Electrochemical determination of nitrate with nitrate reductase-immobilized electrodes under ambient air.
Nitrate monitoring biosensors were prepared by immobilizing nitrate reductase derived from yeast on a glassy carbon electrode (GCE, d = 3 mm) or screen-printed carbon paste electrode (SPCE, d = 3 mm) using a polymer (poly(vinyl alcohol)) entrapment method. The sensor could directly determine the nitrate in an unpurged aqueous solution with the aid of an appropriate oxygen scavenger: the nitrate reduction reaction driven by the enzyme and an electron-transfer mediator, methyl viologen, at -0.85 V (GCE vs Ag/AgCl) or at -0.90 V (SPCE vs Ag/AgCl) exhibited no oxygen interference in a sulfite-added solution. The electroanalytical properties of optimized biosensors were measured: the sensitivity, linear response range, and detection limit of the sensors based on GCE were 7.3 nA/microM, 15-300 microM (r2 = 0.995), and 4.1 microM (S/N = 3), respectively, and those of SPCE were 5.5 nA/microM, 15-250 microM (r2 = 0.996), and 5.5 microM (S/N = 3), respectively. The disposable SPCE-based biosensor with a built-in well- or capillary-type sample cell provided high sensor-to-sensor reproducibility (RSD < 3.4% below 250 microM) and could be used more than one month in normal room-temperature storage condition. The utility of the proposed sensor system was demonstrated by determining nitrate in real samples.
Quan
De
D
Chemical Sensor Research Group, Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea.
Shim
Jun Ho
JH
Kim
Jong Dae
JD
Park
Hyung Soo
HS
Cha
Geun Sig
GS
Nam
Hakhyun
H
D000388:Air; D015374:Biosensing Techniques; D004563:Electrochemistry / Q000379:methods*; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D050901:Nitrate Reductase / Q000737:chemistry / Q000378:metabolism*; D009566:Nitrates / Q000737:chemistry* / Q000378:metabolism*; D045483:Rivers / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry
D004800:Enzymes, Immobilized; D009566:Nitrates; D014874:Water Pollutants, Chemical; D014867:Water; D050901:Nitrate Reductase