Andrew G. Sharkey

Determination of sulfur forms on coal surfaces by X-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy (XPS or ESCA) was used to monitor changes in the amount of organic and pyritic sulfur, and inorganic sulfur present on coal surfaces following hydrochloric and nitric acid treatments. The results show that after treatment with HCl the oxidized sulfur was totally removed from the surface. Subsequent leaching with HNO 3 decreased the atomic abundance of sulfide forms on the coal surface.

A quantitative study of in vitro hepatic metabolism of tacrolimus (FK506) using secondary ion and matrix-assisted laser desorption/ionization mass spectrometry.

The identification and simultaneous quantification of Tacrolimus and its hepatic metabolites in baboons has been achieved using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry and static secondary-ion mass spectrometry (TOF-SIMS). Little fragmentation, high sensitivity and tolerance to contamination are the major advantages of these methods, allowing facile identification and quantification of metabolites produced in vitro with minor analyte isolation. Based on the MALDI and TOF-SIMS results, seven metabolites have been identified: de-methylated, di de-methylated, hydroxylated, di hydroxylated, de-methylated hydroxylated, dihydrodiol, and di de-methylated hydroxylated. The concentrations of the parent drug and its major metabolites (e.g. de-methylated, di de-methylated) were measured using Rapamycin as an internal standard. The time course of Tacrolimus and its major metabolites as a function of incubation time was calculated. Good correlation between SIMS and MALDI results was obtained.

Effect of Grinding Conditions on the Performance of a Selective Agglomeration Process for Physical Coal Cleaning

Abstract An extensive experimental study was conducted to investigate the effect of grinding conditions on the performance of a selective agglomeration process using n-pentane as agglomerant. Upper Freeport, Pittsburgh # 8, and Illinois # 6 coal samples were dry and wet ground to 28 mesh × 0 and 200 mesh × 0 particle sizes using a pulverizer, a ceramic jar mill, and a specially designed stirred-ball mill. The ground ;, samples were subjected to a standardized agglomeration test procedure using a Waring blender as the agglomeration unit. The effects of various operating variables, such as n-pentane to coal ratio, slurry concentration, mixing speed, and agglomeration time on energy recovery and ash rejection were statistically evaluated. The agglomeration test data showed dramatic differences between wet and dry grinding methods and between 28 mesh × 0 and 200 mesh × 0 particle sizes. Grinding to 200 mesh × 0 resulted in higher energy recoveries. Moreover, 200 mesh × 0 particle size obtained with wet grindi...

Investigation of porphyrins and metalloporphyrins by liquid matrix-assisted laser desorption mass spectrometry

Laser desorption mass spectrometry with liquid matrix-assistance has been used to study a series of selected porphyrins and metalloporphyrins. This work presents the results of using a liquid matrix with fibrous material as the substrate for liquid matrix assisted laser desorption of porphyrins and metalloporphyrins. The liquid matrices used for porphyrin studies were o-nitrophenyl octyl ether (NPOE) and 15-crown-5. The use of a liquid matrix with soft laser ionization enhances molecular ion formation. We also have investigated the use of NPOE as a liquid matrix for identifying mixtures of up to six porphyrins in a single shot spectrum without prior separation. The (M + H)+ peak of each metalloporphyrin component in the mixture is clearly indicated in the spectra and no obvious interference effects were observed.

Use of a nitrocellulose matrix in laser mass spectrometry

SummaryA simple method for obtaining laser mass spectra (LMS) of liquids is described using a nitrocellulose membrane or fibrous material as the sample substrate. Laser mass spectra of liquids are presented along with those of solutes in aqueous systems. The use of a liquid matrix with the laser soft ionization method enhances molecular ion formation. Results are presented for charge-transfer derivatization and the influence of solution pH on LMS.

Laser Mass Spectrometry of Organophosphorus Pesticides and Related Compounds

Abstract Laser mass spectra obtained for 20 organophosphorus (OP) compounds were systematically evaluated for groups containing analogous structural features. Variations in fragmentation can be understood based on simple organic reactions. While detailed mechanistic interpretations of the laser mass spectra (LMS) were not possible, the qualitative features in the LMS obtained from five compounds, not in the original set, could be predicted based on the characteristics of the other OP compounds studied. The success of the prediction lends credence to the qualitative models developed for rationalizing the LMS. A specific feature in the LMS of aromatic thionophosphates is a thiono-thiolo rearrangement. Detailed investigation into the phenomena involved comparison of LMS obtained from aromatic thionophosphates with spectra from electron impact, chemical ionization, field desorption, and secondary ion mass spectrometry. These results led to the conclusion that the rearrangement in laser mass spectrometry must ...

Study of cationization of saccharides by laser mass spectrometry

SummaryMetal ions introduced in the +1 oxidation state are better for the cationization of saccharides than cations in other oxidation states. This effect is related to the ease of formation of singly charged adduct ions by reaction with singly charged metal ions. Sample preparation had little effect on the reproducibility of the spectra. Use of a nitrocellulose matrix can introduce competition between the matrix and saccharide for cations, leading to lower ion intensities. The concentration of the salt and saccharide had little effect on cationization signal intensity once a threshold concentration was exceed: 0.1 M metal ion and 0.5 M saccharide.

Determination of Water Loss Mechanism in Amine Terminous Amino Acids Using Laser Mass Spectrometry

The water loss process in Laser Mass Spectrometry of amine terminal amino acids was studied. Water loss is proposed to occur via a thermal decomposition mechanism for a protonated amino acid forming a protonated lactam ring. The magnitude of the water loss peak is correlated with the stability of the protonated lactam ring. Semi-empirical MNDO calculations of the heat of reaction of a protonated amino acid forming a protonated lactam ring and water support the correlation. The substrate (matrix) appears to have little effect on the process; results are essentially the same with the use of different substrates and sample preparation methods.

A freshwater bioprobe: Periostracum of the Asian Clam, Corbicula fluminea (Müller) combined with laser microprobe mass spectrometer.

A freshwater bioprobe, combining the Asiatic Clam, Corbicula fluminea (Müller) and the laser microprobe mass spectrometer (LAMMA), can determine anthropogenic chemical contamination of freshwater systems. Laser generated mass spectra from the periostracal layers of clams contaminated with either a salt, potassium bromide, or an aromatic compound, phenol, produce distinctive mass spectral signatures that are different from uncontaminated clams. Uncontaminated clams have characteristic signatures with distinctive spectral peaks less than m/z 41; while exposed clams have many strong peaks well above this m/z. This freshwater bioprobe, using LAMMA to analyze the surface of clams, can be used as a screening tool for monitoring the water-treatment systems, for determining the source of contaminated baseflow and return flow discharge to streams, and for monitoring the water chemistry of a body of water. This system exploits the facility of using the shell instead of soft tissue with the LAMMA and has potential to detect anthropogenically-derived chemical stress.