State, CDFA validate three new drinking‑water methods; ELAP accreditation available

The State Water Resources Control Board received an informational presentation on November 4 from the Division of Drinking Water (DDW) and the California Department of Food and Agriculture Center for Analytical Chemistry (CDFA CAC) on three analytical methods developed for drinking‑water monitoring.

The methods — for saxitoxins, benzotriazoles and trifluoroacetic acid (TFA) — were developed by CDFA CAC under an interagency agreement with DDW and then evaluated in multilaboratory validation studies involving eight participating labs. Assistant Deputy Director Robert Brownwood said the project produced “three methods for us, drinking water methods for the division of drinking water.”

Why it matters: the availability of standardized, validated laboratory methods is necessary before regulatory programs can rely on routine monitoring and reporting. Accreditation through the Environmental Laboratory Accreditation Program (ELAP) enables commercial and municipal labs to produce data that the State will accept for compliance, public health response and trend analysis.

What the presentation reported: CDFA CAC described methods and validation outcomes for each analyte.

- Benzotriazoles (LC‑MS/MS, direct injection): the lab reported a single‑lab detection limit around 0.17 parts per billion (ppb), an LCMRL of 0.44 ppb and confirmed a practical minimum reporting limit of 0.5 ppb. Single‑lab recoveries and precision were satisfactory and the analyte proved stable in stored samples over 28 days. CAC emphasized a direct‑injection approach to reduce sample preparation time and cost.

- Saxitoxins (ELISA kit): CDFA used commercially available ELISA kits that report a calibration range of 0.02–0.4 ppb. CAC reported a method detection limit of about 0.13 ppb and used conservative reporting practices to confirm a minimum reporting limit of 0.03 ppb for total saxitoxins measured by the kits. Because saxitoxins are not highly stable in chlorinated water, the method requires sample buffering and chlorine quench steps and has a short practical holding time.

- Trifluoroacetic acid (TFA; LC‑MS): CAC reported a method detection limit of 0.018 ppb, an LCMRL of 0.083 ppb and confirmed a minimum reporting limit of 0.085 ppb. TFA’s ubiquitous presence in environmental waters made it challenging to find matrices free of incurred analyte for low‑level testing; CAC used a PFAS‑minimizing instrument kit and QC metrics (for internal standard area) to manage background concerns.

Multilaboratory validation and accreditation: CAC led multilab rounds in which participating labs received method supplies and blind test samples; overall the multilab results showed the methods were robust and reproducible across laboratories. DDW staff confirmed that all three methods are now available under ELAP’s field of accreditation, enabling wider routine monitoring.

Next steps and program use: DDW’s Melissa Hall said that completion of the methods now allows program work such as the agency’s planned cyanotoxin notification and response levels (for cylindrospermopsin, anatoxin‑a, saxitoxins and microcystin), expected to be proposed this winter before spring algal blooms. DDW will continue evaluating TFA relative to the broader PFAS regulatory plan and will monitor ongoing data to determine additional method needs.

Quotes: “They developed three methods for us, drinking water methods for the division of drinking water,” said Robert Brownwood of DDW. John Kelly (CDFA CAC) said, “So we aim to simplify that as much as possible,” referring to direct‑injection approaches and use of commercial ELISA kits to ease implementation in a broader laboratory community.

What the board said: board members thanked DDW and CDFA for the interagency work and stressed the importance of ELAP accreditation and laboratory participation in multilaboratory validation.