By Scot Cocanour, Laboratory Director, and Marshall Pattee, Inorganic Laboratory Manager, NCA Laboratories,
Seattle WA (U.S.A.)
North Creek Analytical, Inc. (NCA) has achieved an 82% increase in sample throughput since we
implemented the Agilent Technologies Integrated Sample Introduction System on our 4500 Series ICP-MS.
In addition, the frequency of routine maintenance and our operating costs have been dramatically reduced.
Eliminating the need for manual sample handling, combined with a rigorous quality assurance protocol,
ensures that our clients continue to receive the highest-quality analytical data on a timely basis.
NCA, an affiliate of the Sequoia Laboratory Network, is the largest provider of environmental testing
services in the Pacific Northwest. NCA employs 140 staff members and operates six Pacific Rim facilities
with ISO quality programs in Washington, Oregon, Hong Kong, Shanghai, and Bangkok. We currently have two
Agilent 4500 ICP-MS instruments in our laboratories in Seattle, WA and Portland, OR. Typical analyses
conducted with the ICP-MS instruments include EPA Methods 200.8 and 6020 on drinking water, wastewater,
groundwater, marine waters, soil, sediment, biological tissues, and Toxicity Characteristic Leaching
Procedure (TCLP) extracts.
Former Maximum: 180 Analyses
Representative sample sequences using EPA protocols, which include all required EPA QC performance samples
(continuing calibration verification [CCV], continuing calibration blank [CCB], etc.), range from 250 to
300 analyses. Before implementing the Integrated Sample Introduction System (ISIS), the maximum sample
throughput during a 24-hour period was approximately 180 analyses, not including maintenance or sample
preparation.
Previously, two analysts shared daily responsibilities operating the instrument, including monitoring,
loading samples, and performing dilutions and data reduction. Neither person had time for sample
preparation. NCA routinely used a modem connection to monitor the system late at night to verify its
performance and make any operational adjustments.
Productivity Up 82 Percent
Now, NCA uses ISIS (Figure 1) to provide intelligent, automated on-line dilution and rapid sample
introduction and washout. It implements the constant-flow nebulization technique, thereby increasing
sample throughput and washout. In constant-flow nebulization, the ISIS pumps are operated at a high
sample flow rate to transport the sample rapidly from the autosampler vial to a second pump operating
at 500 µL/min. The second pump delivers the sample to the nebulizer at a constant flow rate to avoid
overloading the spray chamber with heavy matrix samples or elements with very high concentrations.
 
Figure 1. Agilent Technologies' Integrated Sample Introduction System for ICP-MS
|
In addition, since the plasma is not disturbed by pump speed alterations while delivering sample to the
nebulizer, the equilibrium time is dramatically reduced. NCA now produces a peak performance of 327 analyses
per 24-hour period—an increase in throughput of 82%.
Long Analytical Sequences Without Interruption
The reduced sample loading technique allows NCA to run the instrument for extended time periods without
interruption. One of the longest analytical sequences achieved to date contained 440 discrete runs.
This sequence complied with all EPA performance requisites and required only one recalibration during the
56 hours of operation (Figure 2). It included the analyses of samples submitted from a galvanizing
facility with zinc concentrations ranging from 10-100 ppm.
Figure 2. Long-term stability demonstrated in the recovery of the Continuing Calibration Verification Standard
during a 56-hour analytical run containing 440 samples. The first 10 hours included the analysis of samples from a
zinc-galvanizing facility.
|
ISIS can also be used with the software's Chained Sequencing function that allows for the unattended
switching of analytical methods and tuning parameters, thereby enabling users to configure the ICP-MS
for automated overnight analysis of a variety of matrix types. Overnight runs could typically consist
of high-matrix EPA 6020 soil samples (hazardous waste screening for 0.5-200 ppm As and Cr), followed
by EPA 200.8 and EPA 6020 samples for 15 trace metals, and finishing with specific marine analysis
conditions. During marine analyses, NCA has seen no evidence of any instability or cone clogging (Figure 3).
Products & Services
