Eugene F. Barry

Atmospheric deposition of polycyclic aromatic hydrocarbons near New England coastal waters

Wet and dry deposition of polycyclic aromatic hydrocarbons (PAHs) was measured at Nahant, Massachusetts, a peninsula jutting into Massachusetts Bay and Wolf Neck, a peninsula jutting into Casco Bay, Maine. Wet deposition (rain and snow) was collected in a funnel which drains into a shielded, temperature controlled receiving bottle. Dry deposition of gaseous and particulate PAHs was collected onto an exposed water surface. PAHs were analyzed by solid phase extraction and gas chromatography-mass spectrometry. Sixteen PAH species were analyzed, ranging from acenaphthylene to coronene. The mean wet deposition rate of the sum of the 16 species is 720 ng m � 2 cm � 1 precipitation at Nahant, and 831 ng m � 2 cm � 1 precipitation at Wolf Neck. Wet deposition is attributed to regional PAH emitting sources. Storm patterns appear to bring somewhat higher wet deposition of PAHs to Wolf Neck than to Nahant. The mean dry deposition rate is 95 ng m � 2 h � 1 at Nahant and 9.3 ng m � 2 h � 1 at Wolf Neck. The large difference is attributed to the fact that Nahant is close to the urban-industrial metropolitan Boston area and Logan International Airport, whereas Wolf Neck has no major PAH-emitting sources nearby. Individual measurements have an error bracket of 730%. The Chemical Mass Balance model was used to apportion the dry deposition to source categories. At Nahant, nine samples gave valid statistical attributes with a mean apportionment: jet exhaust 35%, gasoline fueled vehicles 32%, diesel fueled vehicles 17%, wood combustion 13%, others 3%. At Wolf Neck, six samples yielded a mean apportionment: jet exhaust 30%, gasoline vehicles 28%, diesel vehicles 18%, wood combustion 16%, others 8%. There is a considerable variation between the samples. The apportionment is greatly dependent on the quality and selection of the model inputs, i.e. source signatures, which for PAHs are questionable. r 2001 Elsevier Science Ltd. All rights reserved.

Use of transition metal chlorides as salt modifiers in gas-solid chromatography

Abstract This work focuses on the modification of silica gel with several transition metal salts. The chlorides of Mn(II), Co(II) and Zn(II) were employed as modifiers. The gas-solid chromatographic behavior of several alkanes, alkenes and aromatic sorbates is discussed in terms of sorbate-sorbent interactions and is compared to their interaction with unmodified silica gel. Salt modification adds another dimension to column parameters which may be varied to achieve selective analytical separations.

Determination of grinding aids in portland cement by pyrolysis gas chromatography-mass spectrometry

Abstract The pyrolysis of Portland cement followed by gas chromatography/mass spectrometry is described for the determination of chemical additives interground with cement clinkers known as grinding aids. This technique, coupled with in situ derivitization using BSTFA-TMCS reagent, has been found to be readily applicable for detecting phenol, along with five glycol and alkanolamine-type compounds in cement. The recovery rate was found to be highly dependent upon the grinding process and the binding capacity of the various additives. Using a relatively short grinding process conducted at ambient temperature, most of the additives tested can be recovered at greater than 85% of their originally added concentration. However, in the case of a longer, more intense grinding procedure conducted at 105°C, only phenol had recovery rates greater than 50%. The formation of salts or stable complexes between the grindings aids and cations at the freshly fractured cement surfaces, is proposed as the major cause of the variable recovery rates for the various grinding aid compounds.

Response prediction of the thermal conductivity detector with light carrier gases

Abstract In gas chromatography the response of thermal conductivity detectors is dependent on the physical properties of the solute. This investigation determined that signal strengths represented as relative molar response factors can be calculated from the critical properties of both the chromatographic fraction and a carrier gas of low molecular weight. The approach suggested by L ittlewood has been adopted and appropriately modified with the incorporation of a molecular weight term. The equation is applicable to both polar and non-polar compounds when helium or hydrogen are carrier gases. More significantly, the decrease in response with increased molecular symmetry for isomeric compounds is accurately predicted.

Determination of organotin species by capillary gas chromatography with alternating current plasma emission detection

Abstract An alternating current plasma (ACP) emission detector is used as a detector for capillary gas chromatography (GC) in the determination of organotin compounds in environmental marine samples. Detection limits for tributyltin chrloride (TBT) and tetrabutyltin (TEBT) were found to be 131 and 116 pg/s (as Sn), respectively. Calibration curves exhibited linearity over three orders of magnitude. Precision was found to be less than 8.5% relative standard devision ( n = 10) for both TBT and TEBT. Results for the separation and detection of organotin compounds in complex sample matrices are presented to illustrate the selectivity of the ACP emission detector. No prior hydride formation or alkylation reactions were performed on the organotin species prior to gas chromatographic detection. Recovery data ranged from 77 to 100%. The results obtained in this study demostrate the variability, selectivity and ease of use of the GC-ACP detector for the determination of organotin compounds.

Novel pyrolysis-gas chromatography/mass spectrometric techniques for the characterization of chemical additives in portland cement and concrete

Abstract The application of pyrolysis gas chromatography mass spectrometry (py-GC/MS) has been improved for the determination of chemical additives that are either interground with cement clinker during the manufacture of Portland cement or admixed with a mixture of cement, sand, and stone, and water for the production of concrete. This technique has been found to be readily applicable for phenol-based cement grinding aids and naphthalene sulfonate formaldehyde condensate (NSFC)-based concrete admixtures. Furthermore, pyrolytic decomposition of a nitrite-based corrosion inhibitor incorporated into a concrete mixture was found to produce abundant dinitrogen oxide (N 2 O), a unique indicator of the nitrite additive. Volatile methyl esters of fatty and rosin acid-based air entraining agents can be formed from the pyrolysis of powdered concrete treated with methanolic tetramethylammonium hydroxide (TMAH). Overall, the py-GC/MS analysis of cement and concrete has the potential to be far more specific and less tedious than the common extraction-spectroscopic based methods currently used. In-situ pyrolytic reactions can further expand the capability of py-GC/MS by volatilizing otherwise thermally stable or strongly adsorbed additives in cement and concrete.

Evaluation of an alternating current plasma emission detector for high-performance liquid chromatography

Abstract The details of construction and operation of an alternating current plasma (ACP) detector supported with helium gas for reversed-phase high-performance liquid chromatography is described. The system is evaluated as a selective detector for the determination of organomercury compounds. The chromatographic eluent is introduced into the plasma by means of a frit nebulizer and the plasma can tolerate the nebulization of 100% methanol without extinguishment. Detection limits of methylmercury chloride and ethylmercury chloride were found to be 4.5 and 2.2 ng Hg/sec, respectively. In the nanogram to microgram mass range studied the precision was found to be less than 10% (relative standard deviation). The deduction of organomercurials in complex sample matrices elustrates the selectivity of the ACP detector.

Determination of (methylcyclopentadienyl)manganesetricarbonyl in gasoline by capillary gas chromatography with alternating current plasma emission detection

Abstract (Methylcyclopentadienyl)manganesetricarbonyl (MMT) commonly used as an antiknock agent in gasoline is determined by capillary gas chromatography with an alternating current plasma (ACP) detector. The ACP selectivity, the ratio of the peak area response of MMT per gram Mn to the peak area response for a hydrocarbon per gram of carbon, was found to exceed five orders of magnitude. Detection limits for MMT and a closely related organomanganese analyte, bis(pentamethylcyclopentadienyl)manganese (BPM), were calculated to be 62 and 69 pg/s (as Mn), respectively. Precision of the methodology was 6.6% relative standard deviation ( n = 10) for both MMT and BPM.

Thermodynamic study of a liquid crystal as a liquid phase in gas—liquid chromatography II. A cholesteric liquid crystal

Gas-liquid chromatography is utilized for the determination of thermodynamic solution parameters for various organic solutes at infinite dilution in the meso- and isotropic phases of cholesteryl palmitate. The thermodynamic data and trends in values of the activity coefficients for the solutes are discussed in relation to their structure and to the orientations of the liquid crystal.

A molecular property approach for the response prediction of the thermal conductivity detector

Abstract The response of the gas chromatographic thermal conductivity detector has been correlated with the physical properties of the solute. In this investigation we have determined that detector response represented as relative molar response factors can be accurately predicted from the critical constants, thermal conductivity coefficient and molecular weight of both the chromatographic fraction and the carrier gas. The “molecular diameter” approach has been employed in conjunction with appropriate thermal conductivity and molecular weight terms which appear in our relative molar response equation. This expression is applicable to polar and non-polar compounds when helium, hydrogen, and nitrogen are carrier gases.