State, CDFA labs validate three new drinking‑water tests for cyanotoxins, benzotriazoles and TFA

California regulators on Nov. 4 announced three laboratory methods for contaminants of emerging concern in drinking water and described multilaboratory validation that officials said makes the tests suitable for routine monitoring. The Division of Drinking Water outlined methods developed in collaboration with the California Department of Food and Agriculture Center for Analytical Chemistry (CAC) for saxitoxins, 1H‑benzotriazole and trifluoroacetic acid (TFA), and CAC staff described single‑lab and interlab validation results.

The methods use a range of common laboratory techniques: saxitoxin testing uses an ELISA kit for rapid, low‑cost screening; benzotriazoles are measured by liquid chromatography‑tandem mass spectrometry (LC‑MS/MS) with direct injection; and TFA — a highly mobile breakdown product that can arise from PFAS and other precursors — was analyzed by LC‑MS/MS with PFAS‑aware instrument practices. CAC senior environmental scientist John Kelly said the benzotriazole and TFA methods were designed to avoid extensive sample concentration steps so they can be implemented with ordinary drinking‑water laboratory workflows.

“These methods have been validated in our lab and across participating laboratories and are suitable for use in monitoring at this point,” Kelly said. CAC reported single‑lab method detection limits (MDLs) and minimum reporting levels (MRLs) as follows: benzotriazoles MDL ~0.17 parts per billion (ppb) with an MRL of 0.5 ppb; saxitoxin ELISA MDL ~0.13 ppb with an MRL ~0.03 ppb (kits limit quantitation range); and TFA MDL ~0.018 ppb with an MRL confirmed at about 0.085 ppb in reagent‑water calibration and in select low‑incurred matrices. CAC said multilaboratory studies excluded only results that failed defined quality‑control metrics and otherwise showed consistent performance across participating labs.

Division of Drinking Water staff said the validated methods were accepted by the Environmental Laboratory Accreditation Program’s (ELAP) scope last month, enabling accredited labs to seek coverage for routine testing. Melissa Hall of the Division of Drinking Water said the new methods allow the program to propose cyanotoxin notification and response levels for cylindrospermopsin, anatoxin‑a, saxitoxin and microcystin this winter, with the goal of having levels in place before the spring algal bloom season.

CAC and Division of Drinking Water staff told the board that the TFA method presented particular challenges because TFA is ubiquitous at low levels and it is hard to find truly blank matrices for validation. CAC said it used reagent‑water calibration and added a laboratory QC metric — internal standard area deviation within ±40% — to limit matrix interference. CAC emphasized storage stability testing (28 days) and interlab proficiency testing as important parts of the validation package.

Division of Drinking Water assistant deputy director Robert Brownwood told the board the methods will help the state detect and monitor emerging contaminants, inform public‑health response and feed data into broader PFAS regulatory planning. Staff said they will continue evaluating TFA relative to the board's broader PFAS strategy and will track benzotriazole health‑risk information to consider any monitoring needs.

The board received brief public appreciation for the work and asked staff to continue outreach. Staff said funding and lab‑capacity challenges remain and that the Division will continue to work with ELAP and laboratory providers to expand testing capacity across the state.

Ending note: the validated methods are now available for ELAP accreditation and staff said they plan to propose cyanotoxin notification and response levels this winter to prepare for the 2026 bloom season.