A fractional exhaled nitric oxide sensor based on optical absorption of cobalt tetraphenylporphyrin derivatives

For the control of asthma symptoms at home via fractional exhaled nitric oxide (FeNO) monitoring, precise, small, and inexpensive measurement systems are necessary. We studied the feasibility of a photochemical NO sensor based on Co tetraphenylporphyrin (Co-TPP) derivatives, the absorption spectra of which are changed when NO is coordinated onto central Co metal. The sensors were fabricated by embedding Co-TPP derivatives into porous nonwoven fabrics. The absorption of the sensors was enhanced by the multiple absorption in the porous fabrics, which led to high sensitivity and low noise. The use of porous fabrics was also effective for reducing the response time to within 1 s. Fast recovery was obtained by optimizing the intensity of illuminated light from the LED to the sensor. A prototype FeNO analyzer was developed using the present Co-TPP-based optochemical sensors. The analyzer was shown to have an accuracy of +/-1 ppb using the test gas based on the compensation of the individual difference of sensors and the drift in sensor response. A comparison of the NO concentration in breath measured with the prototype analyzer and that measured with the chemiluminescence equipment showed substantial agreement between the two. (C) 2016 Elsevier B.V. All rights reserved.