University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Mass spectrometry

Citations 5

"The Analytical Characterisation Of Sub-minute Measurement Duty Cycles In Flow Injection Analysis Mass Spectrometry, By Their Carry-over"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 287-294

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Ramsay Richmond

Abstract: A high-throughput flow injection analysis mass spectrometry system was developed in-house for the purity estimation of multiple parallel combinatorial chemistry syntheses. A Visual Basic application called RackViewer allows a fast and easy on-screen inspection of these estimates at dispersed laboratory workbenches via the corporate computer network. Due to the increasing numbers of samples to be measured, there is an constant incentive to reduce the measurement duty cycle in order to develop faster throughput rates. Consequently, one threat to the accuracy of these purity estimates is surreptitious inter-sample carry-over. By analogy with the computer screen color rendering of the purity estimates, carry-over was automatically calculated, then color depicted within RackViewer. In an earlier report, this carry-over visualisation tool facilitated a stepwise reduction in the measurement duty cycle to 70 s, while maintaining median inter-sample carry-over at levels well below 1%. However, a limiting factor in further optimization was the physical speed of the autosamplers sampling head. A recent increase in this speed by the autosamplers manufacturer allowed a second attempt at achieving well characterized sub-minute measurement duty cycles. Six injection variations involving different syringe and loop wash combinations were examined for their characteristic inter-sample carry-over, using over four hundred samples drawn equally from five diverse combinatorial chemistries. One emerged as the best, with a median inter-sample carry-over of 0.01% and a measurement duty cycle of 44 s.
Combinatorial chemistry Synthesis Optimization

"Mass Spectrometric Detection And Identification Of Polar Pesticides And Their Degradation Products: A Comparison Of Different Ionization Methods"
Environ. Monit. Assess. 1997 Volume 44, Issue 1-3 Pages 503-513

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H. FR. Schröder

Abstract: Due to increasing use of polar pesticides, they are found together with their degradation products in ground- and surface waters serving for drinking water treatment. The triazine derivatives acetamido-atrazine, ametryne, atrazine, cyanazine, deethylatrazine, deethyldeisopropyl-hydroxyatrazine, deethyl-hydroxyatrazine, deisopropyl-atrazin, deisopropyl-hydroxyatrazine, desmetryn, hydroxyatrazine, prometryne, propazine, simazine, terbumeton, terbutryne and terbutylazine, and the pesticides 2,4-D, dichlorprop, isoproturon, diuron, metolachlor, glyphosate, metsulfuronmethyl and dalapon, all of them belonging to this type of pesticides, have been studied. For determination of triazine derivatives UV detection by means of diode array detector (DAD) as well as mass spectrometric (MS) detection coupled by thermospray interface (TSP) have been used successfully after liquid chromatoraphic (LC) separation. Interfaces like thermospray (TSP), electrospray (ESP) and atmospheric pressure chemical ionization (APCI) were examined with regard to their suitability for substance-specific detection of polar pesticides by flow injection analysis (FIA) with MS- and tandem mass spectroscopic detection (MS/MS) without preceding LC separation. Optimized detection conditions for these pesticides using FIA are presented, and solutions for occurring problems are offered.
Pesticides Ground Surface Optimization

"Evaluation Of A Dual Electrospray Ionization/atmospheric Pressure Chemical Ionization Source At Low Flow Rates For The Analysis Of Both Highly And Weakly Polar Compounds"
J. Am. Soc. Mass Spectrom. 1998 Volume 9, Issue 11 Pages 1196-1203

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Marshall M. Siegela, Keiko Tabeia, Frank Lamberta, Leonard Candelaa and Bart Zoltana

Abstract: The atmospheric pressure ionization (API) source for a commercial mass spectrometer was modified to operate as a dual source in both the electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) techniques by simultaneously utilizing the electrospray probe and the corona discharge needle. A switching box was designed to operate in either manual or programmable modes to permit rapid switching between ionization techniques without changing sources, probes, or breaking vacuum. The source can be operated using the following ionization techniques: ESI only, APCI only, ESI/APCI simultaneously, and ESI/APCI alternatingly. The optimum operating conditions for these ionization techniques were similar to the manufacturer's original specifications except that the APCI flow rate was lower (~50 µL/min versus 1000 µL/min) and externally heated nebulizing gas was found to be desirable. A four-component mixture, introduced by flow injection, was used to demonstrate the versatility of the dual ESI/APCI source.
Organic compounds

"Determination Of The Alcohol Denaturants Denatonium Benzoate (Bitrex) And Diethyl Phthalate By Direct Flow Injection APCI-MS Analysis"
J. High Resolut. Chromatogr. 1997 Volume 20, Issue 6 Pages 321-324

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Ma Elena Alvarez-Piñeiro, Ma Joséa López De Alda-Villaizán, Perfecto Paseiro-Losada, Ma Asunción Lage-Yusty

Abstract: The recently developed tandem technique, mass spectroscopy with atmospheric-pressure chemical ionization (APCI-MS) coupled with direct flow injection, was applied to the determination of Bitrex (denatonium benzoate) and diethyl phthalate in ethanol. The compounds were identified from their total-ion chromatograms (m/z 50-500) and, simultaneously, quantified using selected-ion chromatograms recorded at m/z 223 for diethyl phthalate and m/z 325 for Bitrex. Operating conditions were optimized for soft ionization (positive ion-mode) with fragmentation limited to that necessary for analyte identification, which was by the external-standard method. Calibration curves were rectilinear in the concentration ranges 2-30 µg mL-1 (Bitrex) and 0.075-1.2% v/v (diethyl phthalate); measurement precision (RSDs were 11.48% for Bitrex and 2.22% for diethyl phthalate), and detection limits (0.017 µg mL-1 and 0.010% v/v, respectively) were adequate for simultaneous quantitation and with high sensitivity. The lack of any sample pretreatment and the use of flow injection analysis meant that the procedure was more straightforward and rapid than previously reported methods.
Phthalate, diethyl Organic compound Method comparison Optimization Standard method

"An Eluent-jet Interface For Chemical Ionization Mass Spectrometry And Coupling Of Microcolumn Liquid Chromatography With Electron Ionization Mass Spectrometry"
Rapid Commun. Mass Spectrom. 1998 Volume 12, Issue 1 Pages 5-10

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Reyer J. Dijkstra, Ben L. M. Van Baar, Charles E. Kientz, Wilfried M. A. Niessen, Udo A. Th. Brinkman

Abstract: An improved eluent-jet interface was used to combine flow injection analysis (FIA) and micro-column liquid chromatography (LC) online with mass spectrometry (MS) in the electron ionization (EI) and solvent-independent chemical ionization (CI) modes. Good results were obtained for a series of pesticides and for 2-(diethylamino)ethanol (DEAE), a precursor of the chemical warfare V-agents. When using single-ion monitoring, 50 pg of DEAE could be detected in the CI mode, and a linear calibration plot was obtained in the test range of 50-1000 pg. EI-MS spectra obtained in both FIA and micro-LC experiments were closely analogous to those in conventional mass spectral libraries.
Pesticides 2-Diethylaminoethanol Interface