31Which metrics should be considered when evaluating a high-performance spectrometer?32Why are nucleic acids commonly quantified at 260 nm?33Can dsDNA, RNA and ssDNA use the same conversion factor?34Why are sequence-specific extinction coefficients preferable for oligonucleotides?35What does A260/A280 represent?36What are common A260/A280 reference values for DNA and RNA?37Does a normal A260/A280 mean a sample is definitely pure?38Can pH affect A260/A280?39What is A260/A230 used for?40Why are purity ratios often unstable at low concentration?

Why are purity ratios often unstable at low concentration?

Purity ratios divide one absorbance by another. At low concentrations, sample signals may approach blank variability; a small denominator makes the ratio particularly sensitive to small changes.

Inspect individual absorbances and replicate blanks before interpreting the ratio. Repeated cleanup solely to improve a ratio may lose more sample and weaken the signal further.

To quantify dilute nucleic acids, consider a fluorescence assay suited to the target and concentration range, calibrated as instructed. Fluorescence concentration does not replace integrity checks or assessment of suitability for downstream reactions.