| Author | Message | ||
     Gavriel Levin (levin) Senior Member Username: levin Post Number: 39 Registered: 1-2006 |
Hi Leandro, When you get an offer like that - at no charge - go for it. There is nothing to loose - so give it a shot. Gabi Levin | ||
| Kenneth Gallaher (ken_g) Intermediate Member Username: ken_g Post Number: 20 Registered: 7-2006 |
Well I can say transmission is not an option because I have tried it. I agree NIR is Yes more than No within spectroscopic reason. So the price is right - why not try it... | ||
| David W. Hopkins (dhopkins) Senior Member Username: dhopkins Post Number: 114 Registered: 10-2002 |
Hi Leandro, To add another opinion, I would like to say that I have learned that I never say "No" when someone asks if I think NIR can measure something. If you have access to some NIR company reps, you might ask them to run some samples for you and get an opinion of feasibility. I would recommend trying reflection measurements with both FTNIR and scanning monochromator instruments. If you would like to send me samples of high and low moisture content, I would be glad to scan them with a Foss/NIRSystems 6500 monochromator system and post the results so we can all see them. I have had good success with highly absorbing materials, and it is worth the postage to try it. I am a NIR Consultant, and I am not affiliated with any one instrument manufacturer. If you are interested, please send me your email address, and I will send you my address. I do not want to compromise the rules about advertising on the discussion site. You can click on my name to obtain my email address. Best regards, Dave | ||
| Gavriel Levin (levin) Senior Member Username: levin Post Number: 38 Registered: 1-2006 |
Hi Howard, The question about conductivity of the coke I can only say that I am not familiar with how much it is conductive. To absorb the electromagnetic radiation same way as metals do will require that you can produce "micro" circuits (by the way the method of detection of small cracks in metals is based on that - Eddy currents) which can "flip flop" the direction of the current with the same frequency of the electromagnetic radiation. If this is going to happen in the coke (which needs to be checked) then yes - he will not be able to measure. If those circuits can not flip flop the current direction at same frequency they will not absorb the microwaves. If he only needs lab work with limited number of samples per day rather than online - why bother with NIR even if it did work. Tews Elektronic has a nice set-up that they can measure the moisture from one side, they do not need to go through the whole thickness of the material so they have a ceramic "window" through which they can measure in pipes, etc. I hope Leandro is still listening to us. Gabi Levin Brimrose | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 107 Registered: 9-2001 |
Gavriel - yes, I understand that - it's basically the same physics that goes on inside a microwave oven; the difference is how it's applied. In fact, for a non-homogenous sample of the type that Jim is concerned with, however, this would seem to be an almost-ideal technique, since it would penetrate the sample and absorbtion of the microwaves would occur due to internal moisture as well as surface moisture - a definite plus. On the other hand, a material such a coke, which is essentially carbon and likely to be at least partially electrically conductive, would absorb the microwaves itself, leading to errors in the measurement of moisture, which is based on the assumption that only the moisture was absorbing the microwaves. The alternate that I was proposing is essentially to use the microwaves as a high-tech form of drying the sample, and weighing (by difference) the amount of moisture that comes off - this is the basis of some microwave moisture meters. This is not a perfect method either, since it is subject to errors due to loss of other volatiles besides the moisture, as any drying method would be subject to. I think the bottom line is that coke is a very diffcult sample to measure moisture in, and the best method will depend on the nature of the particular cokes that Leandro has. It may be that the best method for his samples might be a simple, low-tech, oven-drying (or vacuum oven drying) despite the disadvnatages of that. \o/ /_\ | ||
| Gavriel Levin (levin) Senior Member Username: levin Post Number: 37 Registered: 1-2006 |
Hi Howard, Microwave is not microscopy in the general sense - you measure loss of energy due to absorption of the water molecule dipole when it aligns with the electric field of the microwave and as the sinus goes the dipole has to change direction to follow the the electric field. This flip flopping of the dipole requires energy and the loss is measured. There are complications, because within a given volume there can be more or less molecules, depending on the density. This will affect the amount of energy lost - Tews Elektronik has developed an instrument that compenstae automatically for changes in density. Thnaks, Gabi Levin Brimrose | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 106 Registered: 9-2001 |
Leandro - if "coque" means "coke", the material left from pyrolysis of coal, then Kenneth and Gavriel are correct: the material is so highly absorbing that you are not likely to see any absorbance bands at all, not even from water in the mid-IR, much less in the NIR. I've never done microwave spectroscopy, so I don't know how feasible Gavriel's suggestion is. But I tend to suspect that this application is one that is not very suitable for any form of spectroscopy. On the other hand, moisture can be measured with microwaves: by using them to dry the sample. Microwave-based moisture meters of that sort are available as COTS units; you may want to look into that. \o/ /_\ | ||
| Gavriel Levin (levin) Senior Member Username: levin Post Number: 36 Registered: 1-2006 |
Hi, I have planned to post a question - what is coque - if it is what Kenneth refers to as coke than he is absolutley right - it is black everywhere in the spectrum - I doubt it will measure moisture with any reliability. I would suggest to go to microwave method - there the coke shall allow to meaure because it does not absorb in the microwave as badly, but again, it could still be a problem. There is a German company Tews Elektronik that has a very interesting microwave method that is insensitive to the density of the product, a very important issue with any microwave method. Do a google serach for the name - it shall pop up. You should consult with them. Thanks, Gabi Levin Brimrose | ||
| Kenneth Gallaher (ken_g) Intermediate Member Username: ken_g Post Number: 19 Registered: 7-2006 |
I'm not on vacation .... but Coke is about as close a sample as you can get to a blackbody....not sure it can be done. It is "black" everywhere. | ||
| James Malone (jmalone) Junior Member Username: jmalone Post Number: 8 Registered: 8-2006 |
Dear Leandro: I'm surprised that nobody has responded to this - everybody must be on vacation. Almost any spectrometer operating in the 1200 - 2200 nm region could be used to make this measurmenet. Water has two major absorbance bands in this area and their use for quantitation of water has been extensively reported. Sampling will be a bigger problem, generally this measurement will be a surface measurement, so you will need to consider if the water content inside the material is the same as that on the surface. Good luck | ||
| Leandro Valim de Freitas (leandro) New member Username: leandro Post Number: 1 Registered: 3-2007 |
I�m needing to make a question in NIR Discussion Forum about petroleum products: We would like to predict humidity in coque using NIR. Could you say me what equipament can we use? Thanks |