Why is polystyrene solvant detected through IR analysis?

Question

Using chromatography polystyrene is detected from the IR machine, why? Isn't the molecule linear?

Answer 1

polystyrene is detected because of the pendant group which has the ability to diffract light and that is what an IR analysis does.

Answer 2

Molecules absorb light in the IR range and translate that energy into mechanical motion. The types of motion can be visualized by thinking about the bonds between the atoms as springs. IR is not based on diffraction.

The bonds can compress and expand between two atoms.
The bonds between two atoms can twist.
Three atoms can wag closer or farther from each other.

Depending on the bond lengths, the types atoms involved and the structure nearby, very specific wavelengths of light are absorbed. We use the frequency and the amount of absorbance relative to other absorbances at differing frequencies to identify a “finger print” for specific types of chemical bonds in the sample.

IR is a very useful tool, but it is not considered a stand-alone tool for characterizing molecular structure. Polystrene has an unsubstituted aromatic ring in it. I’d look for sharp peaks at 3100 to 3000 cm-1, 1600 cm-1, 1500 cm-1, 1150 to 1000 cm-1, 750 to 700 cm-1, and 500 to 400 cm-1.

Polystyrene also has a methyl group, and no double or triple bonds. I’d look for the absence of peaks around 1800 cm-1. And of course the absence of signs of other chemical bonds like alcohols.

A chromatography method like HPLC may have difficulties with polymers like Polystyrene, and of course they are destructive.

BTW it is OK to vote for one of these answers as best answer.

Answer 3

JUst guessing. Probably detected due to when a sample is directly pyrolyzed and determined by the the peak area of the evolved styrene is determined in the single ion monitoring mode, and polystyrene concentration is calculated from the appropriate calibration curve. Linear plots of styrene peak area versus polystyrene content are obtained. To make it short it has probably a low transference of heat. That is why it is good insulation.