Samples and Sample Preparation for NMR

Liquid samples are the simplest samples to analyze by NMR. Neat nonviscous liquids are run as is by placing about 0.5 mL of the liquid in a glass NMR mbe. Liquids can be mixed in a suitable solvent and mn as solutions the analyte concentration is generally about 2-10%. For the examination of liquid samples, the sensitivity is sufficient to determine concentrations down to about 0.1%. NMR is not considered a trace analytical technique, but that is changing as instmmentation continues to improve. Micrombes with as 

Soluble solid samples are dissolved in a suitable solvent for analyses. A typical sample size is 2-3 mg dissolved in 0.5 mL of solvent. Some solid polymer samples may be run under liquid conditions, that is, without MAS, by soaking the solid in solvent and allowing it to swell . This gives enough fluidity to the sample that it behaves as a liquid with respect to the NMR experiment. Other solid samples must be mn in an instrument equipped with MAS, as has been discussed. 

NMR does not have sufficient sensitivity to analyze gas phase samples directly. Gases must be concentrated by being absorbed in a suitable solvent, condensed to the liquid phase, or adsorbed onto an appropriate solid phase. 

---