pH meter and good practices in pH

pH is -log[H+]

we use pH meter to check the pH of the sample solution.

pH meter does not know about pH.

the pH electode conducts charge from sample in milli volts(mV)

This mV gets converted into pH units

(0-14 is the scale of pH)

1 pH unit
Approximately 59 millivolts per pH unit

normally if pH is 7, it is neutral, no coduction of charge from the sample solution , so that the net charge mV=0.

at pH=8, the mV=59
at pH=9, the mV=59 x 2=118
at pH=10, tge mV=59 x 3= 177 like wise pH meter works for 7-14 pH.

at pH=6 the value will be negative
that is -59.
at pH=5 the mV= -118.
at pH=4 the mV= -177  like wise pH meter works for 7-0 pH.



AlwayspH is electrode  keep in a buffer solution or in tap water or 0.1 M HCl when not in use.

Do not keep in Purified water(DM or DI Water),
Reason: the electode sensitivity will be damaged, if it is kept is purified water.

Calibration .USP<791>
Select two buffers such that the sample pH should fall between the range.
 pH meter accuracy with buffer as a standard +/- 0.04

Analysis:

Always verify the pH meter with one  standard buffer when analysing the pH of a sample .

Take the stable readings only..