Monitoring Drinking Water Quality

Fresh drinking water is required for life, in addition to being a valuable source of crucial minerals for health. Water for consumption is sourced from several resources, including groundwater, surface freshwaters, and even seawater. The source usually dictates the level of pre-treatment needed before it is thought to be safe for consumption.

Although groundwater is naturally filtered and may only need minimal pre-treatment, changing seawater to potable water involves a much more intrusive and complex process, including disinfection, desalination, water conditioning, and remineralization.

Contaminants and nutrients will either be added or removed over the course of any water treatment and due to the treatment processes, those not demineralized may still undergo significant changes in their mineral content.

Another source of toxic metal contamination that can have adverse effects on human health is the corrosion of plumbing material. ICP-MS has become the method of choice for monitoring drinking waters. The multi-element, quick capability enables large amounts of samples to be routinely analyzed.

The ability to accurately quantify from ultra-trace to major levels means toxic metals, minerals, and other contaminants can be established via a single measurement. The drinking water analysis by ICP-MS is an uncomplicated application where regulated limits are reached easily.

The multiple interference management systems available today take away many common spectroscopic interferences to enable simple and routine analysis. Water quality testing laboratories demand greater productivity, faster turnaround times, and lower operating costs.

The PlasmaQuant^® MS provides quick, interference-free, multi-element analysis with one noticeable difference: robust plasma conditions suitable for drinking water analysis are attained with only 7.5  L/min of plasma (coolant) gas.

Utilizing the optimum collision or reaction gas for the job, the integrated Collision Reaction Cell (iCRC) supplies effective, quick removal of spectroscopic interferences. Enabling the lowest possible detection limits to be achieved for each element, the high pressure/low volume reaction zone also means switching between gas modes takes a matter of seconds.

Instrumentation

For the analysis, a PlasmaQuant^® MS with Cetac ASX-520 autosampler and an ASXpress rapid sample introduction system was employed. The Aspect MS software enables the automatic optimization of the ion optics, iCRC, and plasma gas flows.

It also provides comprehensive quality control protocols that are developed to meet the needs of crucial regulated methodology, including USEPA 200.8.

Table 1. PlasmaQuant^® MS operating conditions.

Table 2. Analyte mass, iCRC gas mode, and potential interferences.

Samples and Reagents

For all solution preparations, the high purity reagents below were utilized:

• Suprapur 65% nitric acid (Merck)
• Deionized water (>18.2 MΩ/cm, Millipore MiliQ)

Calibration Standards

Calibration solutions were prepared from high-purity, multi-element solutions in 1% HNO_3, which covered the concentration range between 0 to 100 mg/L for major elements, and 0 to 100 µg/L for trace elements.

Internal Standard

The internal standard was added online via the 3^rd channel on the peristaltic pump and contained 1 µg/L of Sc, Rh, Ir in 1% HNO₃.

Sample Preparation

NIST Certified Reference Materials 1640; Trace Elements in Natural Water and 1643e; Trace Elements in Water were directly analyzed.

Results and Discussion

The average result of triplicate measurements of NIST Certified Reference Materials 1643e and 1640 Trace Elements in Water are listed in Tables 3a and 3b. Excellent recoveries were documented and usually fell in the range of ±5%.

Using three optimized gas modes, no-gas, He, and H₂, analysis times were below 1.5 minutes per sample. The stabilization time between gas modes was less than five seconds. Total argon consumption was 9.55 L/min, which is half the amount usually needed on competitive ICP-MS instruments.

Table 3a. The average result of major elements from triplicate analyses of NIST 1643e and 1640.

Table 3b. The average result of trace elements from triplicate analyses of NIST 1643e and 1640.

Conclusion

This study shows that the PlasmaQuant^® MS supplies accurate and quick analysis for monitoring the quality of drinking water. The advancement of sample introduction accessories decreases the analysis times to below 1.5 minutes while iCRC technology eliminates problematic interferences quickly and without compromise.

A new RF generator design supplies robust plasma conditions with only half the argon gas usually needed by competitive systems, reducing instrument downtime and operating costs greatly.

The capability of the all-digital detector to measure all analyte concentrations from ultra-trace to majors levels in a single ‘pulse-counting’ mode is a huge advantage in the analysis of waters. It takes away the need for carrying out inaccurate analog measurements when measuring strong signals.

This information has been sourced, reviewed and adapted from materials provided by Analytik Jena US.

For more information on this source, please visit Analytik Jena US.