Stephen J. Swarin

Determination of Formaldehyde and Other Aldehydes in Automobile Exhaust with an improved 2, 4-Dinitrophenylhydrazine Method

Abstract An improved, simple and rapid method for the determination of formaldehyde and other aldehydes in automobile exhaust was developed. Sample collection and derivatization are performed directly in a midget impinger containing an acetonitrile solution of 2,4-dimitrophenylhydrazine and catalyst. This scheme eliminates the time-consuming and lengthy recovery steps required in other procedures and allows direct injection of an aliquot of the sample into a high-performance liquid chromatograph for analysis. Detection limits for formaldehyde, acetaldehyde, acrolein and benzaldehyde are 20, 10, 5 and 4 ppb*, respectively, for a 20-l exhaust sample. The analysis time is as short as 10 min if only formaldehyde and acetaldehyde are of interest. The technique was used to measure aldehyde emissions from ethanol-, gasoline- and diesel-fueled vehicles.

Determination of aldehydes and ketones by derivatization and liquid chromatography-mass spectrometry

Abstract A method for determining nanogram amounts of carbonyl compounds was developed. Carbonyl compounds were collected as their 2,4-dinitrophenylhydrazine derivatives, and the derivatives were analyzed by high-performance liquid chromatography—mass spectrometry (HPLC—MS) via a moving-belt interface. The method employed reversed-phase gradient LC on 2 mm I.D. columns and methane chemical ionization. Negative ion mass spectra were recorded to distinguish aldehydes from ketones. The analysis of engine exhaust, vapors from decomposed polymers, and liquid soaps illustrate three applications for LC—MS: confirmation of identifications made by LC, determination of compounds in unresolved chromatographic peaks, and characterization of unidentified LC peaks.

Determination of Formaldehyde and Other Aldehydes by High Performance Liquid Chromatography with Fluorescence Detection

Abstract A sensitive, uncomplicated, and rapid method for the determination of formaldehyde and other aldehydes has been developed. The method is based on the reaction of the aldehyde species with 2-diphenylacetyl-1,3-indandione-1-hydrazone to form fluorescent azine derivatives. The fluorescence excitation and emission spectra have been obtained for several derivatives. The method developed eliminates the lengthy recovery steps required in other methods by performing the sample collection and derivatization directly in midget impingers containing an acetonitrile solution of the reagent. High performance liquid chromatography with fluorescence detection is used to separate and quantitate the individual aldehydes. The detection limits for formaldehyde, acetaldehyde, acrolein, and benzaldehyde are 6 ppb, 4.5 ppb, 0.6 pb, and 0.15 ppb, respectively, in the exhaust gas. The analysis time for the method is about 10 minutes if only one or two aldehydes are of interest. This technique has been used to measure ald...

Liquid Chromatographic Determination of Azide as the 3,5-Dinitrobenzoyl Derivative

Abstract A method for the determination of azide after conversion to 3,5-dinitrobenzoyl azide has been developed. The derivatization reaction is fast (3 min.), quantitative, and yields a product with strong ultraviolet absorption. The derivatization reaction mixture is separated by high performance liquid chromatography so that the azide derivative can be easily quantitated. The detection limit of the method is 10 ng NaN3/mL. The total analysis time is 20 minutes per sample.

Combined thermogravimetric and infrared analysis of polymers

Abstract The techniques of thermogravimetry and infrared spectroscopy have been combined in a unique method to provide quantitative and qualitative analyses of polymers. The amounts of additives, polymers, carbon black, and inorganic fillers are determined by thermogravimetry, and the additives and polymers are identified by infrared spectroscopy, all in one set of experiments. The method involves condensing the effluent from the thermogravimetric analyzer in replaceable glass tubes for transport to the infrared spectrometer. The method is illustrated with thermogravimetric and infrared analysis data for a Hypalon fuel hose and for a fluorosilicone fuel gasket. The main advantage of the method is the ability to collect as many separate fractions of the thermogravimetric effluent as required to identify the minor and major components of a polymer.

A Method for Determining Reaction Kinetics by Differential Scanning Calorimetry

Knowledge of the degree of cure and the optimum molding conditions of thermosetting materials is important for molding good parts using minimum processing time. From the practical point of view, analytical data in the form of isothermal composition curves (concentration or percent cured vs. time) are the most valuable. These curves are used by the processor to determine the temperature and time required for a particular degree of cure. A number of experimental techniques and studies relating to thermosetting cure reactions have been reported in the literature with emphasis on the chemical, physical, and mechanical property changes with time at constant temperature. These methods have recently been enumerated by Sourour and Kamal (1). However, these traditional methods use the approach of measuring a particular chemical, physical, or mechanical property of a large number of molded parts which have been cured under different conditions of time and temperature. While this approach does lead to the desired isothermal composition curves, it requires a long time period during which valuable production equipment is tied up before the „optimum“ cure conditions can be found.