Frequently asked questions

38Can pH affect A260/A280?39What is A260/A230 used for?40Why are purity ratios often unstable at low concentration?41Can UV absorbance distinguish dsDNA, ssDNA and RNA?42Why does RNA contamination lead to an overestimate of DNA concentration?43How do absorbance and fluorescence methods differ?44Can purity ratios indicate nucleic acid integrity?45Why can proteins be quantified directly using A280?46Can all proteins use the same A280 conversion factor?47What are the limitations of direct A280 quantification?

What is A260/A230 used for?

A260/A230 compares absorbance at two wavelengths and can flag extraction-reagent or matrix background; it does not identify a contaminant. Assess a low ratio alongside the full spectrum, blank composition and extraction history.

Reblank with matched buffer and measure a fresh aliquot. If the blank is normal but the sample remains abnormal, investigate possible reagent carryover and verify it through suitable cleanup or an independent method.

A near-zero or negative denominator can produce a very large or negative ratio, not exceptional purity. Suitability also depends on the requirements of the downstream method.

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Main measurement needs