Sampling for Selected Aldehyde and Ketone Emissions from Stationary Sources
This method provides procedures for the collection and analysis of free carbonyl compounds (aldehydes and ketones) from stationary sources by derivatization with 2,4-dinitrophenylhydrazine (DNPH). The method is specifically referenced for the determination of the destruction and removal efficiencies of five aldehydes and ketones. The five analytes for which the method is validated are: acetaldehyde, acetophenone, formaldehyde, isophorone and proprionaldehyde. Note that the method does state the procedures is applicable for other aldehydes and ketones (see the analyte list for those analytes specifically referenced in the method). However, the method does note it is NOT applicalbe for quinone, methyl ethyl ketone, acrolein and methyl isobutyl ketone.
Samples are collected isokinetically using a modified Method 5 train which consists of a probe and a series of impingers. DNPH reagent is added to the first three impingers, the fourth impinger is empty and the fifth impinger contains silica gel. The DNPH reagent derivatizes the aldehydes and ketones in the gas stream. The probe, first three impingers and connecting glassware are rinsed with a minimal amount of methylene chloride followed by a water rinse. All yellow color should be removed from the impingers. The contents of the first three impingers can be combined along with the rinses unless a breakthrough check is needed. If a breakthrough determination is needed, the impinger contents and rinses of the first two impingers must be kept separately.
The impinger contents and rinses are extracted, solvent exchanged to acetonitrile and analyzed using high performance liquid chromatography (HPLC) with ultraviolet/visible (UV/vis) detection to identify and quantitate the target analytes.
Before use in the field, the DNPH reagent needs to be analyzed to ensure it has acceptable background levels of contaminants. Formaldehyde and acetone are common components. There are strict time frames specified for the preparation and use of the DNPH reagent. The reagent needs to be used within 5 days of preparation and within 48 hours of opening the sealed container in the field.
Acetone is a commonly used as a train glassware rinse when using a Method 5 train for particulate or SVOC collection. Since acetone is a contaminant of the DNPH reagent used in this method and can cause a high bias for formaldehyde results, it is especially important that all probes and glassware is thoroughly cleaned and baked (if necessary) prior to use with this method.
Quality Assurance/Quality Control samples required by the method include a field spike sample, a sample blank and a matrix spike samples. The field spike sample requires that a spike of formaldehyde info an impinger containing DNPH reagent. The impinger contents are recovered at the same time and in the same manner as the field samples. This is to serve as a check of the sample handling and recovery. The sample blank consists of a portion of DNPH reagent and methylene chloride used in sample recovery. The matrix spike consists of a fourth train collected during the same time or collocated (simultaneously), if possible, with the field samples. This matrix spike should contain the same level of analytes as found in the field samples and spiked after collection. If you have a compliance project, you should collect this sample unless your regulatory allows you to disregard it.
Appendix A of the method allows for the determination of particulates during the sampling run. The method suggests adding the filter between the second and third impingers.