From The Editor | July 27, 2017

The New Method For NDMA Detection

Peter Chawaga - editor

By Peter Chawaga, Associate Editor, Water Online

Gas Chromatograph

N-Nitrosodimethylamine (NDMA), a compound known as a nitrosamine, was once a fairly common part of industrial production, used to create rocket fuel, antioxidants, lubricants, and softeners. However, as it was found to be toxic to the liver and other organs, as well as a probable carcinogen, it has since been banned from industrial processes in the U.S.

Sadly, NDMA still finds its way into water sources as an unintentional byproduct from tanneries, pesticide production, rubber and tire manufacturers, and fish-processing facilities. It can also result as a byproduct of chlorination at wastewater and drinking water treatment plants.

As such, water systems need to remain vigilant against the presence of NDMA, an often-onerous proposition. To help cut back on the time and labor required to screen for the contaminant, the Water Environment & Reuse Foundation (WE&RF) has teamed up with the Orange County Water District in California (OCWD) to develop a better analysis method.

Many laboratories test a sample for NDMA using solid phase extraction, which separates compounds in a liquid mixture based on their chemical properties, followed by gas chromatography and tandem mass spectrometry. Others will use methods known as liquid-liquid extraction and high-performance liquid chromatography instead. Whatever current method they use, there is room for improvement.

“These methods are very labor intensive, [taking] several hours for expert analysis; expensive given the equipment required; require large sample volumes; and require spiking isotope-labelled NDMA into each sample as a surrogate to track NDMA losses during pre-concentration,” said a research spokesperson.

In particular, the pre-concentration requirement, the need to concentrate a sample so that trace components aren’t missed, is a large burden on laboratories. And a way around this was introduced in a 2009 study that combined three advanced approaches: high-performance liquid chromatography, photochemical reaction, and chemiluminescence.

“In brief, the method requires only a small sample volume and does not require any sample pre-concentration, while achieving the same or a better detection limit compared to the current methods of analysis,” the spokesperson said.

To fully vet the method, OCWD is using water from its advanced purification facility to establish its accuracy, range, stability, detection limits, and more. The agency expects to complete its vetting in 2018 and remains optimistic about what this could mean for the future of NDMA analysis and the labs that perform it.

“Traditional methods take an expert analyst several hours and the method being validated in this project would be simpler and faster (to the tune of a few minutes) to perform,” said the spokesperson. “From a research perspective, it would allow for more experiments to be conducted because they will not be constrained by the need to collect large samples and will be able to use environmentally-relevant levels of NDMA instead of having to spike the samples … to avoid having to do the time-consuming sample pre-concentration steps.”

Researchers believe there is even the chance to streamline the analysis process completely, enabling utilities to react to NDMA contamination more quickly. It’s a development with potentially historic ramifications for contaminant detection.

“It has the potential to be a real-time, online method which would allow utilities to test more frequently and respond faster in the event that the levels of nitrosamines in the water are found to be elevated,” the spokesperson said. “In fact, an online prototype has already been developed by the project team… The project team believes this will be the first online, real-time method that measures a trace organic contaminant in water instead of relying on indicators or surrogates. Online capability would also allow treatment plants to confirm that the treatment steps that reduce NDMA/nitrosamines are working suitably.”

In addition to time savings, the project team is confident that a more streamlined method would also reduce costs, though the spokesperson was unable to provide specific estimates.

After fully vetting the method and developing a standard operating procedure that can be applied universally by labs, it would still not be ready for widespread adoption. Work would have to be done to develop the equipment necessary.

“Because the current study uses a prototype instrument, widespread adoption would require a commercial instrumentation company to produce and sell the specialized reactor and detector,” the spokesperson said. “The objective of the current research and validation is to lay the groundwork for that next step to occur, hopefully within just a couple years.”

Image credit: "Gas Chromatography," NOAA's National Ocean Service, 2010, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/