
59-1
e measurement of pH is arguably the most widely performed test in the chemical laboratory, reect-
ing the importance of water as a ubiquitous solvent and reactant. In the 90 years since the rst use of an
el
ectrode
to de
termine
hy
drogen
io
n
co
ncentration,
th
e
gl
ass
el
ectrode
an
d
it
s
va
riants
ha
ve
ma
tured
in
to
ro
utine
too
ls
of an
alytical
an
d
pr
ocess
ch
emists
. Ye
t,
th
ere
co
ntinue
to be de
velopments
th
at
pr
om-
ise
to br
oaden
th
e
sc
ope
an
d
re
ach
of th
ese
me
asurements
. Am
ong
re
cent
de
velopments
ar
e
mi
niature
pH
-sensitive
e
ld-eect
tr
ansistors
(p
HFETs)
be
ing
in
corporated
in
to
po
cket-sized
pH “p
ens,”
me
tal/
metal oxide pH sensors for measurements ...