UV/visible/NIR Spectral Data

UV/visible spectra are collected on either a Perkin-Elmer (Shelton, CT) Lambda-35 UV/visible absorption instrument or a Lambda-950 UV/visible/NIR absorption instrument equipped with a Labsphere, Inc. (North Sutton, NH) 60mm integrating sphere.

Solution phase spectra
These data are collected in 1cm pathlength microcells. Due to solvent effects, it is critical that the solvent is specified.

It is desired to collect several solution phase UV/visible/NIR spectra for each compound that possesses ionizable Hs:
1) dissolved in a commonly used solvent
2) dissolved in a solvent with the pH adjusted to where the compound is singly dissociated.

Solid phase spectra
Note that the Spectralon sample disks on the integrating sphere (composed of a specialty fluoropolymer) are easily damaged by samples dissolved in certain organic solvents. To avoid damaging these disks (which are very expensive to replace!) the samples were deposited on a piece of filter paper following the following procedure:
  1. Deposit 100 uL of a 10mM matrix solution on a piece of P5 filter paper (Fisher Brand, medium porsity, slow flow rate, 7.0 cm diameter, cat. no.: 09801A)
  2. Allow the filter paper to dry completely
  3. Sandwich the filter paper with the dried solution between the opening of the sample port of the integrating sphere and the Spectralon disk. A clean piece of filter paper is similarly sandwiched into the reference port
  4. Take the absorption spectrum as usual

Note that you should autozero the instrument with pieces of clean filter paper sandwiched in both the sample and reference ports of the diffuse reflectance sphere.