The present invention provides a method for detection or determination of vitamin C by luminescence that employs a redox-responsive fluorogenic probe consisting of porphyrin or phthalocyanine with a nitroxide radical(s), or that employs a liposome preparation comprising the said redox-responsive fluorogenic probe. The present method can overcome the problems of prior art methods, and in particular, are applicable for bioimaging to allow elucidation of the behavior of vitamin C in vivo.