Ethylene glycol residue determination is a critical quality and safety control step for leave-on (no-rinse) hand sanitizers, where low-level contamination from denatured alcohol or humectant excipients can pose serious health risks. This article outlines the regulatory context, applicable standards, sample types, and validated chromatographic methods—primarily GC-FID, GC-MS, and HPLC-RI—used by accredited third-party laboratories to quantify ethylene glycol down to ppm levels. Read on for a complete technical overview of residue limits, method validation parameters, and practical applications across manufacturing and compliance workflows.
Technical Overview
Leave-on hand sanitizers, also referred to as rinse-free or waterless hand rubs, rely on high concentrations of ethanol (typically 60–80% v/v) or isopropyl alcohol to inactivate microorganisms on the skin. Because the product is applied without rinsing and is used repeatedly throughout the day, any toxic impurity present in the alcohol stream or excipient chain represents a direct and cumulative dermal and hand-to-mouth exposure risk. Ethylene glycol (EG, CAS 107-21-1) is one of the most closely watched of these impurities.
Ethylene glycol is never an intentional ingredient in hand sanitizer formulations. It typically enters products through one of the following routes:
- Use of industrial-grade or improperly sourced denatured ethanol contaminated with glycols.
- Glycerol or propylene glycol humectants of sub-pharmaceutical quality containing EG or diethylene glycol (DEG) impurities.
- Cross-contamination on shared production or filling lines previously used for coolant, antifreeze, or glycol-based products.
- Deliberate substitution or adulteration of solvents in counterfeit or grey-market supply chains.
From a toxicological standpoint, absorbed ethylene glycol is metabolized to glycolic and oxalic acids, which can cause metabolic acidosis, central nervous system depression, and acute renal failure through calcium oxalate crystallization. Children are particularly vulnerable, both through accidental ingestion of the product and through repeated dermal contact with compromised skin. These hazards explain why regulatory attention to glycol residues in alcohol-based hand rubs intensified sharply during the global demand surge of 2020–2022, when numerous product recalls and import alerts were issued worldwide.
The primary quantitative benchmark used by accredited third-party laboratories and regulatory assessors is the ICH Q3C classification, which designates ethylene glycol as a Class 2 residual solvent with a permitted daily exposure (PDE) of 6.2 mg/day and a corresponding concentration limit of 620 ppm. Pharmacopoeial monographs for alcohol and glycerin similarly restrict glycol impurities, and WHO handrub formulation guidance requires ingredients of defined pharmaceutical quality. Many brand owners apply stricter internal specifications, commonly in the range of 50–100 ppm, to provide a safety margin for consumer products.
Testing Samples
Finished Hand Sanitizer Products
Commercial finished goods constitute the largest sample category, including alcohol-based gels, foams, sprays, liquid rubs, and impregnated wipes. For wipes and other non-pourable formats, the impregnating solution is mechanically expressed or solvent-extracted prior to analysis. Samples are typically collected as at least two intact retail units or 100 mL of bulk product per batch.
Raw Materials and Excipients
Incoming material screening is the most effective preventive control point. Testable materials include ethanol and isopropyl alcohol (including denatured grades), glycerol, propylene glycol, carbomer gelling agents, botanical extracts, and fragrances. Supplier qualification programs frequently require full-strength certificate-of-analysis verification supported by independent laboratory testing.
Stability and Retention Samples
Retained batch samples from accelerated (40°C/75% RH) and long-term stability programs are analyzed to confirm that glycol levels do not increase over shelf life, for example through container-closure interaction or degradation of excipients. Retention samples also support post-market complaint investigations and recall verification.
Proper sample handling is essential: containers must be sealed airtight to prevent loss of volatile alcohol (which would artificially concentrate the residue), filled with minimal headspace, and transported at ambient temperature away from heat sources.
Testing Items
A standard ethylene glycol residue determination report typically includes the following deliverables:
- Qualitative identification of ethylene glycol in the sample matrix (retention time and spectral confirmation against reference standards).
- Quantitative EG content expressed in mg/kg (ppm), reported on an as-received basis.
- Optional extended impurity screening for diethylene glycol, methanol, and 1-propanol, which frequently co-occur as alcohol-stream contaminants.
- A pass/fail conclusion against the applicable limit, such as the ICH Q3C 620 ppm threshold or a stricter contractual specification.
- Full method and validation references, chromatograms, calibration data, and measurement uncertainty where required by the client or regulator.
Testing Methods
Gas Chromatography with Flame Ionization Detection (GC-FID)
GC-FID is the workhorse technique for quantifying ethylene glycol in hand sanitizer. A typical procedure involves accurately weighing approximately 0.5 g of sample, diluting with purified water or a water–acetonitrile mixture, adding an internal standard such as 1,3-propanediol or 1,4-butanediol, and filtering through a 0.45 µm membrane before injection. Separation is performed on a polar polyethylene glycol (WAX-type) capillary column, for example 30 m × 0.32 mm × 0.25 µm, with a programmed oven ramp from approximately 40°C to 200°C. Multi-point calibration covering the range of interest (commonly 5–1000 µg/mL) yields linearity with r² values of 0.999 or better.
Derivatization for Trace-Level Analysis
Because ethylene glycol is polar, low-volatility, and prone to peak tailing, silyl derivatization (for example with BSTFA containing 1% TMCS to form the bis-trimethylsilyl ether) is often employed when detection limits below approximately 10 ppm are required. Derivatization sharpens chromatographic peaks, improves detector response, and allows practical LOQs in the low ppm range.
GC-MS Confirmatory Analysis
Gas chromatography coupled with mass spectrometric detection in selected-ion monitoring mode provides unambiguous identification in complex matrices such as gels containing glycerol, aloe extracts, and fragrances. Confirmation criteria include retention time matching within ±2% of a calibration standard and the correct relative abundance of characteristic fragment ions. GC-MS is the preferred confirmatory technique whenever a positive GC-FID result approaches the specification limit or is disputed.
HPLC with Refractive Index Detection (HPLC-RID)
For matrices where derivatization is impractical, high-performance liquid chromatography on an amino or HILIC column with an acetonitrile–water mobile phase and refractive index detection offers a robust orthogonal method, particularly for glycerol-rich products where early-eluting glycol peaks must be resolved from the bulk humectant.
Method Validation
Whichever platform is selected, methods are validated in accordance with ICH Q2(R2) principles. Key acceptance criteria include: specificity with baseline resolution from ethanol, isopropanol, glycerol, propylene glycol, and DEG; linearity (r² ≥ 0.999); accuracy demonstrated by spike recovery of 90–110% at levels bracketing the specification; repeatability with RSD ≤ 5%; a LOQ no higher than 10–20% of the applicable limit; and robustness against deliberate variations in oven temperature, flow rate, and injection volume. Reference procedures may be adapted from recognized frameworks such as USP <621> Chromatography, USP <467> Residual Solvents, ASTM E202 for glycol analysis, and relevant GB/T gas chromatographic methods for ethylene glycol determination.
Applications
Manufacturing Quality Control and Supplier Qualification
Integrating EG residue testing into incoming-material release and finished-goods QC provides early detection of contaminated alcohol lots before they reach the filling line, protecting both consumers and brand equity. Periodic supplier requalification and certificate-of-analysis verification reinforce the control strategy under a quality management framework aligned with ISO 22716 cosmetics GMP.
Regulatory Compliance and Market Access
Test reports from accredited third-party laboratories support product dossiers, customs clearance, e-commerce platform documentation, and responses to regulatory inquiries. Following waves of hand sanitizer recalls linked to toxic alcohol contamination, many marketplaces and importing authorities now explicitly demand impurity data covering glycols and methanol.
Research, Development, and Stability Programs
Formulators use residue data to compare excipient grades, evaluate denaturant systems, and demonstrate that glycol levels remain stable across the claimed shelf life. Contract manufacturers rely on the same data during technology transfer and process validation.
FAQ
What detection limits can be achieved for ethylene glycol in hand sanitizer?
With derivatized GC-FID or GC-MS, practical limits of detection of approximately 1–3 ppm and limits of quantification of approximately 3–10 ppm are routinely achievable, comfortably below the 620 ppm ICH Q3C limit and typical internal specifications of 50–100 ppm.
What acceptance limit applies to ethylene glycol residue?
The most widely cited benchmark is the ICH Q3C Class 2 residual solvent limit of 620 ppm (PDE 6.2 mg/day). Pharmacopoeial monographs for alcohol and glycerin impose their own glycol impurity restrictions, and many brand owners enforce stricter contractual limits, so the governing specification should always be confirmed with the intended market and client.
Can the same analysis also detect diethylene glycol and methanol?
Yes. A validated multi-residue GC method can quantify EG, DEG, and methanol in a single run, which is highly recommended since these contaminants share common sources in the alcohol supply chain and regulators typically evaluate them together.
How should samples be submitted for testing?
Submit at least two sealed retail units or 100 mL of bulk product per batch in the original or equivalent airtight containers, labeled with batch number and production date, and ship at ambient temperature. Containers should be full or nearly full to prevent alcohol evaporation that would bias residue results upward.
Why does ethylene glycol appear in hand sanitizer in the first place?
Ethylene glycol is not a formulation ingredient; it appears through contaminated industrial-grade or denatured ethanol, low-purity glycerol or propylene glycol humectants, line cross-contamination, or deliberate solvent substitution in counterfeit production.
How long does the determination take?
Standard turnaround is typically five to seven working days from sample receipt, including extraction, calibration, analysis, and reporting. Expedited two- to three-day services are commonly available from accredited third-party laboratories for urgent release or investigation cases.