| Blood capillary glass electrode, a recent development in
medical electronics is used in conjunction with anaesthesia
monitoring equipment to observe and record the hydrogen
ion concentration of blood, particularly when the patient
undergoes a surgical operation. With a view to develop the
electrode, a systematic investigation was undertaken using
the glasses from the following systems (i) Na20-Ca0-
Si02, (ii) Li20-Ca0-Si02, (iii) Li20-La20 3-Cs20-
Si0., (iv) Li20-La20 3-Ba0-Ce02-Si02• The glasses
were melted and capillary tubes were drawn. Keeping in view
the monitoring system in medical electronics, an arrangement
was set up for ascertaining the suitability of the capil·
lary fibres made out of the glass for pH measurement.
It was found that only glass no. (iii) responded to the activity
of hydrogen ions and produced slope values very close
to the ideal Nurnst value at room temperature when the
measured emf data were plotted against the corresponding
pH showing thereby that the remaining three glasses were
not suitable for making defect-free capillary fibres although
the glasses were well known for manufacturing pH electrodes.
Further, the sodium ion error of the glass selected
was very low such that voltage departure could be recorded
ouly after pH 12.5. With a suitable correction chart for
sodium ion error, the electrodes were found to work satis·
factorily up to pH 14. The D.C. impedance of the capillary
were within the order of 108 ohms which showed their
capability to work with ordinary potentiometer. |
