Matsushita Electric Industrial Co., Ltd.

Jipsei Miyazaki

Hiroshi Nakayama

Keiko Yugawa

Tadayasu Mitsumata

Nobuyuki Shigetoh

A labelling color of pentamethine, its intermediate and a method for preparing and using the same to detect methamphetamine with high sensitivity. The invention is exemplified by pentamethine of the following Formula (1): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each are a C.sub.1-6 alkyl group, and X is an anion. A method for using the labelling color to detect methamphetamine. The method comprises preparing a solution of the labelling color and methamphetamine-antibody in a buffer, measuring its fluorescent intensity at 660 nm in a 600 nm excited state, adding methamphetamine in a buffer to the solution, measuring its fluorescent intensity similarly, and examining the change in fluorescent intensity between both solutions.

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Osaka, Japan

Jipsei Miyazaki