Determination of Volatile Organic Compounds (VOCs) in Printing Inks: Standards, Methods, and Complia

Volatile organic compounds (VOCs) released from printing inks are a significant source of industrial air pollution and a key compliance parameter under mandatory regulations such as China's GB 38507-2020. Determination of VOC content in inks relies on standardized gas chromatographic and gravimetric methods, including ISO 11890, GB/T 23986, and US EPA Method 24A, typically performed by accredited third-party laboratories. This article explains the testing scope, sample requirements, analytical methods, regulatory background, and practical considerations for ink manufacturers, printers, and packaging brand owners.

Technical Overview

Volatile organic compounds (VOCs) are organic chemicals that readily evaporate at ambient temperature. In regulatory practice, a VOC is generally defined as any organic compound with an initial boiling point not exceeding 250 °C at a standard pressure of 101.3 kPa. In printing inks, VOCs originate mainly from the solvent phase of the formulation: alcohols, esters, ketones, aromatic hydrocarbons, glycol ethers, and, in some products, halogenated solvents. During printing, drying, and storage, these compounds are released into the workplace and the atmosphere, where they act as precursors to ground-level ozone and secondary particulate matter and may pose occupational health risks. Benzene, for example, is a recognized human carcinogen, while toluene and xylene exhibit neurotoxicity upon repeated exposure.

Regulatory pressure on ink VOC emissions has increased sharply worldwide. In China, the mandatory national standard GB 38507-2020 establishes category-specific VOC content limits for printing inks, including offset inks, solvent-based gravure and flexographic inks, water-based inks, and energy-curing inks, with the strictest requirements applied to water-based and UV/EB-curable systems. The standard took effect in April 2021 and functions as a market-access requirement. Complementary frameworks include the environmental labeling requirements of the HJ 371 series for printing inks, the fugitive emission control standard GB 37822-2019 for industrial facilities, and international references such as ISO 11890, EN ISO 11890, ASTM D3960, and US EPA Method 24A. Demonstrating compliance requires accurate, standards-based analytical determination, which is normally carried out by accredited third-party laboratories under an ISO/IEC 17025 quality system.

Testing Samples

Offset Printing Inks

Sheet-fed, cold-set, and heat-set offset inks are paste inks based on hydrocarbon resins and mineral distillates. Although traditionally considered lower in VOC reactivity, heat-set systems may contain higher-boiling fractions that fall within or near the regulatory VOC definition, making quantitative verification necessary for classification under GB 38507.

Solvent-Based Gravure and Flexographic Inks

Liquid inks for gravure and flexography typically contain large proportions of fast-evaporating solvents such as ethyl acetate, ethanol, isopropanol, methyl ethyl ketone, toluene, and cyclohexanone. These product categories carry the highest VOC content and are the primary target of reduction and substitution programs in packaging printing.

Water-Based Inks

Water-based gravure and flexographic inks use water as the main carrier but frequently contain co-solvents, glycols, glycol ethers, and amine neutralizers. Water-based does not mean VOC-free, and these products still require full testing to confirm conformity with the low-VOC limits of their category.

UV and EB Energy-Curing Inks

Energy-curing inks are essentially 100 percent reactive systems, yet they may contain small quantities of residual solvents, diluents, or volatile monomers. Testing confirms that they remain within the very low VOC thresholds assigned to energy-curing inks.

Screen Printing, Digital, and Specialty Inks

Screen printing inks, inkjet fluids (solvent, eco-solvent, UV, and aqueous types), conductive inks, and other specialty formulations are also tested, since their solvent profiles differ substantially from conventional printing inks.

Sample Submission and Storage Requirements

A representative sample of approximately 50 to 100 g should be supplied in clean, airtight glass or metal containers filled as completely as practicable to minimize headspace. Sampling should follow the principles of ISO 15528 and GB/T 3186. Samples must be stored cool and dark, protected from evaporation and contamination, homogenized gently before analysis, and delivered to the laboratory promptly. Volatile losses caused by open containers or prolonged storage can bias results low and are a common cause of disputed findings.

Testing Items

Depending on the applicable standard and the client's purpose, testing may cover the total VOC content as well as individual regulated solvents. Typical test items include:

• Total volatile organic compound (TVOC) content, reported in percent by mass and, after density measurement, in grams per liter
• Benzene, toluene, ethylbenzene, and o-, m-, p-xylene (BTEX)
• Esters: ethyl acetate, isopropyl acetate, n-butyl acetate
• Alcohols: methanol, ethanol, isopropanol, n-propanol, n-butanol
• Ketones: acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone
• Glycol ethers and their acetates used as coalescing or retarding agents
• Halogenated solvents such as dichloromethane, chloroform, 1,2-dichloroethane, and trichloroethylene
• N,N-dimethylformamide and other amide-type solvents
• Water content and non-volatile (solids) content, required as inputs to the difference method
• Density at 23 °C, required for unit conversion to g/L
• Residual monomers and volatile additives relevant to UV-curing systems, where applicable

Test reports normally state the measured values together with the ink category defined in GB 38507-2020 and an explicit pass/fail judgment against the corresponding limit.

Testing Methods

Total VOC by Gas Chromatography (GC-FID)

The gas chromatographic method described in ISO 11890-2, GB/T 23986, and related procedures such as ASTM D6886 is the preferred approach for inks with low to moderate VOC content, typically between 0.1 and 15 percent by mass. A accurately weighed portion of homogenized ink is dissolved in a suitable solvent, such as N,N-dimethylformamide or another medium compatible with the resin system, containing an internal standard that is absent from the formulation. The solution is sealed immediately to prevent volatilization losses and analyzed by GC with flame ionization detection. Individual solvents are quantified against multipoint calibration curves using relative response factors, and the total VOC result is obtained by summing all components with boiling points at or below 250 °C.

Total VOC by the Difference Method

The gravimetric difference method of ISO 11890-1, GB/T 23985, ASTM D2369, and US EPA Method 24A is applied to inks expected to contain higher VOC levels. The total VOC content is calculated as follows: VOC (percent by mass) = 100 minus the non-volatile content minus the water content. Non-volatile matter is determined gravimetrically by drying a weighed specimen, commonly at 105 to 110 °C for about one hour, in accordance with ISO 3251 or GB/T 1725. Water is determined separately by gas chromatography or Karl Fischer titration so that it is not erroneously counted as organic VOC.

Target Compounds and Screening by Headspace GC-MS

Headspace gas chromatography coupled with mass spectrometric detection is used to identify unknown volatile components and to quantify restricted solvents such as benzene and halogenated hydrocarbons at low concentrations. A small aliquot of ink is sealed in a headspace vial, equilibrated at an elevated temperature, and the equilibrated vapor is transferred to the GC-MS system. This approach follows the general principles of standard VOC methods such as US EPA SW-846 Method 8260 and provides screening capability for full solvent profiling, method development, and failure investigations.

Supporting Measurements

Water content is determined by direct-injection gas chromatography or by Karl Fischer titration with appropriate matrix adaptation. Density is measured at 23 °C using a pycnometer or an oscillating U-tube densitometer in accordance with ISO 2811-1 or ASTM D1475. These supporting data are indispensable, because VOC limits are frequently expressed in grams per liter and because water must be excluded from the organic VOC mass balance.

Method Selection and Unit Conversion

The choice between the GC method and the difference method depends on the expected VOC level, the complexity of the solvent package, and the applicable regulatory definition. For reporting in volumetric units, the mass fraction result is converted as follows: VOC (g/L) = VOC (percent by mass) multiplied by the ink density in g/cm³ multiplied by 10. For example, an ink containing 3.0 percent VOC by mass with a density of 1.10 g/cm³ corresponds to 33 g/L.

Quality Assurance and Validation

Reliable results require validated methods executed under an ISO/IEC 17025 management system. Essential quality control measures include multipoint calibrations with acceptable linearity, procedural blanks, duplicate analyses with controlled relative deviation, spike recovery checks, and the use of certified reference materials or consensus samples where available. Quantification limits at the milligram-per-kilogram level for individual solvents are routinely achievable, which comfortably supports demonstration of compliance with stringent low-VOC requirements.

Applications

VOC determination for printing inks supports a wide range of compliance, commercial, and technical objectives:

• Mandatory compliance with GB 38507-2020 for inks manufactured, imported, or sold in the Chinese market
• Environmental labeling certification and green printing programs under the HJ 371 series
• Food-contact and sensitive packaging supply chains, where solvent residues must be documented alongside food-contact material requirements
• Export compliance with customer specifications and regional chemical control regulations in the EU, North America, and Asia-Pacific markets
• Verification of tobacco packaging, publications, toys, and children's printed products against stringent customer and industry requirements
• Research, development, and reformulation of low-VOC and solvent-free ink systems
• Incoming quality control of purchased inks and supplier audits by printers and brand owners
• Corporate VOC emission inventories, pollution discharge permits, and cleaner production assessments conducted under frameworks such as GB 37822-2019

FAQ

Which compounds are counted as VOCs in ink testing?

In most regulatory frameworks, VOCs are organic compounds with an initial boiling point at or below 250 °C at 101.3 kPa. In chromatographic practice, all detected volatile components meeting this criterion are summed for the total VOC result, and restricted solvents such as benzene are additionally reported individually.

Which standards govern VOC limits and test methods for printing inks?

In China, GB 38507-2020 sets mandatory VOC content limits by ink category and references GB/T 23986 and GB/T 23985 as core test methods. Internationally, ISO 11890-1 and ISO 11890-2, their European adoption EN ISO 11890, ASTM D3960 and D2369, and US EPA Method 24A are widely used reference procedures. Accredited third-party laboratories select the appropriate method based on the target market and expected VOC level.

Do water-based inks still require VOC testing?

Yes. Water-based inks contain water as the principal carrier but may include alcohols, glycols, glycol ethers, and amine additives that are classified as VOCs. Testing is required to demonstrate conformity with the strict low-VOC limits applicable to the water-based ink category.

How should ink samples be collected and shipped for VOC analysis?

Samples should be taken homogeneously from well-mixed production batches, placed in airtight containers with minimal headspace, kept cool and dark during transport, and analyzed promptly. Careless sampling and storage are the most common sources of falsely low VOC results.

When is the difference method preferred over gas chromatography?

The difference method is suitable for inks with relatively high expected VOC content, where weighing-based determinations of solids and water provide adequate precision. Gas chromatography is preferred for low-VOC products and whenever identification and individual quantification of solvents are required.

What detection capability and turnaround can be expected?

With GC-FID and headspace GC-MS techniques, individual solvents can typically be quantified down to the milligram-per-kilogram range. Standard VOC content determinations are generally completed within five to ten working days after receipt of a valid sample, subject to laboratory workload and the scope of the requested test program.