Residues of unregulated contaminants may be present in drinking water, however little is known about their prevalence in the environment. To protect human health, EPA scientists have developed a number of EPA methods to detect unregulated contaminants.

Per- and Polyfluoroalkyl Substances (PFAS)

• Method 537.1: Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction (SPE) and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). Released in 2018 and updated in 2020 to version 2.0; the only updates were editorial and did not include any technical revisions. Since the development of Method 537, more PFAS, that have the potential to contaminate drinking water, have been identified or introduced as PFOA/PFOS alternatives in manufacturing. This updated method can be used to quantitate 18 PFAS in drinking water, including HFPO-DA (one component of the GenX processing aid technology) and three additional PFAS. 
• Method 537: Determination of Selected Perfluorinated Alkyl Acids in Drinking Water by SPE and LC/MS/MS . EPA Method released in 2009 for the determination of 14 PFAS in drinking water using SPE and LC/MS/MS. This method was updated in 2018 to Method 537.1 (above).

Cyanobacteria Toxins (Cyanotoxins)

• Method 544: Determination of Microcystins and Nodularin in Drinking Water by Solid Phase Extraction and LC/MS/MS
• Method 545: Determination of Cylindrospermopsin and Anatoxin-a in Drinking Water by Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry (LC/ESI-MS/MS)
• Method 546: Determination of Total Microcystins and Nodularins in Drinking Water and Ambient Water by Adda Enzyme-Linked Immunosorbent Assay (ELISA)

Volatile and Semivolatile Organic Compounds

• Method 521: Determination of Nitrosamines in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography with Large Volume Injection and Chemical Ionization Tandem Mass Spectrometry (MS/MS)
• Method 522: Determination of 1,4-Dioxane in Drinking Water by Solid Phase Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS) with Selected Ion Monitoring (SIM)
• Method 525.3: Determination of Semivolatile Organic Chemicals in Drinking Water by SPE and Capillary Column GC/MS
• Method 528: Determination of Phenols in Drinking Water by SPE and Capillary Column GC/MS
• Method 529: Determination of Explosives and Related Compounds in Drinking Water by SPE-GC/MS
• Method 530: Determination of Select Semivolatile Organic Chemicals in Drinking Water by SPE-GC/MS

Other Inorganic Contaminants

• Method 200.5: Determination of Trace Elements in Drinking Water by Axially Viewed Inductively Coupled Plasma - Atomic Emission Spectrometery
• Method 332.0: Determination of Perchlorate in Drinking Water by Ion Chromatography with Suppressed Conductivity and Electrospray Ionization Mass Spectrometry

Other Organic Contaminants

• Method 559: Determination of Nonylphenol and 4-tert-Octylphenol in Drinking Water by SPE-LC/MS/MS
• Method 415.3 Rev 1.2: Determination of Total Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water
• Method 415.3 Rev 1.1: Determination of Total Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water
• Method 535 Rev. 1.1: Measurement of Chloroacetanilide and Other Acetamide Herbicide Degradates in Drinking Water by SPE-LC/MS/MS
• Method 538: Determination of Selected Organic Contaminants in Drinking Water by Direct Aqueous Injection-LC/MS/MS
• Method 540: Determination of Selected Organic Chemicals in Drinking Water by SPE-LC/MS/MS
• Method 543: Determination of Selected Organic Chemicals in Drinking Water by On-line SPE-LC/MS/MS
• Method 556: Determination of Carbonyl Compounds in Drinking Water by Pentafluorobenzylhydroxylamine Derivatization and Capillary Gas Chromatography with Electron Capture Detection