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 -> formula -> baby

Citations 7

"Enzymic Flow Injection Determination Of Free L-Carnitine In Infant Formulae"
Analyst 1997 Volume 122, Issue 12 Pages 1539-1541
Isabel M. P. L. V. O. Ferreira, Marta N. Macedo and Margarida A. Ferreira

Abstract: Infant formula samples were analyzed to determine their free L-carnitine content by using flow injection (FI) with an incorporated immobilized carnitine acetyltransferase bioreactor. The methodology was based on the spectrophotometric determination through its reaction with carnitine acetyltransferase coupled with acetyl coenzyme A (acetyl-CoA) and dithiobenzoate. The merging zones technique was used to minimise acetyl CoA consumption. Linearity was observed over the concentration range 10^-80 mg L-1 with L-carnitine as standard (r = 0.9998) and the rate of analysis was 50 h-1 infant formula samples. The enzymatic FI method afforded a low RSD (2.2%). Comparisons were made with other methods of known accuracy. The enzymatic reactors were stable for 3 months when used daily at the optimum pH.
Carnitine Spectrophotometry Immobilized enzyme Method comparison Optimization Merging zones

"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

"Colorimetric Determination Of Iron In Infant Fortified Formulas By Sequential Injection Analysis"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1153-1156
A. N. Araújo, Joan Gracia, José L. F. C. Lima, Manel Poch, M. Lúcia M. F. S. Saraiva

Abstract: Commercial infant formulas (3-5 g) were heated at 550°C to constant wt. then treated with 50 mL 0.2 M HNO3 as described previously (AOAC, Official Methods of Analysis (15th ed.), 1990, 777). Sequential injection analysis was then carried out (details of system and diagram given). The digest (140 µL) was aspirated to a holding coil (200 cm x 0.8 mm i.d.) via a sampling tube (15 cm x 0.5 mm i.d.) and mixed with 70 µL 2 M potassium thiocyanate. The resultant mixture was propelled at a flow rate of 5 ml/min from the holding coil through a mixing coil (75 cm x 0.8 mm i.d.) to the detector. The detector was a Pye Unicam SP6-350 spectrophotometer with a Hellma 178. 712Q flow cell (18 µl). Calibration graphs were linear from 0.5-20 mg/l. The sampling rate was 100 samples/h; RSD was n=12).
Iron Spectrophotometry Selectivity Sequential injection

"Rapid And Sensitive Determination Of Nitrite In Foods And Biological Materials By Flow Injection Or High Performance Liquid Chromatography With Chemiluminescence Detection"
J. Chromatogr. A 1994 Volume 673, Issue 1 Pages 77-84
Nrisinha P. Sen*, Philander A. Baddoo and Stephen W. Seaman

Abstract: Cured meats and baby foods were homogenized, extracted with water, and the extract processed and filtered as described by Sen and Donaldson (cf. J. Assoc. Off. Anal. Chem., 1978, 61, 1389). Urine and saliva were analyzed directly. All samples were diluted (2-100 fold) with HPLC mobile phase. In the HPLC method, the sample (50-100 µL) was injected into a mobile phase (1 or 2 ml/min) of 0.05 M KH2PO4 of pH 6/5 mM tetrabutylammonium hydrogensulfate and passed through a column (25 cm x 4.6 mm i.d.) of Techsil C18 (5 µm). The nitrite-containing eluate was mixed with 10% H2SO4 in acetic acid and then with 10% KI (0.5 ml/min) and the solution was transported to a coiled PTFE tubing reactor kept at 70°C. Chemiluminescence detection of the NO thus formed was effected with a thermal energy analyzer.. The flow injection method was performed in the same way, but without the HPLC column. A diagram of the system used is given. The calibration graph was linear from 1-1000 ng of nitrite; the detection limit was 0.1 ng. The RSD (n = 4 or 5) was 0.2-4%. Recoveries were 92-108%.
Nitrite HPLC Chemiluminescence

"A Rapid Ion-pair HPLC Procedure For Determination Of Tyramine In Dairy Products"
J. Food Sci. 1986 Volume 51, Issue 1 Pages 84-86

Abstract: A 2-g sample (yogurt, cheese or infant formula) was homogenized with ~40 mL of methanol, the homogenate was heated at 60°C for 15 min and the cooled product was diluted to 50 mL with methanol. A 20 µL portion of the filtered solution was analyzed by HPLC on a radially compressed column of Nova-Pak C18 (5 µm) equipped with a guard column of µBondapak C18/Corasil (37 to 50 µm). The mobile phase (1.5 mL min-1) was methanol - 0.05 M Na2HPO4 (3:17) containing heptanesulfonic acid as counter-ion, adjusted to pH 3.0 with 6 M H3PO4. Post-column derivatization was effected with phthalaldehyde and the products were detected by fluorimetry at 425 nm (excitation at 338 nm). The calibration graph for 20 to 400 ng of tyramine was rectilinear. Average recoveries (and coefficient of variation) were 95.3% (9%) for infant formula, 102% (1.6%) for yogurt and 95.2% (8.4%) for cheese.
Tyramine HPLC Fluorescence Post-column derivatization

"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

"Automated Determination Of Nitrate And Nitrite By Flow Injection Analysis"
Voeding. Tech. 1995 Volume 28, Issue 4 Pages 11-14
Klomp, H.;Ellen, G.;De Jong, E.A.M.

Abstract: Application of a Tecator FIA (flow injection analysis) method to determine nitrate and nitrate in milk products is discussed. Trials showed that this method permits easy, rapid and accurate analysis of nitrate and nitrite. Determination of low nitrite concentrations in cheese and baby foods requires some method modifications to achieve sufficient sensitivity. Using the modified method, the detection limit for nitrite in cheese is 0.1 mg/kg. In dried products with a high content of lactose or other compounds which pass through the dialysis membrane, a systematic positive error may occur of the order of 0.05-0.1 mg/kg product; the detection limit is therefore matrix-dependent. Recoveries of nitrate and nitrite (determined by the method of standard additions) are 95-100% for most products. For nitrate concentrations of 10 mg/kg DM and nitrite concentrations of 0.5 mg/kg DM, relative s.d. are approximately 5%.
Nitrate Nitrite Dialysis Standard additions calibration Tecator