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: Fruit -> orange -> juice

Citations 13

"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

"Determination Of Antimony Species With Fluoride As Modifier And Flow Injection Hydride Generation Inductively-coupled Plasma Emission Spectrometry"
Anal. Chim. Acta 2000 Volume 417, Issue 2 Pages 201-209
Nina Ulrich

Abstract: A new method for the determination of species of antimony(III) [Sb(III)], antimony(v) [Sb(V)] and trimethylstiboxide [TMeSbO] with fluoride as modifier is introduced. A flow injection (FI) system for hydride generation was used in combination with an inductively-coupled plasma atomic emission spectrometer as detector. The pre-reduction was accomplished with potassium iodide dissolved in hydrochloric acid and the reduction with sodium borohydride. The influence of fluoride on the reduction and pre-reduction step was investigated by adding different amounts of sodium fluoride to the solvent stream. At a concentration of 100 mg/l fluoride and 1.2% potassium iodide, the hydride formation of Sb(V) and Sb(III) was suppressed below the detection limit, while TMeSbO showed no signal depression. The use of 100 mg/l fluoride without potassium iodide led to complete signal suppression for Sb(V) with apparently no influence on the signal intensity of Sb(III) and TMeSbO. The concentration of TMeSbO was measured directly, the concentrations of Sb(III) and Sb(V) were calculated on the basis of the three analyzing steps, giving detection limits and relative standard deviations of 1.1 (2.6%), 1.2 (5.3%) and 1.4 µg/l (8.1%), respectively. The method was applied to orange juice samples.
Antimony(3+) Antimony(5+) Trimethylstibine oxide Spectrophotometry Speciation Interferences Method comparison

"Flow Injection Analysis With A Fluorimetric Detector For Determinations Of Glycine And Albumin"
Anal. Chim. Acta 1979 Volume 106, Issue 2 Pages 395-399
Joy I. Braithwaite and J. N. Miller

Abstract: Flow injection analysis with fluorometric detection was used in the determination of glycine and albumin, with o-phthalaldehyde being used in determination of the latter. Preliminary variables and applications of flow injection analysis were examined, using quinine sulfate and m-hydroxybenzoic acid which are intrinsically fluorescent. System response was linear in the range of 0-8 µg/mL for glycine and concentrations as low as 2 pg/mL were detectable. The level of glycine in orange juice and dietetic cola was 0.33-0.41 and 0.17 g/dL, respectively. Serum albumin determinations flow injection analysis had a relative standard deviation of 1.8%. The method allowed sampling rates of 180/h for both glycine and albumin.
Glycine Albumin Clinical analysis Fluorescence Optimization

"Simultaneous Flow Injection Determination Of 2- And 4-nitrophenol Using A Photodiode-array Detector"
Anal. Chim. Acta 1992 Volume 258, Issue 2 Pages 269-273
M. E. León-González*, L. V. Pérez-Arribas, M. J. Santos-Delgado and L. M. Polo-Díez

Abstract: The sample, e.g., fruit juice, was injected into a carrier stream of 0.5 M phosphate buffer of pH 7.4 (2 mL min-1) and mixed with 0.13% tetrabutylammonium nitrate solution (1.2 mL min-1). The ion pairs were extracted into 1,2-dichloroethane and the absorbances at 260 and 410 were measured for 2- and 4-nitrophenol, respectively. The calibration graphs were rectilinear from 0.1 to 12 mg l-1, with detection limits of 0.03 mg l-1. The coefficient of variation (n = 8) at 6 mg L-1 of either compound was 0.15%. Recoveries of 1 to 10 mg L-1 from fruit juice were between 90 and 105%. A batch method was also examined, but gave a coefficient of variation of 2.1%. A flow injection method for the simultaneous determination of o- and p-nitrophenol in apple and orange juices is based on formation and extraction of ion pairs by using Bu4N+ as counter ion at pH 7.4 and diode-array spectrophotometric detection at 260 and 410 nm for o- and p-nitrophenol, respectively. The calibration graphs were linear for 0.1-12 mg/L. The relative standard deviation at 6 mg/L was 0.15% for both o- and p-nitrophenol and the detection limits were 0.03 mg/L.
2-Nitrophenol 4-Nitrophenol Spectrophotometry Sample preparation Simultaneous analysis Method comparison Ion pair extraction Organic phase detection

"Determination Of L-asparagine Using Flow Injection Systems With Spectrophotometric And Potentiometric Detection"
Anal. Chim. Acta 1996 Volume 336, Issue 1-3 Pages 113-122
Kathrin Stein*, Renbing Shi and Georg Schwedt

Abstract: Two FIA methods were developed for determining asparagine in foods. The first method was based on the catalyzed hydrolysis of asparagine by immobilized asparaginase to yield NH3. The NH3 diffused through a PTFE membrane and was detected (i) spectrophotometrically using an acid-base indicator solution as the acceptor or (ii) potentiometrically using a pH electrode and water as the acceptor. The linear ranges and RSD (n = 5) were 0.2-2.3 mM and 1.7% (at 0.75 mM asparagine), respectively, for spectrophotometric detection and 0.1-4 mM and 2.5% (at 1 mM asparagine), respectively, for potentiometric detection. The sampling frequency was 35/h. The second method used a biosensor fabricated by attaching a membrane with immobilized asparaginase on to a pH electrode. The linear range and RSD (n = 5) of this method were 0.1-2 mM and 2.3% (at 1 mM asparagine), respectively. The sampling frequency was 30/h. The methods were applied to apple and orange juice, oranges and asparagus. The sample preparation procedure involved diluting the fruit juices or filtering the homogenates of the solid foods. Recoveries of 50 mg/l or 50 mg/100 g asparagine from spiked foods were >94.3%.
l-asparagine Potentiometry Electrode Spectrophotometry Sensor Immobilized enzyme Teflon membrane Gas diffusion

"Pulse Injection Analysis With Chemiluminescence Detection: Determination Of Citric Acid Using Tris-(2,2'-bipyridine) Ruthenium(II)"
Talanta 1998 Volume 47, Issue 2 Pages 301-304
He Zhike*, Gao Hua, Yuan Liangjie, Lu Shaofang, Meng Hui, Li Xiaoyan and Zeng Yun'e

Abstract: A chemiluminescence method for the determination of citric acid was developed. The method is based on the enhancement of citric acid on the chemiluminescence light emission of tris-(2,2'-bipyridine)ruthenium(II). In the presence of tris-(2,2'-bipyridine)ruthenium(II), upon the addition of Ce(IV), resulted in intense light emission. The emission intensity is greatly enhanced by the presence of citric acid. The linear range and detection limit of citric acid are 3.0 x 10^-8 ~ 6.0 x 10^-6 mol L-1 and 3.0 x 10^-8 mol L-1, respectively. The precision of the proposed method is determined by analyzing 11 samples containing 1.0 x 10^-7 mol L-1 citric acid. The relative standard deviation is 3.0%. The enhanced mechanism of citric acid was studied. The method was evaluated by carrying out an interference study with common ions and compounds, by a recovery study and by anal. of human urine and orange juice. A satisfactory result was obtained.
Citric acid Chemiluminescence Indirect Interferences

"Application Of Oscillating-reaction-based Determinations To The Analysis Of Real Samples"
Analyst 1997 Volume 122, Issue 3 Pages 287-292
Rafael Jiménez-Prieto, Manuel Silva and Dolores Pérez-Bendito

Abstract: The use of an oscillating reaction involving the H2O2/NaSCN/CuSO4 system in an alkaline medium for the continuous-flow analysis of real samples by the analyte pulse perturbation technique is described. The method involves the addition of small amounts of the analyte to the oscillating system and measuring the changes in the oscillation amplitude and/or oscillation period produced. The method was applied to the determination of vanillin (I) in food, paracetamol (II) in pharmaceuticals, and ascorbic acid (III) in orange juice and pharmaceuticals. The calibration graphs were linear from 1-40, 0.5-6 and 0.5-5 µmol I, II and III, respectively. RSD were n = 11). Sample throughput was 6-10 samples/h.
Acetaminophen Ascorbic acid Vanillin Spectrophotometry Oscillating chemical reaction Indirect

"Continuous Determination Of Ascorbic Acid By Photobleaching Of Methylene Blue"
Anal. Chem. 1972 Volume 44, Issue 7 Pages 1267-1269
Vance R. White and J. M. Fitzgerald

Abstract: An apparatus for the determination of ascorbic acid, via the photobleaching of the methylene blue carrier stream, was discussed and the appropriate diagram presented. The signal was measured by an Atomic Absorption (AA) spectrophotometer and a major advantage to the system is its ability to regenerate the methylene blue carrier stream via the oxidation of methylene blue by diatomic oxygen. Day to day reproducibility was very good and a discussion of interferences (mostly from aromatic components) is presented along with a table outlining the various interference levels. A discussion of the results for the analysis of orange juice, water, and vitamin C tablets are presented.
Ascorbic acid Spectrophotometry Apparatus Indirect Interferences Photochemistry

"Separation Of Ascorbic Acid, Dehydroascorbic Acid, Dioxogulonic Acid And Glucose By Isocratic Elution From A Column Of A Hydrophilic Gel"
J. Chromatogr. A 1985 Volume 332, Issue 1 Pages 283-286
Tokuichiro Seki, Yoshihisa Yamaguchi, Kohji Noguchi and Yuzo Yanagihara

Abstract: Orange juice was applied to a mixed-bed ion-exchange column (10 cm x 6 mm) of Amberlite CG-50 and Amberlite XAD-2 with elution with aqueous 15 mM tartrate buffer (pH 3) containing 2 mM EDTA and 0.05% of 2,2'-thiodiethanol. The eluate was analyzed by HPLC on a column (50 cm x 7.6 mm) of Asahipak GS-320 at 30°C with the above mobile phase, and the eluate was subjected to post-column derivatization, at 90°C, with a 1:1 mixture of 0.02 M benzamidine hydrochloride and 0.25 M potassium borate buffer (pH 10) containing 0.25 M K2SO3 before fluorescence measurement at 400 nm (325-nm excitation). Separation of glucose, dioxogulonic acid, dehydroascorbic acid and ascorbic acid was achieved; the calibration graph was rectilinear for 5 to 500 ng of ascorbic acid.
Ascorbic acid dehydroascorbic acid Diketogulonic acid Glucose HPLC Fluorescence Amberlite Heated reaction Post-column derivatization

"Spectrophotometric Determination Of Ascorbic Acid In Vitamin C Tablets, Beverages, Orange And Urine With 2,6-dichloroindophenol By Flow Injection Analysis"
Fenxi Huaxue 1991 Volume 19, Issue 2 Pages 182-184
Ma, H.C.;Feng, J.Z.;Cao, B.

Abstract: Sample is injected into a carrier stream of potassium hydrogen phthalate buffer of pH 3.6 (2 mL min-1) for reaction with a reagent stream of 0.2 mM dichloroindophenol (1.5 mL min-1) in a 15-cm reaction coil before kinetic spectrophotometric detection at 525 nm. For the analysis of vitamin C tablets, oranges, beverages and urine by use of the standard-additions method, recovery was 72 to 117%. For 50 µg mL-1 of I, the coefficient of variation was 0.5%. Detection limit was 0.5 µg mL-1. The calibration graph was rectilinear up to 50 µg mL-1. Interference was observed from Fe(III); most co-existing ions (e.g., Zn and Cu), sugars, amino-acids and organic acids (such as citric acid) did not interfere.
Ascorbic acid Spectrophotometry Buffer Interferences Kinetic Standard additions calibration

"Determination Of Total Acidity In Wines And Fruit Juices By Flow Injection Analysis"
GBF Monogr. Ser. 1989 Volume 11, Issue 1 Pages 277-280
Flossdorf, Josef; Wansheng, Yang (SFS)

Abstract: Procedures developed by J. Ruzicka were used for flow-injection anal. of total acidity in beverages. Agreement with the standard method is better than ±2%. Up to 30 determinations per h are possible with each 100-150 µL sample volume (SFS)
Acidity, total

"Simultaneous Analysis Of Ascorbic And Dehydroascorbic Acid By High Performance Liquid Chromatography With Post-column Derivatization And UV Absorbance"
J. Agric. Food Chem. 1986 Volume 34, Issue 2 Pages 271-274
Bechir Kacem, Maurice R. Marshall, Richard F. Matthews, and Jesse F. Gregory

Abstract: Samples of fruit, vegetables or orange juice were mixed with 3% H3PO4 and filtered and the filtrate was purified on Sep-Pak C18. The resulting solution was analyzed by anion-exchange HPLC on a column of Alltech NH2 with a mobile phase of 75% acetonitrile in 0.05 M phosphate buffer (pH 5.9). Post-column derivatization of dehydroascorbic acid(I) was carried out with o-phenylenediamine to form a fluorescent quinoxaline derivative for fluorimetric detection. Ascorbic acid(II) was detected by absorbance measurement at 254 nm. Calibration graphs were rectilinear for up to 0.1 mg mL-1 and up to 40 µg mL-1 of II and I, respectively. Detection limits were 0.01 and 0.05 µg for I and II, respectively.
Ascorbic acid dehydroascorbic acid HPIC Fluorescence Spectrophotometry Post-column derivatization

"Semiautomatic Determination Of Furanic Aldehydes In Food And Pharmaceutical Samples By A Stopped-flow Injection Analysis Method"
J. AOAC Int. 1993 Volume 76, Issue 6 Pages 1255-1261
Espinosa Mansilla, A.;Munoz De La Pena, A.;Salinas, F.

Abstract: Sample solution was injected into a carrier stream of water which merged sequentially with a stream of 5 M HCl and a stream of 0.03 M 2-thiobarbituric acid. The procedure was carried out at 40°C and the reaction was monitored at 425 nm. A schematic diagram of the stopped-flow FIA system is presented. The method was used to determine 5-hydroxymethyl-2-furfuraldehyde (I) and furfural in honey, orange and grape juice, red wine and pharmaceuticals. The calibration graph was linear for 1.1-14.6 µg/ml of I and the detection limit was 0.47 µg/ml. The RSD for 5.6 µg/ml of I (n = 10) was 2.4%. Sample throughput was ~40/h; details are given of the manual and automatic steps of the procedure. A kinetic study of the reactions of 5-hydroxymethyl-2-furfuraldehyde and furfural with 2-thiobarbituric acid (TBA) by a stopped-flow flow injection analysis technique has been undertaken. A semiautomatic method for the analytical determination of these furanic aldehydes is proposed on the basis of reaction with TBA. The proposed stopped-flow method was successfully applied to several commercial pharmaceutical preparations and food samples. The procedure is faster than the earlier procedure for determination of these compounds in foods and pharmaceuticals.
Aldehydes, furanic Spectrophotometry Stopped-flow Kinetic