hyl parathion is an organophosphate (OP) pesticide, used as insecticide in agriculture to protect the crops from insects. Although in India, Central Insecticide Board and Registration Committee (CIBRC) has recommended methyl parathion as a restricted pesticide for controlling the insect pests in the field of cotton, paddy, wheat, pulses such as green gram and black gram and oilseeds such as ground nut and mustard crops only, however, many newspapers have reported the presence of this pesticide in vegetables and spices even after washing. Methyl parathion causes inhibition of acetylcholinesterase that lead to excess accumulation of acetylcholine and causes overstimulation of muscle and nerve fibers, uncontrollable twitching, convulsions, difficulty in breathing or death. There is an urgent need to develop a rapid, selective, reliable and economically feasible method for onsite monitoring of samples.

BARC has developed a prototype of handheld colorimetric biosensor, which can detect methyl parathion pesticide in the range of 1 - 10ppm. This biosensor consists of biocomponent disc (Figure A) and handheld colorimetric device (Figure B). Biocomponent disc comprised immobilized microbial cells that hydrolyse methyl parathion pesticide into detectable yellowish colour product which is detected by handheld colorimeter in the range of 1 - 10ppm. The total response time of biosensor is 10 - 20 min. This biosensor is specifically detects methyl parathion pesticide in sample in 10 - 20 min while traditional analytical techniques are not specific and required 3-5 days.

Methyl parathion is an organophosphate (OP) pesticide, which is being used as insecticide in agriculture to protect the crops from insects. In India, Central Insecticide Board and Registration Committee (CIBRC) has recommended methyl parathion as restricted pesticides in two different concentrations either in 2% DP or 50% EC for controlling the insect pests in the field of cotton, paddy, wheat, pulses such as green gram and black gram and oilseeds such as ground nut and mustard crops. As per statistical reports by Directorate of PPQS, India, consumption of methyl parathion in India was 8408 MT during 2005 - 2010 and indigenous demand of production was 4691 MT during 2010 - 2016. 

Methyl parathion causes inhibition of acetylcholinesterase and that lead to excess accumulation of acetylcholine and causes overstimulation of muscle and nerve fibers, uncontrollable twitching, convulsions, difficulty in breathing or death. Thus, it has been classified by the World Health Organization (WHO) under 'Category Ia' (extremely toxic) and by the United States Environmental Protection Agency (US EPA) under 'Toxicity Category I' (most toxic) insecticide. There is an urgent need to develop a method that is rapid, selective, reliable and economically feasible for onsite monitoring of samples. 

BARC has designed and developed a prototype of handheld colorimetric biosensor, which can detect methyl parathion pesticide in the range of 1 - 10ppm. This biosensor consists of two components; first is the biocomponent disc (5mm diameter) and second is handheld colorimetric device. Biocomponent disc consist of immobilized microbial cells that convert specifically methyl parathion pesticide (transparent) into detectable yellowish colour product (Figure 1) in 5 min which is detected by handheld colorimeter and determine the concentration of methyl parathion if it is in the range of 1 - 10ppm (Figure 2). The concentration is being displayed in LCD panel of handheld device. Total response time of biosensor is 10 - 20 min.

SALIENT FEATURE OF METHYL PARATHION HANDHELD BIOSENSOR

Switch On Instructions

• The instrument can work both on Power adaptor and on Battery. To power on the instrument, use adaptor provided with the instrument. Insert the adaptor pin in to the adaptor socket on right side of the instrument. Switch on the supply and LED will glow on keypad. LED indicates that the instrument is on as well as battery is charging.
• Switch on the instrument by sliding key on right side. If battery voltage is not sufficient for driving the instrument and goes below the operating voltage, 'Low Battery' message will be displayed on meter. Recharge the battery if message displayed on instrument.

Operating Manual (Calibration and analysis)

• There are two operating modes of an Instrument - Calibration mode and Analysis mode.
• Every time before analysis of new samples it is recommended to calibrate the instrument.

Calibration steps

• The calibration of an instrument is based on a sample available (buffer sample).
• Note that same buffer should be use for same slot of analysis. If buffer is changed or contaminated then you need to calibrate the instrument again.
• Put the buffered sample in washed and dried glass cuvette (provided with instrument) and fill it completely (3/4^th part) with the buffer sample.
• Turn on the instrument by sliding the ON/OFF switch on right side of an instrument.
• To set calibration mode, press "Read/OK" button after displaying the message "Calibration Y/N?". If you don?t want to calibrate the instrument just press "CANCEL" key, this time instrument will enter to the analysis mode directly.
• In calibration mode Instrument will ask first to "Insert Buffer". Now insert the buffer sample filled in cuvette into the sampling slot provided, close the black cap and press "ENTER/OK Key".
• Buffer reading in mV will be displayed. Press "ENTER/OK" key to store the buffer value and to go onto next step of analysis. You can also cancel or redo the step by pressing "CANCEL" Key.
• Once the instrument calibrated with buffer sample, it will ask for ?Start Analysis?.
• Press "ENTER/OK" key to proceed analysis or "CANCEL" key to repeat calibration step.

Analysis steps

1. Analysis of the sample is based on the calibrated Buffer samples.
2. If you enter into Analysis mode after calibration then result of the analysis is as per newly calibrated buffer sample and if you enter into the Analysis mode directly (By pressing CANCEL key at starting) then result of the analysis is as per the previously calibrated Buffer Sample.
3. In analysis mode result of the calibrated buffer stored in the memory in mV will be displayed first.
4. Then the instrument will display "INSERT SAMPLE".
5. Now put cells immobilized biocomponent disc in the sample filled Cuvette and wait for 5 minutes, samples colour will change to yellowish.
6. Now insert the sample filled Cuvette into the sampling slot provided, close the black cap and press "ENTER/OK Key".
7. Concentration of the Sample in ppm will be displayed on LCD. Press "ENTER/OK" key for next sample analysis.

Application

• Methyl parathion biosensor can be used for onsite detection of methyl parathion pesticides in the field condition.

Advantages

• This biosensor is specifically for detecting methyl parathion pesticide in sample in 10 - 20 min while conventional analytical techniques are not specific and require 3-5 days. It can be used for onsite detection of samples.