A salt-independent pH sensor

Abstract A polymer swelling-based pH sensor is described that operates independently of background salt concentration. The pH sensor is comprised of two magnetoelastic thick-film elements; one is coated with the pH and salt concentration sensitive mass-changing polymer poly(acrylic acid-co-isooctylacrylate) (pAA-IOA), while the other is coated with poly(3-sulfopropyl methacrylate-co-isooctylacrylate) (pSPMA-IOA), a polyelectrolyte gel the mass of which is salt-dependent but pH-independent. The magnetoelastic elements mechanically vibrate at a resonant frequency f r , inversely dependent upon the mass of the attached polymer layer. Cross-correlation between the frequency response of the two sensor elements is used to eliminate the effect of salt concentration on the pH measurements, which are linear between pH 5.4 and 7.2, with a slope of 310 Hz/pH (0.6% f r /pH).

[1]  C A Grimes,et al.  Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors. , 2000, Sensors and actuators. A, Physical.

[2]  M. Traube.  The spectrum of the symptoms and presentations of gastroesophageal reflux disease. , 1990, Gastroenterology clinics of North America.

[3]  H. Oguey.  Sensitive Flux Measurement of Thin Magnetic Films , 1960 .

[4]  C. Grimes,et al.  A remote query magnetoelastic pH sensor. , 2000, Sensors and actuators. B, Chemical.

[5]  Alexei R. Khokhlov,et al.  pH-Responsive Gels of Hydrophobically Modified Poly(acrylic acid) , 1997 .

[6]  E. E. Mitchell,et al.  A New Metglas Sensor , 1986, IEEE Transactions on Industrial Electronics.

[7]  David S. Ballantine,et al.  Acoustic wave sensors : theory, design, and physico-chemical applications , 1997 .

[8]  M. E. Langmuir,et al.  A sensor for pH based on an optical reflective device coupled to the swelling of an aminated polystyrene membrane. , 1997, Talanta.

[9]  Mike R. J. Gibbs,et al.  A micromachined magnetostrictive pressure sensor using magneto-optical interrogation , 2000 .

[10]  Craig A. Grimes,et al.  Magnetoelastic sensors for remote query environmental monitoring , 1999 .

[11]  W. Seitz,et al.  Derivatized, swellable polymer microspheres for chemical transduction , 1999 .

[12]  L. Lanotte,et al.  Application of magnetoelastic waves for sensors of displacement , 1997 .

[13]  L. Bromberg.  Temperature-sensitive star-branched poly(ethylene oxide)–b-poly(propylene oxide)–b-poly(ethylene oxide) networks , 1998 .

[14]  C A Grimes,et al.  A remote query magnetostrictive viscosity sensor. , 2000, Sensors and actuators. A, Physical.

[15]  V. Iannotti,et al.  Direct magnetostriction and magnetoelastic wave amplitude to measure a linear displacement , 2000 .

[16]  Franz R. Aussenegg,et al.  The use of metal-island-coated pH-sensitive swelling polymers for biosensor applications , 1995 .

[17]  M. Lesho,et al.  Electrical conductivity of pH-responsive hydrogels. , 1997, Journal of biomaterials science. Polymer edition.

[18]  Holloway Rh,et al.  Pathophysiology of gastroesophageal reflux. Lower esophageal sphincter dysfunction in gastroesophageal reflux disease. , 1990, Gastroenterology clinics of North America.

[19]  J. Gutiérrez,et al.  Magnetoelastic sensors based on soft amorphous magnetic alloys , 1997 .

[20]  P. Jurs,et al.  Neural network classification and quantification of organic vapors based on fluorescence data from a fiber-optic sensor array. , 1997, Analytical chemistry.

[21]  A. Khokhlov,et al.  Conformational transitions in polymer gels: Theory and experiment , 1993 .

[22]  M. F. McCurley,et al.  An optical biosensor using a fluorescent, swelling sensing element , 1994 .

[23]  Gary M. Hieftje,et al.  Simple Near-Infrared Spectrometric Sorption-Based Vapor Sensor , 1995 .