Keith L. Olson

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.

Characterization of additives in plastics by liquid chromatography-mass spectrometry

Abstract Additives in plastics, separated by liquid chromatography (LC), were characterized and identified with a tandem detection system which consisted of an

Combination of photocatalysis and HC/SCR for improved activity and durability of DeNOx catalysts.

A photocatalytic HC/SCR system has been developed and its high deNOx performance (54.0-98.6% NOx conversion) at low temperatures (150-250 °C) demonstrated by using a representative diesel fuel hydrocarbon (dodecane) as the reductant over a hybrid SCR system of a photocatalytic reactor (PCR) and a dual-bed HC/SCR reactor. The PCR generates highly active oxidants such as O3 and NO2 from O2 and NO in the feed stream, followed by the subsequent formation of highly efficient reductants such as oxygenated hydrocarbon (OHC), NH3, and organo-nitrogen compounds. These reductants are the key components for enhancing the low temperature deNOx performance of the dual-bed HC/SCR system containing Ag/Al2O3 and CuCoY in the front and rear bed of the reactor, respectively. The OHCs are particularly effective for both NOx reduction and NH3 formation over the Ag/Al2O3 catalyst, while NH3 and organo-nitrogen compounds are effective for NOx reduction over the CuCoY catalyst. The hybrid HC/SCR system assisted by photocatalysis has shown an overall deNOx performance comparable to that of the NH3/SCR, demonstrating its potential as a promising alternative to the current urea/SCR and LNT technologies. Superior durability of HC/SCR catalysts against coking by HCs has also been demonstrated by a PCR-assisted regeneration scheme for deactivating catalysts.

Tests for fluorocarbon and other organic vapor release by fluorocarbon film bags

Tests were performed on several bags made from fluorinated ethene-propene copolymer film, commonly referred to as FEP-Teflon, to see if they release fluorocarbon vapors, as was recently reported by others. Special attention was given to determining if tetrafluoroethene and hexafluoropropene, the monomer units used to synthesize the film, were released. By use of an instrument that measured total gas-phase carbon, it was determined that at most 0.06 ppm of C of non-methane organic contamination was released into bags of clean air stored outdoors for up to 2 days. A more sophisticated technique was used to confirm that neither of the two precursor fluorocarbons was released into the bag at concentrations above the detection limit of approx.25/sup 0/C in a room as well as one stored in an irradiated chamber at 30-40/sup 0/C. These findings are contrary to those recently reported by another group who found large releases of fluorocarbon contaminants, especially hexafluoropropene, from similar bags. We conclude that no all FEB-Teflon film releases fluorocarbon vapors.

Evaluation of a High Speed, High Resolution Gas Chromatography Instrument for Exhaust Hydrocarbon Speciation

The ozone forming potential (OFP) and specific reactivity (SR) of tailpipe exhaust are among the factors that determine the environmental impact of a motor vehicle. OFP and SR measurements require a lengthy determination of about 190 non-methane hydrocarbon species. A rapid gas chromatography (GC) instrument has been constructed to separate both the light (C2 -C4) and the midrange (C5 - C12) hydrocarbons in less than 10 minutes. The limit of detection is about 0.002 parts per million carbon (ppmC). Thirty exhaust samples from natural gas vehicles (NGVs) were analyzed to compare the rapid GC method with the standard GC method, which required 40-minute analyses on two different instruments. In general, evaluation of the commercial prototype from Separation Systems, Inc., indicates that a high speed, high resolution gas chromatograph can meet the need for fast, efficient exhaust hydrocarbon speciation. Recommended improvements to the rapid GC include a trap to remove carbon dioxide and water vapor, which interfere with the light-hydrocarbon analysis. Suitable gas standards for calibrating the flame ionization detectors and incomplete recovery of the heaviest midrange hydrocarbons are other issues that require further consideration.