The system I work with is a lubricant system with contaminants, which is a fairly complex mixture with polarities involved from both additives and water.
yes it is. but there are 2 kind of water, the first is surface entrapped water and the second is water molecule as part of a crystal structure namely hydrate. The second kind of hydrate will be appear as a peak (spectra) at about wave number 3500/cm, that the first kind of water as entrapped on the surface of substance will interact with KBr and make noise.
Does it interact that instantaneously? What is the best way of measuring water, if that is the aim? Raman?
Potassium bromide (KBr) is hygroscopic and will absorb water and change its state (and spectra, of course). To measure water and water compounds is better to use liquid cell made of non-hygroscopic materials, but transparent for infrared light, for example, CaF2, ZnSe or BaF2. Raman is also can be used for the measuring water, but there is a problem with absolute value of concentration.
Water dissolves KBr but do not react with that salt. Quartz is used for UV-visble cells and is not affected by water. It is not used for IR cells because it is not transparent in that spectral region. I agree with Boldyrev´s answer.
water or OH bands either stretching or bending will mask the real bands in your samples . it will give a very broad band between 3300-3500 cm-1 and also can mask the c=o band of proteins (amide I) around 1650 cm-1. Also water makes the KBr disc very opaque which will reduce the absorption of the IR by the samples.
Yes, Raman is the best solution as according to its selection rule water is Raman inactive
what do you suggest as a cell to analyze water by IR? what do you think about ZnSe?
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