EDTA determination in pharmaceutical formulations and canned foods based on ion chromatography with suppressed conductimetric detection

A novel direct method for the determination of EDTA was developed and validated based on ion chromatography with suppressed conductimetric detection and anion exchange column (Dionex AS-14, 4 mm × 250 mm). Depending on coexisting substances, suitable eluents are 10 mM carbonate buffer/pH 11.0 or 10.5 (tR,EDTA = 5.5 and 9.4 min, respectively), and 120 mM borate buffer/pH 8.5 (tR,EDTA = 16.2 min). For 10 mM carbonate buffer/pH 11.0 and isocratic flow rate of 1.0 ml min−1, a linear calibration curve was obtained from 2.7 to 100 μg ml−1 (r > 0.998), with LOD 0.87 μg ml−1 and %RSD 1.5 (5 μg ml−1, n = 9). Good resolution was achieved from commonly coexisting anions (chloride, metabisulphite, ascorbate and citrate), and other aminopolycarboxylic acids (EGTA, NTA and DTPA). The potential interference of pharmaceutical substances (caffeine, phenytoin, nembutal, tolbutamide, dicumarol, acetylsulphisoxazole and paracetamol) and metal cations (Ca2+, Cu2+ and Fe3+) was also examined. The ion chromatographic method was applied for the assay of EDTA in contact lens care solutions, synthetic injection drug solutions, canned mushrooms and mayonnaise, with simple treatment and good recovery (range 74-108%).