MINIATURE FLOWPROBE(TM) CHEMICAL SENSOR

The FlowProbe(TM) is a new type of chemical sensor that integrates tra ditional reagent-based chemical analysis techniques, fiber-optic spect roscopic detection, and membrane sampling in a compact rugged system. The FlowProbe is novel relative to other immobilized-reagent fiber-opt ic sensors in that the reagent in the FlowProbe sensor is replenished between each analysis. In a typical application the probe is inserted in the sample matrix and fresh reagent is pumped into the probe head. The analytes then diffuse across the sampling membrane where they reac t with the reagent to form a colored product, Fiber optics guide light to the probe tip where the differential optical absorption resulting from the product formation is measured spectroscopically. The analyzer monitors multiple wavelengths during the reaction, and advanced mathe matical calibration techniques (i.e., chemometrics) are employed to pr ovide a robust calibration model, and probe diagnostics to the user. T wo field-portable FlowProbe prototype designs have been constructed. T he first design is an insertion, or dip sensor consisting of a 1/2 inc h OD stainless-steel probe attached to a case containing the fluid-del ivery system, The optical components, spectrometer, and computer are l ocated in a second case. The second design also separates the fluid de livery and optical systems, however the sensor head and fluid-delivery system are engineered into a 2 inch OD unit that can be deployed up t o 250 feet down a well casing for in situ groundwater monitoring, This work describes the FlowProbe instrumentation and focuses on the devel opment of the chemistries and membranes for the analysis of copper in a simulated cooling-tower rig using the insertion FlowProbe prototype.