For best results the sample solution should be filtered through a glass wool plug in a Pasteur pipet directly into the NMR tube. This procedure removes any particles which would interfere with the spectrum. Special care must be taken to avoid magnetic particles in the solutions because they would compromise the spectral quality. The choice of solvent is also important in UV-VIS for two reasons. One, the solvent must be transparent in the wavelengths to be scanned, and two the solvent may very well influence the wavelength of maximum absorption for certain chromophores.
Concentrations usually range from the micromolar to millimolar range for average chromophores.
Usually UV quality or HPLC double glass distilled solvents are used. These solvents some of the most expensive available and care must be taken not to waste them. The solvents used for IR must not have strong absorptions in the regions of the infrared spectrum where the major absorptions of your sample will be found. The concentrations used are dependent upon the sample used and are usually determined empirically. The liquid sample cells have different thickness lead or teflon spacers so that the amount of sample in the beam path can be changed with preparing a new sample concentration.