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
Website: @unf

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Classification: Pharmaceutical -> syrup

Citations 11

"A New Simple And Accurate Turbidimetric Method For Determination Of Ascorbic Acid In Pharmaceuticals And Fruits"
J. Chin. Chem. Soc. 2002 Volume 49, Issue 5 Pages 949-956
Mir Ali Farajzadeh and Sepideh Nagizadeh

Abstract: An accurate, simple, solvent free and inexpensive turbidimetric method is presented for the determination of ascorbic acid in pharmaceutical preparations and fruits. It needs no special reagents or precautions. In this method HgCl2 oxidizes ascorbic acid in citrate buffer at a pH of about 4 and produced Hg2Cl2 precipitate as monitored by turbidance measurements. The procedure is very simple and the experimental conditions such as temperature, ionic strength, stirring and time are not critical. High sensitivity and selectivity are two other advantages of this method. Linear dynamic range of the calibration curve is between 3-120 µg/mL with limit of detection (LOD) 1 µg/mL, which allows the ascorbic acid contents of most fruits and vegetables to be analyzed. On the other hand, the interference studies show that common compounds in real samples and colored substances have no considerable effect on the determination. Only filtration of some samples is necessary and other treatments, which are performed prior to determination of ascorbic acid by other analytical methods, are eliminated. Finally, ascorbic acid concentration in different samples is determined by the proposed method and obtained results are compared with the results of the official 2,6-dichlorophenolindophenol or iodimetric methods and a good agreement is obtained. This method is very sensitive in comparison with iodimetry and is very fast relative to the 2,6-dichlorophenolindophenol method.
Ascorbic acid Turbidimetry Interferences Optimization Method comparison

"Flow Injection Spectrophotometric Determination Of Paracetamol In Pharmaceuticals By Means Of Online Microwave-assisted Hydrolysis And Reaction With 8-hydroxyquinoline (8-quinolinol)"
Anal. Chim. Acta 1996 Volume 330, Issue 1 Pages 59-69
Zouhair Bouhsain, Salvador Garrigues, Angel Morales-Rubio and Miguel de la Guardia*

Abstract: An automated flow injection spectrophotometric method was developed for determining paracetamol in pharmaceuticals. The method was based on the alkaline hydrolysis of paracetamol to yield p-aminophenol which was reacted with 8-hydroxyquinoline in the presence of potassium periodate oxidant to form a blue indophenol dye. An extract of the pharmaceutical preparation in 1.5 M NaOH was injected into a 1.5 M NaOH carrier stream (1.9 ml/min) via a 500 µL sample loop and passed through a reaction coil (6 m x 0.8 mm i.d.) mounted in a focused microwave cavity operating at 200 W. The flow was then merged with 4 mM KIO3 and 2.76 mM 8-hydroxyquinoline (both in 1.5 M NaOH and at 1.9 ml/min) and the absorbance was measured at 608 nm (70 µL detection cell). Calibration graphs were linear up to 158 µM-paracetamol with a detection limit of 1.25 µM and RSD (n = 5) for 39.7 µM-paracetamol of 1.9%. The method was applied to tablets, capsules, syrup and suppositories. The recoveries of 10.6-31.7 µM-paracetamol from spiked pharmaceutical formulations were 96.3-102%. The sampling frequency was 70/h.
Acetaminophen Spectrophotometry Microwave 8-Hydroxyquinoline

"Determination Of Ascorbic Acid By Flow Injection With Chemiluminescence Detection"
Analyst 1993 Volume 118, Issue 6 Pages 639-642
Abdulrahman A. Alwarthan

Abstract: Flow injection and chemiluminescence detection were used to determine 30 amol of ascorbic acid based on the reducing effect of ascorbic acid on Fe(III) and measuring the Fe(II)-catalyzed light emission from luminol oxidation by H2O2. The method was used to determine ascorbic acid levels in tablets, capsules, syrup and fruit juices. The flow cell was a coil made of 1.3 mm i.d. glass tubing spiralled to a diameter of 35-mm. The photomultiplier tube was operated at 400 V. The acidified Fe(III) solution was used as the carrier stream for the sample which was acidified with 1% metaphosphoric acid. The luminol was mixed with the carrier solution at the reaction coil. Each solution was pumped (2.03 mL min-1) by a peristaltic pump. The calibration plot was rectilinear from 10 pM to 100 nM ascorbic acid. The detection limit was 30 amol. The coefficient of variation (n = 10) was 1.4% (for an injection of 1 µM). Recoveries ranged from 90.8 to 101.1% and 95.5 to 106.4% for pharmaceutical preparations and fruit juices, respectively.
Ascorbic acid Chemiluminescence

"Indirect Flame Atomic Absorption-spectrometric Determination Of Papaverine, Strychnine And Cocaine By Continuous Precipitation With Dragendorff Reagent"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 8 Pages 1117-1120
Marcelina Eisman, Mercedes Gallego and Miguel Valcárcel

Abstract: Samples of injection solution, oral drops or syrup were dissolved in H2O; ground tablets were extracted with water and the extract was filtered. The FIA system comprised blank and sample streams, into either of which Dragendorff reagent (0.8 mM tetraiodobismuthate of pH 2.0) was injected. The pH of the sample stream was 5.1-7.2 for papaverine (I), 3.5-7.5 for strychnine (II) or 3.0 for cocaine (III). The resulting stream was passed through a 200 cm mixing coil and filter and analyzed for Bi by flame AAS. The difference in absorbance between the sample and blank (H2O for I or II, 1 mM HCl for III) streams was related linearly to the concentrations of I, II and III over the ranges 1.5-18, 4-60 and 6-100 µg/ml with detection limits of 0.8, 1.5 and 2.5 µg/ml, respectively. The effects of pH, flow rate and temperature were investigated. The tolerance limits towards other common alkaloids are reported.
Papaverine Strychnine Cocaine Spectrophotometry Indirect Precipitation Interferences Filter

"Plastic Membrane Electrodes For The Potentiometric Determination Of Codeine In Pharmaceutical Preparations"
Microchim. Acta 1997 Volume 126, Issue 1-2 Pages 147-151
Eman M. Elnemma and M. A. Hamada

Abstract: The precipitates resulting from the mixing of codeine phosphate and tetraphenylborate or ammonium reineckate solutions were dried and ground. Portions were dissolved in THF, along with PVC powder and plasticizer (dioctyl phthalate or dibutyl sebacate), and the mixtures were evaporated in petri dishes, giving codeine-PVC membranes which were used to fabricate ISE. Crushed tablets were dissolved in aqueous citrate/phosphate buffer solution and potentiometrically analyzed using a codeine-PVC membrane electrode with a Ag/AgCl reference electrode. Pharmaceutical syrup was diluted with the same buffer and similarly analyzed. The electrode was also used for the potentiometric titration of codeine (I) solutions against sodium tetraphenylborate. The applicability of the electrode to FIA was investigated by determinations of I in samples injected into a flow of buffer and potentiometric detection using a sandwich cell incorporating the electrode. For the bulk methods, the calibration graphs were linear from 0.1-10 mM I and detection limits were 0.03-0.07 mM I. The electrodes were stable from pH 3-7. Recoveries from pharmaceuticals averaged 100.6%, and RSD (n = 3) averaged 0.8%. Titrimetric and FIA methods performed similarly, and the FIA method enabled the detection of down to 1 µM-I.
Codeine Potentiometry Electrode Buffer Method comparison Sensitivity

"Determination Of Papaverine And Cocaine By Use Of A Precipitation System Coupled Online To An Atomic Absorption Spectrometer"
J. Pharm. Biomed. Anal. 1994 Volume 12, Issue 2 Pages 179-184
Marcelina Eisman, Mercedes Gallego and Miguel Varcarcel*

Abstract: In the reversed flow injection system (diagram given) incorporating an AAS instrument operated at 357.9 nm, portions (30 µL) of the precipitating reagent, aqueous 0.2% (for papaverine; I) or 0.25% (for cocaine; II) Reinecke's salt of pH 5, was injected into a stream (3.3 ml/min) of 10 mM HCl and passed through a reaction coil (130 cm x 0.5 mm i.d.) producing a high Cr peak. Samples of I or II in 10 mM HCl were then continuously pumped into the system and another injection of Reinecke's salt produced a precipitate which was retained on the filter producing a low peak. The difference between the two peaks represented the amount of precipitated Cr (proportional to the drug concentration). The calibration graphs were linear from 5-85 µg/ml of I and 50-850 µg/ml of II; the corresponding detection limits were 2 and 25 µg/ml and the corresponding RSD were 1.3% and 3.2%. Sample throughput was 150/h. Tolerated amounts of foreign drugs are tabulated. The method was applied to powdered tablets (0.4 or 3 g), oral drops (0.8 ml), syrup (20 ml) and an ampoule of injectable solution dissolved in 100 or 250 mL of H2O.
Papaverine hydrochloride Drugs Spectrophotometry Precipitation Reverse

"FIA Titrations Of Ephedrine In Pharmaceutical Formulations With A PVC Tetraphenylborate Tubular Electrode"
J. Pharm. Biomed. Anal. 1995 Volume 13, Issue 4-5 Pages 459-464
Manuel N. M. P. Alçada, JoséL. F. C. Lima and M. Conceição B. S. M. Montenegro*

Abstract: To prepare membranes for the tubular electrodes, 25 mL 0.1 M sodium tetraphenylborate were mixed with 20 mL 0.1 M tetrapentylammonium bromide in acetone, and the acetone was evaporated. The resulting crystals (0.06 g) were dissolved in 2.42 g 2-nitrophenyl-phenyl ether and portions (0.4 ml) of the resulting solution were mixed with 0.18 g PVC. Tubular electrodes were constructed as described previously (Lima et al., J. Flow Injection Anal., 1990, 7, 19) and applied to the flow injection analysis of ephedrine hydrochloride (I) in pharmaceuticals. Liquid samples equivalent to 2.5 mg I were diluted to 25 mL in phosphate buffer of pH 6.3. Powdered tablets equivalent to 12.6 mg I were dissolved in 25 mL phosphate buffer. Portions (80 µL) were injected into a carrier stream (6.8 ml/min) of 0.1 mM sodium tetraphenylborate in phosphate buffer. After passage through a mixing chamber (details given), potentiometric measurements were made vs. an Orion 90-02-00 double-junction reference electrode. The calibration graph was linear from 0.2-2 mM I and the RSD were 1.5%. Sample throughput was 60/h. The mean recovery of I in pharmaceuticals was 98.6% with a RSD of 2.5%. A flow injection system for the titration of ephedrine in pharmaceutical products with potentiometric detection was developed. For this purpose a tetraphenylborate tubular electrode was constructed. The electrode was prepared without inner reference solution and with a PVC membrane based on tetrapentylammonium tetraphenylborate as ion exchanger and 2-nitrophenylphenyl ether as mediator solvent. Its operational characteristics were evaluated in a low dispersion manifold and compared with more conventionally shaped electrodes using the same sensor. In the pH range 2.5-11.5, the electrodes showed linear response between 3.8 x 10^-6 and 0.1 M with a slope of -56.4 mV/log[BPh4]. Ephedrine determinations in pharmaceutical products were carried out in a single channel manifold with a mixing chamber incorporated and using the tubular electrode as detector. Recovery rates of 98.6±2.5% were obtained in the analysis of tablets, nasal drops and syrups with a sampling rate of about 60 h-1.
Drugs Ephedrine hydrochloride Electrode Potentiometry Electrode Mixing chamber Titrations

"Construction And Evaluation Of PVC Conventional And Tubular Tripelennamine-selective Electrodes: Their Application In Pharmaceutical Preparations"
J. Pharm. Biomed. Anal. 1996 Volume 14, Issue 8-10 Pages 931-938
J. L. F. C. Limaa, M. C. B. S. M. Montenegroa,* and M. G. F. Salesa

Abstract: Conventional membrane-ISE for tripelennamine were fabricated using PVC membranes doped with tripelennamine tetraphenylborate as ionic-exchanger and 2-nitrophenyl octyl ether (type A), dibutylphthalate (type B) or bis-(2-ethylhexyl)sebacate (type C) as plasticizer. These electrodes gave a linear response to 40 µM-0.1 M tripelennamine in 0.1 M phosphate buffer at pH 7 with a fast response time (20 s) and a high reproducibility (±0.2 mV per day). Type A electrode exhibited good selectivity towards tripelennamine in the presence of interferents such as sodium, potassium, lithium, ammonium, chlorpheniramine, diphenydramine, promethazine, meclizine and pentazocine. The type A membrane was used to construct a tubular detector for used in FIA systems. In FIA systems with 0.1 M phosphate carrier stream (6 ml/min), the performance of the tubular detector was similar to that of conventional ISE. The FIA system was used to analyze pharmaceutical preparations (creams, syrups and gels) and mean recoveries of 99.8-100.6% were achieved.
Tripelennamine Electrode Interferences

"Colorimetric Flow Injection Determination Of Resorcinol-type β2-adrenergic Drugs With Phenanthro[9,10-d]imidazole-2-chloroimide"
Anal. Sci. 1989 Volume 5, Issue 5 Pages 513-516

Abstract: For the determination of fenoterol hydrobromide, orciprenaline sulfate or terbutaline sulfate, a portion of ground tablets was extracted with 10 mM HCl (30 ml) by shaking for 10 min. The mixture was diluted with 10 mM HCl to 50 ml, filtered, and the filtrate was diluted 10-fold with water before introduction into the flow injection system; 50 mM borate buffer (pH 11.5) was used as carrier solution (0.8 mL min-1), and reaction with ethanolic 0.003% phenanthro[9,10-d]imidazole-2-N-chloroimide was effected in a 1-m PTFE reaction coil (0.33 mm) at 60°C. Absorbance was measured at 530 nm. Calibration graphs were rectilinear from 0.5 to 200 µM for each drug. Recoveries were >99%; the coefficient of variation (n = 10) were better than 2%. The method was also applied to injection solution and syrup.
Drugs Fenoterol hydrobromide Orciprenaline sulfate Terbutaline sulfate Sample preparation Spectrophotometry Heated reaction Optimization

"Application Of Super Modified Simplex Optimization To The Flow Injection Spectrophotometric Determination Of Promethazine Hydrochloride In Drug Formulations"
Anal. Sci. 1992 Volume 8, Issue 6 Pages 841-843

Abstract: The flow injection system described earlier [Analyst (London), 1991, 116, 177) was applied to the determination of promethazine hydrochloride by using Ce(IV) in H2SO4 medium to oxidize promethazine hydrochloride to a reddish product having maximum absorption at 515 nm. Reaction coil length, Ce(IV) and H2SO4 concentration and flow rate were optimized by the super modified simplex procedure. The max. sampling frequency was 200 h-1 and the calibration graph was rectilinear for 60 to 200 ppm of promethazine hydrochloride. The coefficient of variation for standard solution was 0.8%. The results on tablet and syrup formulations were as accurate as those obtained by the BP method. An accurate, reproducible, flow injection spectrophotometric method for the assay of promethazine was developed using cerium(IV) as an oxidant. The super modified simplex program was utilized for the optimization of dependant parameters. In the method, a 110 µL drug sample was injected into a flowing stream of 6.19 x 10^-4 M cerium(IV) dissolved in 0.512 M H2SO4. The reaction takes place in a reaction coil 62 cm long. Finally, the colored oxidized form of the drug was monitored at 515 nm. Promethazine in the range 60-200 ppm with a 200-sample/h throughout was determined, 0.80% relative standard deviation being attained. The method was successfully applied to the determination of promethazine in proprietary drugs, its accuracy was statistically compared with the British Pharmacopeia official method.
Promethazine hydrochloride Spectrophotometry Optimization Modified simplex Method comparison Standard method

"Electrochemical Derivatization Of Thiamine In A Flow Injection System-application To Thiamine Analysis"
Chem. Pharm. Bull. 1983 Volume 31, Issue 10 Pages 3589-3594
Kusube, K.;Abe, K.;Hiroshima, O.;Ishiguro, Y.;Ishikawa, S.;Hoshida, H.

Abstract: The method is based on electrochemical oxidation of thiamine to thiochrome. A flow-through electrolytic cell, consisting of a vitreous-carbon tube (10 cm x 5 mm) as working electrode and a vitreous-carbon rod (15 cm x 3 mm) as counter-electrode, is described and illustrated. For determination of thiamine, the sample (10 µg mL-1 in methanol) was injected into a flow (0.5 mL min-1) of aqueous 90% methanol 0.05 M in NaClO4 and containing 1% NaOH, and a potential of +0.4 V was applied vs. silver - AgCl. Detection was by fluorimetry at 430 nm, with excitation at 375 nm. The calibration graph was rectilinear for 1 to 100 ng of thiamine and the time required was 3 min for each determination. The results for analysis of a vitamin capsule, a tablet and a syrup were in good agreement with those obtained by a chemically induced fluorimetric and a HPLC method, without interference from other B-group vitamins or a number of other vitamins.
Thiamine Electrode Fluorescence Potentiometry Interferences