| Author | Message | |||
     Tony Davies (td) Moderator Username: td Post Number: 266 Registered: 1-2001 |
Hi, Here is the .PDF that Ana was trying to post. Tony
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| Tony Davies (td) Moderator Username: td Post Number: 265 Registered: 1-2001 |
Hi Rong, If you go to the list of topics in the "Bruce Campbell" section and click on the most appropriate topic, then you will find the "Start New Thread" button at the VERY bottom of the page. Best wishes, Tony | |||
| Ana Garrido-Varo (garrido) Member Username: garrido Post Number: 13 Registered: 1-2006 |
Eva, I hope that now you can get the pdf. If not, please send me your e-mail address and I�ll mail it.Maybe I�m doing something wrong when uploading attachment! Ana | |||
| Rong Zhou (rongz) New member Username: rongz Post Number: 4 Registered: 12-2010 |
Dear all: I cannot find the Create New Conversation Button even though I see this instruction "To ask a new question, press the Create New Conversation button". I have access to a FOSS NIRSystem 6500. I want to use it to analyze a single seed such as a canola seed. I was wondering whether I can use some special attachment (such as fiber optics?). Any suggestion? Best regards Rong | |||
| Daniel Alomar (dalomar) Junior Member Username: dalomar Post Number: 10 Registered: 2-2009 |
Eva There should be a thin layer of milk between quartz window and gold reflector (aluminium in our case). Otherwise, you could not have a reading of the sample! Light needs to go through the sample, be reflected, through the sample again and to detectors... I have scanned colostrum actually, which is "thicker" than milk and easier to see. Regards Daniel | |||
| Jose Miguel Hernandez Hierro (jmhhierro) Advanced Member Username: jmhhierro Post Number: 22 Registered: 4-2008 |
Hi Eva, The answer is yes, there is a thin layer between the aluminium disk (gold in your case) and the quartz window and I can see it. I have used this device for recording fats and oils (I put 50 microliters of oil)and the layer is noticeable. Best regards Jose Miguel | |||
| Eva Lewis (evalewis) New member Username: evalewis Post Number: 3 Registered: 8-2011 |
Hi all, Thank you so much for all your very useful comments. It is very helpful. Ana - I cannot see the powerpoint. Maybe I am looking in the wrong place? Can you let me know where it is please? Or if you need my email address just let me know. Daniel and Jose - when you look in the glass do you have a layer of milk between the glass and the gold reflector disk? Can you see this layer? Or is it almost invisible? Thanks again, Eva | |||
| Ana Garrido-Varo (garrido) Member Username: garrido Post Number: 12 Registered: 1-2006 |
Eva We have experience for the analysis of milk both by reflectance (modification of DESIR) and by ttansflectance. Good sample preparation, and cup filling together with the use of repeatability files are key for developing robust calibrations.I prepared a ppt for you with some tips and useful readings. If you have further questions you can also contact Dr. Nieves Nu�ez (NIRsoluciones), her PhD thesis subject was analysis of milk, cheese and whey by NIRS Hope you find useful the ppt Ana | |||
| Nguyen Thi Dat (nguyenthidat) New member Username: nguyenthidat Post Number: 3 Registered: 2-2011 |
Hi Karl, I do not read your paper in NIRnews. It is nice if you send to me at [email protected] Thank you. Dat | |||
| Karl Norris (knnirs) Senior Member Username: knnirs Post Number: 56 Registered: 8-2009 |
Dat, Evidently, you have not read my paper in NIRnews. I can send you a copy if you give me your email address. The instrument was a Foss-NIRSystems On-Line Instrument with fiber optics to provide for adjustable pathlength measurements of liquids. Karl | |||
| Nguyen Thi Dat (nguyenthidat) New member Username: nguyenthidat Post Number: 2 Registered: 2-2011 |
Hi Karl, Please let me know the type of the instrument you use for measuring milk? Thank you. Dat | |||
| Karl Norris (knnirs) Senior Member Username: knnirs Post Number: 55 Registered: 8-2009 |
Eva, I had my best success in measuring the fat content of whole milk using transmission in a vertical path through a cell with 1 mm pathlength,"Karl H. Norris, NIR news 13(3), 8�11 (2002)". The use of a vertical path for the light minimizes the effect of fat movement in the sample as described by others. Karl | |||
| Daniel Alomar (dalomar) Junior Member Username: dalomar Post Number: 9 Registered: 2-2009 |
Eva We place the sample on the reflective surface controlling sample size in an analytical balance. Then the lid (quartz window) is tightened so the liquid is spread between quartz and the reflective bottom. Some viscous liquids are messy, as sometimes bubbles are formed... Good luck with your work! Daniel | |||
| Jose Miguel Hernandez Hierro (jmhhierro) Advanced Member Username: jmhhierro Post Number: 21 Registered: 4-2008 |
Eva, I have used these ring cups (aluminium reflector plate).As Daniel has said, it works well, just a piece of advise,in order to avoid drops put your FOSS in horizontal position if the sample is not viocous enough. The movement of the ring cup will be righ-left. Regards Jose Miguel PS:I am out of office and I do not have any picture but if you need one I can send it early in September | |||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 448 Registered: 9-2001 |
Eva - since milk is mainly water, even a thin layer will give appreciable absorbance because water is so highly abosrbing. On the other hand this may give problems in that you might not be able to see anything EXCEPT the water, if the layer is too thin. You may need some trial-and-error to figure out the best conditions for making the measurement. However, there is another, more subtle problem involved in measuring milk. Milk is not static. Even in commercially homongenized milk, the fat (butterfat) in the milk will tend to rise and give a continual change in the spectral readings. If the milk is not homogenized, the butterfat will actually separate out as a separate layer on the top of the milk. We tend to forget about that effect since we all invariably get homogenized milk at the supermarket and the effect is generally too small to affect us when we're drinking it. But it is still large enough to affect NIR measurements. When we tried measuring milk (in the mid-1980s, at Technicon) we ran into that effect, and had to design and construct a special high-pressure homogenizer to make the fat form small enough globules that they wouldn't separately measurably during the scan. Also, milk must be heated to 35 deg C or higher (to melt the butterfat) in order to homogenize it. Howard \o/ /_\ | |||
| Tony Davies (td) Moderator Username: td Post Number: 264 Registered: 1-2001 |
Hello Eva, Welcome to the group! I'm not familiar with this piece of kit so perhaps the others can advise you. Is there a spacer missing? Could I add two notes of caution? 1. Is there any facility for controlling the sample temperature? NIR spectra of liquid water are very sensitive to temperature changes. 2. A considerable amount of work was done in the 80s and 90s to make fat content of milk by NIR into an official method but without success. It does work but not as well as other techniques. Good luck! Best wishes, Tony | |||
| Eva Lewis (evalewis) New member Username: evalewis Post Number: 2 Registered: 8-2011 |
Hi all, Thank you so much for the very rapid responses! I am interested in using the cell in conjunction with milk - so similar to you Daniel. We have the gold reflector disk. The instructions I received were to - place the round cell on the desk with the glass facing down - add the sample (milk) - place in the gold reflector disk with the button/silver ball facing upwards - screw on the back of the round cell This is all fine. But when we put in the gold reflector disk it displaces the milk so that when you look in the glass all you see is the gold disk because the milk is behind it. I can't understand how scanning this will produce a milk spectrum. Is there a small layer/film of milk which I cannot see? Or have I got the wrong instructions? Or have I got the wrong equipment? I can provide photographs if necessary. Many thanks, Eva | |||
| Daniel Alomar (dalomar) Junior Member Username: dalomar Post Number: 8 Registered: 2-2009 |
Eva I have made a couple of calibrations (milk, meat juice) with that cell (0.1 mm sample thickness). It is called a transflectance or folded transmission cell. Ours has an aluminium reflector plate, which is not so expensive (although still very dear!) as the gold reflector cell. We use it with the spinning module of the 6500 and works pretty well. Hope this helps. Daniel | |||
| Jose Miguel Hernandez Hierro (jmhhierro) Intermediate Member Username: jmhhierro Post Number: 20 Registered: 4-2008 |
Hi Eva, This device is often used for measuring fats, oils etc. The aforementioned matrix are viocous ones. There is an onther device which is only used for liquid and the spectrum is recorder in transmitance mode istead of trasflectance. Regards Jose | |||
| David von Boisman (david_von_boisman) Advanced Member Username: david_von_boisman Post Number: 25 Registered: 2-2006 |
Hi Eva, that cell should have a gold reflector fitted inside it, if so it work fine for liquids. Its a pretty common for analyzing animal fats, however they may need to be heated before pouring them into the cup. What sort of information do you need? Cheers, David | |||
| Eva Lewis (evalewis) New member Username: evalewis Post Number: 1 Registered: 8-2011 |
Hi all, The organisation I work for use a FOSS 6500 to analyse animal feed for nutritional composition. But we recently purchased a round sample cup which sits into a transport cell for presenting liquids to the machine. Has anyone worked with this equipment? Many thanks, Eva |
Ana's .PDF