The Analysis of Ultra-trace Mercury in Bottled Water

Why Analyse Bottled Water?
To ensure the safety of consumers, bottled drinking water must be tested for contaminants, including mercury. European Directive 98/83/EC on the quality of supplied drinking water sets a maximum mercury level in supplied water at 1 ppb. Directives 2003/40/EC and 2009/54/EC (Mineral Water) duplicate this limit. In practice, most labs require a method detection limit at least 10 times lower than this value for confident detection and it is highly desirable to have detection and quantification limits significantly lower than this to reduce the number of ‘not detected’ results reported.

Experimental
Commercially available bottled water samples were obtained from 11 countries. Analyses were performed on the CETAC

QuickTrace™ M-8000 Cold Vapor Atomic Fluorescence Mercury Analyser in gold trap mode after preservation with hydrochloric acid, and digestion with 0.1 N potassium bromide / potassium bromate solution, followed by reduction with 12% hydroxylamine hydrochloride. Reduction of the inorganic mercury to elemental mercury was carried out by excess online addition of 10% stannous chloride, in 7% hydrochloric acid.

Results
Careful attention was given to minimise contamination in reagents, acids, and deionised water. Prior to analysis of samples method detection limit (MDL), precision and accuracy study was performed to validate the sensitivity, stability and trueness of measurements with the QuickTrace™ M-8000 Mercury Analyser. A MDL of 0.05 ppt was achieved, with accuracy of 103% and relative standard deviation of 0.3% over 4 measurements at the 5 ppt level. Sample spikes (at 0.5 and 1 ppt) produced recoveries in the range 94-103%. The analysis of the 11 bottled water samples showed that all of the samples contained mercury at levels significantly below the legislative value of 1ppb (1000 ppt). In fact, all except the Australian sample returned values below 1 ppt. The Australian bottled water had the highest mercury concentration at 1.8 ppt.

Conclusion
The CETAC QuickTrace M-8000 Mercury Analyser offers more detection power, more precise, and more accurate results for ultra-trace mercury analysis.

For more information on CETAC mercury analysers, visit www.cetac.com/domore and browse to mercury analysers