The present invention provides an indicator rapidly responding to a subtle pH change, comprising of an acid-base indicator, a stable protein having an isoelectric point of 3.0-10.0 and a molecular weight of 10 kDa-200 kDa, and a buffer solution. The color change interval of the indicator of the present invention can be controlled within a pH range of 0.1-0.2, the color change is obvious, and a solid matrix containing the indicator can be used for rapid detection of pH in different human metabolites.

According to one embodiment, an analysis method includes a first analysis and a second analysis. The first analysis detects a presence or absence of phthalates in a sample by irradiating ultraviolet light on a plate. The sample is developed on the plate by thin-layer chromatography. The second analysis detects a presence or absence of butyl benzyl phthalate in the sample by supplying a color reagent to the plate on which the sample is developed.