A fluid sample is brought into contact with {HEAD ~ a pair} of spaced apart electrodes and a voltage is applied across {TAIL ~ the electrodes} 
A fluid sample is brought into contact with { HEAD ~ a pair } of spaced apart electrodes and a voltage is applied across { TAIL ~ the electrodes }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL