Determination of Active Ingredients in Foam Concentrates: Analytical Methods, Standards, and Applica

Determining the active ingredients in foam concentrates is essential for verifying the quality, fire performance, and environmental compliance of fire extinguishing foam agents. This article explains the key active components of foam concentrates, the sample types suitable for analysis, the testing items and analytical methods used by accredited third-party laboratories, and the relevant international standards such as GB 15308, ISO 7203, EN 1568, and UL 162.

Technical Overview

Foam concentrates are complex chemical formulations designed to suppress Class A and Class B fires by forming an aqueous film, a stable foam blanket, or a protective gel layer on the fuel surface. The functional components of these products, commonly referred to as active ingredients, include fluorinated surfactants, hydrocarbon surfactants, protein hydrolysates, foam stabilizers, polymeric thickeners, organic solvents, and inorganic salts. The type and concentration of these components directly determine critical performance characteristics such as film formation speed, expansion ratio, drainage time, alcohol resistance, and extinguishing efficiency.

Active ingredient determination is a core element of product conformity assessment under standards such as GB 15308, the ISO 7203 series, the EN 1568 series, and UL 162. In modern analytical practice, classical gravimetric and titrimetric methods are combined with advanced instrumental techniques, including high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The increasing international restriction of per- and polyfluoroalkyl substances (PFAS) has further elevated the importance of accurately quantifying fluorinated surfactants and verifying the authenticity of fluorine-free foam alternatives.

Testing Samples

Aqueous Film-Forming Foam (AFFF and FFFP) Concentrates

These low-expansion concentrates, typically supplied at nominal mixing ratios of 1%, 3%, or 6%, rely on fluorinated surfactants to produce a thin aqueous film on hydrocarbon fuel surfaces. Samples are analyzed to confirm fluorosurfactant content, verify batch consistency, and screen for regulated PFAS compounds such as PFOS, PFOA, PFHxS, and fluorotelomer sulfonates.

Protein-Based and Alcohol-Resistant Foams

Protein foam (P), fluoroprotein foam (FP), and film-forming fluoroprotein foam (FFFP) concentrates contain hydrolyzed protein together with stabilizers and, in fluorinated grades, fluorochemical additives. Alcohol-resistant variants (AR-AFFF, AR-FFFP) additionally contain polysaccharide polymers that form a protective membrane on polar solvent surfaces. Testing focuses on protein content, polymer content, and the balance between surfactant fractions.

Synthetic and Class A Foam Concentrates

Medium- and high-expansion synthetic detergent foams are based on hydrocarbon surfactant systems, while Class A foams contain wetting agents and stabilizers designed for deep penetration into porous combustible materials. Analysis confirms total active matter, solvent content, and the absence of unauthorized fluorinated components.

Field, Environmental, and Stability Samples

Besides neat concentrates, laboratories accept premixed foam solutions, samples drawn from storage tanks and proportioning systems, aged concentrates from accelerated storage-stability studies, and environmental matrices such as groundwater, surface water, and soil collected near fire training grounds, airports, and fuel-handling facilities for PFAS investigation.

Testing Items

Typical testing programs for foam concentrate active ingredients cover the following parameters:

• Total active matter and total solids content
• Hydrocarbon surfactant content (anionic, nonionic, and amphoteric fractions)
• Fluorinated surfactant content and total fluorine-based surface-active agent concentration
• Target PFAS quantification, including PFOS, PFOA, PFHxS, PFBS, 6:2 FTS, and related precursors
• Total organic fluorine (TOF) and absorbable organic fluorine (AOF) screening
• Protein hydrolysate content for protein-based concentrates
• Organic solvent content, including glycol ethers and co-solvents
• Water content, pH, sediment, and freeze point
• Corroborating physicochemical parameters: density, viscosity, surface tension, and interfacial tension
• Functional indicators that reflect active ingredient effectiveness: expansion ratio, 25% drainage time, and film sealing performance

Testing Methods

Gravimetric and Titrimetric Determination

Total solids are determined gravimetrically by drying a weighed aliquot of the concentrate to constant mass at 105 ± 2 °C, while ethanol extraction procedures separate insoluble salts and residues from organic active matter. Anionic hydrocarbon surfactants are quantified by the classic two-phase titration technique described in ISO 2271, using a cationic titrant with a mixed indicator system; potentiometric variants improve precision and reduce solvent consumption for routine quality control.

Chromatographic Determination of Surfactants and PFAS

Fluorinated surfactants are separated and quantified by HPLC coupled with UV, charged aerosol, or evaporative light-scattering detection, depending on the chromophoric properties of the specific formulation. For regulated PFAS compounds, isotope-dilution LC-MS/MS provides quantitative results at trace levels, following internationally recognized procedures such as ASTM D7979. The total oxidizable precursor (TOP) assay converts unspecified precursors into measurable perfluoroalkyl acids, and combustion ion chromatography (CIC) delivers a robust screen for total organic fluorine, which is particularly valuable for verifying fluorine-free claims.

Solvent, Moisture, and Elemental Analysis

Glycol ethers and volatile co-solvents are determined by gas chromatography with flame ionization detection (GC-FID) or mass spectrometric detection (GC-MS), often using headspace sampling. Water content is measured by Karl Fischer titration, metal content by inductively coupled plasma optical emission spectrometry (ICP-OES), and inorganic anions by ion chromatography. Fourier-transform infrared (FTIR) spectroscopy provides a rapid qualitative fingerprint of the formulation, while nuclear magnetic resonance (NMR) spectroscopy supports structural confirmation of individual surfactants where required.

Standard Frameworks and Performance Corroboration

Chemical results are interpreted alongside the performance requirements of GB 15308, ISO 7203, EN 1568, and UL 162, which specify expansion ratio, drainage time, extinguishing, and burnback tests. Surface and interfacial tension measurements, performed according to methods consistent with ISO 304, provide a direct link between surfactant concentration and film-forming capability. Accelerated aging studies at elevated temperature, followed by re-testing of active content and performance, are used to evaluate shelf life and storage stability claims.

Applications

Active ingredient determination serves a wide range of technical and regulatory purposes across the fire protection industry:

• Product certification and conformity assessment against GB 15308, ISO 7203, EN 1568, and UL 162 requirements
• Manufacturing quality control, batch release, and incoming material verification for foam producers and formulators
• Procurement acceptance testing by airports, petrochemical plants, tank farms, and municipal fire brigades
• Shelf-life verification and storage-stability assessment of concentrates held in fixed systems or long-term inventory
• Transition management from fluorinated foams to fluorine-free alternatives, including verification that replacement products contain no added PFAS
• Environmental site investigations of soil and groundwater near fire training areas and emergency response scenes
• Failure analysis and fire scene investigation, where deficient active content may explain poor extinguishing performance
• Research and development support for new surfactant systems and fluorine-free foam technologies

FAQ

What are the active ingredients in a foam concentrate?

Active ingredients are the functional chemicals that create and sustain fire suppression capability, principally fluorinated and hydrocarbon surfactants, protein hydrolysates, foam stabilizers, polymeric thickeners in alcohol-resistant products, and the organic solvents that keep the formulation homogeneous. Inert components such as water, buffering salts, and preservatives are determined separately as supporting parameters.

Why is separate quantification of fluorinated surfactants necessary?

Fluorinated surfactants drive the film-forming and fuel repellency performance of AFFF and FFFP products, but many PFAS compounds are subject to international restriction due to environmental persistence and toxicity. Separate quantification demonstrates both product performance and regulatory compliance, and total organic fluorine testing verifies whether a product marketed as fluorine-free truly contains no added PFAS.

Do chemical results alone prove compliance with fire performance standards?

No. Chemical determination confirms what is in the concentrate and at what concentration, but full conformity with GB 15308, ISO 7203, EN 1568, or UL 162 also requires standardized fire tests, including expansion ratio, drainage time, extinguishment time, and burnback resistance, conducted on correctly proportioned foam solution.

What samples and volumes are typically required?

For a neat concentrate, laboratories generally request 500 mL to 1 L of homogenized sample in sealed, chemically compatible containers. Environmental PFAS investigations require specific sampling protocols, including PFAS-free containers and blanks, to prevent cross contamination at the low reporting limits involved.

Can aged, diluted, or contaminated samples still be tested?

Yes. Aged concentrates from storage-stability programs, premixed solutions, and samples containing visible sediment or phase separation can all be analyzed. Results for such samples are interpreted with care, since degradation, evaporation of solvents, or contamination may shift the apparent balance of active components, and comparison with a retained fresh reference batch is often recommended.