bundles sold for reflectance utilized the concentric ring concept.
Has that feature perhaps been "value engineered" out of newer designs?
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weyer
Posted on Thursday, November 08, 2001 - 9:04 am:   

Yes, Dave Hopkins was correct. This fiber bundle is randomized. This is an FT instrument I am discussing and, yes, they seem to have value engineered out, forgotten, or never knew some of the concepts needed for good NIR analysis.
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hlmark
Posted on Thursday, November 08, 2001 - 10:26 am:   

Lois - my money is on "they never knew it": you'd be amazed at how parochial some companies can be. SInce they're an FTIR company there's a good chance they never even heard of Karl, or what he's done in the past, since it wasn't in the FTIR world.

Howard
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Bruce H. Campbell (Campclan)
Posted on Thursday, November 08, 2001 - 11:12 am:   

Lois,
You might need a spacer between then end of the bundle and the powder. If this distance is too short, the light coming back from the powder has too large of an angle when entering the return fibers, and thus it doesn't get to the detector. Try a spacing of about three to five millimeters, or thereabouts to find the optimum separation between the fibers and the powder.
Bruce
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Art Springsteen
Posted on Thursday, November 08, 2001 - 11:25 am:   

All,

I've been reading with interests the postings on the fiber probes. Bruce's last comment spurred me to respond.
1) Bruce is right, sort of. If the powder is packed and doesn't scatter much, a spacer would be helpful in getting better signal return. If the powder is loose and is very lambertian, the opposite will be true- you want to be as close to the surface as possible, or you will lose significant signal and your S/N will go right down the tubes.
2) On the fiber bundle themselves- I've used concentric (6 around 1, etc.), randomized (which, actually, ain't all that bad if you can get a truly randomized bundle but those are very expensive), and even two half moons. If the material being measured is very lambertian, it didn't seem to matter much which configuration was used. It was the not-so-perfect reflectors that cuased measurement geometry to be more crucial.
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Qingyu Wang (Wangq002)
Posted on Sunday, April 17, 2005 - 11:46 pm:   

i want to develope a method which is quantitative analyse use in drug tablet .
My question is how to make the reference standard tablet?
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Lois Weyer (Lois_Weyer)
Posted on Monday, April 18, 2005 - 6:53 am:   

Does anyone out there know of an old Foss Model 6500 that they would sell me for $5K or under?

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