FAQ

The concentration of RNA isolated with RNeasy Kits can be determined by measuring the absorbance at 260 nm (A260) in a spectrophotometer. Absorbance readings should be greater than 0.15 to ensure significance. An absorbance of 1 unit at 260 nm corresponds to 40 µg of RNA per ml (A260 = 1 = 40 µg/ml). This relationship is valid for measurements in water. Therefore, dilute RNA in water to quantify it spectrophotometrically.

An example of the calculations involved in RNA quantification is shown below. Use the buffer in which the RNA is diluted to zero the spectrophotometer:

• Volume of RNA sample = 100 µl
• Dilution = 10 µl of RNA sample + 490 µl distilled water (1/50 dilution)
• Absorbance of diluted sample measured in a 1 ml cuvette (RNase-free): A260 = 0.23
• Concentration of original RNA sample = 40 x A260 x dilution factor = 40 x 0.23 x 50

• RNA concentration: 460 µg/ml

• Total yield = concentration x volume of sample (ml) = 460 µg/ml x 0.1 ml

• RNA yield: 46 µg

For additional information on RNA quantitation and handling, see the Appendix section in the RNeasy Mini Handbook.