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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Frederick F. Cantwell

Abbrev:
Cantwell, F.F.
Other Names:
Address:
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
Phone:
(780) 492-5927
Fax:
NA

Citations 11

"Adsorption Of Tetrahexylammonium - Bromothymol Blue Ion-pairs At The Chloroform-water Interface"
Can. J. Chem. 1991 Volume 69, Issue 1 Pages 88-93
Lawrence Amankwa and Frederick F. Cantwell

Abstract: Porous membrane phase separators are used to study the adsorption of the cation tetrahexylammonium (Q+) of the anion bromothymol blue (HB-) and of the ion-pair formed between them (QHB) at the liq.-liq. interface in a rapidly stirred mixture of CHCl3 and aqueous buffer. Adsorption isotherms in all 3 cases follow the Langmuir equation. The anion HB- is much more strongly adsorbed than the ion-pair QHB. The porous membrane technique readily permits measurement of simultaneous adsorption of the 2 species HB- and QHB, and thereby allows a study of their competitive adsorption. When WHB is adsorbed in the presence of an excess of HB- both the saturated (monolayer) interfacial concentration. of QHB and the logarithm of the adsorption equilibrium. constant for QHB decrease linearly with an increase in interfacial concentration. of HB-. This shows quant. that coadsorption of QHB and HB- involves a direct competition for space at the interface and also that the presence of adsorbed HB- changes the adsorbent properties of the interface. Anal. implications for solvent extraction are discussed.
Tetrahexylammonium ion Bromothymol blue Sample preparation Ion pair extraction Kinetic Phase separator Solvent extraction Surfactant

"Use Of Peak Height For Quantification In Solvent Extraction/flow Injection Analysis"
Can. J. Chem. 1985 Volume 63, Issue 9 Pages 2559-2563
Jamal A. Sweileh and Frederick F. Cantwell

Abstract: An equation is presented which expresses peak height in terms of the concentration. of sample injected, detector sensitivity, dilution due to band dispersion, the fraction extracted, the flow rates of carrier, organic phase and compensating solvent and the flow rate of the organic extract through the membrane phase separator. Each term in the equation was evaluated experimentally with the determination of Zn, by AAS or UV detection, after solvent extraction of Zn(SCN)2.
Zinc Spectrophotometry Spectrophotometry Sample preparation Dispersion Theory Solvent extraction Phase separator Membrane

"Role Of The Compact Part Of The Electrical Double Layer In The Simultaneous Sorption Of Different Ions Of The Same Charge On A Reversed-phase Bonded-phase Liquid Chromatography Packing"
Anal. Chem. 1993 Volume 65, Issue 22 Pages 3299-3307
Laura L. M. Glavina and Frederick F. Cantwell

Abstract: A version of the Stern-Gouy-Chapman (SGC) theory of the electrical double layer (Liu and Cantwell, Ibid., 1991, 63, 993) was tested for its applicability to the simultaneous sorption of two ions having the same charge. The test species were tetrabutylammonium (TBA) and trimethyl-(4-nitrobenzyl)ammonium (TNBA) ions, which were sorbed on a stainless-steel column (2 cm x 2 mm i.d.) packed with Partisil-10 ODS-3 (10 µm) and maintained at 25°C, with a flow rate of 2 ml/min during loading. The concentration of TBA was 5-500 µM, while the TNBA concentration was maintained at 1.86 mM in a medium of 0.1 M acetic acid/sodium acetate buffer of pH 5. The eluent was aqueous 50% methanol containing 0.01 M NaCl at 1 ml/min. The concentration of TNBA was determined by spectrophotometry at 260 nm and that of TBA by solvent extraction of the TBA/picrate ion pair coupled with FIA (loc. cit.). The capacitance C1 of the whole compact part of the double layer decreased as the activity of TBA ions increased, suggesting that TBA and TNBA ions were adsorbed at different locations and that C1 was a differential capacitance; the SGC model was modified to permit the centres of charge of the two ions to lie in different planes. The potentials at the TBA and TNBA charge surfaces could be evaluated by treating the compact layer as two capacitors in series.
Tetrabutylammonium ion Spectrophotometry Theory

"Mechanism Of Extraction And Band Broadening In Solvent Extraction-flow Injection Analysis"
Anal. Chem. 1989 Volume 61, Issue 2 Pages 107-114
Charles A. Lucy and Frederick F. Cantwel

Abstract: Studies were performed in an aqueous/chloroform segmented flow stream. The absorbance of each chloroform segment was measured as it passed through an on-tube photometer located at various distances along the Teflon extraction tube. Band broadening, studied by injecting iodine into a single chloroform segment, is intermediate in magnitude between that predicted by using a mixing chamber model and that predicted by assuming only diffusional mixing between the segments and the wetting film of chloroform on the tube wall. Extraction from aqueous Into chloroform segments was studied by generating iodine within a single aqueous segment using the "Iodine clock" reaction. Application of a "successive reaction" model to the axial extraction from the front of the aqueous segment reveals that, in straight tubes, solute extracts at the same rate per unit area across ail of the interface, at both the segment ends and side.
Sample preparation Solvent extraction Band broadening Theory

"Kinetics Of Solvent Extraction-flow Injection Analysis"
Anal. Chem. 1989 Volume 61, Issue 2 Pages 101-107
Charles A. Lucy and Frederick F. Cantwell

Abstract: The effect of instrumental parameters on the rate of extraction in solvent extraction-flow injection analysis was studied. In straight tubes, the extraction rate Increases rapidly with decreasing segment length for short segments and Is approximately constant for longer segments. Increasing the hear velocity results in less than a proportional increase in the extraction rate. Changes in extraction rate with tubing diameter are correlated with the interfacial area of the segment and with the segment aspect ratio. The convection within long segments is toroidal with the flow streamlines parallel to the tube wall except near the segment ends, whereas the convection In short segments exhibits a significant radial flow component along the entire segment. In coiled tubes, the extraction rates are much higher than In comparable straight tubes. This enhancement is due to the generation of tangential secondary flow within the segments and is greater for long segments than for short.
Sample preparation Kinetic Solvent extraction

"Simultaneous Determination Of Phenylephrine Hydrochloride And Pheniramine Maleate In Nasal Spray By Solvent Extraction Flow Injection Analysis Using Two Porous-membrane Phase Separators And One Photometric Detector"
Anal. Chem. 1986 Volume 58, Issue 13 Pages 2727-2731
Charles A. Lucy and Frederick F. Cantwell

Abstract: Sample spray was injected at 2-min intervals into water as the carrier stream. Interfering thimerosal, maleate and benzalkonium ion species were removed by passage through beds (length 10 mm) of Amberlyst A-26 macroporous anion-exchange resin (100 to 140 mesh), and, after the addition of 0.2 M NaOH, A15 cation-exchange resin. Following quantitative extraction at pH 13 of pheniramine maleate into CHCl3 via segmented flow, a portion of the CHCl3 phase was separated by a porous PTFE membrane and was directed to the sample flow cell of the spectrophotometric detector. A portion of the aqueous phase, containing phenylephrine, was separated by a paper membrane located further downstream in the segmented flow and was directed to the reference flow cell. Absorbances were measured at 258.3 nm. The spectrophotometer was modified to allow electronic switching of the sample/reference designation of its two flow cells. The precision and accuracy of the technique were 1 to 2%.
Phenylephrine Pheniramine maleate Pharmaceutical Clinical analysis Spectrophotometry Sample preparation Interferences Phase separator Teflon membrane Solvent extraction

"Determination Of Acidity Constants By Solvent Extraction/flow Injection Analysis Using A Dual-membrane Phase Separator"
Anal. Chem. 1985 Volume 57, Issue 4 Pages 922-926
Lynette Fossey and Frederick F. Cantwell

Abstract: The absorbances of both the organic and aqueous phases in a solvent extraction/flow injection analysis system are simultaneously monitored. Acidity constants are determined from straight line plots relating the ratio of peak areas in the aqueous and organic phases, A,/A,, to the hydrogen ion activity of the aqueous phase. Theoretical equations describing this relationship for both HA and BH' charge type acids are derived and verified experimentally using 3,5-dimethylphenol (pK, = 10.09±0.01) and p-toluldinium ion (pK, = 5.28 f 0.01). The distribution coefficient of the neutral conjugate species is also obtained during the experiment. Some distinct practical advantages to using the dual-membrane device over the single-membrane device are discussed.
Acidity Sample preparation Acidity constants Theory Membrane Phase separator Solvent extraction

"Sample Introduction By Solvent Extraction/flow Injection To Eliminate Interferences In Atomic Absorption Spectroscopy"
Anal. Chem. 1985 Volume 57, Issue 2 Pages 420-424
Jamal A. Sweileh and Frederick F. Cantwell

Abstract: The automated solvent extraction - flow injection analysis system used employs constant pressure pumping and a porous PTFE membrane phase separator. The analyte is extracted as a metal - ligand complex into isobutyl methyl ketone and the extract is introduced directly and continuously into the nebulizer for AAS (Perkin-Elmer 4000 instrument). Zinc was determined in synthetic samples containing 2% of Fe by its extraction as Zn(SCN)2 and the results were compared with those obtained by direct-aspiration AAS At added levels (ppm) of Zn of 0.5, 0.9, 1.25, and 1.6, recoveries were 0.47, 0.90, 1.28 and 1.66, compared with 0.92, 1.33, 1.78 and 2.25 found by direct aspiration. The detection limit (3:1 signal-to-background ratio) was 0.2 ppm. Diverse matrix effects can be eliminated as well as spectral interferences.
Zinc Spectrophotometry Sample preparation Interferences Phase separator Solvent extraction Teflon membrane

"Hydrodynamic And Interfacial Origin Of Phase Segmentation In Solvent Extraction/flow Injection Analysis"
Anal. Chem. 1985 Volume 57, Issue 1 Pages 329-331
Frederick F. Cantwell and Jamal A. Sweileh

Abstract: A semi-quantitative physico-chemical model has been developed to establish the theoretical basis for understanding the segment-forming process of the cited technique. The segmentor design used for the experimental data was based on a simple T-joint made of Kel-F, which has been used successfully in several applications of this technique.
Sample preparation Modeling Phase separator Theory Solvent extraction

"Simultaneous Monitoring Of Both Phases In The Solvent Extraction/flow Injection Analysis Of Dramamine Tablets"
Anal. Chem. 1983 Volume 55, Issue 12 Pages 1882-1885
Lynette Fossey and Frederick F. Cantwell

Abstract: The extraction - flow injection system described and illustrated is equipped with a dual-membrane phase separator having a PTFE membrane that permits passage of organic phase and a hydrophilic membrane (Whatman No. 5 paper) that permits passage only of aqueous phase.A solution (44 µL) of the finely ground tablets [containing diphenhydramine(I) and 8-chlorotheophylline(II)] in phosphate buffer solution (pH 7) is injected into a flowing carrier solution (aqueous NH3 - NH4Cl to give aqueous 0.66 M NH3 at pH 10.2) into which a stream of cyclohexane flows.In an extraction coil, I is quantitatively extracted into the cyclohexane; II remains in the aqueous phase. The phases are separated, and the absorbance is measured at 254 nm (for I in the organic phase) and 300 nm (for II in the aqueous phase). Calibration graphs (based on peak areas) are prepared with 0.25 to 2 mM I in cyclohexane and with 0.25 to 2.5 mM II in aqueous solution Precision and accuracy are excellent. One analysis takes ~0.5 min.
8-Chlorotheophylline Diphenhydramine Pharmaceutical Spectrophotometry Sample preparation Phase separator Teflon membrane Hydrophilic membrane Hydrophobic membrane Simultaneous analysis Organic phase detection Solvent extraction

"Characterization Of Solvent Extraction/flow Injection Analysis With Constant Pressure Pumping And Determination Of Procyclidine Hydrochloride In Tablets"
Anal. Chem. 1982 Volume 54, Issue 11 Pages 1693-1697
Lynette Fossey and Frederick F. Cantwell

Abstract: A flow injection extraction apparatus utilizing a membrane phase separator and constant pressure pumping is described and characterized In terms of extraction coil length, sample injection volume, and flow rates. Equations are derived and verified that show that under conditions where the sample component is quantitatively extracted into the organic phase, the peak area depends only on the number of moles of sample injected and the total flow rate of organic solvent. A sampling frequency of 4 samples/min is readily achieved. Procyclldlne hydrochloride is assayed in tablets with 1% precision and accuracy.
Procyclidine Pharmaceutical HPLC Sample preparation Phase separator Constant pump pressure Review Solvent extraction Membrane