4.1Choice of wavelength
The UV-1 can be operated at either 254 nm, 280 nm or 405 nm. The choice of wavelength will depend on the spectral properties of both the eluent and the substances to be detected. Proteins and poly- pep-tides containing aromatic amino acids are usually best detected at
280and 254 nm. Nucleic acids and poly-nucleotides are usually best detected at 254 nm and ferroproteins i.e. hemoglobins, cytochrome and porphyrin derivatives at 405 nm.
4.2Choice of AU or transmission (%T)
The UV-1 may be set to monitor either the absorbance or % transmittance of a flowing liquid. Absorbance measurements give recorder responses which are proportional to the solute concentration when Lambert Beers Law is obeyed. The AU setting is thus most appropriate for general use, particularly when quantitative results are required. However, even with the 3 mm path length cell, there is always a slight risk that the peak will go off scale. Under these conditions, peak maxima can still be located by monitoring transmission.
The relationship between AU and Optical density (OD) is AU = L x OD
where L is the optical path length in cm.
The relationship between OD and transmission expressed as %T is
100
T % = anti log10 (L.OD)
where L is the optical path length in cm.
