If you buy reagents for a protein lab, you already know the pain: a "99%" SDS lot that smears bands, ghosts the gel background, or leaves unexplained artifacts in a purification run. Sodium dodecyl sulfate for SDS-PAGE is a different product from detergent-grade SLS — same molecule (CAS 151-21-3), completely different quality demands. This guide explains what electrophoresis-grade actually means and how to specify it when sourcing in bulk.
What SDS does in SDS-PAGE
SDS-PAGE separates proteins by size. SDS binds to proteins at a roughly constant mass ratio, unfolds them by disrupting non-covalent bonds, and coats them with uniform negative charge — so migration through the polyacrylamide gel depends on molecular weight, not on the protein’s own charge or shape. The technique only works cleanly if the reagent itself adds nothing else to the system: no nucleases, no UV-absorbing impurities, no short-chain homologs that change binding behavior.
The specifications that matter
| Specification | Typical electrophoresis-grade requirement | Why it matters |
|---|---|---|
| Assay / purity | ≥ 99% (as fatty alcohol sulfate) | Impurity homologs alter protein binding and band sharpness |
| C12 content | ≥ 98% C12-OH fraction | Chain-length consistency keeps migration reproducible |
| UV absorbance | Low absorbance at 230 nm and 280 nm (e.g. ≤ 0.4 / ≤ 0.1 for 0.1% solution) | Prevents background in UV-based detection and quantification |
| Nucleases | DNase- and RNase-free | Protects samples in combined protein/nucleic-acid workflows |
| pH (1% solution) | ≈ 8.5–10 | Buffer compatibility |
These are the kinds of values published by major life-science suppliers for electrophoresis-grade SDS — use them as your benchmark when evaluating any bulk source.
Lab grade vs industrial grade: the cost trap
Industrial SLS at 92–95% active looks dramatically cheaper per kilogram. In a gel, that discount buys you smeared bands and failed runs: the missing 5–8% is unsulfated alcohols, inorganic salts and chain-length homologs that interfere precisely where electrophoresis is most sensitive. For buffer preparation, protein extraction and PAGE, only ≥ 97–99% material with documented low UV absorbance belongs in the lab. Reserve industrial grades for what they are made for — detergents and cleaners.
Packaging and documentation for lab supply
Research and QC labs typically order 100 g to 5 kg units; core facilities and reagent manufacturers order 25 kg and up. Whatever the size, require:
- A lot-specific certificate of analysis covering assay, absorbance and nuclease testing where claimed
- A safety data sheet (SDS — the document, not the molecule)
- Moisture-protective packaging; SDS is hygroscopic and clumps in humid storage
Beyond PAGE: other high-purity uses
The same ≥ 99% grade serves protein extraction and purification, hybridization buffers, and as a reference standard in surfactant analysis. For low-temperature electrophoresis work, lithium dodecyl sulfate (LDS) is the classic alternative — it stays soluble where SDS crystallizes in the cold. See our Lithium Dodecyl Sulfate (LDS) page for that specialty salt.
Our laboratory-grade range
We supply high-purity material for research, QC and reagent manufacturing: SDS 99% for electrophoresis and analytical use, and SDS 97% as an economical high-purity option, with lot-specific COA and SDS documentation. Contact us with your required specification and pack size for a quotation.
References
- Published specifications of electrophoresis-grade sodium dodecyl sulfate from major life-science reagent suppliers (assay, absorbance, DNase/RNase testing)
- Standard SDS-PAGE methodology literature for protein separation by molecular weight
