A unit conversion can be arithmetically correct and still mislead a report review if the numbers describe different quantities. First identify the measured property and denominator. Only then convert between compatible units. The worked examples below are fictional arithmetic aids, not peptide test results, specification limits or acceptance recommendations.
Identify the quantity before the symbol
A percent sign may describe mass fraction, chromatographic area proportion or another stated ratio. These are not interchangeable. Write the measured property and reporting basis beside the number. If the report does not explain the basis, ask the issuer. Do not convert an HPLC area percentage to mg/g simply because a purchasing spreadsheet asks for a content field.
Use compatible mass-fraction conversions
For the same mass-fraction basis, 1 percent equals 10 mg/g and 10,000 ppm by mass. The hypothetical values in the table follow that relation. The denominator is essential: ppm by mass should not be silently equated with another ppm convention or a mass-per-volume result. These calculations translate units only; they do not independently establish identity, analytical method suitability or conformity with a project requirement.
| Original value | Equivalent mg/g | Equivalent ppm by mass |
|---|---|---|
| 1% by mass | 10 mg/g | 10,000 ppm |
| 0.1% by mass | 1 mg/g | 1,000 ppm |
| 0.02% by mass | 0.2 mg/g | 200 ppm |
| <0.01% by mass | <0.1 mg/g | <100 ppm |
| HPLC area % | No automatic mass conversion | Different quantity unless justified |
Preserve less-than and basis qualifiers
A result written as less than a value should retain that inequality after conversion. Do not replace it with the numeric threshold as though the threshold were the measured result. Keep dry-basis, as-received and other qualifiers visible. If the basis changes, the same arithmetic may no longer represent the same reported quantity. Ask for the missing definition rather than manufacturing a correction from unrelated water or purity fields.
Keep original values alongside calculated values
The review worksheet should store the report’s original wording, converted value, formula and any assumptions. Label converted values as calculations, not new laboratory results. A colleague should be able to reproduce the arithmetic without guessing which denominator was used. Do not add decimal places that imply more precision than the inputs or remove a reported uncertainty or detection-limit qualifier to make the table easier to read.
Compare with the correct specification
A limit and a result should use compatible quantities and bases before comparison. If the limit is undefined or belongs to another material, leave the decision open. The laboratory reviewer should confirm the interpretation. Do not transfer an external product’s numerical limit into a research-peptide order without an approved requirement. The output is a transparent unit worksheet, not a declaration that any example concentration is acceptable or clinically relevant.
Before closing this review
- The measured quantity precedes unit conversion.
- All example values are explicitly fictional.
- Inequalities and basis qualifiers are retained.
- Converted values are not new analytical results.
Continue with check the scope of a batch report; find or request the relevant batch record. Save the relevant product or guide link alongside the written response so another reviewer can reconstruct the decision.
Editorial scope: research-material procurement and document review. Not medical guidance, dosing instructions or a claim of suitability for human use. Requirements and availability must be confirmed for the quoted material.