Surfactants Database

Quality Parameters and Testing. Active matter is determined by potentiometric titration with Hyamine 1622 according to ASTM D4251-89(2024) , which eliminates the chlorinated solvent required in the older methylene blue two-phase titration (ASTM D1681). Color is measured on the 5 % active matter aqueous solution by the APHA/Pt-Co scale (ASTM D1209); acceptance limit <80 . Free oil and unsulfated matter are determined by petroleum-ether extraction. Sulfuric acid content is titrated alkalimetrically. Neutralization index is approximately 13 g NaOH per 100 g LABSA (100 % basis), a value used to calculate caustic demand during LAS production.

Compatibility and Formulation Notes. LABSA is compatible with most anionic, nonionic, and amphoteric surfactants. It is the dominant cost-effective anionic surfactant in powder and liquid laundry detergents, accounting for approximately 68–70 % of global LAS consumption in household laundry products . In hard water, LABSA forms calcium salts that reduce solubility; therefore, builders (STPP, zeolites, or citrates) are co-formulated to sequester calcium and magnesium ions. LABSA exhibits excellent biodegradability (>98 % in OECD 301 tests) because of its linear alkyl chain . Under aerobic conditions, the half-life is approximately 1–3 weeks; anaerobic degradation is slow .

Storage and Safety. Store LABSA acid in dry, ventilated areas away from alkalis and oxidizing agents. Use corrosion-resistant pumps, valves, and tanks (stainless steel 316L or lined carbon steel). The acid is classified as a corrosive liquid (UN 2586, Class 8). Neutralized LAS powder should be kept dry to prevent caking; moisture absorption above 5 % can cause agglomeration and flow problems in dry-blend operations.

Quality Parameters and Testing. The key quality parameters for SLES are active matter, pH, sodium chloride, unsulfated matter, color, and viscosity. Active matter is measured by potentiometric titration (ASTM D4251 or ASTM D6173) . Sodium sulfate and unsulfated matter are gravimetric determinations after extraction. Dioxane, a potential process impurity from ethoxylation, is quantified by gas chromatography–mass spectrometry (GC-MS) with a typical acceptance limit of 30 ppm. The Hazen color (Pt-Co) of a 5 % active matter solution should not exceed 20 units .

Compatibility and Formulation Notes. SLES is the primary liquid detergent surfactant because of its excellent solubility, foaming profile, and broad compatibility. The ethylene oxide chain (1–3 EO units) imparts milder skin characteristics compared to SLS . SLES shows favorable hard-water resistance and high biodegradation potential. It thickens effectively with electrolytes (sodium chloride) and forms viscosity synergies with amphoteric surfactants such as CAPB and amine oxides. In shampoo and body-wash formulations, SLES serves as the principal anionic backbone, with CAPB added at 2–5 % to boost foam and build viscosity. SLES is hygroscopic; the 70 % paste absorbs moisture if exposed to air .

Storage and Safety. Store SLES 70 % paste at 20–35 °C to maintain pumpable viscosity; avoid temperatures below 15 °C where the product may become too viscous to handle. The 28 % liquid may be stored at ambient temperature. Both grades should be kept in closed containers. SLES is classified as a skin irritant (H315) and serious eye irritant (H319) under GHS . Wear protective gloves and eye protection during handling.

Quality Parameters and Testing. Active matter is determined by potentiometric titration with Hyamine 1622 (ASTM D4251) or by two-phase titration with methylene blue (ASTM D1681) . Sodium sulfate is determined gravimetrically as barium sulfate after precipitation. Free fatty alcohol (unsulfated matter) is extracted with petroleum ether. Whiteness is measured on the Hunter Lab scale for cosmetic-grade material where visual appearance is critical. Loss on drying is determined at 105 °C for 2 hours.

Compatibility and Formulation Notes. SLS is a high-foaming anionic surfactant with strong wetting, dispersing, and emulsifying properties. It is widely used in toothpaste (as the standard foaming agent), powdered detergents, and dishwashing formulations . In emulsion polymerization, SLS serves as an effective anionic emulsifier for acrylic and SBR latex production. Compared to SLES, SLS produces denser foam but is less mild to skin and eyes; it should be combined with milder co-surfactants (CAPB, APG) in leave-on personal care products. SLS is readily biodegradable (95 % in OECD 301B, 28 days) .

Skin Irritation Considerations. SLS at concentrations above 10 % in leave-on products can disrupt the stratum corneum lipid barrier, causing erythema and dryness. In rinse-off formulations, concentrations up to 15 % are generally well tolerated. The irritation potential is mitigated by co-formulation with amphoteric surfactants (CAPB) or nonionic glucosides (APG), which reduce the critical micelle concentration and lower the concentration of free monomeric surfactant in solution.

Storage and Safety. SLS powder is classified as a flammable solid (Category 2, H228) with a flash point of 170 °C . Store in a cool, dry place away from ignition sources. Avoid dust generation; use dust-collection systems during dry blending. SLS is harmful if swallowed (H302) and causes serious eye damage (H318) . Wear dust masks, gloves, and eye protection during handling. SLS liquid (28–30 %) is non-flammable and easier to handle in liquid detergent plants.

Quality Parameters and Testing. Active matter is determined by potentiometric titration (ASTM D4251 or ASTM D6173) . For AOS, the titration curve may show two potential jumps corresponding to the hydroxyalkane sulfonate and alkene sulfonate fractions; the total active matter includes both species. Petroleum-ether solubles represent unsulfated hydrophobes. Free alkalinity is titrated with standard acid to phenolphthalein endpoint. Color is measured by the Hazen method on a 5 % active matter solution.

Compatibility and Formulation Notes. AOS offers excellent hard-water tolerance, maintaining foam stability and detergency at water hardness levels up to 300 ppm CaCO₃ . The critical micelle concentration of AOS C14–16 is approximately 0.60 mmol/L at 25 °C, comparable to LAS (0.65 mmol/L) . AOS exhibits good hydrolytic stability across a broad pH range (4–10) and is particularly valued in non-phosphate detergent formulations where builder levels are reduced. It is milder to skin than LAS and SLS, making it suitable for baby shampoo and facial cleanser applications . AOS is biodegradable and exhibits low aquatic toxicity .

Storage and Safety. Store AOS liquid in sealed containers at 10–40 °C; protect from freezing, which can cause phase separation. AOS powder should be kept in a cool, dry place in sealed containers to prevent moisture uptake. AOS is classified as a mild irritant; wear standard protective equipment during handling. The liquid product is non-flammable.

Quality Parameters and Testing. Active matter is determined by potentiometric titration of the anionic site with sodium dodecyl sulfate at pH 2–3, or by two-phase titration (ISO 2271) . Sodium chloride is titrated argentometrically (Mohr or potentiometric endpoint). The critical trace impurities—sodium monochloroacetate, amidoamine, and DMAPA—are quantified by HPLC or ion chromatography because these by-products are associated with skin sensitization . Modern grades from leading manufacturers control DMAPA below 15 ppm and amidoamine below 0.3 % . pH is measured potentiometrically on a 5 % aqueous solution at 25 °C.

Compatibility and Formulation Notes. CAPB is an amphoteric surfactant that functions as a zwitterion across its typical formulation pH range (4.5–6.5). It provides exceptional viscosity-building synergy with anionic surfactants, particularly SLES; the addition of 3–5 % CAPB to a 12 % SLES solution can increase viscosity by 200–500 % depending on electrolyte level. CAPB also stabilizes foam and reduces the irritation potential of primary anionics by forming mixed micelles. In sulfate-free shampoo formulations, CAPB serves as a co-surfactant alongside APG and amine oxides. CAPB is stable in acidic to mildly alkaline conditions; avoid prolonged exposure above pH 8.5 where hydrolysis of the amide bond may occur.

Storage and Safety. Store CAPB in tightly closed containers at 10–40 °C, away from direct heat and sunlight. CAPB is stable for at least 12 months under recommended conditions. It is classified as a skin irritant (H315) and serious eye irritant (H319) at concentrate levels; dilute formulations (≤5 % active) are generally non-irritating in rinse-off applications.

Quality Parameters and Testing. Active matter is determined by potentiometric titration in acidified aqueous medium with sodium dodecyl sulfate, or by the two-phase Epton titration (ISO 2271) . Free tertiary amine is titrated acidimetrically to a methyl orange endpoint; levels above 0.5 % may cause odor issues and reduce flash foam. Residual hydrogen peroxide (from the amine oxidation manufacturing step) is determined iodometrically; high residual peroxide can degrade fragrance components and dyes. pH is measured on a 1 % aqueous solution.

Compatibility and Formulation Notes. Amine oxides are fundamentally nonionic at alkaline pH and protonate to cationic character below pH 4–5. This pH-dependent behavior makes them compatible with anionic surfactants across the typical detergent pH range (6–9) without forming insoluble complexes. Lauramine oxide (C12 chain) is preferred in hard-surface cleaners and dishwashing liquids for its grease-cutting efficiency and foam stability . Cocamine oxide (C12–C18 mixture) offers slightly richer foam and improved conditioning properties, making it suitable for hair care formulations. Both materials build viscosity effectively in SLES-based systems through the formation of elongated wormlike micelles; 2–4 % amine oxide added to 10 % SLES can increase viscosity from <100 cP to >3,000 cP at 25 °C. Amine oxides also function as hydrotropes, improving the solubility of fragrance oils and other lipophilic additives.

Storage and Safety. Store amine oxides in tightly closed containers at 10–30 °C; protect from freezing and prolonged exposure to direct sunlight. Freezing can cause irreversible phase separation in some grades . Shelf life is 12–24 months in original sealed packaging. Amine oxide concentrates are skin and eye irritants; handle with protective gloves and eye protection.

Quality Parameters and Testing. Hydroxyl number is determined by acetylation (ASTM D1957) and is inversely proportional to the degree of ethoxylation; target 104–114 mg KOH/g for AE7 . Cloud point is measured on a 1 % aqueous solution by warming until persistent turbidity appears (EN 1890) . The cloud point is a rapid quality indicator: values significantly below 45 °C suggest under-ethoxylation or high polyethylene glycol (PEG) content. PEG content is determined by HPLC/GPC (EN 12139) and should not exceed 2 % . 1,4-Dioxane, an ethoxylation by-product, is limited to <1 mg/kg and determined by GC-HS (headspace gas chromatography) . Color is measured by the Pt-Co method (ASTM D1209); acceptance <50 .

Compatibility and Formulation Notes. Fatty alcohol ethoxylates are nonionic surfactants whose surface activity is independent of water hardness. With an HLB of 12.2, AE7 is optimally balanced for detergent applications, providing excellent oil emulsification and particulate soil dispersion . FAEs produce low foam relative to anionics, a desirable characteristic in machine-dishwashing and textile-scouring applications. They act as degreasing agents in hard-surface cleaners and as emulsion stabilizers in agricultural formulations. FAEs are compatible with all classes of surfactants and are often combined with LABSA or SLES to improve detergency on oily soils while the anionic component provides foaming. Biodegradability is excellent (>90 % in OECD 301 tests). AE7 and AE9 are supplied at 100 % active matter, simplifying inventory and dosing calculations.

Storage and Handling. Store in sealed containers at ambient temperature. FAEs may become hazy or solidify below their pour point (~20 °C for AE7); gentle warming to 25–30 °C restores fluidity without quality loss . Keep away from strong oxidizing agents. FAEs are combustible liquids with flash points above 180 °C; standard fire precautions apply.

Quality Parameters and Testing. Active matter is determined by gravimetric analysis after removal of volatile components, or indirectly by total solids minus inorganic ash. The average degree of polymerization (DP) is determined by GC analysis of the silylated hydrolysate or by NMR spectroscopy; DP values of 1.3–1.6 indicate predominantly monoglucoside with some diglucoside . Residual fatty alcohol is extracted with petroleum ether; high residual alcohol (>1 %) can increase turbidity and odor. Sulfate ash is determined by ignition at 800 °C. pH is measured on a 10 % aqueous solution at 25 °C. Viscosity is measured by Brookfield viscometer at 20 °C and 20 rpm.

Compatibility and Formulation Notes. APG surfactants are derived from renewable fatty alcohols and glucose, giving them a natural origin index of 1.0 . They exhibit excellent mildness, low irritation potential, and synergistic behavior when combined with anionic surfactants: APG reduces the irritation of SLS and SLES while enhancing foam volume and stability. Short-chain APG (C8–C10) offers superior wetting speed and rapid foam development, making it suitable for facial cleansers and spray cleaners . Long-chain APG (C12–C14) provides stronger detergency and emulsification, preferred in shampoos and laundry detergents. APG is compatible with electrolytes, acids, and alkalis over a broad pH range (3–11) and tolerates high concentrations of sodium hydroxide, a property exploited in industrial and institutional cleaners. Biodegradability exceeds 60 % in closed-bottle tests and typically reaches 73–88 % for C12–C14 grades at 28 days .

Storage and Safety. Store APG in original sealed containers at 5–40 °C. The product is stable for at least 24 months under recommended conditions. APG is non-irritating to mildly irritating at use concentrations; the 50–70 % concentrate may cause eye irritation (H319). APG is non-flammable with no flash point. It is not classified as hazardous for transport.

Table 15.9 consolidates the analytical methods applicable to the four anionic surfactants and the nonionic fatty alcohol ethoxylates covered in this chapter. The potentiometric titration methods (ASTM D4251, ASTM D6173, EN 14480) have largely superseded the classical two-phase methylene blue titration (ISO 2271) in laboratory practice because they eliminate chlorinated solvents and improve reproducibility . The surfactant-selective electrode responds to the formation of a 1:1 ion pair between the anionic surfactant and the cationic titrant (Hyamine 1622 or benzethonium chloride) at the endpoint. For blends containing soaps, the titration pH must be adjusted: at pH 3.0 only anionic surfactants are titrated, whereas at pH 10.0–13 the sum of soaps and anionics is obtained . Unsulfated matter, determined by petroleum-ether extraction, is a critical purity indicator: high levels indicate incomplete sulfonation and can compromise foaming performance and odor. The dioxane limit of 30 ppm for SLES reflects both regulatory requirements (EU Regulation 1223/2009 for cosmetics) and process control in ethoxylation.

Table 15.10 assembles the analytical methods for the nonionic and amphoteric surfactants. CAPB and amine oxides are not directly titratable as amphoterics under neutral conditions; however, at pH 2–3 the betaine carboxyl group is protonated and the amine oxide is positively charged, allowing titration with an anionic surfactant standard solution (sodium dodecyl sulfate) . The determination of trace impurities in CAPB—specifically DMAPA and amidoamine—has become critical because these by-products are responsible for the majority of reported skin sensitization reactions to CAPB-containing products . Leading manufacturers now control DMAPA below 15 ppm through optimized betainization conditions and pH control. For APG, active matter is determined indirectly because APG lacks an ionic group amenable to titration; total solids minus sulfate ash provides the organic active content. The degree of polymerization, measured by GC of the silylated glucosidic hydrolysate, distinguishes commercial APG grades and influences solubility and foaming behavior .

Legend: C = Compatible (no interaction under normal formulation conditions); S = Synergistic (viscosity/foam/mildness enhancement); I = Incompatible (precipitation or phase separation risk).

Table 15.11 cross-references the compatibility of all eight primary surfactants. The matrix reveals several important synergistic pairings that form the basis of modern detergent formulation. The SLES–CAPB combination is the most widely exploited synergy: CAPB builds viscosity in SLES solutions through the formation of mixed micelles and enhances foam creaminess while reducing skin irritation . The SLES–amine oxide pairing similarly produces dramatic viscosity increases (up to 10-fold at equivalent active levels) and stabilizes foam against fatty soil deactivation . The SLES–APG combination reduces the irritation potential of the anionic backbone while maintaining detergency; this synergy is the foundation of “sulfate-free” personal care formulations. LABSA is compatible with all listed surfactants but is most commonly paired with FAE for improved oil removal or with CAPB for milder liquid detergents. AOS is fully compatible across the matrix and serves as a drop-in replacement for LAS or SLES in hard-water formulations. FAE, being nonionic, is compatible with all ionic surfactants without complexation; its primary role is as a degreasing co-surfactant that operates independently of water hardness. No incompatible (I) pairings are recorded for the nine surfactants at typical formulation pH (6–9) and concentrations (2–20 %), reflecting the broad formulation latitude available to the detergent chemist.

A ninth surfactant entry is implicit in the amine oxide category: lauramine oxide and cocamine oxide share the same compatibility profile and are interchangeable in most matrices without reformulation, differing primarily in foam texture and hydrophobicity. Formulators may substitute one for the other at equivalent active weight to modulate foam richness (cocamine oxide) versus grease cutting (lauramine oxide). In commercial practice, LABSA/LAS remains the highest-volume synthetic surfactant by a considerable margin, with estimated global production of 3,300–4,200 kt/year, reflecting its dominant cost position in emerging-market laundry powder formulations . SLES ranks second in volume, driven by the global shift toward liquid laundry detergents and the continued growth of personal care markets in Asia. APG, though the smallest volume category, exhibits the highest growth rate (~8–10 % per year) driven by consumer demand for renewable and mild surfactants in premium personal care products . FAE volumes are significant and growing as alkyl phenol ethoxylates face regulatory restrictions under REACH and equivalent frameworks. The impurity profiles that differentiate commodity grades from premium specification materials—dioxane limits for SLES, DMAPA control for CAPB, and biodegradability certification for LAS—should be specified in procurement contracts alongside active matter and physical properties. -e

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