# OD260/230 Nucleic Acid Purity Ratio Calculator Check salt/organic-solvent contamination with A260/A230 (pure 2.0–2.2; below 2.0 = guanidinium/phenol/EDTA/salt carryover from TRIzol or columns), with an optional A260/280 cross-check. Derived from Thermo Fisher T042, Sambrook & Russell, Manchester 1995. Educational use only. > Canonical page: https://elysiatools.com/en/tools/od260-230-ratio - **Category:** Education - **Keywords:** od260/230 ratio, a260/a230 ratio, nucleic acid purity, salt contamination dna, guanidinium contamination, trizol carryover, phenol contamination, nanodrop 260/230, secondary purity check, spectrophotometer purity, molecular biology, lab calculator ## Overview The OD260/230 Nucleic Acid Purity Ratio Calculator evaluates salt and organic-solvent carryover in DNA or RNA samples from A260 and A230 absorbance readings. Enter an optional A280 value for an A260/280 cross-check, choose the nucleic acid type, and receive a concise JSON result for educational use. ## Inputs - **Nucleic Acid Type** (select): 260/230 expectations are identical for DNA and RNA; the type only tunes the optional A260/280 cross-check. - **A260 Absorbance** (number): Absorbance at 260 nm (nucleic acid peak), same diluted sample as the A230 reading. - **A230 Absorbance** (number): Absorbance at 230 nm (guanidine/phenol/salt peak) of the same diluted sample. - **A280 Absorbance (optional)** (number): Absorbance at 280 nm; enter 0 to skip the A260/280 cross-check. - **Decimal Places** (number) ## When to use - Check whether a DNA or RNA preparation may contain guanidinium, phenol, EDTA, or salt carryover. - Review the purity of samples extracted with TRIzol or column-based purification kits. - Add an optional A260/280 cross-check when you want a second nucleic acid purity indicator. ## How it works - Choose DNA or RNA as the nucleic acid type. - Enter A260 and A230 absorbance values measured from the same diluted sample. - Optionally enter A280, or use 0 to skip the A260/280 cross-check. - The calculator divides A260 by A230, compares the result with the 2.0–2.2 clean range, and returns the ratio and interpretation in JSON. ## Use cases - Screening column-purified plasmid DNA for guanidinium or salt carryover. - Checking TRIzol-derived RNA before downstream molecular biology work. - Comparing OD260/230 and optional OD260/280 results during nucleic acid quality review. ## Frequently asked questions ### What does the OD260/230 ratio measure? It helps indicate contamination from salts and organic compounds such as guanidinium or phenol. ### What is a clean OD260/230 ratio? A ratio of approximately 2.0–2.2 is generally associated with clean nucleic acid. ### What does a ratio below 2.0 mean? It suggests possible guanidinium, phenol, EDTA, or salt carryover. ### Is A280 required? No. A280 is optional; enter 0 to skip the A260/280 cross-check. ### Does DNA or RNA selection change the OD260/230 expectation? No. The OD260/230 expectation is the same for DNA and RNA, while the selection tunes the optional A260/280 cross-check. ## Related tools - [DNA Concentration Calculator (A260 Absorbance)](https://elysiatools.com/en/tools/dna-concentration-a260): Beer–Lambert DNA quantitation: c = A260 × dilution factor × K / path length with 1 OD = 50 µg/mL dsDNA or 33 µg/mL ssDNA, plus ng/µL, total yield, and a 0.1–1.5 linear-range check. Derived from Marmur & Doty, Sambrook & Russell, Thermo Fisher NanoDrop notes. Educational use only. - [OD260/280 Nucleic Acid Purity Ratio Calculator](https://elysiatools.com/en/tools/od260-280-ratio): Judge DNA/RNA purity from A260/A280 (pure DNA ~1.8, pure RNA ~2.0; low = protein/phenol contamination, DNA > 2.0 = RNA contamination) plus the optional A260/A230 secondary check. Derived from Manchester 1995, Sambrook & Russell, Thermo Fisher T042. Educational use only. - [RNA Concentration Calculator (A260, 1 OD = 40 µg/mL)](https://elysiatools.com/en/tools/rna-concentration-a260): Beer–Lambert RNA quantitation: c = A260 × dilution factor × 40 / path length, plus ng/µL, total yield, a 0.1–1.5 linear-range check, and the RNA OD260/280 ≈ 2.0 purity reminder. Derived from Marmur & Doty, Sambrook & Russell, Manchester 1995, Thermo Fisher NanoDrop notes. 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