EMSL: Paul Gassman's Publications

Blake TA, JF Kelly, NB Gallagher, PL Gassman, and TJ Johnson. 2009. "Passive Standoff Detection of RDX Residues on Metal Surfaces via Infrared Hyperspectral Imaging." Analytical and Bioanalytical Chemistry 395(2):337-348. doi:10.1007/s00216-009 Abstract Hyperspectral images of galvanized steel plates, each containing a stain of RDX, were recorded using a commercial longwave infrared imaging spectrometer. Demonstrations of passive RDX chemical detection at areal dosages between 16 and 90 µg / cm2 were carried out over practical stand-off ranges between 14 and 50 m. Efforts to develop better chemical anomaly and target detection through chemometric analyses are described.

Hu Q, P Wang, PL Gassman, and J Laskin. 2009. "In situ Studies of Soft- and Reactive Landing of Mass-Selected Ions Using Infrared Reflection Absorption Spectroscopy." Analytical Chemistry 81(17):7302-7308. doi:10.1021/ac901149s Abstract Grazing incidence infrared reflection absorption spectroscopy (IRRAS) for in situ and in real time characterization of substrates modified by soft- and reactive landing (SL and RL) of complex ions was implemented on a mass-selected ion deposition instrument. Ions produced by electrospray ionization were mass-selected using a quadrupole mass filter and deposited onto inert and reactive self-assembled monolayer (SAM) surfaces. Surface composition during and after ion deposition was monitored using IRRAS. Physisorption of a cyclic peptide, Garmicidin S (GS), was studied for 8 hrs during deposition and additional 12 hrs after the end of deposition. The integrated signal of the characteristic amide bands followed a linear increase during the deposition and stayed unchanged after the deposition was finished. Similar linear increase in IRRAS signal was obtained following reactive deposition of the protonated dodecanediamine onto SAMs of dithiobis (succinimidyl undecanoate) (NHS-SAM) and 16-mercaptohexadecanoic acid fluoride (COF-SAM) on gold. IRRAS allowed us to monitor for the first time the formation of the amide bond between reactive SAM surfaces and the projectile molecule.

Peretyazhko T, JM Zachara, JF Boily, Y Xia, PL Gassman, BW Arey, and WD Burgos. 2009. "Mineralogical transformations controlling acid mine drainage chemistry." Chemical Geology 262(3-4):169-178. Abstract The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed that schwertmannite and goethite were the principal Fe(III) phases in the sediments. Schwertmannite transformation occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The goethite in GB sediments had spherical morphology due to preservation of schwertmannite structure by adsorbed sulfate. Results of chemical extractions showed that poorly-crystallized goethite was subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and AMD waters with different pH and chemical composition. The pH decreased to 1.9-2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiment demonstrated that schwertmannite transformation controlled AMD water chemistry during “closed system” laboratory contact.

Badireddy AR, S Chellam, S Yanina, PL Gassman, and KM Rosso. 2008. "Bismuth Dimercaptopropanol (BisBAL) Inhibits the Expression of Extracellular Polysaccharides and Proteins by Brevundimonas diminuta: Implications for Membrane Microfiltration." Biotechnology and Bioengineering 99(3):634-643. doi:10.1002/bit.21615 Abstract A 2:1 molar ratio preparation of bismuth with a lipophilic dithiol (3-dimercapto-1-propanol, BAL)significantly reduced extracellular polymeric substances (EPS) expression by Brevundimonas diminuta in suspended cultures at levels just below the minimum inhibitory concentration (MIC). Total polysaccharides and proteins secreted by B. diminuta decreased by approximately 95% over a 5-day period when exposed to the bismuth-BAL chelate (BisBAL) at near MIC (12 μM). Fourier-transform infrared spectroscopy (FTIR) suggested that a possible mechanism of biofilm disruption by BisBAL is the inhibition of carbohydrate Oacetylation. FTIR also revealed extensive homology between EPS samples with and without BisBAL treatment, with proteins, polysaccharides, and peptides varying predominantly only in the amount expressed. EPS secretion decreased following BisBAL treatment as verified by atomic force microscopy and scanning electron microscopy. Without BisBAL treatment, a slime-like EPS matrix secreted by B. diminuta resulted in biofouling and inefficient hydrodynamic backwashing of microfiltration membranes.

Badireddy AR, BR Korpol, S Chellam, PL Gassman, MH Engelhard, AS Lea, and KM Rosso. 2008. "Spectroscopic Characterization of Extracellular Polymeric Substances from Escherichia coli and Serratia marcescens: Suppression using Sub-Inhibitory Concentrations of Bismuth Thiols." Biomacromolecules 9(11):3079-3089. doi:10.1021/bm800600p Abstract Free and capsular EPS produced by Escherichia coli and Serratia marcescens were characterized in detail using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Total EPS production decreased upon treatment with sub-inhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount expressed. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, anti-fouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structures in addition to total EPS secretion.

Gallagher NB, PL Gassman, and TA Blake. 2008. "Detection of Low Volatility Organic Analytes on Soils Using Infrared Reflection Spectroscopy." Journal of Near Infrared Spectroscopy 16(3):179-187. doi:10.1255/jnirs.776 Abstract Previous work on detection of low-volatility liquid organic (and organophosphorus) analytes on soil indicated strong signal in FTIR spectra in the 2966–2855 cm-1 range attributed to C–H vibrational stretching modes. This range is the focus of detection strategies examined here as an anticipated prelude to subsequent detection and classification approaches utilizing additional spectral bands. This laboratory study is being used to test detection algorithms that may be useful for rapid standoff detection of organics compounds on soil. Six signal processing methods (designed to minimize irrelevant variability in the recorded soil reflection-absorption spectra while enhancing signal from analyte compounds possibly present on soil) were studied. These included Savitzky-Golay second derivatives, extended multiplicative scatter correction (EMSC), and a novel alternative to piece-wise EMSC. The preprocessed signal was then used for detection. Previous work utilized principal components analysis (PCA) based multivariate statistical process control methodologies for detection. Six alternative anomaly detection statistics were examined here that were based on the preprocessed signal, weighted signal, and generalized weighted signal. The latter statistic can be considered easier than PCA with many of the same benefits. Two tests corresponding to different monitoring strategies were examined: test data ‘local’ and ‘non-local’ to the calibration data. Although the results are expected to be optimistic, the generalized weighted approach worked extremely well for the ‘local’ detection test, but was less successful for ‘non-local’ test. Results suggest that good characterization of analyte-free soil prior to monitoring will lead to the best detection performance. Second derivative preprocessing showed the best results on receiver operator characteristic curves and it’s ease of application is a distinct advantage. However, it may not be universally successful for all bands to be considered in the future. Both EMSC and the novel ‘piece-wise’ EMSC methodology showed promise, but some improvements may be necessary.

Gallagher NB, PL Gassman, and TA Blake. 2008. "Strategies for Detecting Organic Liquids on Soils Using Mid-Infrared Reflection Spectroscopy ." Environmental Science & Technology 42(15):5700-5705. doi:10.1021/es8005404 Abstract Stand-off monitoring for chemical spills can provide timely information for clean-up efforts and mid-infrared reflection-absorption spectroscopy is one approach being investigated. Anomaly and target detection strategies were examined for detection of four different low-volatility organic liquids on two different soil types. Several preprocessing and signal weighting strategies were studied. Anomaly detection for C−H bands was very good using second derivative preprocessing and provided similar performance to target detection approaches such as generalized least squares (GLS) and partial least squares (PLS) with detections at soil loads of approximately 0.6 to 1.5 mg/cm2. Good performance was also found for detection of P=O, O–H and C=O bands but the optimal strategy varied. The simplicity and generality of anomaly detection is attractive, however target detection provides more capability for classification.

Liu Y, Z Yang, Y Dessiaterik, PL Gassman, H Wang, and A Laskin. 2008. "Hygroscopic Behavior of Substrate-Deposited Particles Studied by micro-FT-IR Spectroscopy and Complementary Methods of Particle Analysis." Analytical Chemistry 80(3):633-642. doi:10.1021/ac701638r Abstract The application of Microscopic Fourier Transform Infrared (micro-FTIR) spectroscopy combined with complementary methods of particle analysis is demonstrated here for investigations of phase transitions and hygroscopic growth of micron-sized particles. The approach utilizes the exposure of substrate-deposited, isolated particles to humidified nitrogen inside a sample cell followed by micro-FTIR spectroscopy over selected sample area. Phase transitions of NaCl, sea salt, NaNO3 and (NH)4SO4 particles are monitored with this technique to evaluate its utility and applicability for particle hydration studies. The results are found in excellent agreement with literature data in terms of (a) reliable and reproducible detection of deliquescence and efflorescence phase transitions, (b) quantitative measurements of water-to-solute ratios in particles as a function of relative humidity, and (c) changes in the IR spectra resulting from phase transitions and changing relative humidity. Additional methods of particle analysis are employed to complement and assist in the interpretation of particle hygroscopicity data obtained from micro-FTIR measurements. The analytical approach and the experimental setup presented here are relatively simple, inexpensive, readily available, and therefore may be practical for hydration studies of environmental particles collected in both laboratory and field studies.

Liu G, J Wang, RC Barry, CE Petersen, C Timchalk, PL Gassman, and Y Lin. 2008. "Nanoparticle-Based Electrochemical Immunosensor for the Detection of Phosphorylated Acetylcholinesterase: An Exposure Biomarker of Organophosphate Pesticides and Nerve AgentsOrganophosphate Pesticides and Nerve Agents ." Chemistry - a European Journal 14(32):9951-9959. doi:10.1002/chem.200800412 Abstract A nanoparticle-based electrochemical immunosensor has been developed for the detection of phosphorylated acetylcholinesterase (AChE) adducts, which is a potential exposure biomarker for organophosphate pesticides (OP) and chemical warfare nerve agent exposures. Zirconia nanoparticles (ZrO2 NPs) were used as selective sorbents to capture the phosphorylated AChE adduct, and quantum dots (ZnS@CdS, QDs) were used as tags to label monoclonal anti-AChE antibody to track the immunorecognition events. The sandwich-like immunoreactions were performed among the ZrO2 NPs, which were pre-coated on a screen printed electrode (SPE) by electrodeposition, phosphorylated AChE and QD-anti-AChE. The captured QD tags were determined on the SPE by electrochemical stripping analysis of its metallic component (cadmium) after an acid-dissolution step. Paraoxon was used as a model OP insecticide to prepare the phosphorylated AChE adduct to demonstrate the proof of principle for this sensor technology. The paraoxon-AChE adduct was characterized by Fourier Transform Infrared Spectrum, and the binding affinity of anti-AChE to the paraoxon-AChE was validated with an enzyme-linked immunosorbent assay. The parameters (e.g., amount of ZrO2 NP, QD-anti-AChE concentration,) that govern the electrochemical response of immunosensors were optimized. The voltammetric response of the immunosensor is highly linear over the range of 10 pM to 4 nM paraoxon-AChE, and the limit of detection is estimated to be 8 pM. This new nanoparticle-based electrochemical immunosensor thus provides a sensitive and quantitative tool for biomonitoring exposure to OP pesticides and nerve agents.

Wang Z, JM Zachara, C Liu, PL Gassman, AR Felmy, and SB Clark. 2008. "A cryogenic fluorescence spectroscopic study of uranyl carbonate, phosphate, and oxyhydroxide minerals." Radiochimica Acta 96(9-11):591-598. doi:10.1524/ract.2008.1541 Abstract In this work we have applied liquid-helium temperature (LHeT) time-resolved laser-induced fluorescence spectroscopy (TRLIF) to characterize a series of natural and synthetic minerals of uranium carbonate, phosphate and oxyhydroxides including rutherfordine, zellerite, liebigite, phosphuranylite, meta-autunite, meta-torbernite, uranyl phosphate, sodium-uranyl-phosphate, bequerelite, clarkeite, curite, schoepite and compregnacite, and compared their spectral characteristics among these minerals as well as our previously published data on uranyl silicates. For the carbonate minerals, the fluorescence spectra depend on the stoichiometry of the mineral. For the phosphate minerals the fluorescence spectra closely resemble each other despite the differences in their composition and structure. For all uranium oxyhydroxides, the fluorescence spectra are largely red-shifted as compared with those of the uranium carbonates and phosphates and their vibronic bands are broadened and less resolved. The much enhanced spectra resolution at LHeT allows more accurate calculation of the O=U=O symmetrical stretch frequency, ν1, corresponding to the average spacing of the vibronic peaks of the fluorescence spectra and the spectral origin as reflected by the position of the first vibronic band. It was found that both the average ν1 and λ1 values correlate well with the average basicity of the inorganic anion.