Shodex Column Recommendation for Short-Chain Fatty Acids and Anions in Environmental Water Samples

Record: 792

Category: Column Selection
Product: IC/SB
Sample: Short chain fatty acids and common anions

Question
A customer needs a system capable of analyzing short-chain fatty acids (up to C5) and common anions (nitrate, nitrite, phosphate, sulfate, thiosulfate, etc.) in environmental water samples within a single run.
The system should:

• Achieve low-ppb detection limits without a pre-concentration column
• Handle both anions and short-chain fatty acids
• Support high-precision gradient analysis and automated eluent preparation
• Include an autosampler (~50-place) and a fraction collector
• Offer a way to remove humic acid interferences if possible
  What Shodex columns and configurations are recommended?

Answer
For simultaneous analysis of short-chain fatty acids and anions in environmental samples, the Shodex IC SI-90 4E or SI-52 4E column is recommended.

Both are polymer-based anion exchange columns suitable for high-sensitivity analysis of inorganic anions and small organic acids such as formate and acetate.

The SI-90 4E provides faster elution and strong resolution for nitrate, nitrite, phosphate, sulfate, and short-chain organic acids up to C2:
Anions and Organic Acids – SI-90 4E

If separation of slightly longer fatty acids such as propionic acid is needed, the SI-52 4E column offers improved selectivity for organic acids up to C3 while maintaining excellent resolution for oxyhalides and standard EPA 300.0 analytes:
Oxyhalides and Organic Acids – SI-52 4E

Both columns are compatible with suppressor and non-suppressor systems and can achieve low ppb-level detection without preconcentration when paired with conductivity detection and clean sample preparation.

For removing humic substances or high-molecular-weight organic interferences, a guard or SEC pre-column such as the SB-805 HQ can be used ahead of the IC column to trap large organic molecules prior to analysis. Humic acid on SB-805

If environmental cations also need to be analyzed, a YS-50 column (cation exchange mode) can be added to the system for Na⁺, K⁺, Ca²⁺, Mg²⁺, and NH₄⁺ determination.

Additional Comments

Download or Print PDF