9045D
­
1
Revision
4
August
2002
METHOD
9045D
SOIL
AND
WASTE
pH
1.0
SCOPE
AND
APPLICATION
1.1
Method
9045
is
an
electrometric
procedure
for
measuring
pH
in
soils
and
waste
samples.
Wastes
may
be
solids,
sludges,
or
non­
aqueous
liquids.
If
water
is
present,
it
must
constitute
less
than
20%
of
the
total
volume
of
the
sample.

2.0
SUMMARY
OF
METHOD
2.1
The
sample
is
mixed
with
reagent
water,
and
the
pH
of
the
resulting
aqueous
solution
is
measured.

3.0
INTERFERENCES
3.1
Samples
with
very
low
or
very
high
pH
may
give
incorrect
readings
on
the
meter.
For
samples
with
a
true
pH
of
>
10,
the
measured
pH
may
be
incorrectly
low.
This
error
can
be
minimized
by
using
a
low­
sodium­
error
electrode.
Strong
acid
solutions,
with
a
true
pH
of
<
1,
may
give
incorrectly
high
pH
measurements.

3.2
Temperature
fluctuations
will
cause
measurement
errors.

3.3
Errors
will
occur
when
the
electrodes
become
coated.
If
an
electrode
becomes
coated
with
an
oily
material
that
will
not
rinse
free,
the
electrode
can
(
1)
be
cleaned
with
an
ultrasonic
bath,
or
(
2)
be
washed
with
detergent,
rinsed
several
times
with
water,
placed
in
1:
10
HCl
so
that
the
lower
third
of
the
electrode
is
submerged,
and
then
thoroughly
rinsed
with
water,
or
(
3)
be
cleaned
per
the
manufacturer's
instructions.

4.0
APPARATUS
AND
MATERIALS
4.1
pH
Meter
with
means
for
temperature
compensation.

4.2
Glass
electrode.

4.3
Reference
electrode:
A
silver­
silver
chloride
or
other
reference
electrode
of
constant
potential
may
be
used.

NOTE:
Combination
electrodes
incorporating
both
measuring
and
referenced
functions
are
convenient
to
use
and
are
available
with
solid,
gel­
type
filling
materials
that
require
minimal
maintenance.

4.4
Beaker:
50­
mL.

4.5
Thermometer
and/
or
temperature
sensor
for
automatic
compensation.

4.6
Analytical
balance:
capable
of
weighing
0.1
g.
9045D
­
2
Revision
4
August
2002
5.0
REAGENTS
5.1
Reagent
grade
chemicals
shall
be
used
in
all
tests.
Unless
otherwise
indicated,
it
is
intended
that
all
reagents
shall
conform
to
the
specifications
of
the
Committee
on
Analytical
Reagents
of
the
American
Chemical
Society,
where
such
specifications
are
available.
Other
grades
may
be
used,
provided
it
is
first
ascertained
that
the
reagent
is
of
sufficiently
high
purity
to
permit
its
use
without
lessening
the
accuracy
of
the
determination.

5.2
Reagent
water.
All
references
to
water
in
this
method
refer
to
reagent
water,
as
defined
in
Chapter
One.

5.3
Primary
standard
buffer
salts
are
available
from
the
National
Institute
of
Standards
and
Technology
(
NIST)
and
should
be
used
in
situations
where
extreme
accuracy
is
necessary.
Preparation
of
reference
solutions
from
these
salts
requires
some
special
precautions
and
handling,
such
as
low­
conductivity
dilution
water,
drying
ovens,
and
carbon­
dioxide­
free
purge
gas.
These
solutions
should
be
replaced
at
least
once
each
month.

5.4
Secondary
standard
buffers
may
be
prepared
from
NIST
salts
or
purchased
as
solutions
from
commercial
vendors.
These
commercially
available
solutions,
which
have
been
validated
by
comparison
with
NIST
standards,
are
recommended
for
routine
use.

6.0
SAMPLE
PRESERVATION
AND
HANDLING
Samples
should
be
analyzed
as
soon
as
possible.

7.0
PROCEDURE
7.1
Calibration:

7.1.1
Because
of
the
wide
variety
of
pH
meters
and
accessories,
detailed
operating
procedures
cannot
be
incorporated
into
this
method.
Each
analyst
must
be
acquainted
with
the
operation
of
each
system
and
familiar
with
all
instrument
functions.
Special
attention
to
care
of
the
electrodes
is
recommended.

7.1.2
Each
instrument/
electrode
system
must
be
calibrated
at
a
minimum
of
two
points
that
bracket
the
expected
pH
of
the
samples
and
are
approximately
three
pH
units
or
more
apart.
Repeat
adjustments
on
successive
portions
of
the
two
buffer
solutions
until
readings
are
within
0.05
pH
units
of
the
buffer
solution
value.
If
an
accurate
pH
reading
based
on
the
conventional
pH
scale
[
0
to
14
at
25
E
C]
is
required,
the
analyst
should
control
sample
temperature
at
25
±
1
E
C
when
sample
pH
approaches
the
alkaline
end
of
the
scale
(
e.
g.,
a
pH
of
11
or
above).

7.2
Sample
preparation
and
pH
measurement
of
soils:

7.2.1
To
20
g
of
soil
in
a
50­
mL
beaker,
add
20
mL
of
reagent
water,
cover,
and
continuously
stir
the
suspension
for
5
minutes.
Additional
dilutions
are
allowed
if
working
with
hygroscopic
soils
and
salts
or
other
problematic
matrices.

7.2.2
Let
the
soil
suspension
stand
for
about
1
hour
to
allow
most
of
the
suspended
clay
to
settle
out
from
the
suspension
or
filter
or
centrifuge
off
the
aqueous
phase
for
pH
measurement.
9045D
­
3
Revision
4
August
2002
7.2.3
Adjust
the
electrodes
in
the
clamps
of
the
electrode
holder
so
that,
upon
lowering
the
electrodes
into
the
beaker,
the
glass
electrode
will
be
immersed
just
deep
enough
into
the
clear
supernatant
solution
to
establish
a
good
electrical
contact
through
the
ground­
glass
joint
or
the
fiber­
capillary
hole.
Insert
the
electrodes
into
the
sample
solution
in
this
manner.
For
combination
electrodes,
immerse
just
below
the
suspension.

7.2.4
If
the
sample
temperature
differs
by
more
than
2
E
C
from
the
buffer
solution,
the
measured
pH
values
must
be
corrected.

7.2.5
Report
the
results
as
"
soil
pH
measured
in
water
at
E
C"
where
"
E
C"
is
the
temperature
at
which
the
test
was
conducted.

7.3
Sample
preparation
and
pH
measurement
of
waste
materials
7.3.1
To
20
g
of
waste
sample
in
a
50­
mL
beaker,
add
20
mL
of
reagent
water,
cover,
and
continuously
stir
the
suspension
for
5
minutes.
Additional
dilutions
are
allowed
if
working
with
hygroscopic
wastes
and
salts
or
other
problematic
matrices.

7.3.2
Let
the
waste
suspension
stand
for
about
15
minutes
to
allow
most
of
the
suspended
waste
to
settle
out
from
the
suspension
or
filter
or
centrifuge
off
aqueous
phase
for
pH
measurement.

NOTE:
If
the
waste
is
hygroscopic
and
absorbs
all
the
reagent
water,
begin
the
experiment
again
using
20
g
of
waste
and
40
mL
of
reagent
water.

NOTE:
If
the
supernatant
is
multiphasic,
decant
the
oily
phase
and
measure
the
pH
of
the
aqueous
phase.
The
electrode
may
need
to
be
cleaned
(
Step
3.3)
if
it
becomes
coated
with
an
oily
material.

7.3.3
Adjust
the
electrodes
in
the
clamps
of
the
electrode
holder
so
that,
upon
lowering
the
electrodes
into
the
beaker,
the
glass
electrode
will
be
immersed
just
deep
enough
into
the
clear
supernatant
to
establish
good
electrical
contact
through
the
groundglass
joint
or
the
fiber­
capillary
hole.
Insert
the
electrode
into
the
sample
solution
in
this
manner.
For
combination
electrodes,
immerse
just
below
the
suspension.

7.3.4
If
the
sample
temperature
differs
by
more
than
2
E
C
from
the
buffer
solution,
the
measured
pH
values
must
be
corrected.

7.3.5
Report
the
results
as
"
waste
pH
measured
in
water
at
E
C"
where
"
E
C"
is
the
temperature
at
which
the
test
was
conducted.

8.0
QUALITY
CONTROL
8.1
Refer
to
Chapter
One
for
the
appropriate
QC
protocols.

8.2
Electrodes
must
be
thoroughly
rinsed
between
samples.

9.0
METHOD
PERFORMANCE
9.1
No
data
provided.
9045D
­
4
Revision
4
August
2002
10.0
REFERENCES
1.
Black,
Charles
Allen;
Methods
of
Soil
Analysis;
American
Society
of
Agronomy:
Madison,
WI,
1973.

2.
National
Bureau
of
Standards,
Standard
Reference
Material
Catalog,
1986­
87,
Special
Publication
260.
9045D
­
5
Revision
4
August
2002
METHOD
9045D
SOIL
AND
WASTE
pH
