August 2012, Vol. 24, No.8

Problem Solvers

Utility installs sensitive, speedy system to test water samples

Problem: An ICP–MS system reaching the end of its expected life needed replacement.
Solution: Install a new system capable of testing more samples to detect low levels of metals at both lower costs and environmental effects than previous system.

 

South West Water (Exeter, England) supplies water to one of the largest and fastest-growing regions in the United Kingdom. In recent years, South West Water has been challenged with supplying safe, clean water to more than 1.6 million residents.

To ensure its ability to deliver, the water utility has a laboratory with a rolling replacement program to ensure that the technology relied on is updated and relevant. In early 2010, the laboratory’s existing inductively coupled plasma–mass spectrometry (ICP–MS) system was reaching the end of its expected life and due for replacement.

Finding a replacement 

“The utility needed to replace the system and ensure improved performance compared to the existing instrument,” said Alan Clark, South West Water laboratory quality scientist. The replacement system “had to be capable of a high daily throughput of samples for metals analysis,” he said. In addition, the utility “was looking for a system that would provide savings on operating costs while deriving environmental benefits,” he said. The new system had to operate reliably (there was no in-house backup system), test a range of different drinking water elements, adapt to varying workflows, and conduct rapid screening.

South West Water evaluated three instruments from different manufacturers. After assessing each instrument’s performance, specifications, operating features, ease of maintenance, engineering support requirements, and environmental effects, South West Water chose to install the PerkinElmer (Waltham, Mass.) NexION® 300 ICP–MS platform.

Increased operation, reduced costs and environmental effects 

The new system represents the latest technology in advanced analytical monitoring with low operating costs and minimal environmental effects, Clark said. It is an analytical platform that tests 28 different elements in drinking water and wastewater with rapid, high sample-throughput capability. The system, designed to be reliable and flexible, can adapt to changes in workflow and detection requirements. It is used primarily for potable water and associated samples for the determination of metals, including major cations and toxic metals, such as mercury.

The system uses an Elemental Scientific ES8 autosampler with a FAST sample introduction system to increase throughput. “It can be used with the collision cell to remove potential interferences,” Clark explained. “Following introduction to the plasma through the nebulizer, the ion beam is focused through a triple-cone interface (TCI) and quadrupole ion deflector (QID) before reaching the universal cell. The beam then enters the quadrupole mass spectrometer, where the metal concentration is measured.”

The TCI enables the system to focus an ion beam to minimize drift and eliminate the need for cell cleaning. The QID ensures that only ions are introduced into the cell to keep signal responses stable.

The system can run either in the standard mode, in which cell gas is turned off, for no analyte loss and using correction equations to remove any interference, or in the collision mode, in which nonreactive gas collides with interfering ions to reduce their kinetic energy and remove unknown interferences. Collision mode is used for zinc, vanadium, iron, and nickel; it also can be used for sodium, potassium, magnesium, and calcium to reduce sensitivity and increase the life of the detector.

South West Water enjoys rewards 

The South West Water testing facilities now can handle changes in sample matrices by choosing among different testing modes. Analyses are streamlined without increasing sample times. Cycle times have been increased further using NexION’s FAST system for optimizing automatic sample handling, stabilization, data acquisition, rinse, and reporting.

The system has helped ensure a safe and uninterrupted analytical service. Benefits include signal stability and faster method development, higher capacity, and reproducible results. 

South West Water expects to see a reduction in operating costs and use of argon gas, Clark said. The new equipment “also will improve analytical results by having improved interference correction, compared with the previous ICP–MS,” he said.

“The instrument should be more cost- and energy-effective than the previous ICP–MS,” Clark said. “The detector, which is a major cost replacement item, is predicted to have a significantly longer life than that that of the ICP–MS that it replaced, as it operates at a lower voltage.”

In addition, the system minimizes maintenance downtime, which is critical to keep up with South West Water’s high volume analysis schedule, Clark said.

 

©2012 Water Environment Federation. All rights reserved.