| Author | Message | ||
     Art Springsteen (artspring) Junior Member Username: artspring Post Number: 6 Registered: 2-2003 |
In response to Tony Davies query: Hi Tony, 1) Quite a bit! I just measured one of the ceramics from a 5000 (compliments of Mike Zapf of McCormick Spices). They are much lower in reflectnace than a Fluorilon part. In fact. it's closer to an 80% reflectance Fluorilon part. And there are some hydroxyl bands in the ceramic. 2) Well, yes and no. All sintered PTFE materials are sensitive to contmaination (of course, so are ceramics) and they are somewhat soft. But we've found a way of making them fairly inexpensively and they are VERY consistent, piece to piece, so they could be easily swapped out. So the answer to #2 is, yes, it could/would be practical. We're doing this for a couple of NIR manufacturers right now. Best regards, Art | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 101 Registered: 9-2001 |
Don - like all "reference" materials used for NIR reflectance measurments, the PTFE is intended more to put the measurements on a consistent scale, but not necessarily an absolute scale. Like all high-porosity, small-particle-size materials (including the ceramic references), it absorbs and desorbs moisture from the atmosphere, leading to small variations in its optical properties. There's reason to believe that PTFE will vary less than, say, the alumina ceramic references, but I don't know that anyone has demonstrated that in actuality. On the other hand, the ceramic references definitely have better physical properties: harder, stronger, more resistant to heat, etc. \o/ /_\ | ||
| Donald J Dahm (djdahm) Junior Member Username: djdahm Post Number: 10 Registered: 2-2007 |
While we're asking questions: Does sintered PTFE represents a straighforward method to routinely put measurements on an absolute scale? | ||
| Tony Davies (td) Moderator Username: td Post Number: 157 Registered: 1-2001 |
Hello Art! 1) How much spectral difference is there between ceramic and Fluorilon? 2) Would it be practical for users to have a Fluorilon standard for regular checks on the instrument reference? Best wishes, Tony | ||
| Dennis Karl (dennisk) New member Username: dennisk Post Number: 9 Registered: 4-2004 |
Hi Juan, All the previous advise is good BUT...... We had a similar situation a few weeks ago where we had a fish oil contamination. Despite all our efforts to try and clean using boiling MeOH/CHCL3/H20 and ultrasonic cleaning we were unsuccessful. A new ceramic is quite cheap and is the most cost effective option. If you do replace the ceramic don't forget to check for any bias effects introduced to your predictions. Best of luck. Dennis | ||
| Art Springsteen (artspring) New member Username: artspring Post Number: 5 Registered: 2-2003 |
Hello Juan, Howard is right- it's probably a ceramic. To clean, use distilled water to soak, dry, then wash with reagent grade ethanol. This should take out the pigments from the pepper, then all of the active oils. You can tell easily if the standard is ceramic or sintered PTFE (Spectralon or our Fluorilon). The sintered PTFE will be 'whiter' and, if you touch an edge of the standard with a knife blade or spatula, the sintered PTFE will feel 'soft' while the ceramic is quite hard. We've recently replaced a number of these ceramic standards with our Fluorilon in 5000 aand 6500 instruments. Art Springsteen | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 100 Registered: 9-2001 |
Juan - the "ceramic" in the Foss instruments is just that: a piece of high-purity alumina ceramic. It's made by Coors, surprisingly (they use it to filter the beer, but also sell it for any other application anyone can come up with, such as optical references!) As usual, you can get the best advice from the manufacturer, in this case, I would say ask Foss first, then Coors. Failing that, since it's a real ceramic, it could be baked at high temperature to oxidize the organic parts of the glop that fell on it, but that doesn't guarantee that there won't be any residue that could affect the readings. But anything else that you do, even buying a new piece of ceramic and replacing the stained one with it, will likely have the same effect. So you can try the ultrasonic cleaner, or any solvents that you might want to use, or baking as I suggested above. Since visible absorbers are often more strongly absorbing than their NIR absorbances, it may be that there isn't enough there to affect the NIR properties; clean it up as well as you can, dry it out, and see if it doesn't come back to it's original performance. Howard \o/ /_\ | ||
| JUAN GARCIA OLMO (jgolmo) New member Username: jgolmo Post Number: 1 Registered: 6-2007 |
Hello, A drop of liquid pepper paste has fallen on the reference (ceramic tile) of my Foss NIRSystems 6500 instrument with a transport module. Now, the white ceramic tile is a bit red just in the middle. I would like to know if anybody had a similar problem and could give me any recommendations to clean it. What do you think about to clean this ceramic tile with a brief immersion in an ultrasound bath? Do you think that this reference material is Spectralon�? Thanks in advance. Regards, |