David G. Leddy

Interlaboratory comparison of HPLC-fluorescence detection and GC/MS: analysis of PAH compounds present in diesel exhaust.

For laboratories involved in polycyclic aromatic hydrocarbon (PAH) analyses in environmental samples, it is very useful to participate in interlaboratory comparison studies which provide a mechanism for comparing analytical methods. This is particularly important when PAH analyses are routinely done using a single technique. The results are reported for such an interlaboratory comparison study, in which the four selected participating laboratories quantitatively analyzed several PAH compounds in diesel exhaust samples. The samples included particle and vapor phase extracts collected and prepared at Michigan Technological University (MTU PE and MTU VE, respectively), a diesel particle extract prepared by the National Institute for Standards and Technology (NIST, SRM 1975), and a fully characterized diesel particle sample (NIST SRM 1650). One of the laboratories used only HPLC-FLD, one used only GC/MS and two laboratories used both methods for the routine analysis of PAH in environmental samples. Data were obtained for five PAH compounds: fluoranthene, pyrene, benz[a]anthracene, benzo[a]pyrene, and benzo[g, h,i]perylene. The mean PAH levels found for SRM 1650 were outside the range reported by NIST. The range in the reported means was from 24% lower than certified for benz[a]anthracene to 41% higher for benzo[g,h,i]perylene. For the previously uncharacterized samples in this study (SRM 1975, MTU PE and MTU VE), two-thirds of the reported results were higher for the HPLC-FLD method than for the GC/MS. The range in differences between methods was from-54 to+31% calculated as the difference in GC/MS value relative to the HPLC value for each of the compared compounds. Coefficients of variation for the uncharacterized samples appeared to be higher, in most (but not all) cases, for the HPLC-FLD than for the GC/MS. The resolution of certain PAH isomers (e.g. benz[a]anthracene and chrysene, or the benzofluoranthenes), was better, as expected, for HPLC than for GC. Generally lower detection limits (by an order of magnitude or more) were reported for GC/MS than for HPLC-FLD. On the basis of this limited study, it seems as though significant differences may exist between laboratories, if not between methods, in the analysis of certain PAH compounds in real diesel samples by HPLC-FLD compared to GC/MS. If possible, measurements should be made using both methods. This is particularly important where potential interferences are undefined or subject to change, as is frequently the case with real environmental samples.

Characterization of mutagenic subfractions of diesel exhaust modified by ceramic particulate traps

Protocols were developed for collection and characterization of heavy-duty diesel exhaust hydrocarbons. Dichloromethane extracts of particulate and gaseous-phase samples were partitioned between hexane and methanol, and the highly mutagenic (Ames TA98) methanolic fractions were further separated with reverse-phase HPLC. Twenty-eight polycyclic aromatic hydrocarbons (PAH), including 4-nitro- and 13 oxy-PAH derivatives, were tentatively identified in the active (moderately polar) HPLC fractions with GC/MS. In terms of raw exhaust emissions (milligrams per cubic meter), the use of the ceramic traps caused reduced levels of particulate and associated organic compounds. Total mutagenic activity also decreased with the traps,but to a lesser extent than the decrease in particulate. Many of the identified PAH were common to both the particulate and gaseous-phase samples collected under the same conditions. Calculated hydrocarbon balances showed that more hydrocarbons passed through the samplers when the ceramic traps were used. 46 references, 5 figures, 5 tables.

The Characterization of the Soluble Organic Fraction of Diesel Particulate Matter

This paper is concerned with the demonstration of a methodology for chemically characterizing diesel particulate organic matter (POM) emissions. The procedure begins with a Soxhlet extraction of the POM with dechloromethane to obtain a soluble organic fraction (SOF). The acidic and basic portions of the SOF are isolated by liquid-liquid extraction techniques with aqueous base and aqueous acid, respectively. The neutral portion of the extract is separated into paraffin, aromatic, transitional, and oxygenated fractions by column chromatography on silica gel. Two additional fractions, the ether insoluble and hexane insoluble fractions, are also separated. Quantitative mass data are presented on the extraction and fractionation of twelve particulate samples from the exhaust of a medium-duty diesel engine collected in a dilution tunnel at a volume dilution ration of 8 to 1. Three fuels with a range of properties and two steady-state engine conditions from the EPA 13 Mode Cycle were used as experimental variables.

EFFECT OF FUELS AND DILUTION RATIO ON DIESEL PARTICULATE EMISSIONS

An experimental investigation of the effect of fuel variables and exhaust dilution on diesel particulate emissions from a Caterpillar 3208 direct injection naturally aspirated engine is presented. Three test fuels with widely varying gravity, volatility, aromatic and sulfur content were used. Exhaust dilution was varied from 50 to 1 volume dilution ratio to 1 to 1 (undiluted). Particulate characterization of the total particulates, sulfates, soluble organic fraction, and the fractional break down of the soluble fraction are shown. Both fuel variables and exhaust dilution were shown to have a significant effect on the measured particulate emission levels.

The Characterization of the Hydrocarbon and Sulfate Fractions of Diesel Particulate Matter

One of the most objectionable aspects of the use of diesel engines has been the emission of particulate matter. A literature review of combustion flames, theoretical calculations and dilution tunnel experiments has been performed to elucidate the chemical and physical processes involved in the formation of diesel particulate matter. A comparative dilution tunnel study of diluted and undiluted total particulate data provided evidence supporting calculations that indicate hydrocarbon condensation should occur in the tunnel at low exhaust temperatures. The sample collection system for the measurement of total particulate matter and soluble sulfate in particulate matter on the EPA 13 mode cycle is presented. A method to correct for hydrocarbon interferences in the EPA barium chloranilate method for the determination of sulfate in particulate matter is discussed.

Ceramic Particulate Traps for Diesel Emissions Control - Effects of a Manganese-Copper Fuel Additive

The effect of the use of a manganese-copper fuel additive with a Corning EX-47 particulate trap on heavy-duty diesel emissions has been investigated

Polarography of metal ions in hexamethylphosphoramide

Summary The polarographic behavior of oxygen, halide ions and selected metal ions in HMPA was investigated. Solvation of metal ions was found to be stronger than in water but generally similar to that in dimethyl sulfoxide.

The Effect of Fuel Injection Rate and Timing on the Physical, Chemical, and Biological Character of Particulate Emissions from a Direct Injection Diesel

Formation of pollutants from diesel combustion and methods for their control have been reviewed. Of these methods, fuel injection rate and timing were selected for a parametric study relative to total particulate, soluble organic fraction (SOF), sulfates, solids and NO and NO/sub 2/ emissions from a heavy-duty, turbocharged, after-cooled, direct-injection (DI) diesel. Chemical analyses of the SOF were performed at selected engine conditions to determine the effects of injection rate and timing on each of the eight chemical subfractions comprising the SOF. Biological character of the SOF was determined using the Ames Salmonella/microsome bioassay. 54 refs.

Effects of a Ceramic Particle Trap and Copper Fuel Additive on Heavy-Duty Diesel Emissions

This research quantifies the effects of a copper fuel additive on the regulated [oxides of nitrogen (NO{sub x}), hydrocarbons (HC) and total particulate matter (TPM)] and unregulated emissions [soluble organic fraction (SOF), vapor phase organics (XOC), polynuclear aromatic carbons (PAH), nitro-PAH, particle size distributions, and mutagenic activity] from 1988 Cummins LTA10 diesel engine using a low sulfur fuel. Engine was operated at two steady state modes (EPA modes 9 and 11, which are 75 and 25% load at rated speed, respectively) and five additive levels (0, 15, 30, 60, and 100 ppm Cu by mass) with and without a ceramic trap. Measurements of PAH and mutagenic activity were limited to the 0, 30, and 60 ppm Cu levels. The fuel additive had little effect on baseline emissions (without the trap) of TPM, SOF, XOC, HC, or NO{sub x}. The trap reduced TPM from 72 93% compared to baseline, had no effect on NO{sub x}, and reduced HC about 30% at mode 9 with no consistent change at mode 11. 23 refs., 15 figs., 15 tabs.

THE EFFECTS OF A POROUS CERAMIC PARTICULATE TRAP ON THE PHYSICAL, CHEMICAL AND BIOLOGICAL CHARACTER OF DIESEL PARTICULATE EMISSIONS

Physical, chemical, and biological characterization data for the particulate emissions from a caterpillar 3208 diesel engine with and without Corning porous ceramic particulate traps are presented. Measurements made at EPA modes 3,4,5,9,10 and 11 include total hydrocarbon, oxides of nitrogen and total particulate matter emissions including the solid fraction (SOL), soluble organic fraction (SOF) and sulfate fraction (SO4). Chemical character was defined by fractionation of the SOF while biological character was defined by analysis of Ames Salmonella/microsome bioassay data. The trap produced a wide range of total particulate reduction efficiencies (0-97%) depending on the character of the particulate. The chemical character of the SOF was significantly changed through the trap as was the biological character. The mutagenic specific activity of the SOF was generally increased through the trap but this was offset by a decrease in SOF mass emissions. Some extremely biologically active subfractions were found at mode 4 with the Corning trap. NO2 emissions and HC emissions were generally decreased through the trap. A computer performance model based on membrane filter theory was used to explain the solid particulate filtering efficiency data. The model showed how key variables influence particulate trapping efficiency.