Rapid, Accurate and In-Situ Quantification of Lead for Drinking Water Applications

Metals and Metals Speciation Analysis in Environmental Samples
Oral Presentation

Prepared by , M. Peterman

Contact Information: merwan@ondavia.com; 510-229-9197


No quantity of lead is safe, yet regulations are defined to allow an average of 15-ppb to be present in a community’s drinking water supply. Moreover, the definition of how water should be tested and how results should be interpreted provide ample opportunity for the data falsification, as evidenced by the failures in Flint, Michigan.
But lead is not limited in scope to Flint. It is present everywhere, likely at some level in every tap in this country. Maine, New York, Illinois, Washington—recent news stories are available nationwide. Even our tap water here in Hayward, California—coming from one of the cleanest water sources in the world—contains a measureable amount of lead. In fact public water sources are not the main cause of lead contaminations in the U.S.; frequently the household pipe network that connects to the main is at fault. These networks can age and release lead in the water, it is recommended that households regularly test their tap water
There are ample evidence that lead is dangerous to infants and children, leading to delays in physical and mental development, neurological disorders, kidney disease, and learning disabilities. There is a pressing public health need for faster, more accurate testing methods that can enable widespread data collection and monitoring for water contamination.
The standard laboratory technique to accurately measure trace levels of lead is ion chromatography coupled to mass-spectrometry (ICP-MS). It is an expensive and labor-intensive operation that is not adequate for a timely-response. For rapid analysis, the most common technique used is the chromate-based colorimetric method. This method is sensitive to interference from other ions likely to be present in water such as iron, which makes it unreliable. Like any colorimetric test, it is semi-quantitative, the user needing to compare the color of the reaction with colors of known concentrations. It also requires hazardous chemical like strong acids.

The quantitative detection of lead from 20-ppb down to 1-ppb is shown for lab and field samples with an accuracy of 10%. The apparatus, the procedure, its optimization, and its benefits compared to standard techniques are described. No pretreatment process was necessary to remove potential interfering ions present in tap water. The technique employed is based on Surface Enhanced Raman Spectroscopy (SERS), it uses active gold- nanoparticles combined with a linker molecule 2-mercaptoisonicotinic acid (2-MNA), which interaction with the Pb ions is noticeable on its SERS spectrum. The test consists of a serial addition of various amounts of lead as well as sodium sulfide, which forms an insoluble precipitate with lead at low concentrations. The experiments take less than five minutes to complete.
Quantitative analysis down to the 1-ppb levels in complex-matrices in lab and in various water samples is demonstrated, as well as specificity to lead. A side-by-side comparison with standard analysis equipment proves the high accuracy of this technique.
The successful results obtained for both lab and field samples demonstrates the capabilities of this cost-effective analysis technology to generate quickly meaningful data so desperately needed. This technology can enable widespread monitoring, ensure public safety and ultimately save lives.