On‐site Colorimetric Forensic Sensor ( II ): Quantitative Detection of Toxic S 2 – Ion in Blood Plasma Using Metal‐Ion‐modified Silica Powders

Immensely sensitive, accurate, and simple on‐site colorimetric sensor has been developed for the quantitative detection of the sulfide ion in human blood plasma. The colorimetric sensor consists of lead‐ion‐modified silica‐gel powders placed in a glass tube. The powder color changes upon reaction with sulfide ions in blood plasma. It is capable of easily detecting toxic sulfide ion by using a glass tube with an inner diameter of 3 mm. By employing the type of colorimetric sensor to a blood sample, it is possible to detect the sulfide ion with a concentration limit of 0.1 ppm and excellent reproducibility, thus making it superior to conventional analysis methods that need multiple preparation processes and various sophisticated instruments. Since the sensor reported here is insensitive to environmental conditions such as temperature or humidity, and is featured by simplicity, fast response, high sensitivity, and easily understandable results based on absolute affirmative/negative response, it is expected to be effectively used for on‐site applications such as detecting poisonous ions in blood samples.