Document ID: EPA-HQ-OW-2003-0002-0308
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-10-29T04:00Z

July
13,
2004
Possible
Approaches
to
Setting
Detection
Limits
and
Levels
of
Quantitation
[
These
are
preliminary
concepts
for
discussion
only,
not
to
be
taken
as
the
final
views
of
any
municipal,
industrial,
or
laboratory
organization.]

Process
The
group
of
municipal,
laboratory,
and
industry
organizations
began
by
looking
at
comments
filed
in
the
rulemaking
docket,
particularly
the
comments
by
stakeholders
that
signed
the
"
Consensus
Principles"
letter
of
August
15,
2003.
In
our
current
deliberations,
we
divided
the
issues
into
two
groups:
one
for
detection
limits
and
one
for
quantitation.
For
detection
limits,
we
started
with
the
ACIL
approach,
which
has
attracted
wide
acceptance
and
has
been
developed
in
detail.
In
the
discussion
below,
we
have
harmonized
this
approach
with
Osborn
and
Georgian,
which
is
based
on
the
internationally
accepted
definitions
for
detection
(
LC,
LD)
and
quantitation
(
LQ).

Detection
1.
For
routine
laboratory
operations:

a.
Estimates
of
Lc
and
Ld
will
be
calculated
using
the
K
statistic:

i.
Lc=|
X|
+
Ks
ii
Ld=|
X|+
2Ks
b.
An
initial
estimate
of
the
Type
I
detection
limit
(
Lc)
and
Type
II
detection
limit
(
Ld)
will
be
determined
at
method
start­
up.

c.
A
long­
term
Lc
and
Ld
will
replace
the
initial
estimates
of
Lc
and
Ld
as
soon
as
possible,
within
one
year
of
method
start­
up.

i.
Verification
of
the
Lc
and
Ld
estimates
will
be
done
by
routine
monitoring
of
the
false
positive
and
false
negative
error
rate.

ii.
Long­
term
Lc
and
Ld
will
be
calculated
from
routine
batch
method
blanks
and
false
negative
quality
control
check
samples,
which
will
be
at
a
concentration
approximately
equal
to
Ld.

d.
Reporting
rules
will
be
prescribed.
For
example,
the
detection
limit
Ld
could
be
listed
on
reports
and
results
reported
down
to
the
critical
value
2
Lc.
Detections
near
Lc
but
less
than
Ld
could
be
reported
as
"
estimated"
values.

Quantitation
2.
Terminology.
We
would
like
first
to
clarify
discussions
by
referring
to
a
"
method
promulgated
quantification
level,"
which
is
not
necessarily
intended
to
be
a
permanent
addition
to
the
lexicon
but
only
a
temporary
term
to
clarify
discussion.
The
method
promulgated
quantification
level
is
the
QL
determined
from
an
interlaboratory
test
of
the
analytical
method
and
is
determined
one
time
only,
when
the
method
is
first
approved
for
inclusion
in
40
CFR
Part
136:

ML:
Unchanged
from
EPA's
use(
s)
of
this
term.

Method
Promulgated
Quantitation
Limit
(
MPQL):
the
quantification
limit
that
will
be
promulgated
as
part
of
the
method
when
incorporated
into
40
CFR
Part
136.

Compliance
Evaluation
Threshold:
The
concentration
level
specified
in
a
permit
when
a
water
quality­
based
effluent
limitation
(
WQBEL)
is
below
analytical
method
"
sensitivity."

3.
For
new
methods
that
EPA
is
validating
for
40
CFR
Part
136
for
the
first
time:

a.
EPA
defines
minimum
precision
and
accuracy
(
with
accuracy
defined
as
recovery)
required
for
analytical
methods
to
be
used
for
NPDES
compliance
monitoring
­­
for
example,
a
precision
of
10%
and
a
recovery
of
90%.

b.
EPA
then
conducts
a
study
according
to
ASTM
D6512­
03
to
establish
the
IQE
for
the
minimum
allowable
precision
(
e.
g.,
IQE10%)
for
selected
analytes.

c.
This
LQ
is
set
at
the
IQE,
which
is
the
lowest
concentration
to
consider
for
the
quantitation
level
of
the
method
for
each
analyte
tested.

d.
EPA
then
examines
the
recovery
of
the
analyte
at
that
IQE
concentration.
If
the
recovery
does
not
meet
the
minimum
allowable
recovery
(
90%
in
the
example
above),
then
EPA
works
upward
until
it
finds
the
lowest
concentration
where
accuracy
(
recovery)
achieves
the
prescribed
minimum
(
90%
in
the
example).
This
concentration
then
becomes
the
LQ
or
quantitation
level
for
the
method
for
that
analyte.

e.
We
are
still
exploring
how
to
devise
a
practical
and
cost­
effective
way
of
dealing
with
matrix
effects.
3
3.
For
existing
methods,
already
included
in
40
CFR
Part
136,
we
are
considering
approaches
that
would
leave
most
such
methods
in
place
without
additional
validation.

48681.000007
RICHMOND
1246400v6