DETERMINATION OF EDETIC ACID (EDTA) IN WATER BY ONLINE COUPLING OF HPTLC AND FTIR

A method based on on-line coupling of HPTLC and FTIR has been develope d for the determination of edetic acid (EDTA) in water. Problems arise in the development of EDTA with normal thin layer chromatography. Wit h the advantages of automated multiple development (AMD), it is possib le to chromatograph EDTA with a R(F) value of 0.73 with high reproduci bility. Sample treatment consists of addition of cobalt(II) acetate an d formic acid to the water sample, and solid phase extraction (SPE; an ion-exchange) for enrichment. The cobalt(II) - EDTA complex thus forme d is applied directly to the HPTLC plate and developed by AMD. The mob ile phase for separation contains ammoniacal methanol (1:2) and dichlo romethane in a 30 step gradient. The method has been validated for 0.5 -3.75 mug EDTA; validated limits of detection and determination were c alculated to be 250 ng and 450 ng, respectively. Samples containing fr om 10 to 100 mug/l EDTA can be analyzed without the derivatization req uired by other methods. Discrimination against related substances e.g. nitrilotriacetic acid (NTA) is possible. EDTA was determined in an au thentic sample of surface water.