1. Field of the Invention
The present invention relates to detection of organic compounds. More particularly, the present invention relates to fiber optic probes for detection and measurement of organic wastes in groundwater.
2. Discussion of Background
Fiber optic sensing devices for detecting the existence and extent of chemicals or changes in chemical or physical parameters are well known. Such devices, whether they are probes for continuous remote operation or sensors used for laboratory analysis techniques, typically contain some type of indicator responsive to the presence of an analyte in fluids or gases. The indicator, upon mixing with the chemical compound, may react with it or be changed in some other way, to indicate the presence and concentration of the compound. Indicators are known for detecting such analytes as oxygen, carbon dioxide, hydrogen (i.e. pH), certain metal ions, and biological fluids such as glucose and ammonia.
When used in conjunction with fiber optic devices, the optical characteristics of these indicators in response to the presence of a corresponding analyte offer a range of possibilities for detection and analysis. For example, analytes may affect the fluorescent emission, reflection, or absorption spectrum of light passing through the indicator in the presence of that particular analyte.
Fiber optic detecting systems using spectrometric absorption analysis techniques typically include a light source, a sample cell containing the fluid of interest, an indicator and a detector, such as a spectrophotometer. Light is passed through the sample cell and received by the spectrophotometer, which measures the absorption spectrum of the received light. Devices for remote operation are typically in the form of probes using fiber optics to transmit and receive light signals.
Numerous methods exist for securing the indicator within these probes. Typically, polymer matrices positioned in the probes are used to carry the indicators through absorption, adsorption, or other methods.
Specific examples of sensing devices include U.S. Pat. No. 4,842,783, issued to Blaylock, and U.S. Pat. No. 5,119,463, issued to Vurek et al. Blaylock discloses a fiber optic sensor for detecting certain metal ions and pH, among other analytes. The sensor uses an indicator dye absorbed into a polymeric gel contained within the sensor. Similarly, Vurek et al disclose a fiber optic probe for determining the presence of O.sub.2, CO.sub.2, and pH using analyte indicators disposed on polymer matrices.
In U.S. Pat. No. 5,096,671, Kane et al disclose a fiber optic sensor using a detection indicator dispersed within a hydrogel matrix. Also, Yafuso et al, in U.S. Pat. Nos. 4,999,306 and 4,886,338, disclose a fiber optic sensor for detecting the concentration of an ionic component in a medium, using a sensing material chemically bonded to an ionic matrix contained within the sensor. In one particular embodiment, sulfonic acid absorbed within a hydrogel is used as a pH indicator for the fiber optic sensor.
Still, despite the abundance of fiber optic probes using well known indicators, it is believed that certain monitoring and detection needs have yet to be met adequately. For instance, the identification of trace amounts of organic compounds in aqueous solutions has been difficult to achieve due to high water content in the solutions interfering with the detection response. The detection of low levels of organic species, particularly in aqueous solutions, is a growing health and safety concert for our environment, thus, there is an immediate need for detectors of this kind.
It is believed that no effective sensor or remote probe exists for detecting small amounts of organic species in aqueous solutions.