Development of a novel decay odor sensor which is working at normal temperature on the basis of electrochemiluminescence

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1. Basic examination in aqueous solution.(1) Preparation of miniaturized cell: The cell was made where tris (bipyridine)ruthenium(II) complex was used as a luminescent. The electrochemiluminescence (ECL) measurement of amino acids and peptides showed that proline and peptides having an N-terminal proline residue gave strong responses. The use of the cell allowed us to determine analytes with a secondary or tertiary amine in the concentration range of 10^-6 M.(2) Preparation of the flow-through detector having protein-modified electrodes : The detector having a lysozyme-modified Au electrode showed the high selectivity for proline and the detector was applicable to a proline sensor.2. Preparation of decay-odor sensor.(1) Measurement conditions ; An electrolytic polymer gel was prepared by mixing tris(bipyridne) ruthenium complex, organic electrolyte, propylene carbonate, and an anionic polymer Nafion. A flow-through gas sensor was equipped with a Pt gauze working electrode, a Pt plate counter electrode, and a Ag wire reference electrode ; the gel was packed between the working and counter electrodes. The sensor strongly responded to trimethylamine gas and the stable work was attained with pulse electrolysis (El, +1.2V vs. Ag ; E2, +0.2V ; interval times of El and E2, each 0.1 Hz). The stability may be due to smaller heat evolution than that at direct electrolysis. A linear calibration curve was obtained in the concentration range from 10 to 310 ppb with low detection limit of 3 ppb (S/N = 3) ; the sensitivity was superior to that of the sense of smell in human.(2) Application to practical samples ; Seafood samples were allowed to stand in bags for 30 min and the gas evolved in bag was monitored by our sensor. The ECL response profile for squid was in good accordance with that obtained by the K value, showing that the sensor is also applicable to freshness sensor.