1. VOC Content: Regulating Beyond What Can Be Measured?
Valerie Sherbondy, PCS
Technical Manager – Analytical Laboratory Services
KTA-Tator, Inc.

2. The US Environmental Protection Agency defines "Volatile Organic Compounds (VOC)" in:
40 CFR (s)
as:
“any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.”

3. Exempt Solvents – VOC Exempt Compounds
These compounds EPA has classified as negligibly photochemical reactive based on scientific studies, revealing no appreciable contribution to ozone formation.
This list of compounds is established and modified by regulation. The list of exempt compounds is available within EPA’s document 40 C.F.R (s).

4. Both Methods reference other ASTM methods
Standard methods utilized to determine compliance with current US VOC content regulations are:
• EPA Method 24, “Determination of Volatile Matter Content, Water Content, Density, Volume Solids, and Weight Solids of Surface Coatings”
EPA Reference method
• ASTM D3960, “Standard Practice for Determining Volatile Organic Compound (VOC) Content of Paints and Related Coatings”
Both Methods reference other ASTM methods
The EPA allows “any reasonable means of determining the amount of VOC in the coating”; however, Method 24 is the reference method.

5. California’s South Coast Air Quality Management District (SCAQMD)
Rule 1113 for Architectural and Industrial Maintenance coatings recently adapted two methods for measuring VOCs
SCAQMD Method 313 “Determination of Volatile Organic Compounds (VOC) by Gas Chromatography/Mass Spectroscopy (GC/MS)
ASTM D6886 “Standard Test Method for Determination of the Individual Volatile Organic Compounds in Air-Dry Coatings by Gas Chromatography”
SCAQMD Specifies more stringent VOC limits
Maintains it own list of exempt VOCs
Referenced for LEED VOC content limits

6. weight of non-volatiles density percent water percent exempt solvent
ASTM indirect methods for calculating VOC are dependent upon four content determinations:
weight of non-volatiles
density
percent water
percent exempt solvent
Water
VOC =
Volatiles
– Water
– Exempt Solvents
Exempt VOCs
VOCs
Solids

7. Weight of Non-volatiles:
ASTM D2369 Test Method for Volatile Content of Coatings
ASTM D2697 Test Method for Volume Nonvolatile Matter in Clear or Pigmented Coatings
ASTM D5095 Test Method for Determination of the Nonvolatile Content in Silanes, Siloxanes and Silane-Siloxane Blends Used in Masonry Water Repellent Treatments .

8. Weight of Non-volatiles (continued):
ASTM D5403 Test Methods for Volatile Content of Radiation Curable Materials
ASTM D6093 Test Method for Percent Volume Nonvolatile Matter in Clear or Pigmented Coatings Using a Helium Gas Pycnometer
ASTM D6419 Test Method for Volatile Content of Sheet-Fed and Coldset Web Offset Printing Inks

9. However, EPA Method 24 specifies only:
ASTM D5403 for Radiation Curable Materials
ASTM D2369 for water- or solvent-borne coatings

10. Density
The density is the mass per volume
Measured by method
ASTM D1475, “Test Method for Density of Liquid Coatings, Inks, and Related Products.”

11. Percent Water
The two options for determining the percent water content are:
•ASTM D4017 Test Method for Water in Paints and Paint Materials by Karl Fischer Method
•ASTM D3792 Test Method for Water Content of Coatings by Direct Injection Into a Gas Chromatograph

12. Percent Exempt Solvent -ASTM D3960 specifies several methods:
•ASTM D4457 Test Method for Determination of Dichloromethane and 1,1,1-Trichloroethane in Paints and Coatings by Direct Injection into a Gas Chromatograph
•ASTM D6133 Test Method for Acetone, p-Chlorobenzotrifluoride, Methyl Acetate or t-Butyl Acetate Content of Solventborne and Waterborne Paints, Coatings, Resins, and Raw Materials by Direct Injection Into a Gas Chromatograph
•ASTM D6438 Test Method for Acetone, Methyl Acetate, and Parachlorobenzotrifluoride Content of Paints, and Coatings by Solid Phase Micro extraction-Gas Chromatography

13. EPA Method 24 specifies only
ASTM D4457 for determination of the total exempt solvent content.

14. VOC Calculation :
VOC = (Wv)(Dc)
100 %
where:
Wv = weight of total volatiles, %, (100% - weight % solids)
Dc = density of the coating, g/L

15. The formula is more involved for coatings that contain water and exempt solvents:
VOC = (Wo)(Dc)
100 % - Vw – Vex
= (Wv – Ww – Wex) (Dc)
100 % - (Ww)(Dc/Dw) – (Wex)(Dc/Dex)

16. Wo=weight of organic volatiles,%
Where:
Wo=weight of organic volatiles,%
Wv=weight of total volatiles, %, (100% - weight % solids)
Ww=weight of water, %
We=weight of exempt volatile compound, %
Vw=volume of water, %, (Ww) (Dc/Dw)
Vex=volume of exempt volatile content, %, (Wex) (Dc/Dex)
Dc=density of the coating, g/L
Dw=density of water, g/L
Dex=density of exempt volatile compound, g/L

17. Determination of Confidence Interval for VOC
Intra-laboratory Precision from ASTM reproducibility statements
Percent Volatile Content
Density
Percent Water
Individual Exempt Solvents
Total Solvent
ASTM D2369
ASTM D1475
ASTM D4017
ASTM D3792
ASTM D6133
ASTM D6438
ASTM D4457
ASTM D6886
Waterborne
100% Solids
Solventborne
1.8%
5.5%
5.0%
12.4% PCBTF -15.6%t-butyl acetate
0.4%
0.25%
7.5% %
1.84%
4.46%
5.31%

19. Therefore for the example:
Coating Product that has a theoretical VOC of:
120.7 g/L
95 of 100 values (95%) will be between:
67.1 to g/L

20. Other sources of error
Non-volatile content
Water can remain in some samples even after heating.
Karl-Fisher Water content
Titration is pH sensitive
Certain metal oxides (e.g. Zn oxides) can interfere
Aldehydes and ketones can react with water and reagents
Different coatings have different solubility in different solvents

21. Other sources of error (continued)
GC determination of Water Content
Certain paints can trap water within the pigment or resin.
GC determination of Exempt Solvents
Elution time is dependent on boiling point and affinity to column.
Certain coalescents, colorants and additives can cause false positives.
Both issues resolved by Mass Spec identification

22. What does the laboratory do?
We work with our clients to review SDS or other formulation information
Select testing methods based on specific product
Select test parameters based on specific product

23. Some current regulations require a maximum VOC content of :
100g/L
With increasing stringency on VOC
some coating products in areas of the country may be regulated to:
50 g/L

24. What options can the industry provide to coating suppliers for accurately determining compliance to current and future VOC regulations?

25. Current industry method development includes:
an emphasis on the direct identification and quantification of solvents
and specific and applicable parameters of testing based upon the solvent system in the coating, (hydrocarbon vs. water)

26. The current revised ASTM D6886-14e1 standard does provide reproducible results for coatings:
air-dry
with low VOC content
moderate to low solids.

27. The U.S. EPA has agreed to:
accept ASTM D 6886, GC Method for low-VOC waterborne coatings as an alternative method for VOC content determination

28. Modification of EPA Method 24 to include specific determinations based upon coating composition with:
high solids
minimal regulated solvents
still required to meet the challenges of imposed regulations.

29. Some additional options for industry supported change may include:
consideration of new instrumentation or methodology that allows for the direct measurement of VOC content (not based upon calculation of several constituent components)
allowance of additional exempt solvents
levels of exemption for solvents to be included in VOC content determinations
proposed reactivity ratings of solvents in order to standardize conditions for percent volatile content calculations.