Gasdialytic Immersion Probes with Integrated Sample Conditioning and in Situ Calibration

The reliable and representative environmental monitoring and the on line monitoring of waste water purification processes require rapidly responding in situ measuring systems with high operational stability. Known chemo- or biosensors can only seldom applied for in situ monitoring without sample conditioning and other pretreatment steps. Sensor based determination procedures have to be adapted to the sample matrix and recalibrated. Many analytes must be converted into species, which can be detected with the needed sensitivity. Especially under the conditions of process monitoring the reliability of any measuring/detecting system depends decisively on the automated calibration, which takes the sample matrix into consideration. Because, on the other hand, the measurability of any process parameter requires both short response times and high precision, immersion probes with integrated in situ calibration and integrated sample conditioning were constructed. In this paper gasdialytically working immersion probes were presented. At the point of sampling the analyte is immediately converted into a volatile form, which is separated through the microporous and hydrophobic membrane layer of a thin hollow fiber. The acceptor solution contains a converting and/or and an indicator reagent, which can, however, also admixed after the separation step. Therafter the analyte or a product of conversion is detected fluorimetrically or chemiluminometrically. Both detection principles enable the highly sensitive detection in relatively wide concentration ranges.