A suitable optical pH sensor using methyl orange based on
triacetylcellulose membrane for on-line pH determination in the
range of 4.0–12.0 has been developed. The advantages of this
optical sensor include relatively wide range, fast response time,
cheap and easy to prepare. Stability results were shown the sensor
is stable after 3 months of storage in water/ethanol (50:50, v/v)
solution.