Mercury Analysis 27


An eight-point calibration curve was prepared, which included five non-zero standards and three blanks. Calibration and control standards were prepared in the same manner as unknowns with an appropriate aliquot of a 200ng/L (ppt) working standard to prepare the calibration curve that ranged from 0.5ng/L to 100ng/L.


After a successful initial calibration (ICAL) and prior to the samples being analysed, method detection limit (MDL) data was acquired in accordance to 40 CFR Chapter 1 Part 136, Appendix B (see data from software screen shot in Figure 3). This was followed by initial precision recovery (IPR) tests to further validate the system for ultra-trace mercury analysis. Initial calibration verification (ICV), ongoing precision recovery (OPR) and method blanks were analysed with each sample batch to validate the accuracy and stability of the ICAL.


was reported as 0.37ng/L with a standard deviation of 0.029ng/L. The method limits for percent recovery of the low standard must fall within 75 to 125 percent. The standard deviation for the blanks and blank concentration without correction must be less than 0.1ng/L and 0.5ng/L. Before analysing samples, a MDL and IPR study must be performed to validate the sensitivity and stability of the mercury analyser. The MDL study yielded an MDL of 0.053ng/L while the IPR study returned a value of 103.2%, which is in the acceptable range of 79–121%. All OPR samples returned a mercury concentration recovery between 98% and 106%. The method blanks ranged from 0.15 to 0.48ng/L while the ICV samples returned recovery values of 100–108%. The spike and spike duplicates at levels of 0.5 and 1ng/L ranged from a low of 94% recovery to a high of 103% recovery.


Conclusions Mercury levels in each of the bottled water samples pose little or no significant threat to human health. The CETAC QuickTrace™ M-8000 mercury analyser offers phenomenal detection power, giving a method detection limit in this study of about 0.05ng/L (ppt). Accurate and precise results were obtained even at single figure ng/L levels, demonstrating the ability of the system to product high quality quantitative data at ultra-trace levels.


Even though the Cetac QuickTrace™ M-8000 CVAFS mercury analyser exceeds the requirements for ultra-trace mercury analysis detailed care must be taken with stringent clean practices followed for accurate ultra-trace levels of detection. Optimising carrier gas flow, pump speed, sample uptake, and rinse time allows for analysis of a calibration, quality controls, and samples at ultra-trace levels or over a broad dynamic range. As a result, total mercury was accurately quantified in bottled water at the ultra-trace level utilising the various instrument settings of the QuickTrace™ M-8000 Mercury Analyser.


Figure 4: One of three Australian bottled water results showing elevated results above 1 ppt


Figure 3: Software screenshot showing results of MDL characterisation with 0.25ng/L solution


The ICV was prepared with a 0.5mL aliquot of the 200ng/L second source standard into a matrix-matched solution to give a concentration of 5ng/L. The OPR was prepared with a 0.5mL aliquot of the 200ng/L working standard into a matrix- matched solution to give a concentration of 5ng/L. Each matrix spike and matrix spike duplicate was prepared by the addition of 0.1ml of the 200ng/L working standard into a 40mL sample aliquot follow by digestion with 1.2mL of ultrapure hydrochloric acid and potassium bromide / potassium bromate solution.


Results and Discussion


Careful attention was given to minimise contamination in reagents, acids, and deionised water as contamination at ultra-trace analysis can present many problems and can lead to inaccurate results.


Through method development, parameter optimisation, and sample preparation, the QuickTrace™ M-8000 successfully quantified total mercury at the ultra-trace level with minimal reagents and time while giving reliable quantitative data. The ICAL passed all data validation criteria easily: the calibration factor RSD was 3.3%, the 0.5ng/L standard was recovered at 0.47ng/L (94%), and the blank concentration


Each sample, with the exception of the Australian sample returned values at or below the method blank value and would be considered to have essentially zero mercury content. The bottled water from Australia showed the highest concentration with average mercury content of 1.77ng/L (ppt). The Australian sample was the only natural source that was tested; all other samples were either filtered spring water or water from a treated source.


Researchers at CETAC Technologies have validated the QuickTrace™ M-8000 Mercury Analyser by developing and passing all the quality control criteria for US EPA Method 1631, Revision E: Mercury in Water by Oxidation, Purge and Trap and Cold Vapor Atomic Fluorescence Spectrometry. What were the results for bottled water from your region of the world? For complete results of the study, go to www.cetac.com and download the free application note "Ultra-Trace Mercury Determination in Bottled Water, EPA Method 1631, Using the CETAC QuickTrace™ M-8000 CVAFS." For more information on this application and on the CETAC QuickTrace™ M-8000 mercury analyser, visit www.cetac.com/mercury_analyzers


References Bottled Water. Code of Federal Regulations, Part 21, Title 165, Section 110, 2006. (Published in the Federal Register; 70 FR 33694 June 9, 2005, Volume 70, Number 110.)


US EPA. Method 1631, Revision E: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry. August 2002.


Rodwan, John G. Jr. Confronting Challenges: U.S. and International Bottled Water Developments and Statistics for 2008. Bottled Water Reporter [Online]. April/May 2009, pp 12-18. International Bottled Water Association. http://www.bottledwater.org/public/2008 Market Report Findings reported in April 2009.pdf (accessed September 2010).


Figure 5: Graphical peak view of results from the Australian bottled water


5-Minute Mercury Analysis Without Sample Preparation


Milestone’s (Italy) DMA-80 is a direct mercury analyser which can analyse both solid and liquid matrices with equal precision. Analysis takes only 5 minutes per sample and requires no sample preparation.


All mercury is released from the sample through thermal decomposition. This eliminates the need for any acid digestion or wet chemistry sample treatment and, subsequently, purchasing, handling and disposing of hazardous chemicals.


Therefore, the typical bottleneck in the analytical laboratory is eliminated and productivity is dramatically increased. Analysis is reduced to only a fraction of the cost typically associated with


traditional mercury techniques, such as CV-AAS, ICP-AES or ICP-MS.


Typical applications that the DMA-80 is used for include environmental, geochemical, petrochemical, food and feed, clinical and polymer samples.


The DMA-80; achieves a detection limit of 0,0015 ng of mercury, has been shown to save laboratories more than 70% in costs when compared to traditional mercury analysis techniques and is easy to run and maintain.


The DMA-80 is fully compliant with US EPA method 7473 and with ASTM method D-6722-01. Reader Reply Card No. 75


Cost-effective Mercury Testing


We are now being faced with even bigger challenges than ever before when testing our food, water and environment for harmful substances such as Mercury. It is essential for the laboratory personnel that they have simple to use equipment that does not require any sample preparation, particularly with regards to hazardous chemicals and techniques.


Leco Instruments (UK) can offer you the AMA-254 that has proven itself within this UK industry to fulfil all of these requirements complete with automation to allow the operator to simply weigh out the sample directly into a nickel boat and place onto the autosampler for analysis. In the case of liquid samples then they can either be pipetted into the nickel boat or placed into a vile in the liquid sample autoloader from which point the analysis is fully automated even to cleaning the autoloader between samples.


The AMA-254 is very cost effective with vey low running costs and an affordable price.


Reader Reply Card No. 76


AET October / November 2011 www.envirotech-online.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44