Low-level perchlorate detection method shows promise

A relatively new detection method could be capable of detecting perchlorate in water at concentrations of less than one part per billion.

A relatively new detection method could be capable of detecting perchlorate in water at concentrations of less than one part per billion, according to a new study conducted by the Los Alamos National Laboratory.

Perchlorate is a non-radioactive chemical used in gunpowder, rocket fuel, high explosives, fireworks, radiochemistry experiments and automobile airbags. Perchlorate is very soluble in water and has been linked to thyroid dysfunction.

Perchlorate contamination of drinking water became an issue in 1998, when the US Environmental Protection Agency added the chemical to its Safe Drinking Water Act Contaminant Candidate List. This year, the EPA reiterated its previous guidance that perchlorate concentrations in drinking water should remain below four to 18 parts per billion. The agency eventually intends to set a drinking water standard for the chemical, and a standard of one part per billion has been discussed.

The US EPA currently has one approved method for perchlorate detection, but the method is reliable only for concentrations of four parts per billion or greater. Since the detection limit of the EPA-approved method (known as Method 314) falls at the lower end of EPA’s drinking-water guidance level, laboratory scientists and others are interested in finding or developing methods that can reliably detect perchlorate concentrations that are well below any guidance level or proposed standard.

In February, in conjunction with personnel from the New Mexico Environment Department and US Department of Energy, Los Alamos researchers began a rigorous scientific evaluation of a method to detect ultra-low concentrations of perchlorate known as Liquid Chromatography/Mass Spectrometry/Mass Spectrometry, or LC/MS/MS for short. Proponents of the LC/MS/MS method claim a detection limit of 0.05 parts per billion for perchlorate in water. The Los Alamos research team sought to test the reliability and validity of the LC/MS/MS detection method.

For the study, researchers used the LC/MS/MS method to test pure water, pure water spiked with known concentrations of perchlorate, drinking water samples from communities upstream and downstream of the Laboratory, and Los Alamos-area groundwater samples. Two separate outside, independent laboratories used the LC/MS/MS method to test water samples provided as part of the study.

The LC/MS/MS method seemed to be able to reliably detect perchlorate in the pure water samples that had been spiked with a known concentration of the chemical. But when used to test drinking water samples and groundwater samples, the LC/MS/MS method seemed less reliable – perhaps due to the presence of salts and minerals commonly found in groundwater.

The study suggested the presence of miniscule traces of perchlorate in all drinking water samples tested with the LC/MS/MS method; the concentrations potentially ranged from 0.1 to 0.3 parts per billion, all well below EPA’s four-part-per-billion safe-drinking-water guidance. The results of this study suggest that trace levels of perchlorate may be widespread in the environment, but this hypothesis must be further tested.

Los Alamos researchers agree that greater quality control and calibration procedures are necessary at laboratories that use the LC/MS/MS method to test water before the LC/MS/MS detection method can be deemed reliable and accurate.