Changes in Schedule 172
In Reply Refer To: April 20, 1994
Mail Stop 412
OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 94.12
Subject: Changes in Schedule 172
BACKGROUND
Office of Water Quality (OWQ) Technical Memorandum 94.06 announced
the availability of Schedule 172 at the National Water Quality
Laboratory (NWQL). This schedule was implemented for equipment,
field, and other blanks to produce quality-control data to support
the new protocol for low-level inorganic analyses. Schedule 172
includes very low-level analyses for major ions, trace elements,
and nutrients, and a 2-week turnaround time.
PROBLEM WITH ADDING TRACE ELEMENTS
Schedule 172 was established to determine if field equipment and
sample processing contributes contamination of specified inorganic
constituents (see OWQ Technical Memorandum 94.06). Schedule 172
includes two methods--Inductively Coupled Plasma (ICP) and
Inductively Coupled Plasma/Mass Spectrometry (ICP/MS)--for the
analysis of major ions and trace elements. Both methods use a
clean environment for sample pour-up and sample analysis in an
attempt to prevent contamination of samples in the laboratory.
Since the implementation of Schedule 172, several Districts have
requested modifications-- especially the addition of arsenic,
selenium, and mercury. The NWQL analyzes these three elements
by individual methods rather than by ICP or ICP/MS. Consequently,
modifying Schedule 172 to add element-by-element analyses for
these three trace elements would create a difficult problem for
the NWQL. If these additional analyses were made from the same
bottle designated for trace elements under Schedule 172,
contamination could occur either in the handling of the bottles
for ICP and ICP/MS analyses or during handling for the additional
determinations. Therefore, even if trace-element analyses by the
ICP and ICP/MS methods were made prior to analysis by the
additional methods, the potential for contaminating numerous
elements in the sample for possible reruns would be greatly
increased. Thus, because of the ways that samples for selenium,
arsenic, and mercury are handled and analyzed at the NWQL, these
elements will not be added to Schedule 172.
DISTRICT POLL
By copy of this memo, the Regional Water-Quality Specialists are
asked to poll Districts to determine the need to develop low-level
schedules for blanks to determine trace elements other than those
presently determined by Schedule 172. Please compile the
responses by Region and send the results to the Chief, NWQL, by
May 2, 1994. If the poll indicates a high-volume need for
analyzing additional trace elements in blanks, the NWQL will
develop another schedule. If the poll indicates a low-volume
need, the NWQL will provide such services through custom analyses.
SEPARATION OF TRACE ELEMENTS AND NUTRIENTS
INTO SEPARATE SCHEDULES
Under Schedule 172, samples for trace elements and nutrients are
submitted in different bottles and analyzed separately. This
approach was established by the OWQ and the NWQL to facilitate
data analysis and reporting on blank samples. However, several
Districts have asked why both nutrients and trace elements must be
run on all submitted samples. Moreover, this combined schedule
has been found to cause a problem for the NWQL because the
subsamples arrive in different shipments, yet must be logged in
from the same request.
Because of the cited problems, the OWQ and the NWQL have decided
to separate the analysis of trace elements and nutrients in blanks
into separate schedules. There is an existing nutrient schedule
(Schedule 452) that provides identical analyses as the nutrient
part of Schedule 172. This leaves just the trace elements and
major ions to be done under the revised Schedule 172.
COMMENT: AN INAPPROPRIATE USE OF SCHEDULE 172
Schedule 172 is inappropriate as a quality control for Graphite
Furnace Atomic Absorption (GFAA) or other methods. Schedule 172
was not set up for this purpose and using the ICP/MS results from
the schedule as a quality-control check of GFAA cannot guarantee
that GFAA will produce the same analytical precision, accuracy,
and quality.
CONCLUSIONS
Programs and projects are asked to observe the following:
1. The Regional Water-Quality Specialists will conduct a poll
to determine the volume need for analyses of trace elements
presently not included in Schedule 172. If the poll indicates
a high-volume need for analyzing additional trace elements
in blanks, the NWQL will develop another schedule. If the
poll indicates a low-volume need, the NWQL will provide such
services through custom analyses.
2. Districts can arrange custom analyses for trace elements (or
any other analysis) with the NWQL at any time. Such custom
analyses could involve additional costs for establishment of
method detection limits, lower level technology, special
login and handling charges, and special turnaround times.
Contact the Inorganic Program Chief, Merle Shockey (MSHOCKEY)
(303) 467-8101 at the NWQL to arrange custom work.
3. Effective May 16, 1994, Schedule 172 will be redefined to
include the existing major ions and trace elements only.
Nutrients, if desired, must be requested separately as
Schedule 452, which--for the duration of fiscal year (FY)
1994--will cost $34.00. The price for Schedule 172 will be
reduced so that the sum of the two schedule prices equals
the previous Schedule 172 price. Thus, for FY 1994, the
revised Schedule 172 will cost $191.00. A separate Analytical
Services Request Form must accompany each sample submission
for each schedule.
4. Customers must not use the ICP/MS part of Schedule 172 as
a quality control for GFAA or other analytical methods.
David A. Rickert
Chief, Office of Water Quality
This memorandum refers to Office of Water Quality Technical
Memorandum 94.06.
Key Words: National Water Quality Laboratory
Distribution: A, B, S, FO, PO, AH