Analytical Sciences

Determination of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide Hydrochloride by Flow-Injection Analysis Based on a Specific Condensation Reaction between Malonic Acid and Ethylenediamine

Kunihiko SENO,* Kazuki MATUMURA,* Koji OSHITA,** Mitsuko OSHIMA,* and Shoji MOTOMIZU*

*Chemistry and Biochemistry, Graduate School of Natural Science and Technology & Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan
**Department of International Conservation Studies for Cultural Properties, Faculty of Cultural Properties, Kibi International University, 8 Iga-machi, Takahashi, Okayama 716-8508, Japan

A sensitive and rapid flow-injection analysis was developed for the determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), which was used for the formation of amide (peptide) and esters as a dehydration or condensation reagent. The EDC·HCl could be determined by the flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine in aquatic media. The reaction was accelerated at 60°C, and the absorbance of the product was detected at 262 nm. The calibration graph of EDC·HCl showed good linearity in the range from 0 to 0.1% (0 to 0.0005 M), whose regression equation was y = 1.52 × 10⁹x (y, peak area; x, % concentration of EDC·HCl). The proposed method allowed high-throughput analysis; the sample throughput was 12 samples per hour. The limit of detection (LOD) and the relative standard deviation (RSD) were 2 × 10^-6 M and 1.0%, respectively. This reaction is proceeded in aqueous solution and specific for EDC·HCl.

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