Determination of VOCs (Volatile Organic Compounds) in Solvents and Cleaners by

Gas Chromatography

INTRODUCTION:

The World of Analytical Chromatography involves the Separation of the individual components in a Sample, THEN the measurement of their optical / spectral properties. In the realm of Organic Chemicals, there are VOLATILE (low boiling points, easily evaporated, like most Solvents) Compounds and NONVOLATILE (high BP / MP, usually solid materials, like many drug and plastic chemicals) Compounds. If materials can be VOLATILIZED, or turned into a GAS, then they can be analyzed by Gas Chromatography.

PURPOSE:

With concerns about Air Pollution, the amount of Volatile Organic Compounds present in materials like Paints, Lacquers, Thinners, Cleaners, Removers and other Solvents is being closely regulated by Government standards. You can SMELL these VOCs when you open a bottle of Nail Polish Remover or use Spray Enamel to paint something. By trapping these "vapors" in a sampling bag or vial, we can make an injection into a Gas Chromatograph which will separate the different components and show them as Peaks. Using a set of known, common Solvents used in popular formulations of these types of products; and by preparing Samples by a technique known as "Headspace Sampling", we can easily and accurately measure the amount of VOCs in many materials. This is a simple way to COMPARE different brands of similar products (Nail Polish Removers, Paint Thinners, etc), or to see what differences there are between related products (Paint Brush Cleaners, Adhesive Removers, etc).This experiment will focus more on the QUALITATIVE aspect of analysis, with semi-Quantitative ESTIMATIONS based on relative Peak size. A small, measured amount of Sample is placed in a clean vial and sealed with a high temperature Silicone Rubber "septum" and screw cap.The VIAL is HEATED and any "volatile" compounds in the Sample is "volatilized" from the LIQUID phase into the GASEOUS "headspace" phase.This warm vapor is pulled into a Syringe and injected into the GC for analysis.

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INSTRUMENTS NEEDED:

Model 310 Air-GC system w/ CCD Detector and internal Air Pump INFO/Buy IT!

Computer w/ Peak-Simple Software

INFO/Buy IT!

10 uL Syringe INFO/Buy IT!

SUPPLIES:

1. Set of Known Solvent Standards:

· ALIPHATIC H-Cs - Hexane, Octane

· ALCOHOLS - Methanol, Ethanol, IPA (i-Propanol)

· ESTERS - Ethyl Acetate

· KETONES - Acetone, Methyl Ethyl Ketone (MEK

· HALOCARBON - Methylene Chloride

· AROMATIC H-Cs - Benzene, Toluene and Xylenes.

2. Hot-Plate / Mug Warmer (to heat the Samples)

3. Empty, 40ml. Headspace Vials (to prepare the Samples)

4. Disposable Pipets (for measuring the Samples)

5. Paper Towels (for clean-up)

SAMPLE VIALS OF:

· Paint Brush & Roller Cleaner

· Nail Polish Remover

· Glue & Adhesive Remover

· EXTRA CREDIT Have students bring in other "VOC"-type, "smelly" materials; like non-Flammable Nail Polish Remover, Paint Thinner, Turpentine, "Goo Gone", denatured Alcohol, Wood Lacquer, Oil-Based Enamel Paint, etc.

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