Determination of Formaldehyde in Ambient Air

This application note details how Waters sample preparation products, column chemistries and instrumentation meet or exceed the requirement to sample and quantitate carbonyl compounds. 

Carbonyl compounds are known to promote the formation of photochemical ozone. Short term exposure is known to cause irritation of the skin, eyes, and mucous membrane of the upper respiratory tract. For these reasons, regulatory agencies from around the world are interested in monitoring these compounds. Waters sample preparation products, column chemistries and instrumentation meet or exceed the requirement to sample and quantitate these analytes. The agencies include US EPA, NIOSH, ASTM, ISO, and JPMHLW. There are directives being drafted and testing going on in most countries in the world. 

Sep-Pak DNPH-Silica Cartridges for Analyzing Formaldehyde and Other Carbonyl Compounds in Air

Formaldehyde and other carbonyl compounds are receiving increasing attention both as toxic substances and as promoters in the photochemical formation of ozone in air. Source of aldehydes in residential buildings include plywood and particle board, insulation, combustion appliances, tobacco smoke and various consumer products. Aldehydes are released into the atmosphere in the exhaust of motor vehicles and other equipment in which hydrocarbon fuels are incompletely burned. 

The most sensitive and specific method for analyzing aldehydes and ketones is based on their reaction with 2,4-dinitrophenylhydrazine (DNPH) and subsequent analysis of the hydrazone derivatives by HPLC. The hydrazones may be detected by absorbance in the ultraviolet region, with maximum sensitivity obtained between 350 and 380 nm. 

When carbonyl-containing compounds are adsorbed from air samples onto DNPH silica cartridges they are derivatized according to the following scheme: 

Sep-Pak DNPH-Silica cartridges meet the requirements of EPA Method TO -11A, JPM HLW and ISO 16000 providing a convenient device for sample collection. Using a vacuum pump, an air sample is drawn through the new Sep-Pak DNPH-Silica cartridge. The aldehydes and ketones react with the DNPH and form the hydrazone derivatives, which are retained on the cartridge. Later, the hydrazones are eluted from the cartridge with acetonitrile and analyzed by HPLC or Waters ACQUITY UPLC Technology. Detection limits can be as low as 3 ppbv for a 100 liter sample. 

Advantages of Waters Sep-Pak DNPH-Silica Cartridges

These cartridges provide you with significant advantages when compared to other techniques, such as liquid impingers, for the analysis of aldehydes and ketones. In addition, a new high speed, high resolution UPLC Technology application has been developed to provide excellent quantitation capability in the low parts-per-billion range. 

• Sep-Pak DNPH-Silica cartridges meet the requirements of EPA Method TO-11A and ASTM-D-5791-1. 
• Results from impingers and these cartridges are in excellent agreement.
• Solvent consumption, solvent exposure and hazardous waste disposal costs are reduced. 
• Sep-Pak DNPH-Silica cartridges provide superior convenience and reproducibility, making them ideal for field sampling and process monitoring applications.
• Sep-Pak DNPH-Silica cartridges save time and increase productivity.
• Low background for higher sensitivity. 

Ozone Scrubber Cartridge for Removing Ozone Interference When Monitoring Outdoor Air

Ozone has been shown to interfere with the analysis of carbonyl compounds in air samples that have been drawn through cartridges containing silica-coated with 2,4-dinitrophenylhydrazine (DNPH). Waters Ozone Scrubber cartridges are designed to remove this ozone interference. 

These disposable devices are intended for use in series combination with the Sep-Pak DNPH-Silica cartridges or XPoSure Aldehyde Sampler cartridges. One Ozone Scrubber cartridge replaces the 1⁄4” diameter by 36” long copper ozone denuder located in the heated zone of sampling systems used for outdoor air monitoring (PAMS program). 

Each Ozone Scrubber cartridge contains 1.4 grams of granular potassium iodide. When air containing ozone is drawn through this packed bed, iodide is oxidized to iodine, consuming the ozone, according to the following reaction: 

The theoretical capacity of a single cartridge is 4.2 mmoles of ozone (200 μg). The particle size of the potassium iodide granules is optimized for good mass transfer and flow characteristics. 

XPoSure Aldehyde Sampler Cartridges for Monitoring Aldehydes in Indoor Air

Based on an extension of our DNPH coating technology, XPoSure Aldehyde Sampler cartridges are the most sensitive active samplers available today. 

Highest Sensitivity

Compared to existing sampling tube technology which have high and variable backgrounds, XPoSure™ cartridges are guaranteed to give consistent low aldehyde backgrounds, cartridge-to-cartridge, lot-to-lot. 

High-Collection Efficiencies 

You can achieve > 95% collection efficiencies for all aldehydes at flows of up to a liter per minute. And, you only need to use one cartridge - no breakthrough bed is necessary. 

Low Pressure Drop - Use with Portable Personal Sampling Pumps 

Large particle size and higher porosity frits make this new XPoSure cartridge compatible with personal sampling pumps. 

Easy-to-Use 

Sample, elute and shoot, it’s that easy. You’ll never have to break open and manipulate a glass tube again. And because the cartridges are made from high density polyethylene (HDPE), breakage is not a concern. 

Fast Analyses of Aldehydes and Ketones by ACQUITY UPLC Technology

Aldehydes and ketones can be analyzed as DNPH derivatives rapidly and efficiency using Waters ACQUITY UPLC Technology. Results can be obtained several times faster than conventional HPLC technologies.