Analytical Sciences

Spectrophotometric Determination of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide Hydrochloride by Flow Injection Analysis

Kunihiko SENO, Kazuki MATUMURA, Mitsuko OSHIMA, and Shoji MOTOMIZU

Department of Chemistry, Faculty of Science, Graduate School of Natural Sciences and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) is a very useful agent to form amide bonds (peptide bonds) in an aqueous medium. A simple and fast detection system was developed using the reaction with pyridine and ethylenediamine in acidic aqueous solution and spectrophotometric flow injection analysis. The absorbances were measured at 400 nm and the reaction was accelerated at 40°C. The calibration graph showed good linearity from 0 to 10% of EDC·HCl solutions: the regression equation was y = 3.15 × 10⁴x (y, peak area; x, % concentration of EDC·HCl). The RSD was under 1.0%. Sample throughput was 15 h^-1. This method was applied to monitoring the EDC·HCl concentration that remained after the anhydration of phthalic acid in water, esterification of acetic acid in methanol or dehydration condensation of malonic acid and ethylenediamine in water.

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