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: Food -> milk -> powder

Citations 15

"Heat Classification Of Skimmed Milk Powders By Flow Injection Analysis"
Aust. J. Dairy Technol. 2000 Volume 55, Issue 2 Pages 109-109
Louise E Bennett, Jason W Costin, Sunanda Sudharmarajan, Geoffrey W Smithers

Abstract: FIA was applied to this analysis.

"Determination Of Selenium By Means Of Computerized Flow Constant-current Stripping At Carbon Fiber Electrodes. Application To Human Whole Blood And Milk Powder"
Anal. Chim. Acta 1987 Volume 197, Issue 1 Pages 257-264
Chi Hua, Daniel Jagner and Lars Renman

Abstract: The main features of the flow constant-current stripping analysis for selenium(IV) are formation of a mercury film on a carbon fiber sensor in a chloride medium containing mercury(II), electrolysis in the sample at -0.20 V vs. SCE for 15-60 s, and subsequent stripping (reduction) of the mercury(II) selenide formed on the electrode surface, by means of a constant current of 0.40 µA in an acidic magnesium chloride solution containing Triton X-100. During stripping, the potential vs. time gradient is monitored at a real-time measuring rate of 25.6 kHz. All experimental parameters are under computer control. A standard addition method is used and the results are calculated and reported, both digitally and graphically. Equations relating the magnitude of the constant current to the concentration of reducible species, and, in particular, of dissolved dioxygen, are derived. Milk powder and whole blood reference samples were analyzed by high-pressure digestion in nitric acid and dilution with hydrochloric acid, in order to reduce selenium(VI) to selenium(IV), and then constant-current stripping. The results obtained by this method were lower than those obtained by the reference technique, but the values agreed within one standard deviation of the two techniques. Ions, such as iron(III) and lead(II), known to interfere with electrochemical stripping for selenium(IV) in batch analysis did not interfere in the flow approach.
Selenium Amperometry Electrode Computer

"Sensitive Flow-Injection Amperometric Detection Of Iodide Using Mn3+ And As3+"
Anal. Sci. 2005 Volume 21, Issue 5 Pages 525-529
Snezana D. NIKOLIC, Jelena J. MUTIC, Aleksandar D. LOLIC, and Dragan D. MANOJLOVIC

Abstract: A rapid, selective, and sensitive kinetic flow-injection method for iodide content determination with amperometric detection on a platinum electrode was developed. The method is based on the catalytic effect of iodide on the Mn3+ reaction with As3+ in the presence of sulfuric acid. The calibration curve was linear in the concentration range from 5.0 x 10^-7 to 1.0 x 10^-4 mol/L iodide. The limit of detection (LOD) was found to be 5.0 x 10^-9 mol/L iodide. The relative standard deviations (RSD) were 1.68% and 3.03% for 1.0 x 10^-3 mol/L standard and 1.0 x 10^-6 mol/L iodide solution (n = 6), respectively. The method has been successfully applied for determination of iodide in waters, table salts, fodder, organic substances and human blood sera. The results were compared with those obtained by a standard AOAC (Association of Official Analytical Chemists) method, as well as with those obtained by a kinetic spectrophotometric procedure for determination of iodide.
Iodide Amperometry Electrode Method comparison Interferences Catalysis

"Determination Of Cadmium, Lead And Copper In Milk And Milk Powder By Means Of Flow Potentiometric Stripping Analysis"
Talanta 1986 Volume 33, Issue 12 Pages 991-995
L. Alamestrand, D. Jagner and L. Renman

Abstract: A flow potentiometric stripping analysis procedure for the determination of cadmium, lead and copper in milk and milk powder samples is described. The instrumental arrangement consists of a glassy-carbon thin-layer cell through which six different solutions may be drawn by means of a peristaltic pump and magnetically operated valves. The glassy-carbon electrode is pre-coated with a film of mercury which can be employed for several analytical runs. The sample, diluted five-fold with Suprapur hydrochloric acid, is electrolysed for 0.5-4 min prior to stripping in Suprapur hydrochloric acid. Pump-rate, electrolysis time and potential, opening and closing of inlet valves and digital evaluation of stripping times are controlled automatically by the computer. The analytical results agree satisfactorily with the certified values for three milk powder reference samples. The detection limit for cadmium, lead and copper in milk samples after 4, 1 and 0.5 min of pre-electrolysis is 0.8, 4 and 8 µg/l., respectively. An analytical procedure for the determination of lead in samples containing high concentrations of tin is described.
Cadmium Copper Lead Potentiometric stripping analysis

"Online Sorbent Extraction, Preconcentration And Determination Of Lead By Atomic Absorption Spectrometry"
Talanta 1995 Volume 42, Issue 2 Pages 211-218
Yaneira Petit de Peña*, Mercedes Gallego and Miguel Valcárcel*,

Abstract: Skimmed milk powder and mineral reference samples were dried to a constant weight and mineralized by mixing with 14.4 M HNO3 with or without 11.2 M HCl (details given) and heating at 180-200°C until the samples dissolved and N2O fumes were given off. After cooling, the process was repeated until no N2O was evolved and a clear solution remained. The solutions were diluted with water and the mineral samples were adjusted to pH 1 with 2 M HNO3. The sample (3 ml/min) was introduced into a FIA manifold where it merged with a chelating reagent stream (0.3 ml/min) of 0.1% ammonium pyrrolidine dithiocarbamate or saturated dithizone in 0.2 M ammonia. The chelate was retained on an activated carbon minicolumn (2.5 cm x 3 mm i.d.) and the sample matrix was flushed to waste. The injection valve was switched and the column was desorbed with IBMK. The Pb was determined by AAS at 283.2 nm. Linear calibration graphs were obtained in ng/ml range (details tabulated) with detection limits of 10^-15 ng/ml for a 2 min sampling time and RSD of 2.3-3%. The effects of interferences on the method are discussed.
Lead Sample preparation Spectrophotometry Sample preparation Chelation Column Solid phase extraction Interferences Reference material Preconcentration Activated carbon Dithizone MIBK

"Selective Spectrofluorimetric Determination Of Zinc In Biological Samples By Flow Injection Analysis (FIA)"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 7 Pages 597-600
P. Fernández, C. Pérez Conde, A. Gutiérrez and C. Cámara

Abstract: Sample (0.25 g) was heated at 500°C for 2 h in a muffle furnace. The residue was dissolved in 0.5 mL of HNO3 and the solution was diluted to 25 mL with water. A 125 µL portion of the resulting solution was injected into a carrier stream (0.62 mL minmin1) of 0.5 M hexamethylenetetramine adjusted to pH 6 with HClO4 which merged with a stream (0.36 mL min-1) of 0.05% of 5,7-dibromo-8-quinolinol in ethyl ether. The two phases were separated and the organic phase was passed through a flow cell where its fluorescence was measured at 550 nm (excitation at 410 nm). The calibration graph was rectilinear up to 1 µg mL-1 of Zn(II); the detection limit was 3 ng mL-1. Sample throughput was 40 h-1. Among the 30 cations and anions studied, only Ni(II), Mn(II) and EDTA interfered seriously. The method was used to determine Zn in tap and well water, muscle, milk powder and whole diet. The automatization of a spectrofluorimetric method for the determination of zinc at trace level is described. It is based on the formation of the fluorescent complex Zn(II)-5,7-dibromo-8-quinolinol [Zn(II)-DBQ] followed by extraction into diethyl ether using flow injection analysis The optimum fluorescent emission is reached in hexamethylenetetramine (H2MTA+/HMTA) buffer pH 6.0. A membrane phase separator was used. The calibration graph is linear up to 1.5 µg/mL of Zn(II). The proposed method (detection limit 3 ng/mL) is very selective and has been successfully applied to determine Zn(II) in biological samples, tap waters, and various food items.
Zinc Fluorescence Organic phase detection Optimization Interferences Reference material Phase separator

"Direct Determination Of Copper And Iodine In Milk And Milk Powder In Alkaline Solution By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 3 Pages 323-326
S. Stürup and Arne Büchert

Abstract: Milk powder (0.2 g) was dissolved in 50 mL 0.05 M KOH/0.07 M tetramethylammonium hydroxide, or 0.5 mL raw milk was diluted with 9.5 mL of the alkaline mixture. Each sample was spiked twice with 5 and 10 µg/l I2 and Cu for standard-addition calibration to overcome matrix effects. Analysis was performed using a FIA system with a 500 µL injection loop, the alkaline mixture as carrier and ICP-MS detection. The analyte masses were monitored at m/z 63 and 127. The measurement time was 70 s/injection, which resulted in a high sample throughput. The detection limits were 0.45 and 0.94 µg/l for I2 and Cu, respectively. The method was applied to monitoring over 100 milk samples.
Copper Iodine Mass spectrometry Interferences Standard additions calibration

"Extending The Dynamic Range Of Flame Atomic Absorption Spectrometry: A Comparison Of Procedures For The Determination Of Several Elements In Milk And Mineral Waters Using Online Dilution"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 1 Pages 57-64
I. López García, P. Viñas, N. Campillo and M. Hernández Córdoba

Abstract: Three previously described flow injection manifolds (Lopez Garcia et al., J. Anal. Atomic Spectrom., 1992, 7, 1291; Ibid., 1994, 9, 553; Ibid., 1994, 9, 1167) are described and evaluated for their abilities to extend the dynamic range of flame AAS. The systems were used for elemental determination in infant formulae, powdered milk and mineral water. The results obtained by using each manifold are tabulated and discussed. The continuous-flow method is shown to be a reliable alternative to dilution procedures and the systems can be automated or semi-automated.
Trace elements Spectrophotometry Method comparison Linear dynamic range Dilution

"Determination Of Amino-acids By Ion-pair Liquid Chromatography With Post-column Derivatization Using 1,2-naphthoquinone-4-sulfonate"
J. Chromatogr. A 1994 Volume 676, Issue 2 Pages 311-319
J. Saurina and S. Hernández-Cassou*

Abstract: Amino-acids were analyzed by ion-pair HPLC on a column (15 cm x 4.6 mm) of Spherisorb ODS-2 (5 µm) with gradient elution (0.8 ml/min) of 20 mM phosphoric acid/20 mM sodium dihydrogen phosphate/15 mM SDS as eluent A and (25 mM phosphoric acid/25 mM sodium dihydrogen phosphate - 18.5 mM SDS)/propan-2-ol (4:1) as eluent B; 0% B (held for 10 min) to 100% B over 75 min to 0% B (held for 2 min) over 3 min. The column outlet was coupled online to a two channel derivatization system. The reagents 1,2-naphthoquinone-4-sulfonate and 15 mM sodium hydrogen carbonate/0.185 M sodium carbonate were mixed and merged with the column eluate in a reaction coil (4 m x 1.1 mm) at 65°C and spectrophotometric detection at 305 nm. The calibration graph was linear up to 32 nmol for lysine with a detection limit of 0.09 nmol. For the nine amino-acids tested, the repeatability was >4%, reproducibility was >5% and the detection limits were 0.09-0.33 nmol. The method was applied to the determination of amino-acids in animal feed and powdered milks.
Amino Acids HPLC Spectrophotometry Post-column derivatization Heated reaction

"Directly Coupled Sample Treatment-high Performance Chromatography For Online Automatic Determination Of Liposoluble Vitamins In Milk"
J. Chromatogr. A 1995 Volume 694, Issue 2 Pages 399-406
M. M. Delgado-Zamarreño*, A. Sanchez-Perez, M. C. Gomez-Perez and J. Hernandez-Mendez

Abstract: An automated sample treatment and analysis system for the determination of vitamins A, E and cholecalciferol in both powdered and liquid milk is described. Powdered milk (0.5-2 g) was dissolved in 25 mL water and liquid milk was diluted with water to 30%. The samples were hydrolyzed using a two-channel system in a coiled PTFE tubing reactor (5 m x 0.5 mm i.d.) using 60% aqueous NaOH/10% ascorbic acid/ethanol (3:1:10). A third channel containing 2.5 M acetic acid was used to neutralize the solution before pre-concentration on a Sep-Pak C18 cartridge for 5 min. The cartridge was washed with H2O/methanol (3:2) for 4 min. The vitamins were eluted with methanol into a 100 µL injection loop, then analyzed on a 5 µm Brownlee OD-224 RP-18 column (22 cm x 3.2 mm i.d.) with a 7 µm RP18 guard column (1.5 cm x 3.2 mm i.d.), 2.5 mM acetic acid/sodium acetate buffer in aqueous 99% methanol as mobile phase (1 ml/min), UV detection at 280 nm and electrochemical detection at 1.3 V. Recoveries (n = 10) were 80-105% and day-to-day RSD (n = 10) were 1.2-6.8%.
Cholecalciferol Vitamin A Vitamin E HPLC C18 Preconcentration

"Determination Of Trace Platinum By Flow Injection Analysis - Adsorptive Stripping Voltammetry And Catalytic Polarographic Hydrogen Wave"
Fenxi Huaxue 1990 Volume 18, Issue 1 Pages 20-24
Wei Guizhen Lu Zongpeng* Alan M.Bond

Abstract: Platinum solution (0.1 µg mL-1; 100 µL) is injected into the flow injection analyzer. and reacts in a stream (0.27 mL min-1) of 0.002% hydrazine sulfate - 0.36 M H2SO4 and 0.04% formaldehyde - 0.36 M H2SO4. Detection is by adsorptive stripping voltammetry at -0.3 V for 60 s and measurement of the catalytic hydrogen wave at -0.8 V. Recoveries were 93.7 to 100% with a coefficient of variation of 5%. The calibration graph was rectilinear for 10 pg to 1 ng of Pt. Twenty samples can be run per hour. The method was applied in the analysis of urine, fish meal, milk powder, ox liver, minerals and organoplatinum compounds.
Platinum Voltammetry Polarography Catalysis Calibration

"Automation Of Iron And Copper Determination In Milks Using FIA Systems And Colorimetric Detection"
Food Chem. 1998 Volume 62, Issue 1 Pages 117-121
José L. F. C. Lima, Cristina Delerue-Matos* and M. Carmo V. F. Vaz

Abstract: This paper describes a flow injection manifold with a colorimetric detection system that enables the determination of iron and copper in different types of milks, namely cow milk and infant formula powd. milks. The methodology used is based on the formation of colored complexes produced by the reaction of iron (II) with 1,10-phenanthroline and copper(II) with 1,5-diphenylcarbazide. The samples were digested with nitric and sulfuric concentrated acids and inserted in the FIA system without additional treatment. The pH adjustment was carried out inside the manifold including the addition of the reagents needed to form the absorbing species. The sample rate of both species was never lower than 120 determinations h-1. The results obtained were compared with those given by the reference methods, and the relative deviation was less than 5 and 4% for the determinations of iron and copper respectively. The precision of the results evaluated by the relative standard deviation (RSD%) was less than 0.5% for iron and 2% for copper determinations
Iron(2+) Copper(II) Spectrophotometry Sample preparation Complexation pH Method comparison

"Sample Zone Cutting By Relocation Of A Coiled Reactor: An Alternative To Increase Manifold Versatility"
J. Flow Injection Anal. 1998 Volume 15, Issue 1 Pages 47-59
Rocha, F.R.P.;Nobrega, J.A.;Gouveia, S.T.

Abstract: The versatility of flow systems can be extended by relocating manifold components, such as resin columns, flow cells, and coiled reactors. The feasibility of the relocation of a coiled reactor was investigated. This approach was applied to reduce the washing time, to adjust the sample concentration range, and to decrease the amount of sample introduced in the nebulization chamber of a flame atomic absorption spectrophotometer (FAAS). Relocation of the coiled reactor allowed cutting the rear of the sample zone and different strategies were implemented employing the same flow system. In nitrite determination using Griess's reaction, sampling rates were 212 h-1 and 327 h-1 without and with a 200 cm relocating reactor, respectively. The adjustment of the sample concentration to the linear response range of the detector was achieved by changing the delay time for relocating the coiled reactor. Relocation of the a coiled reactor also made feasible the direct determination of calcium in milk by FAAS decreasing by 62% the volume of the milk suspension introduced in the nebulization chamber, which is useful to avoid clogging. The accuracy of this procedure was checked using two kinds of whole milk powders standard reference materials (NIST 8435 and IAEA 153) and the results obtained agreed with the certified values at a 95% confidence level.
Nitrite Calcium Spectrophotometry Reference material Nebulizer Reactor Linear dynamic range

"Determination Of Iron And Copper In Infant Formula Powdered Milks By Flow Injection Atomic Absorption Spectrometry"
Quim. Anal. 1987 Volume 6, Issue 4 Pages 427-435
Burguera, M.;Burguera, J.L.;Garaboto, A.M.;Alarcon, O.M.

Abstract: The sample was dissolved in water (10 mL per 1 g), and a 3 mL portion of the solution was mixed with 1 mL of concentrated HNO3 and 1 mL of water, and heated in a 50 mL phial in a 700-W microwave oven for 5 min. The product was dispersed in 1 mL of 100% Triton X-100 and diluted to 5 mL with water. Portions (100 µL) were injected into a carrier stream of water (2.9 mL min-1 for Fe; 3.7 mL min-1 for Cu) flowing to a nebulizer for AAS in an air - acetylene flame; measurements were made at 248.3 and 324.8 nm for Fe and Cu, respectively. As some other ions interfered, the method of standard additions was used for evaluation. Results agreed with those obtained by conventional AAS, colorimetry and ring colorimetry. The detection limits were 0.02 and 0.01 mg L-1 for Fe and Cu, respectively, and the coefficient of variation was ~5% for 0.38 mg L-1 of Fe or 0.19 mg L-1 of Cu.
Copper Iron Spectrophotometry Interferences Method comparison Standard additions calibration Triton X Surfactant

"Ion-exchange Chromatographic Determination Of Lactulose And Epilactose In The Presence Of Lactose And Other Carbohydrates In Milk And Milk Products"
Z. Lebensm. Unters. Forsch. 1985 Volume 181, Issue 5 Pages 408-411
Ernst H. Reimerdes und K. -D. Rothkitt

Abstract: The fat and protein from heated milk and reconstituted milk powder are removed by treatment with Carrez I and II solution and filtration. The carbohydrates in the filtrates are determined on a column (7.5 cm x 6 mm) of Dionex DA-X8-11 with a pre-column (5 cm x 9 mm) of Dowex 1-X4, and with gradient elution with (A) 0.15M, 0.2M, 0.4 M (each of pH 8.0), 0.8 M (pH 8.3) and 0.15 M (pH 8.0) borate buffers or (B) 0.2M, 0.3 M (each of pH 8.0), 0.8 M (pH 8.3) and 0.2 M (pH 8.0) borate buffers. Post-column derivatization is effected with Cu(I) bicinchoninate and detection is at 570 nm. By using system A, lactulose and epilactose were determined, even in the presence of large amounts of lactose; use of buffer system B permitted detection of lactulose in the presence of fructose. In addition, other carbohydrates, e.g., ribose, mannose, galactose and glucose, can be determined simultaneously.
Lactulose Epilactose HPIC Spectrophotometry Post-column derivatization