| Author | Message | ||
     maria margarida teixeira andrade (margaridaandrade) New member Username: margaridaandrade Post Number: 1 Registered: 11-2006 |
Dear Fred, my name is Daisy and at this moment I go to initiate one project in minerals, as much in fodder plants as in bovine blood and to apply NIR (LabSpec Pro) in these determination. My doubt is which the procedure more correct to have and the calibrations. Where I can find bibliography? | ||
| J.M. Chang (Juimin) |
Some soil scientists use NIRS to detect the NH4-N and NO3-N contents(ppm) in soil. But the NIRS maker (FOSS and BUCHI) says,use NIRS to detect something in sample the % range will be OK.Use NIRS to detect something in sample the ppm range will be doubtful. The truth is... Thanks | ||
| W. Fred McClure (Mcclure) |
Juimin, Both FOSS and BUCHI speak the truth. However, there is such a thing as indirect calibrations. This is where NIR measures a property that is largely determined by the presence of a ppm component. Indirect calibrations are often not as "robust" as when the calibration is directly related to the concentration of an analyte. Nonetheless, indirect calibrations are sometimes useful, particularly if you are set up to do reference checks often. For, example, the literature documents the use of NIRS for determining minerals in plant tissue. Since minerals do not have unique absortpions in the NIR, these calibration may be called "indirect calibrations." In the absence of other rapid analytical techniques, NIRS is a good tool for mineral determinations. If you wish, I can refer you to a database on NIRS applications that contains more than 22,000 references. Just send me an Email - [email protected] . Fred | ||
| Gabi Levin |
Everything said so far is true, but caution is the only guide. In the case of soil, I have done good calibrations on all the parmeters mentioned, and more, but in the % range only. In the soil, unless it is totaly dry, there is usually too much water to allow any measurements below few tenths of %. Talking about ppm - doable quite nicely for some benzene type compounds in gasoline, very much doable if you want to determine down to few tens ppm of water in many organic compnds, including methanol. Major problem getting below few tens water in organic compunds - finding these compounds in such purity where it does not have any water. Thus, having reference values below 30ppm is difficult to achieve. Thanks, Gabi | ||
| fernando Morgado |
Fred : Reading your comment I have a question. You indicate NIR can be a good tool for determinate minerals in plant tissue. Is possible measure minerals add manualy to some sample. For example some food companies add minerals to poultry feed, is possible measure it? Thanks Fernando Morgado Chile | ||
| W. Fred McClure (Mcclure) |
Fernando, Determining certain minerals in plant tissue is possible. I did a study years ago on 14 minerals in dried/ground tobacco plant tissue. I will see if I can find the data - would be glad to share it if I find it. Send me your email address. CAUTION: Determination of minerals probably is not a direct measurement. Most likely, the determination of a mineral by NIR, is that an organic attribute is changed by the presence of the mineral (I never proved this. However, most spectroscopists agree that minerals have no unique NIR handles onto which it can hold. The literature does show considerable interest in indirect measurements like this, particularly related to environmental problems. Fred | ||
| hlmark |
Fred - Ron Rubinovitz gave a dynamite talk at Pittcon just about measurement of inorganics. Most measurements are indirect, as you say, but some CAN be measured directly. This is particularly feasible when the "inorganic" salt contains some organic material (e.g., formates, acetates, etc.) But also, some of the more complex inorganic ions also also have detectable bands. Talc, of course, is a premier inroganic material with known bands, and there are others. Dave Hopkins & I wrote the Pittcon review in NIR News, and we discussed Ron's talk fairly extensively, so there's more info there that you can look up. Howard \o/ /_\ | ||
| J.M. Chang (Juimin) |
Some literatures use NIRS to measure pH IN soil sample. What is the mechanism ? Thanks | ||
| Dr Neil J. Dominy (Neil) |
Fred and Howard, In South Africa the common analyses on soils include pH, Ca, P, Mg, K and Na. Our soils have less than 1% organic matter and our maximum Ca level is 0.4% but is usually around 0.1% with Mg, K and Na or less than 0.02%. As these soils are being analysed for fertilisation application rates and are usually done on an AA accuracy is important. Can this be done by NIR??? Neil | ||
| Dr Neil J. Dominy (Neil) |
Fred and Howard, In South Africa the common analyses on soils include pH, Ca, P, Mg, K and Na. Our soils have less than 1% organic matter and our maximum Ca level is 0.4% but is usually around 0.1% with Mg, K and Na or less than 0.02%. As these soils are being analysed for fertilisation application rates and are usually done on an AA accuracy is important. Can this be done by NIR??? Neil | ||
| J.M. Chang (Juimin) |
Hi Fred, Can you publish "the database on NIRS applications that contains more than 22,000 references"? thank you very much! |