Hysteresis in optical sensing and its impact on the analytical error of a calibration-free acid sensor

Durability tests and statistical analyses of errors have been conducted for an indicator-doped optical sol-gel sensor for concentrated strong acid. Du ring the 9-month tests with no recalibration, the sensor response was stead y in 2, 6, and 10 M HCl. The studies here revealed that the major component of the analytical error was the hysteresis of the sensor response for this bromocresol purple (BSP) doped sol-gel sensor. The contribution of hystere sis to the total variance S-hyst(2)/S-T(2) is 54 (11)% and 62 (13)% for 2 a nd 6 M HCl, respectively. (C) 2001 Elsevier Science B.V. All rights reserve d.