ELECTRONIC TONGUE BY R.PAVAN KUMAR, RIPER-ANANTAPUR.
WHAT IS ELECTRONIC TONGUE? The electronic tongue is an instrument that measures and compares tastes. It is an analytical instrument comprising an array of non-specific, low selective chemical sensors with cross-sensitivity to different components in solution, and an appropriate method of pattern recognition and/or multivariate calibration for the data processing.
MAIN NEED IN PHARMACY FIELD Assessment of the taste of oral drug the preparation-Major interest To date, only method employed for determination of taste intensity was human sensory test. To facilitate the work and address the difficulties associated with human panel test, a safe, reliable, fast analyzing objective instrument was developed called “Electronic Tongue” .
PRINCIPLE Utilization of non-specific or low-selective potentiometric chemical sensors with enhanced cross-sensitivity to as many different components in solution as possible.
CORRELATION WITH HUMAN TONGUE Mechanism involved for taste recognition shows the same three levels in both. The receptor level Taste buds in human. Lipid membrane of sensors. The circuit level Nerve transmission transducers The perceptual level Cognition in thalamus Statical analysis
INSTRUMENTATION Chemical Sensor or Sensor array Liquid Autosampler Acquisition System Data Processing System
CHEMICAL SENSOR ???? Chemical sensors are small devices that perform transformation of chemical or biochemical information of a qualitative or quantitative type into an analytical useful signal by the process of chemical interaction between sample and sensors. Currently these technologies are based on electrochemical sensors(POTENTIOMETRIC). Other sensing methods applied is voltammeter.
The detecting sensor part consist of lipid/polymer membranes and act as the working electrodes. The reference electrodes -Ag/AgCl. Electrode charge density of the lipid/polymer membrane surface and ion distribution near the surface of the membrane is changed due to sample. Therefore the total electrical charge on the lipid membrane gives the response membrane electric potential for the substances.
ACQUISITION SYTEM The acquisition system establishes the communication between the sensor array and data processing system. Converts the electrical signals from sensor array to digital signals with less distortion. Amplifier must be present as the electrical signals from the sensors are always small.
DATA PROCESSING SYSTEMS Chemometric techniques a type of multivariate statistic used in the analytical field provide data processing, which consist of recognition, classification and identification and multivariate calibration. Statistical analysis Broad use Application Principal component analysis (PCA) Qualification, exploration and discrimination Initial formulation studies Discrimination factorial analysis (DFA) Discrimination and identification Recognition of unknown sample Soft independent modeling of class analogy (SIMCA) Good/bad modeling Quality control against reference good product Partial least square (PLS) Quantification Quantification of bitterness against sensory panel
APPLICATIONS Quantify taste masking efficiency of formulations. Analyze medicines stability in terms of taste. Benchmark target products. Analyze flavor ageing in beverages. Quantify bitterness or “spicy level” of drinks or dissolved compounds.
CONCLUSION Electronic tongues are emerging, promising and proved to be a valuable tool for assessment and prediction of the taste of pharmaceuticals and related products.
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