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.
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Key facts
Category
Education
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes
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.
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
1Choose DNA or RNA as the nucleic acid type.
2Enter A260 and A230 absorbance values measured from the same diluted sample.
3Optionally enter A280, or use 0 to skip the A260/280 cross-check.
4The 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.
Examples
1. Clean plasmid with an OD260/230 ratio of 2.00
Molecular biology researcher
Background
A column-purified plasmid has A260 of 0.5, A230 of 0.25, and A280 of 0.278.
Problem
Confirm that the plasmid does not show evidence of salt or organic-solvent carryover.
How to use
Select DNA, enter 0.5 for A260, 0.25 for A230, 0.278 for A280, and set decimal places to 2.
The calculator returns OD260/230 = 2.0, indicating a clean result with no organic or salt carryover indicated. The optional OD260/280 cross-check is 1.8, consistent with clean DNA.
2. TRIzol RNA with a low OD260/230 ratio
RNA laboratory technician
Background
An RNA preparation from TRIzol has A260 of 0.60, A230 of 1.20, and A280 of 0.36.
Problem
Identify whether the sample shows residual guanidinium, phenol, or salt contamination before further use.
How to use
Select RNA, enter 0.60 for A260, 1.20 for A230, 0.36 for A280, and set decimal places to 3.
FAQ
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.
The calculator returns OD260/230 = 0.5, indicating suspected guanidinium, phenol, or salt carryover. The OD260/280 cross-check is 1.667 and also indicates likely contamination for RNA.