Chemistry at Dalhousie circa 1868

Abstract: This article describes details of classes at Dalhousie University in 1868â 1869, of the life of George Lawson, the first Professor of Chemistry and Mineralogy, and of the wide range of chemical concepts known at that time. A comprehensive set of lecture notes from Lawson's chemistry course, written by a student, Alexander Russell, and held in the Dalhousie University Archives, offers a wonderful insight into the state of chemical knowledge and how it was taught at that time. Lawson began with general chemical principles followed by a detailed discussion of the nonmetals. The second half of the class covered a range of metals followed by a small section on mineralogy and a large section on organic and biological chemistry. Lawson used an older set of atomic masses in which many, but not all, of the elements had masses one-half of the accepted values today. When corrected for these errors, Lawsonâ s formulae, even for complex molecules such as morphine, mostly agreed with contemporary usage. Examples of nomenclature, chemical formulae, preparations, processes and properties are presented. A few examination questions are given also. Even though the concepts involved in understanding chemical structure were just being developed, the breadth and depth of descriptive chemical knowledge at that time was remarkable.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Calibration curves for the quantitative determination of regioisomers of triacylglycerols using fractional abundances are intrinsically non-linear

RATIONALE: Regioisomeric analysis of triacylglycerols is important in understanding lipid biochemistry and the involvement of lipids in disease and nutrition. The use of calibration plots employing fractional abundances provides a simple and rapid method for such analyses. These plots are believed to be linear, but evidence exists for non-linearity. The behavior of such plots needs to be understood to allow for proper interpretation of regioisomeric data. METHODS: Solutions of \ufb01ve regioisomer pairs were prepared from pure standards and used to construct calibration plots using triple-stage tandem mass spectrometry (MS\ub3) with electrospray ionization (ESIMS\ub3) and cationization by lithium ions. The data were taken by direct infusion with an AB SCIEX QTRAP 2000 QqLIT mass spectrometer. RESULTS: Non-linear calibration plots were observed for the four isomer pairs containing the polyunsaturated eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids paired with palmitic acid (16:0) or myristic acid (14:0), while the pair including palmitic and stearic (18:0) acids provided a linear plot. A non-linear model was developed for these plots and then veri\ufb01ed experimentally. CONCLUSIONS: The fractional abundance calibration plots used in regioisomeric analysis of triacylglycerols are intrinsically non-linear, but may appear linear if the scatter in data points obscures the curvature, if the curvature is slight, or if the response factors for the two isomers in the regioisomer pair are similar. Therefore, linearity should not be assumed for these types of measurements until con\ufb01rmed experimentally.Peer reviewed: YesNRC publication: Ye

Studying the chemistry of cationized triacylglycerols using electrospray ionization mass spectrometry and density functional theory computations

Analysis of triacylglycerols (TAGs), found as complex mixtures in living organisms, is typically accomplished using liquid chromatography, often coupled to mass spectrometry. TAGs, weak bases not protonated using electrospray ionization, are usually ionized by adduct formation with a cation, including those present in the solvent (e.g., Na+). There are relatively few reports on the binding of TAGs with cations or on the mechanisms by which cationized TAGs fragment. This work examines binding efficiencies, determined by mass spectrometry and computations, for the complexation of TAGs to a range of cations (Na+, Li+, K+, Ag+, NH 4 +). While most cations bind to oxygen, Ag+ binding to unsaturation in the acid side chains is significant. The importance of dimer formation, [2TAG + M]+ was demonstrated using several different types of mass spectrometers. From breakdown curves, it became apparent that two or three acid side chains must be attached to glycerol for strong cationization. Possible mechanisms for fragmentation of lithiated TAGs were modeled by computations on tripropionylglycerol. Viable pathways were found for losses of neutral acids and lithium salts of acids from different positions on the glycerol moiety. Novel lactone structures were proposed for the loss of a neutral acid from one position of the glycerol moiety. These were studied further using triple-stage mass spectrometry (MS3). These lactones can account for all the major product ions in the MS3 spectra in both this work and the literature, which should allow for new insights into the challenging analytical methods needed for naturally occurring TAGs.Peer reviewed: YesNRC publication: Ye

High resolution LC-MS profiling of triaclglycerols and targeted regioisomer abundance determination in omega-3 enriched fish oils

Reversed-phase high performance liquid chromatography (RP-HPLC), followed by post-column addition of lithium salts and electrospray ionisation triple-stage mass spectrometry (ESI-MS\ub3) of lithiated TAG adducts, is shown to provide a useful method for the positional analysis of triacylglycerols (TAGs) in fish oils containing eicosapentaenoic (EPA, 20:5) and docosahexaenoic acids (DHA, 22:6). One prominent fragmentation pathway in the ESI-MS\ub3 of these adduct ions involves the loss of a fatty acid from the sn-1/3 position in the first step followed by the loss of an \u3b1,\u3b2-unsaturated fatty acid from the sn-2 position in the second. Regioisomeric TAGs of the type ABA and AAB produced abundant product ions \u2013 [ABA + Li 12 RACOOH 12 R\u2032BCHCHCOOH]+ and [AAB + Li 12 RACOOH 12 R\u2032ACHCHCOOH]+ \u2013 the relative intensities of which were dependent on the position of acyl substituents. Standard solutions of TAGs containing different ratios of the regioisomeric pairs MME/MEM, PPE/PEP, PPD/PDP, EEP/EPE and DDP/DPD (M = 14:0, P = 16:0, E = 20:5, D = 22:6) were analysed by ESI-MS3 with a quadrupole linear ion trap instrument. Methodology developed on the standards was applied to quantifying the relative isomeric abundances of EPA and DHA in several fish oil samples. DHA was preferentially located at the sn-2 position in both DHA-containing TAGs studied, while EPA was either observed at near equal levels in all positions, or predominantly at the sn-1 and -3 positions in some cases. The analysis protocol allows for quantification of the designated regioisomers in one simple, rapid chromatographic procedure using a single column and has the advantage of specificity over other methods for the positional analysis of TAGs, since it eliminates interferences associated with co-eluting TAGs of the same molecular weight that yield isobaric diacylglycerol-like product ions.Peer reviewed: YesNRC publication: Ye

Thin-layer chromatographic plate scanner interfaced with a mass spectrometer

A device which scans a 1 x 10 cm TLC plate past a source of desorption energy has been developed. This scanner is interfaced to a quadrupole mass spectrometer by means of an isolation valve and a heated transfer line inserted into the direct sample inlet port. Chemical ionization reagent gas transports the desorbed compounds into the ion source. Two sources of desorption energy have been employed, a pulsed CO2 laser and a 150-W incadescent lamp. Sensitivity depends on the compound studied and the desorption energy available, with a minimum detectable amount of about 1 ng. Quantitation can be performed by using an internal standard with a precision of about 20%. Response with silica gel places is not linear. The method is non-destructive; plates can be rescanned or subjected to other detection methods.Peer reviewed: YesNRC publication: Ye

Scald Burns From Hair Braiding

Only one previous case report has described scald burns secondary to hair braiding in pediatric patients. The present case study is the largest to date of scald burns as a result of hair braiding in children and adults. Charts of all 1609 female patients seen at a single burn center from 2008 to 2014 were retrospectively reviewed to identify patients with scald burns attributed to hair braiding. Demographics, injury severity, injury patterns, and complications were analyzed. Twenty-six patients (1.6%) had scald burns secondary to hair braiding with median TBSA 3%. Eighty-five percent of patients were pediatric with median age 8 years. Injury patterns were as follows: back (62%), shoulder (31%), chest (15%), buttocks (15%), abdomen (12%), arms (12%), neck (12%), and legs (4%). No patients required operative intervention. Three patients were admitted to the hospital. Two patients required time off from school for 6 and 10 days post burn for recovery. Complications included functional limitations (n = 2), hypertrophic scarring (n = 1), cellulitis requiring antibiotics (n = 1), and anxiety requiring medical/psychological therapy (n = 2). This peculiar mechanism of injury not only carries inherent morbidity that includes the risks of functional limitations, infection, and psychological repercussions but also increases usage of resources through hospital admissions and multiple clinic visits. Further work in the form of targeted outreach programs is necessary to educate the community regarding this preventable mechanism of injury