1. IR sample preparation for solid samples

2. What is a mull? • a mull a suspension of solid sample in mineral oil • It is used to make a thin-film cell from a solid sample

3. Thin film IR cells • Salt (NaCl) discs are used • To hold the sample • So the holder won’t absorb infrared light • and only sample absorption is detected

4. Sample preparation • so dry the sample well • because water etches the IR discs • and emulsifies with oil letting less light through

5. How do I make a mull? • grind • the sample • to a smooth • powder • add mineral oil • and mix it • well

6. What should the mull be like? • the mull • should look • and spread • like soft butter

7. use clean glovesto work with salt discs • put on an extra pair of gloves • to protect cells • from anything aqueous on your regular gloves

8. applying the mull • use a rubber policeman • to spread • a thin layer • on one disc • lower the 2nd disc • on top of the 1st • and twist the discs • to spread sample evenly

9. placing discs in cell holder • use your finger • to make a platform • in the cell holder • lower in • the NaCl discs • do not wedge them

10. gently • place lid • on top • slide into position • in light beam

11. close • sample • compartment • remove gloves • before using • keyboard

12. to clean discs • add a few drops • of chloroform • to each disc • rub gently • to clean off • all traces of sample • …

13. Keep discs dry • replace • in desiccator • after cleaning • …