Mark Tracy | Northeastern University (original) (raw)

Papers by Mark Tracy

Drug Delivery and Translational Research, Jan 29, 2014

Drug Delivery and Translational Research, 2013

This work describes a liquid chromatography method for determination of perfluorooctanoic acid (P... more This work describes a liquid chromatography method for determination of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in water samples. The method incorporates on-line sample concentration, reversed-phase HPLC using Acclaim ® PolarAdvantage II (PA2) columns for both and suppressed conductivity detection. For tap water samples, the LOD and LOQ are expected to be 1 µg/L and 3 µg/L, respectively, for both PFOA and PFOS. The dynamic range is 1 to 40,000 µg/L.

Lcgc Asia Pacific, Dec 1, 2007

Anionic surfactants are widely used in a variety of applications, such as formulations for laundr... more Anionic surfactants are widely used in a variety of applications, such as formulations for laundry detergents, shampoos, hand soaps,and pesticides. HPLC is the preferred technique to determine anionic surfactants in mixtures. Very often, analysis of anionic surfactants is performed by reversed-phase (RP) chromatography using a C18 or C8 column. In this mode, all compounds are separated according to increasing hydrophobicity. Depending on the surfactant of interest, detection is by ultravioletvisible (UV), refractive index (RI), evaporative light scattering detection (ELSD), mass spectrometry (MS), or suppressed conductivity. UV detection is most useful for compounds with phenyl rings, while ELSD can be used to determine most non-volatile compounds. However, many anionic surfactants lack a chromophore. Moreover, analysis can be complicated as a result of interferences from complex matrices, so that the use of UV and ELSD is limited. Conductivity detection in suppressed mode provides excellent selectivity and sensitivity for ionic species, making it suitable for trace level analysis and sample detection in complex matrices. We report herein a methodology for HPLC analysis of anionic surfactants using a new RP silica column and suppressed conductivity detection on a newly developed liquid chromatography system. The new column features unique selectivity, enhanced hydrolytic stability, compatibility with IC mobile phases, and superior efficiency compared to its polymeric counterparts, facilitating separation of a broad variety of anionic surfactants. In this paper, we will discuss various aspects in method development, including stationary phase, instrumentation, mobile phase selection, linearity, and limit of detection. In addition, analyses of several formulated commercial products will be presented using the new method.

Environmental concerns regarding explosives stem from the mutagenic, carcinogenic, and toxic effe... more Environmental concerns regarding explosives stem from the mutagenic, carcinogenic, and toxic effects of these nitroaromatic, aminoaromatic, and nitramine compounds, including associated impurities/metabolites, as well as their persistence in the environment. 1 For decades, most expired munitions have been disposed of via direct combustion, which does not quantitatively destroy toxic constituents. As a result, a significant amount of disposed-of explosives contaminate soil and groundwater, requiring thorough characterization of contaminated areas for residual explosives. In addition, explosives analysis is important for the forensic analysis of postexplosion residues and monitoring regulated compounds in munitions wastewater. A variety of chromatographic techniques have been applied to separate and detect explosives compounds, including GC, thin layer chromatography (TLC), supercritical fluid chromatography (SFC), capillary electrochromatography

This work describes a liquid chromatography method for determina- tion of perfluorooctanoic acid ... more This work describes a liquid chromatography method for determina- tion of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in water samples. The method incorporates on-line sample concentration, reversed-phase HPLC using Acclaim ® PolarAdvantage II (PA2) columns for both and suppressed conductivity detection. For tap water samples, the LOD and LOQ are expected to be 1 µg/L and 3 µg/L, respectively, for both PFOA and PFOS. The dynamic range is 1 to 40,000 µg/L.

Journal of Chromatography A, 2006

This paper describes a new polar-embedded stationary phase that contains an internal sulfonamide ... more This paper describes a new polar-embedded stationary phase that contains an internal sulfonamide functional group coupled with an ether linkage. The synthesis involves functionalization of spherical silica particles with ligands prepared in a multi-step synthesis. The resulting material contains 16.5% carbon, corresponding to a ligand coverage of 2.4 mol/m 2. Chromatographic evaluations indicates that the new stationary phase exhibits lower polarity than any other polar-embedded packings investigated, with additional features such as low silanol activity, excellent compatibility with 100% aqueous mobile phases, higher shape selectivity for polycyclic aromatic hydrocarbons, and strong affinity to nitro-containing compounds.

Chemistry and Physics of Lipids, 2010

Biotechnology Progress, 1998

This paper reviews the development path for the ProLease injectable microsphere delivery system f... more This paper reviews the development path for the ProLease injectable microsphere delivery system for proteins using human growth hormone as an example. The process consists of four stages, the selection of a lead formulation for clinical testing, the preclinical evaluation of the lead formulation including toxicology and stability studies, the manufacture of phase I clinical supplies, and the scale-up for phase II and phase III clinical trials. The approaches used to overcome obstacles during each stage are summarized including ways of stabilizing the protein, obtaining desirable release kinetics, and manufacturing sterile batches for clinical testing. Stability, release, toxicology, and scale-up results for ProLease recombinant human growth hormone (rhGH) are given. The phase I clinical data show that bioactive rhGH was released for about 1 month in humans. This work shows that processes and procedures have been developed that enable the production of microsphere sustained release formulations for proteins suitable for clinical trails and commercialization.

Angewandte Chemie International Edition, 2012

Special (lipid) delivery: The role of the ionizable lipid pK(a) in the in vivo delivery of siRNA ... more Special (lipid) delivery: The role of the ionizable lipid pK(a) in the in vivo delivery of siRNA by lipid nanoparticles has been studied with a large number of head group modifications to the lipids. A tight correlation between the lipid pK(a) value and silencing of the mouse FVII gene (FVII ED(50) ) was found, with an optimal pK(a) range of 6.2-6.5. The most potent cationic lipid from this study has ED(50) levels around 0.005 mg kg(-1) in mice and less than 0.03 mg kg(-1) in non-human primates.