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.

Parameter Settings
Plasma Gas Flow 7.5 L/min
Auxiliary Gas Flow 1.00 L/min
Nebulizer Gas Flow 1.05 L/min
iCRC Gas Flow 75 mL/min H2, 110 mL/min He
Plasma RF Power 1.10 kW
Dwell Time 20 ms
Scans per Replicate 15 (peak hopping, 1 pt/peak)
No. of replicates 3
Pump Rate 8 rpm - black/black PVC pump tubing
Sample loading time 4 s (1 mL loop volume)
Stabilization delay 10 s (5 s between gas modes)
Ion Optics Auto-optimized

 

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

Element Gas Mode Potential Interference
9Be None  
11B None  
23Na None  
25Mg None  
27Al None  
39K None  
44Ca None  
51V He 16O35Cl
52Cr He 40Ar12C
55Mn He 40Ar15N, 39K16O
56Fe H2 40Ar16O, 40Ca16O
59Co He 43Ca16O
60Ni He 44Ca16O
63Cu He 40Ar23Na
66Zn He 40Ar26Mg
75As H2 40Ar35Cl, 40Ca35Cl
78Se H2 40Ar38Ar
107Ag None  
111Cd None  
121Sb None  
138Ba None  
206,7,8Pb None  

 

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% HNO3, 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 3rd 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.

Element NIST 1643e NIST 1640
Certified (mg/L) Measured (mg/L) Recovery % Certified (mg/L) Measured (mg/L) Recovery %
44Ca 31.5 30.7 98 7.05 6.89 98
25Mg 7.84 8.06 103 5.82 5.92 102
23Na 20.2 20.9 103 29.4 28.9 99
39K 1.98 2.08 105 0.99 0.92 93

 

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

Element NIST 1643e NIST 1640
Certified (mg/L) Measured (mg/L) Recovery % Certified (mg/L) Measured (mg/L) Recovery %
9Be 13.6 13.2 97 34.9 34.8 100
11B 154.0 157.8 102 301.1 303.6 101
27Al 138.3 144.8 105 52.0 53.4 103
51V 36.9 38.0 103 13.0 12.8 99
52Cr 19.9 21.0 106 38.6 39.0 101
55Mn 38.0 38.7 102 121.5 114.6 94
56Fe 95.7 96.5 101 34.3 35.6 104
59Co 26.4 26.3 100 20.3 19.4 96
60Ni 60.9 60.0 99 27.4 27.0 98
63Cu 22.2 22.8 103 85.2 83.9 98
66Zn 76.5 79.3 104 53.2 51.4 97
75As 59.0 56.8 96 26.7 25.9 97
78Se 11.7 11.1 95 22.0 23.0 105
107Ag 1.04 0.99 96 7.62 7.76 102
111Cd 6.41 6.30 98 22.8 22.8 100
121Sb 56.9 57.1 100 13.8 14.1 102
205Tl 7.26 7.06 97 - 0.009  
206,7,8Pb 19.2 18.4 96 27.9 26.9 97

 

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.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Analytik Jena US. (2020, September 22). Monitoring Drinking Water Quality. AZoM. Retrieved on April 23, 2021 from https://www.azom.com/article.aspx?ArticleID=19647.

  • MLA

    Analytik Jena US. "Monitoring Drinking Water Quality". AZoM. 23 April 2021. <https://www.azom.com/article.aspx?ArticleID=19647>.

  • Chicago

    Analytik Jena US. "Monitoring Drinking Water Quality". AZoM. https://www.azom.com/article.aspx?ArticleID=19647. (accessed April 23, 2021).

  • Harvard

    Analytik Jena US. 2020. Monitoring Drinking Water Quality. AZoM, viewed 23 April 2021, https://www.azom.com/article.aspx?ArticleID=19647.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit