Tree Fruit Postharvest Chemical Sensor

Abstract

An electrochemical sensor for organic molecules such as ethylene includes an electrochemical cell, gas sample inlet means and means for detecting current produced by the oxidation of the organic molecule at the anode of the cell. The sensor is capable of sensing multiple organic molecules in some embodiments. A voltage is applied to the anode of the cell to provide energy to drive the oxidation reaction and produce a corresponding current. The sensor of the invention can be made as a small, hand-held unit that is capable of real-time detection of various organic species.

1 . A sensor comprising a) an electrolytic cell having an anode that adsorbs ethylene, b) means for measuring current created by an electrocatalytic reaction of ethylene at the anode, c) and intake means for supplying a sample gas to the anode, wherein the electrolytic cell includes (1) a front housing that includes a gas inlet and a gas outlet, (2) a rear housing that includes a cavity for containing said electrolyte; and (3) an anode positioned between said front and rear housings, wherein said anode is supported to minimize or eliminate flexing and is exposed on one side to the electrolyte contained in the cavity in said rear housing and on the other side to a sample gas in the front housing, and further wherein the front or rear housing or both contains a mechanical support for the anode which provides current collection capability to the anode, wherein the electrolytic cell detects the presence of ethylene in a gas stream at levels as low as 10 parts per billion. 
   
   
       2 . The sensor of  claim 1 , further comprising means for supplying a predetermined voltage to the anode. 
   
   
       3 . The sensor of  claim 2 , further comprising gas movement means for transporting the sample gas through the intake means to the surface of the anode. 
   
   
       4 . The sensor of  claim 3 , further comprising a human-readable display which indicates the presence or absence of the target organic molecule in measurable quantities in the sample gas and optionally the concentration of such target organic molecule in the sample gas. 
   
   
       5 . The sensor of  claim 4 , further comprising an electrical power source and/or means for connection to an electrical power source. 
   
   
       6 . A process for determining the presence and/or concentration of ethylene in a gas stream, comprising bringing the gas stream in contact with an anode of an electrolytic cell under conditions such that ethylene is oxidized at the surface of the anode to create an electrical current, and detecting and/or measuring the electrical current created by the oxidation of ethylene, wherein the electrolytic cell includes (1) a front housing that includes a gas inlet and a gas outlet, (2) a rear housing that includes a cavity for containing said electrolyte; and (3) an anode positioned between said front and rear housings, wherein said anode is supported to minimize or eliminate flexing and is exposed on one side to the electrolyte contained in the cavity in said rear housing and on the other side to a sample gas in the front housing, and further wherein the front or rear housing or both contains a mechanical support for the anode which provides current collection capability to the anode, wherein the electrolytic cell detects the presence of ethylene in a gas stream at levels as low as 10 parts per billion. 
   
   
       7 . A system for removing ethylene from a gas, the system comprising
 1) an electrochemical sensor of  claim 1 , and   2) a scrubbing device for removing ethylene from a gas, wherein the scrubbing device is operable in response to the control signal produced by the electrochemical sensor.   
   
   
       8 . (canceled) 
   
   
       9 . The system of  claim 7  wherein the gas is the atmosphere of a fruit or vegetable storage area or fruit or vegetable transportation vessel or container. 
   
   
       10 . A process for removing ethylene from a gas, comprising
 1) bringing the gas or a sample thereof into contact with an anode of an electrolytic cell under conditions such that ethylene is oxidized at the surface of the anode to create an electrical current indicative of the presence of ethylene in the gas or sample thereof, and   2) when ethylene is present in the gas or sample at a predetermined level, as indicated by the creation of the electrical current, scrubbing the gas or portion thereof to remove ethylene, wherein the electrolytic cell includes (1) a front housing that includes a gas inlet and a gas outlet, (2) a rear housing that includes a cavity for containing said electrolyte; and (3) an anode positioned between said front and rear housings, wherein said anode is supported to minimize or eliminate flexing and is exposed on one side to the electrolyte contained in the cavity in said rear housing and on the other side to a sample gas in the front housing, and further wherein the front or rear housing or both contains a mechanical support for the anode which provides current collection capability to the anode, wherein the electrolytic cell detects the presence of ethylene at levels as low as 10 parts per billion in that portion of the gas that is brought into contact with the anode of the electrolytic cell.   
   
   
       11 . (canceled) 
   
   
       12 . The process of  claim 12  wherein the gas is the atmosphere of a fruit or vegetable storage area or fruit or vegetable transportation vessel or container. 
   
   
       13 . The process of  claim 10 , wherein
 the scrubbing is performed at least in part by contacting the gas or a portion thereof with ozone under conditions such that the ozone reacts with ethylene to convert the ethylene to another species.   
   
   
       14 . (canceled) 
   
   
       15 . The process of  claim 13  wherein the gas is the atmosphere of a fruit or vegetable storage area or fruit or vegetable transportation vessel or container. 
   
   
       16 . The process of  claim 13 , wherein
 a) step 1 is performed by periodically or continuously bringing the gas or a sample thereof into contact with an anode of an electrolytic cell under conditions such that, when present, ethylene is oxidized at the surface of the anode to create an electrical current indicative of the presence of ethylene in the gas or sample thereof, and   b) after step 2), when ethylene is not present in the gas or sample at least said predetermined level, as indicated by the creation of the electrical current or lack thereof, discontinuing contacting the gas or a portion thereof with ozone.   
   
   
       17 . (canceled) 
   
   
       18 . The process of  claim 16  wherein the gas is the atmosphere of a fruit or vegetable storage area or fruit or vegetable transportation vessel or container. 
   
   
       19 . (canceled) 
   
   
       20 . The sensor of  claim 1  wherein the electrical cell detects the presence of ethylene in a gas stream at levels as low as 1 part per billion. 
   
   
       21 . The sensor of  claim 1  wherein the anode includes a solid-semi-permeable membrane that is coated or plated with gold.