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
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Journal of Pharmaceutical Sciences

  • Publisher: Wiley
  • FAD Code: JPSC
  • CODEN: JPMSAE
  • ISSN: 0022-3549
  • Abbreviation: J. Pharm. Sci.
  • DOI Prefix: 10.1002/jps
  • Language: English
  • Comments: Fulltext from 1912 V1

Citations 10

"Amperometric Determination Of Dipyrone In Pharmaceutical Formulations With A Flow Cell Containing Gold Electrodes From Recordable Compact Discs"
J. Pharm. Sci. 2001 Volume 90, Issue 12 Pages 1972-1977
Rodrigo A.A. Muñoz, Renato C. Matos, Lúcio Angnes*

Abstract: A simple, rapid, and precise amperometric method for quantification of dipyrone in pharmaceutical formulations is presented. The proposed method permits determinations in the 10^-7 mol L-1 of the analyte and enables 90 determinations h-1, employing only 100 µL of sample per determination. This method is based on the direct quantification of dipyrone in many pharmaceutical products, avoiding cumbersome processes such as previous separations, solvent extraction, or sample filtration. This new procedure was applied to commercial pharmaceutical tablets, and the results obtained were in excellent agreement with the ones obtained by the classical iodometric method.

"An Integrated Process For Measuring The Physicochemical Properties Of Drug Candidates In A Preclinical Discovery Environment"
J. Pharm. Sci. 2001 Volume 90, Issue 8 Pages 1164-1175
Christopher E. Kibbey, Salwa K. Poole, Ben Robinson, J. Derek Jackson, Douglas Durham

Abstract: Automated log P, pKa, solubility, and chemical stability systems comprise an integrated process that provides early stage physicochemical property data to the discovery research organization. Capillary electrophoresis (CE) techniques are used to experimentally determine pK(a) and log P. Solubility is determined using a quasi-equilibrium approach employing sample quantitation by flow injection analysis with ultraviolet (UV) detection at 256 Jam. Chemical stability is assessed by challenging compounds with pH 2, pH 7, pH 12, and 3% hydrogen peroxide solutions overnight, and comparing the chromatographic profiles of the stability challenged solutions to that of a freshly prepared control. Validation of the log P method using a set of drug-like compounds demonstrates that the method yields log P values within±0.5 units of literature values. The log P method is valid over the range -0.5-5.0, and the technique is compatible with acidic, neutral, and basic compounds. The pK(a) technique yields results within±2 units of corresponding values obtained by potentiometric titration over a pK(a) range of 2 to 12. Solubility is reported in a 3-60 µg/mL range, and the results are generally within 20% of values measured by equilibrium solubility techniques. The current level of automation supports the measurement of the physicochemical properties of 100 compounds per week. Physicochemical property data for similar to 2000 compounds have been generated to date.
Permeability

"Tetracycline-selective Electrode For Content Determination And Dissolution Studies Of Pharmaceuticals By Flow Injection Analysis (FIA)"
J. Pharm. Sci. 2001 Volume 90, Issue 8 Pages 1125-1133
M. Goreti F. Sales, M. Conceição B. S. M. Montenegro

Abstract: The present work describes the construction and evaluation of different tetracycline (TC)-selective electrodes without inner reference solution and with polymer membranes. The several electrodes were prepared with poly(vinyl chloride) or ethylene(vinyl acetate) membranes comprising o-nitrophenyl octyl ether or bis(2-ethylhexyl)sebacate as mediator solvents and tetracycline tetrakis(4-clorophenyl)borate as ion exchanger. The best performance was recorded for the poly(vinyl chloride) membranes with bis(2-ethylhexyl)sebacate. Using solutions with adjusted ionic strength, this type of electrode presented a slope of 57.4 mV decade-1 and a reproducibility of±0.3 mV day-1, for an analytical range from 1.2 x 10^-4 to 10 x 10^-2 M. The pH working range was 2.0-3.8. Tubular-shaped potentiometric detectors based on the same selective membrane were also constructed. When TC solutions with adjusted ionic strength of concentrations ranging from 1.0 x 10^-4 to 1.0 x 10^-2 M were injected into a single-channel flow manifold, the detectors presented a slope of 56.6 mV decade-1 and a reproducibility of±0.5 mV day-1. The pH working range was 1.9-3.9. Both batch and flow procedures were applied to the potentiometric analysis of oral dosage forms. Average recoveries were within 98.6 to 100.3% and the t test indicated the accuracy of these results in comparison to an independent methodology. The flow system with the potentiometric detector was employed in dissolution studies as well.

"Flow Injection Analysis Of Dopamine In Injections With A Periodate-selective Electrode"
J. Pharm. Sci. 2000 Volume 89, Issue 7 Pages 876-884
M. C. B. S. M. Montenegro, M. Goreti F. Sales

Abstract: Dopamine determination in pharmaceutical preparations based on its oxidation with periodate (IO4-) using a new IO4--selective electrode under flow conditions is presented. An electrode with a tubular configuration, no internal reference solution, and a PVC (31.2%) membrane, with metaperiodate bis(triphenylphosphoranylidene)ammonium (1.3%) as ion exchanger and 2-nitrophenyloctylether (67.5%) as mediator solvent, was used. Optimization procedures were directed at potentials versus dopamine readings instead of potential versus the remaining IO4-. This approach was achieved by selecting a 50-cm reactor and an overall flow of 7 mL/min, and injecting 70 µL of dopamine standards in a 3.0 x 10^-4 M IO4- solution. Under these conditions, a linearity range of 8.0 x 10^-3 to 2.7 x 10^-1 g/L, with a slope of 310.1±7.4 mV L g-1 and a reproducibility of±0.4 mV, were recorded (n = 8). Interference from common excipients was negligible. Under these conditions, analysis of dopamine injections (n = 12) presenting 200 mg/injection gave average and standard deviation values of 201.0 and 3.3 mg/injection, respectively. A simple and inexpensive flow injection analysis (FIA) manifold, with a good potentiometric detector, enabled the analysis of 200 samples/h without requiring pretreatment procedures. Comparison with the dopamine injection analysis in the United States Pharmacopoeia monograph showed good accuracy, with a relative deviation of -0.2%.

"Ion-selective Electrodes For Promethazine Determinations In Pharmaceutical Preparations And Application To Flow Injection Analysis"
J. Pharm. Sci. 1997 Volume 86, Issue 11 Pages 1234-1238
Jose L. F. C. Lima, M. Conceicçaão B. S. M. Montenegro *, M. Goreti F. Sales

Abstract: The construction and evaluation of PM-selective electrodes with a conventional configuration and without internal reference solution are described. Two different PVC membranes were prepared with PM tetraphenylborate dissolved in 2-nitrophenyl octyl ether (type A) or bis (2-ethylhexyl)sebacate (type B). When the electrodes were evaluated in 0.01 M ionic strength solutions, both presented linear responses from 5 x 10^-5 to 1 x 10^-2 M, slopes close to the theoretical value, practical detection limits of approximately 2 x 10^-5 M, reproducibilities of±0.2 mV/day, and a quick response (< 20 s). Using phosphate buffer solutions (pH 6.0), type B electrodes presented a lower practical detection limit and a better reproducibility than type A. Selectivity against several cations was assessed by the separated solutions method, and the type B electrodes were generally more selective. The type B membrane was also used for the construction of tubular electrodes for the automatic analysis of pharmaceutical products by flow injection analysis (FIA). These tubular detectors, evaluated in a low dispersion FIA system, presented better selectivity and sensitivity than the corresponding conventional ones. Several pharmaceutical preparations were analyzed with both conventional and tubular electrodes. The results obtained by FIA presented relative deviations of < 2% when compared with those obtained from the United States Pharmacopoeia monographs.
Promethazine Pharmaceutical Electrode Electrode Method comparison Selectivity Sensitivity Dispersion

"Construction Of A Diflunisal Ion Sensor And Its Use In Automated Flow Injection Methods For Assay, Content Uniformity And Dissolution Studies Of Formulations"
J. Pharm. Sci. 1995 Volume 84, Issue 7 Pages 889-894
Petr Solich, Michael A. Koupparis, Panos E. Macheras

Abstract: An ISE for diflunisal (I) of the PVC membrane-type was constructed by trapping the 0.01 M tetraheptylammonium-I liquid ion exchanger in 2-nitrophenyl octyl ether solution in a PVC matrix by the method of Craggs et al. (J. Chem. Educ., 1974, 51, 541). The electroactive membrane (diameter 6 mm) was attached to a commercially available nitrate electrode, placed in a potentiometric flow-through cell with Ag/AgCl (4 M KCl) as reference electrode and transferred to the flow injection analyzer.. Portions (85 µL) of sample in 10 mM NaOH were injected into a carrier stream of 10 mM NaOH (2.6 ml/min), mixed with a flow of 0.05 M Tris buffer of pH 8 (1.4 ml/min) in a 50 cm mixing coil and detected by the potentiometric ISE. The electrode exhibited a Nernstian response over the range 0.1-5 mM I and the detection limit was 0.026 mM. The RSD (n = 10) was 0.38% at 1 mM I. Under optimized conditions, the operative life of the ISE was 3 months. A diflunisal ion selective electrode of the PVC membrane type with an ion-exchanger consisting of the tetraheptylammonium-diflunisal ion pair is described. The sensor exhibits a rapid, near-Nernstian, selective response to diflunisal anion in the pH range 7-10, with a (batch) detection limit of 1 x 10^-5 M. The ion sensor was used as a flow detector in an automated flow injection analyzer to develop routine methods for assays (concentration range 1-50 x 10^-4 M, (flow) detection limit 2.6 x 10^-5 M), content uniformity, and dissolution studies of diflunisal formulations. No serious interference from common ions and tablet excipients was found, and the drug can be directly determined in colored samples without separation steps. Fourty measurements can be performed automatically per hour with a precision of 0.5-1.8% relative standard deviation. The automated method for the dissolution test provides a complete dissolution profile by the end of the experiment. Using the constructed ion sensor, the intramolecular hydrogen bonding of the diflunisal anion was studied, thereby revealing a new application of ion sensor potentiometry.
Diflunisal Pharmaceutical Electrode Potentiometry Electrode Sensor Interferences Dissolution rate Automation

"Determination Of Total Pyridoxal In Human Plasma Following Oral Administration Of Vitamin B6 By High Performance Liquid Chromatography With Post-column Derivatization"
J. Pharm. Sci. 1993 Volume 82, Issue 9 Pages 972-974
Hermann Mascher

Abstract: An HPLC method for determining total pyridoxal from plasma was developed for a relative bioavailability comparison of two oral vitamin B6 (pyridoxine HCl) preparations. After cleavage of the pyridoxal-5-phosphate with the acid phosphatase enzyme, the total pyridoxal was determined by HPLC. Pyridoxal was separated on a reversed-phase column, post-column derivatized to pyridoxal-semicarbazide, and then detected by fluorescence and quantitated. The limit of detection was 2 ng/mL and interday variation (3 days) over the whole concentration range (13-215 ng/mL spiked) was < 4.1%. In the relative bioavailability study, 16 human subjects were put on a low vitamin B6 diet for a period of 3 days. On the 2nd and 3rd days, 14 blood samples were taken per subject at the same times each day. The drug was administered on the 3rd day. Total endogenous pyridoxal detected on the 2nd day varied in plasma between 13 and 17 ng/mL. Pharmacokinetic parameters corrected for background are reported for two vitamin B6 (40 mg) preparations. Briefly, the pharmacokinetic results for the Ratiopharm preparation compared with the Hoffmann-La Roche preparation are, respectively: AUC0-24, 369.2 and 352.6 ng.h/mL; AUC24-48, 1638.2 and 1662.3 ng.h/mL; net Cmax, 193.0 and 197.1 ng/mL; tmax, 1.25 and 1.44 h; and relative bioavailability, 97.9% (Westlake, 88-112%) Plasma (1 ml) was vortex-mixed with 0.15 mL of 3 M perchloric acid and the mixture was centrifuged at >1500 g. A 0.5 mL portion of the clear supernatant solution was incubated for 16 h at 40°C with 0.3 mL of 1 M acetate buffer (pH 4.6) and 0.1 mL of aqueous acid phosphatase solution (10 mg mL-1) before vortex-mixing with 0.15 mL of 3 M perchloric acid. After centrifugation, a 20 µL portion of the supernatant solution was subjected to HPLC on a column (12.5 cm x 4 mm) of Nucleosil 120 5 C18 with a mobile phase (2 mL min-1) of 0.05 M perchloric acid and 0.02 M triethylamine in water. The eluate was mixed with semicarbazide hydrochloride in 1.5 M NaOH (3.35 g l-1) in a PTFE tube (10 m x 0.3 mm) at 70°C before fluorimetric detection at 480 nm (excitation at 365 nm). The detection limit was 2 ng mL-1 of pyridoxal and inter- and intra-day coefficient of variation were 1.7 to 4.1% and 0.1 to 9.1%, respectively. The method was used to study the pharmacokinetics of pyridoxal in human plasma..
Pyridoxal Blood Plasma HPLC Fluorescence Post-column derivatization

"Automated Flow Injection Mercurothiocyanate Determination Of Chloride Salts Of Drugs For Routine Assays: Content Uniformity And Dissolution Studies"
J. Pharm. Sci. 1986 Volume 75, Issue 8 Pages 800-804
Michael A. Koupparis, Evagelos G. Sarantonis

Abstract: An automated flow injection determination of chloride salts of drugs, based on the colorimetric mercurothiocyanate determination of chloride counterion is described. The majority of these drugs can be determined, using chloride ion standards, with a coefficient of variation less than 1% and a measurement rate of 120 samples per hour. The method is evaluated by determining the interference caused by common inorganic ions, representative organic functional groups, and excipients, and by the analysis of pure drugs and their commercial formulations. The results compare well with those obtained by the official procedures. The benefits of the method are demonstrated in content uniformity tests and in automated monitoring of dissolution studies. To determine chloride salts of drugs, the Cl- is determined by automated flow injection analysis. The sample is dissolved in HNO3 solution and mixed with Hg(SCN)2 - Fe(III) solution The resulting Fe(SCN)2+ complex is determined at 460 nm. The absorbance is rectilinearly related to concentration. of Cl- up to 50 mg L-1 (200 µL sample) or 100 mg L-1 (100 µL sample). The coefficient of variation was <1%. Thiocyanate, Br-, I-, barbiturates, quinolin-8-ol, o-phenylenediamine, diphenylamine, 1-naphthylamine, antipyrine and chlorpromazine interfere. The method is illustrated by indirect determination of chloride salts of 11 drugs in formulations not containing other chlorides.
Drugs Pharmaceutical Clinical analysis Spectrophotometry Interferences

"Automated Flow Injection Pseudotitration Of Boric Acid"
J. Pharm. Sci. 1985 Volume 74, Issue 8 Pages 886-888
Paraskevi I. Anagnostopoulou, Michael A. Koupparis

Abstract: An automated flow injection pseudotitrimetric determination of boric acid, using a flow injection photometric analyzer controlled by a microcomputer, is described. The method is based on the injection of 200 µL of sample in a flowing stream of mannitol-bromothymol blue 'titrant' and measuring the peak width in time units. Equivalent times of 10^-70 s are measured with CV values of 0.1-0.4% (n = 5) and the analytical range is 1.5-309 mg/100 mL (2.5 x 10^-4 - 5 x 10^-2 M of boric acid. The method was evaluated by performing recovery studies in mixtures (mean 99.8%) and assays of commercial preparations which were compared with the official classical titrimetric method. Pharmaceutical preparations containing boric acid were dissolved in water and neutralized with 0.01 M NaOH or HCl. The solution were subjected to flow injection analysis by injection into the reagent stream (5 mL min-1) of 10 µM-phosphate buffer (pH 7) containing 0.1 mM bromothymol blue and 75 g L-1 of mannitol with absorbance measurement at 614 nm. The calibration graph was rectilinear for 0.25 to 50 mM boric acid; recovery was 99.8% and the coefficient of variation were 0.1 (0.06 and 0.31%) to 0.4% (16 ppm). The results agreed well with those obtained by the official titrimetric method.
Boric acid Pharmaceutical Spectrophotometry Computer Method comparison Titrations Peak width

"Amperometric Determination Of Hydralazine Hydrochloride In A Flowing Stream At The Glassy Carbon Electrode"
J. Pharm. Sci. 1984 Volume 73, Issue 7 Pages 989-991
Mumtaz H. Shah, James T. Stewart

Abstract: A flow injection method for the determination of hydralazine hydrochloride based on electrochemical oxidation at the glassy carbon electrode is presented. The amperometric method is highly specific and may be used to determine hydralazine hydrochloride in the presence of other drugs commonly found in its pharmaceutical dosage forms or administered concurrently in therapeutic situations. By using an electrode potential of +650 mV versus an Ag/AgCl reference electrode, a calibration curve was found to be linear in the 1-50 µg/mL concentration range, with minimum detectability at 10 ng (signal-to-noise ratio, 2). When the method was applied to the analysis of hydralazine hydrochloride in selected pharmaceutical dosage forms, it showed good accuracy and precision. Although automation was not used in this study, the method could readily be incorporated in automated systems because it employs the technique of continuous analysis in a flowing stream.
Hydralazine hydrochloride Pharmaceutical Electrode Amperometry