The Importance of the 240 nm Absorbance Measurement

The assessment of nucleic acid purity by the A260/A280 ratio has been used for a number of years. This measurement, however, does not provide all the information that investigator needs to assess nucleic acid preparations. The detection of impurities common to nucleic acid preparations that are not detected with absorbance measurements at 260 nm and 280 nm can in most instances be accomplished by measuring absorbance at 240 nm. Here we describe the use of the BioTek Instruments PowerWave 200TM scanning microplate spectrophotometer to measure nucleic acid preparations at 240 nm in conjunction with the traditional A260/A280 ratio to detect contaminants.