What Are APEOs and Why Are They Restricted?
Alkylphenol ethoxylates (APEOs) are a class of non-ionic surfactant — primarily nonylphenol ethoxylates (NPEO) and octylphenol ethoxylates (OPEO) — used widely as detergents, scouring agents, emulsifiers, dye-dispersing agents, and wetting agents in textile wet processing, leather degreasing, and the production of many consumer and industrial formulations. NPEO accounts for roughly 80–90 % of total APEO output; OPEO accounts for most of the remainder.
The restriction case is built on two properties. First, APEOs biodegrade in the environment to their parent alkylphenols — nonylphenol (NP) and octylphenol (OP) — which are more toxic than the parent ethoxylates, persist in sediments, and bioaccumulate in aquatic organisms. Second, NP and OP are endocrine disruptors: they mimic oestrogen, and chronic exposure is associated with reproductive and developmental effects in aquatic life and, by extension, in humans exposed through food and drinking water. The combination of persistence, bioaccumulation, and endocrine disruption is what put NP and NPEO on the REACH Candidate List of Substances of Very High Concern (SVHC) and on the AFIRM and ZDHC restricted-substance lists for the apparel and footwear industry.
Knowing the chemistry up front matters for testing, because APEO testing must cover both the parent ethoxylates (NPEO, OPEO) and their degradation products (NP, OP) — a report that detects only the ethoxylates and not the phenols is incomplete, and a test method that cannot separate the two will over-report or under-report depending on which species dominates the extract.
What Standards Govern APEO Testing in China?
The Chinese testing framework for APEO covers two distinct product domains, each with its own standard, and the two are not interchangeable.
Textiles — GB/T 23322-2018 Textiles — Determination of Surfactants — Alkylphenols and Alkylphenol Ethoxylates. The 2018 revision replaced the 2009 edition and expanded the scope from APEO-only to AP + APEO — i.e. NP, OP, NPEO, and OPEO together. This is the critical change: a textile laboratory reporting under GB/T 23322-2009 (withdrawn) would test only the ethoxylates, while one reporting under GB/T 23322-2018 (current) tests the full quad. A report that does not state which edition it was tested against is not interpretable.
Food contact materials — GB 31604.50-2020 National food safety Standard — Determination of Nonylphenol Migration in Food Contact Materials and Articles. This is the binding standard for NP migration into food simulants — relevant for paper, plastic, and coating food-contact articles where NP may be present from recycling or from chemical additives. The method is LC-MS/MS with a detection limit of 0.003 mg/kg and a quantification limit of 0.01 mg/kg, three orders of magnitude tighter than the textile residue threshold, because the migration-test framework measures what a consumer ingests, not what is left in the article.
The international method references are ISO 18254-1 (HPLC-MS for APEO in textiles) and ISO 18254-2 (NPLC method, in preparation). For the restriction framework, REACH Annex XVII entry 46 is the binding EU regulation, and OEKO-TEX STANDARD 100 and the AFIRM RSL are the industry RSLs.
How Are APEOs Tested in Textiles?
The textile test under GB/T 23322-2018 is a solvent extraction + LC-MS/MS method. The procedure:
- Sample preparation. Cut the textile (fabric, yarn, fibre, or leather) into small pieces (≤ 0.5 × 0.5 cm), mix, and take a representative subsample (typically 1.0 g).
- Extraction. Add methanol (20 mL per gram of sample) and ultrasonically extract at elevated temperature (~65 °C) for 30 minutes. Decant the supernatant and repeat the extraction on the residue; combine the extracts.
- Clean-up. Filter through a 0.22 µm membrane; if the matrix is complex (dyed fabric, pigment-printed textile), a solid-phase extraction (SPE) clean-up step may be required.
- Analysis. Inject into an LC-MS/MS system. Separation on a C18 reversed-phase column with an ammonium-acetate-buffered water / methanol-acetonitrile-isopropanol gradient; detection by electrospray ionisation (ESI+) in multiple reaction monitoring (MRM) mode.
- Quantification. APEOs are polymeric mixtures — each NPEO or OPEO is a distribution of oligomers with 2–17 ethoxy (EO) repeating units. Quantification is performed as the sum of all detected oligomers, not as a single compound, against a calibration curve covering the EO chain-length distribution.
The MS logic: each EO unit adds 44 Da to the molecular weight, so the NPEO homologous series produces [M+NH4]⁺ ions at m/z (238 + 44n) and the OPEO series at m/z (224 + 44n), for n = 2–17. The [M+NH4]⁺ ammonium adduct is used as the precursor ion because it gives the strongest, most reproducible response in ESI+. The dominant oligomers in commercial NPEO mixtures are typically n = 9–11. A laboratory that quantifies only the n = 9, 10, 11 peaks and not the full distribution will under-report — the full-chain sum is the defensible number.
Typical method performance reported in interlaboratory work: linear range 0.005–10 ppb with r > 0.995, recoveries 84–112 % at three spike levels, RSD 1.3–4.3 %. The detection limit for textile residue is typically reported at 0.2 mg/kg (ppm) — well below the regulatory thresholds.
What Are the Regulatory Limits and Which Applies?
The APEO restriction landscape has three layers, and the layer that applies depends on the product, the market, and the buyer.
REACH Annex XVII, entry 46 (binding in the EU): NP and NPEO may not be placed on the market or used as a substance or constituent of preparations at concentrations ≥ 0.1 % (1000 mg/kg) for specified purposes including textile and leather processing (with exemptions for closed-loop processes). A separate restriction, widened to cover textile articles that can be washed in water, sets the limit at 0.01 % (100 mg/kg) — any textile article intended to come into contact with the skin that would release NP/NPEO above this threshold in normal laundering is banned from the EU market. This is the limit that catches most textile export shipments.
OEKO-TEX STANDARD 100 (product ecolabel): NP + OP + NPEO + OPEO total ≤ 100 mg/kg across all product classes, with tighter limits (e.g. 25 mg/kg) for some product categories and buyers.
AFIRM RSL (brand consortium) and brand-specific RSLs: apparel and footwear brands impose their own limits, typically at 100 mg/kg total APEO, but some at 25 mg/kg or lower. The AFIRM RSL and ZDHC MRSL drive the supply-chain chemical-management programmes — a chemical formulation with APEO above the ZDHC MRSL limit cannot enter a ZDHC-compliant supply chain regardless of whether the finished article would meet the REACH threshold.
GB 31604.50-2020 (binding in China for food contact): the NP migration into food simulants is measured, not the NP residue in the article. The detection limit of 0.003 mg/kg reflects that the question is "how much NP does a consumer ingest" — and the limit applied is the specific migration limit (SML) for NP under the food-contact regulation, far below the 100 mg/kg textile threshold.
The operational rule: a textile or leather article is tested against the 100 mg/kg total APEO threshold (REACH / OEKO-TEX / AFIRM), while a food-contact article is tested against the NP migration SML (much tighter, measured in µg/kg). A report that applies the textile threshold to a food-contact article, or the food-contact SML to a textile, is using the wrong framework.
How Do APEOs Get Into a Product That Never Used Them?
The most common APEO failure mode in a modern, RSL-driven supply chain is unintentional contamination — the product was manufactured without intentionally added APEO, yet tests positive. The contamination routes, in order of frequency:
Shared equipment. A supplier that still uses APEO-containing formulations for other (non-RSL) clients leaves APEO residue in dyeing machines, finishing baths, and printing screens. The next lot run through the same equipment, even with APEO-free chemicals, picks up the residual APEO. This is why AFIRM guidance specifically recommends working with suppliers who have phased out APEO for all clients, not just for the RSL-bound orders.
Cleaning agents. Facility cleaning products and equipment-maintenance detergents may contain APEO surfactants. A cleaning agent used on a dyeing machine between lots introduces APEO into the next batch. The SDS of every facility chemical must be checked, not just the process chemicals.
Recycled and natural inputs. Recycled polyester and recycled cotton can carry APEO from their previous life cycles. Wool scouring historically used NPEO heavily, and wool and wool-blend products still test positive at higher rates than synthetics. Leather, similarly, has a long history of NPEO use in degreasing.
Auxiliary formulations. Spinning lubricants, sizing agents, impregnating agents, binders for interlinings, down/feather fillings, and dye/pigment preparations can all contain APEO as a dispersing agent or emulsifier. The SDS of every chemical formulation in the process must be checked against the APEO CAS-number list.
The CAS numbers to screen for include (non-exhaustive): 9016-45-9, 26027-38-3, 37205-87-1, 68412-54-4, 127087-87-0 (NPEO family); 9002-93-1, 9036-19-5, 68987-90-6 (OPEO family). A chemical SDS listing any of these as an ingredient is an APEO-containing formulation.
This is why an APEO failure investigation is rarely just "re-test the finished product" — the root cause is upstream, in the chemical inputs or the equipment history. A serious failure-analysis report tests the chemical formulations, the equipment rinse-water, and the raw materials alongside the finished product.
How Does the AP Degradation Question Affect the Test?
The AP (alkylphenol) vs APEO (ethoxylate) distinction matters because the restriction and the toxicity profile are different for the two. NPEO is the surfactant used in manufacturing; NP is its degradation product, and NP is the more potent endocrine disruptor. A textile may contain mostly NPEO (if recently manufactured) or a mix of NPEO and NP (if the APEO has partially degraded in storage), or predominantly NP (if the material is old or has been exposed to conditions that accelerate degradation).
GB/T 23322-2018 tests both — this is why the 2018 revision expanded the 2009 scope. A laboratory method that reports "total APEO" without separating the AP fraction is missing the more toxic component. The complete report gives NP, OP, NPEO (sum of oligomers n=2–17), and OPEO (sum of oligomers n=2–16) as four separate numbers, plus a total.
For the regulatory threshold, REACH Annex XVII entry 46 and most RSLs set the limit on NP + NPEO combined (and separately OP + OPEO combined), not on each individually — so a report that gives only "NP = 5 mg/kg, NPEO = 80 mg/kg" needs the 85 mg/kg sum computed and compared against the 100 mg/kg threshold. A report that lists the four species but does not sum them is making the customer do the regulatory arithmetic.
Our Testing Capabilities
Beijing ZKGX Research provides APEO testing against the GB/T 23322-2018 textile method, the GB 31604.50-2020 food-contact migration method, and the ISO 18254 / REACH / OEKO-TEX reference frameworks.
Textile and leather APEO (GB/T 23322-2018):
- NP, OP, NPEO (n=2–17), OPEO (n=2–16) by LC-MS/MS with MRM
- Methanol ultrasonic extraction, SPE clean-up where required
- Detection limit 0.2 mg/kg; reporting against REACH / OEKO-TEX / AFIRM limits
- Full oligomer-distribution reporting (not only n=9–11)
Food-contact NP migration (GB 31604.50-2020):
- NP migration into water, 4 % acetic acid, ethanol, vegetable oil simulants
- LC-MS/MS, detection limit 0.003 mg/kg, quantification limit 0.01 mg/kg
- Reporting against the NP specific migration limit (SML)
failure analysis and contamination tracing:
- Testing of chemical formulations (detergents, scouring agents, dye dispersions) against the APEO CAS-number screen
- Equipment rinse-water and swab testing for shared-machine contamination
- Raw-material and recycled-input testing (wool, recycled polyester, leather)
Standards cross-reference: ISO 18254-1, REACH Annex XVII entry 46, OEKO-TEX STANDARD 100, AFIRM RSL, ZDHC MRSL.
If you need a GB/T 23322 APEO test for a textile or leather shipment, a GB 31604.50 NP migration test for a food-contact article, an APEO contamination root-cause investigation, or a chemical-formulation APEO screen for a ZDHC-compliant supply chain — contact our laboratory with the product type, destination market, and applicable RSL or regulatory limit, and we will scope the test plan.
FAQ
What is the difference between APEO and AP, and why does the test cover both?
APEO (alkylphenol ethoxylate, e.g. NPEO, OPEO) is the surfactant used in manufacturing. AP (alkylphenol, e.g. NP, OP) is its degradation product, formed in wastewater treatment and in the environment. AP is more toxic and is the more potent endocrine disruptor. GB/T 23322-2018 covers both because a textile may contain APEO, AP, or a mixture depending on age and storage — and the restriction threshold applies to the NP+NPEO and OP+OPEO sums, not to one alone.
Why is the food-contact NP limit so much tighter than the textile APEO limit?
Because the food-contact test measures migration — how much NP a consumer ingests via food — while the textile test measures residue — how much is left in the article. The GB 31604.50 detection limit of 0.003 mg/kg reflects a dose-to-consumer framework, three orders of magnitude tighter than the 100 mg/kg textile residue threshold. They answer different questions and are not interchangeable.
How should a textile test report be structured to be defensible?
It should give NP, OP, NPEO (sum n=2–17), and OPEO (sum n=2–16) as four separate numbers, plus the NP+NPEO and OP+OPEO regulatory sums, compared against the applicable threshold (REACH 100 mg/kg, OEKO-TEX 100 mg/kg, or a brand RSL). It should state the test method (GB/T 23322-2018 or ISO 18254-1), the detection limit, the recovery, and the oligomer-distribution coverage. A report that gives only "total APEO = pass" without the species breakdown is not defensible in a dispute.
Can a product test positive for APEO if no APEO was used in its production?
Yes, and this is the most common failure mode in an RSL-driven supply chain. The contamination routes are shared equipment (residual APEO from non-RSL clients), cleaning agents (APEO-containing facility chemicals), recycled inputs (recycled polyester, wool, leather with APEO history), and auxiliary formulations (spinning lubricants, sizes, binders, dye dispersions). A serious failure investigation tests the chemical inputs and equipment, not just the finished product.
Is there a list of APEO CAS numbers to screen chemical formulations against?
Yes. The NPEO family includes CAS 9016-45-9, 26027-38-3, 37205-87-1, 68412-54-4, 127087-87-0. The OPEO family includes 9002-93-1, 9036-19-5, 68987-90-6. A chemical SDS listing any of these as an ingredient is an APEO-containing formulation. The list is not exhaustive — there are many CAS numbers in the APEO class — but these cover the majority of commercial APEO surfactants. A chemical supplier's SDS should be checked against this list before a formulation enters an RSL-compliant supply chain.