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1.
J AOAC Int ; 84(5): 1593-9, 2001.
Article in English | MEDLINE | ID: mdl-11601481

ABSTRACT

A liquid chromatographic (LC) method is described for determination of total vitamin B6 in soy-based infant formula. Total vitamin B6 is quantitated by using ion-pair LC after precolumn transformation of phosphorylated and free vitamers into pyridoxol. The limit of detection is 0.3 ng and the limit of quantitation is 1.0 ng on-column (injection volume = 100 microL). Linear response ranged from 39 to 616 ng/mL (r2 = 0.99986). Analysis of a soy-based infant formula control fortified at 6 different concentration levels gave recoveries that averaged 104%. Assay of SRM 1846 gave results within the certified range (8.6 +/- 0.086 mg/kg versus the certified value of 8.4 +/- 1.0 mg/kg). The method provides a rapid and specific assay for the analysis of total vitamin B6 in fortified soy-based infant formula.


Subject(s)
Glycine max/chemistry , Infant Food/analysis , Vitamin B 6/analysis , Calibration , Chromatography, Liquid , Humans , Indicators and Reagents , Infant , Spectrometry, Fluorescence , Ultrasonics , Vitamin B 6/analogs & derivatives
2.
J AOAC Int ; 84(3): 789-804, 2001.
Article in English | MEDLINE | ID: mdl-11417644

ABSTRACT

A peer-verified, solid-phase extraction (SPE)/anion exchange liquid chromatographic method is presented for the determination of niacin in milk-based and soy-based infant formula. Analysis is in 3 steps: test sample digestion, extraction/cleanup, and liquid chromatography (LC). Digestion uses a standard AOAC digestion procedure that involves autoclaving at 121 degrees C for 45 min in (1 + 1) H2SO4 to free endogenous niacin from protein and to convert added niacinamide to niacin. The digest solution is adjusted to pH 6.5 with 7.5M NaOH. Acidification to pH <1.0 with (1 + 1) H2SO4 precipitates the protein. The clarified solution is then filtered, and the filtrate is brought to volume. SPE of niacin is accomplished by passing an aliquot of the digest solution through an aromatic sulfonic acid-SPE (ArSCX-SPE) column. After the column is washed with methanol and water to remove extraneous material, the niacin is eluted with 0.25M sodium acetate/acetic acid buffer at pH 5.6. An anion-exchange polystyrene-divinylbenzene column with 0.1 M sodium acetate/acetic acid buffer at pH 4.0 is used for LC. Niacin is determined by UV detection at 260 nm. A standard curve is prepared by passing known amounts of niacin through the ArSCX-SPE columns used for niacin extraction. The following values for x and relative standard deviation (RSD) were obtained for National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula with a certified value for niacin of 63.3 +/- 7.6 microg/g: Submitting laboratory.-- x = 59.7 +/- 4.0 microg/g; RSD = >6.7%; confidence interval (CI) = +/- 1.4 microg/g; n = 27. Peer laboratory.--x = 56.6 +/- 6.6 microg/g; RSD = >11.7%; CI =+/- 4.1 microg/g; n = 8.


Subject(s)
Chromatography, Ion Exchange/methods , Infant Food/analysis , Niacin/analysis , Animals , Anions , Humans , Infant , Laboratories/standards , Milk , Reproducibility of Results , Sensitivity and Specificity , Glycine max
3.
J AOAC Int ; 84(1): 218-9, 2001.
Article in English | MEDLINE | ID: mdl-11234817
4.
J AOAC Int ; 83(4): 957-62, 2000.
Article in English | MEDLINE | ID: mdl-10995121

ABSTRACT

A liquid chromatographic (LC) method is described for the determination of vitamin K1 in medical foods. The sample is enzymatically digested with lipase and alpha-amylase and extracted with 1% sodium bicarbonate solution-isopropanol (1 + 1). After C18 solid-phase extraction, vitamin K1 is separated by nonaqueous reversed-phase LC, converted to the hydroquinone by postcolumn zinc reduction, and quantitated by fluorescence detection. The limit of detection is 8 pg (3 sigma), and the limit of quantitation is 27 pg (10 sigma) on column. Linear response ranged from 0.1 to 1.0 ng vitamin K1 (r= 0.9999). The mean recovery (n = 38) for all spiking levels was 101.6 +/- 2.85%. Analysis of Standard Reference Material 1846, Infant Formula, gave a mean value of 0.95 +/- 0.088 mg vitamin K/kg (K or K1?) (n = 31) with a coefficient of variation of 9.26.


Subject(s)
Chromatography, Liquid/methods , Fluorometry , Food, Formulated/analysis , Vitamin K 1/analysis , 2-Propanol , Buffers , Humans , Hydrogen-Ion Concentration , Hydroquinones , Lipase/metabolism , Quality Control , Sensitivity and Specificity , Sodium Bicarbonate , alpha-Amylases/metabolism
5.
J AOAC Int ; 83(2): 407-10, 2000.
Article in English | MEDLINE | ID: mdl-10772179

ABSTRACT

An extraction technique is described for vitamin K1 in medical foods, using accelerated solvent extraction (ASE) in conjunction with matrix solid-phase dispersion (MSPD). The medical food sample is treated as it would be with MSPD extraction, followed by ASE for a hands-free automated extraction. The vitamin K1 in the ASE extract is then quantitated by reversed-phase liquid chromatography with fluorescence detection. The chromatography specifications are identical to those in previous work that used MSPD only, with a limit of detection of 6.6 pg and a limit of quantitation of 22 pg on column. Recoveries, which were determined for an analyte-fortified zero control reference material for medical foods, averaged 97.6% (n = 25) for vitamin K1. The method provides a rapid, automatic, specific, and easily controlled assay for vitamin K1 in fortified medical foods with minimal solvent usage.


Subject(s)
Food, Formulated/analysis , Solvents , Vitamin K 1/analysis , Chromatography, High Pressure Liquid/methods
6.
J AOAC Int ; 82(5): 1140-5, 1999.
Article in English | MEDLINE | ID: mdl-10513014

ABSTRACT

A liquid chromatographic method for vitamin K1 in milk-based infant formula is described. The vitamins are extracted from infant formula by matrix solid-phase dispersion and quantitated by reversed-phase chromatography with fluorescence detection. Vitamin K1 is converted to the fluorescent hydroquinone with a postcolumn zinc reductive reactor. The limit of detection is 12 pg, and the limit of quantitation is 38 pg on-column. Linear responses were obtained in the range 0.55-22.1 ng/ml (r2 = 0.9998). Recoveries of vitamin K1 from an analyte-fortified blank material for milk-based infant formula averaged 91.7% (n = 25). The method provides a rapid, specific, and easily controlled assay for vitamin K1 in fortified infant formula.


Subject(s)
Chromatography, Liquid , Infant Food/analysis , Milk/chemistry , Vitamin K 1/analysis , Animals , Linear Models , Sensitivity and Specificity , Time Factors
7.
J AOAC Int ; 82(3): 663-5, 1999.
Article in English | MEDLINE | ID: mdl-10367385

ABSTRACT

A liquid chromatographic method is described for analysis of beta-carotene in medical food. The nutrient is extracted from medical food without saponification by matrix solid-phase dispersion and quantitated by isocratic normal-phase chromatography with a Si 60 column and a mobile phase of hexane containing 0.125% (v/v) isopropyl alcohol. The limit of quantitation is 0.02 microgram/mL at 436 nm. Standard response was linear over the concentration range of 0.02-1.0 microgram/mL (r2 = 0.99998). Recoveries were determined on a zero control reference material containing added beta-carotene at various levels. Recoveries averaged 91.2% (n = 25) with coefficients of variation from 0.50 to 3.10%. The method provides a rapid, specific, sensitive, and easily controlled assay for analysis of beta-carotene in fortified medical food. In addition, retinyl palmitate can be assayed simultaneously with an in-line fluorescence detector.


Subject(s)
Chromatography, Liquid/methods , Food, Formulated/analysis , beta Carotene/analysis , Diterpenes , Humans , Quality Control , Retinyl Esters , Sensitivity and Specificity , Vitamin A/analogs & derivatives , Vitamin A/analysis
8.
J AOAC Int ; 82(2): 271-5, 1999.
Article in English | MEDLINE | ID: mdl-10232898

ABSTRACT

A liquid chromatographic method is described for analysis of all- rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted in isopropyl alcohol and hexane-ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All rac-alpha-tocopheryl acetate and retinyl palmitate are chromatographed isocratically with a mobile phase of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recovery studies performed on a medical food zero control reference material (ZRM) fortified with the analytes averaged 99.7% (n = 25) for retinyl palmitate and 101% (n = 25) for all- rac-alpha-tocopheryl acetate. Coefficients of variation were 0.87-2.63% for retinyl palmitate and 1.42-3.20% for all-rac-alpha-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in medical foods. Use of chlorinated solvents is avoided.


Subject(s)
Food, Formulated/analysis , Quality Control , Vitamin A/analogs & derivatives , Vitamin E/analogs & derivatives , alpha-Tocopherol/analogs & derivatives , Chromatography/methods , Diterpenes , Infant Food/analysis , Reference Standards , Retinyl Esters , Spectrometry, Fluorescence , Stereoisomerism , Tocopherols , Vitamin A/analysis , Vitamin E/analysis
9.
J AOAC Int ; 82(1): 107-11, 1999.
Article in English | MEDLINE | ID: mdl-10028678

ABSTRACT

A liquid chromatographic method is described for analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted from medical food without saponification by matrix solid-phase dispersion and chromatographed by normal-phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-alpha-tocopheryl acetate are quantitated isocratically with a mobile phase of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results compared favorably with label declarations on retail medical foods. Recoveries determined on an analyte-fortified zero reference material for a milk-based medical food averaged 98.3% (n = 25) for retinyl palmitate spikes and 95.7% (n = 25) for all-rac-alpha-tocopheryl acetate spikes. Five concentrations were examined for each analyte, and results were linear (r2 = 0.995 for retinyl palmitate and 0.9998 for all-rac-alpha-tocopheryl acetate) over the concentration range examined, with coefficients of variation in the range 0.81-4.22%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and all-rac-alpha-tocopheryl acetate in fortified medical foods.


Subject(s)
Food, Formulated/analysis , Vitamin A/analogs & derivatives , Vitamin E/analogs & derivatives , alpha-Tocopherol/analogs & derivatives , Chromatography, Liquid , Diterpenes , Reference Standards , Reproducibility of Results , Retinyl Esters , Stereoisomerism , Tocopherols , Vitamin A/analysis , Vitamin E/analysis
10.
J AOAC Int ; 81(3): 577-81, 1998.
Article in English | MEDLINE | ID: mdl-9606923

ABSTRACT

A liquid chromatographic method is described for analysis of all-rac-alpha-tocopheryl acetate, tocopherols, and retinyl palmitate in soy-based infant formula. The vitamins are extracted in isopropyl alcohol and hexane--ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All-rac-alpha-tocopheryl acetate and retinyl palmitate are quantitated isocratically with mobile phases of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recoveries from zero control reference material soy-based formula averaged 97.2% (n = 25) for retinyl palmitate and 100% (n = 25) for all-rac-alpha-tocopheryl acetate. Coefficients of variation ranged from 1.21 to 2.86% for retinyl palmitate and from 1.49 to 5.16% for all-rac-alpha-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in fortified infant formula. Additionally, the method eliminates use of chlorinated solvents.


Subject(s)
Anticarcinogenic Agents/analysis , Antioxidants/analysis , Chromatography, Liquid/methods , Infant Food/analysis , Vitamin A/analogs & derivatives , Vitamin E/analogs & derivatives , alpha-Tocopherol/analogs & derivatives , Diterpenes , Food Analysis/methods , Reference Standards , Retinyl Esters , Glycine max , Spectrometry, Fluorescence , Stereoisomerism , Tocopherols , Vitamin A/analysis , Vitamin E/analysis
11.
J AOAC Int ; 81(3): 582-6, 1998.
Article in English | MEDLINE | ID: mdl-9606924

ABSTRACT

A liquid chromatographic method is described for analysis of all-rac-alpha-tocopheryl acetate, tocopherols, and retinyl palmitate in milk-based infant formula. The vitamins are extracted from infant formula without saponification by matrix solid-phase dispersion and quantitated by normal-phase chromatography with fluorescence detection. Retinyl palmitate and vitamin E are quantitated isocratically with mobile phases of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results were similar to the certified and non-certified ranges for all-rac-alpha-tocopheryl acetate, retinyl palmitate, and tocopherols in the infant formula standard reference material (SRM) 1846. Results also compared favorably with the label declaration on a retail infant formula. Recoveries were determined on an analyte-fortified zero control reference material for milk-based infant formula and averaged 96.8% (n = 30) for retinyl palmitate and 91.5% (n = 25) for all-rac-alpha-tocopheryl acetate. Examination of 5 concentrations for each analyte gave results that were linear (r = 0.999) over the concentration examined, with coefficients of variation ranging from 1.02 to 5.86%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and vitamin E in fortified infant formula. Additionally, the method minimizes solvent use by using only 14 mL solvent per extraction.


Subject(s)
Anticarcinogenic Agents/analysis , Antioxidants/analysis , Chromatography, Liquid/methods , Infant Food/analysis , Vitamin A/analogs & derivatives , Vitamin E/analogs & derivatives , alpha-Tocopherol/analogs & derivatives , Animals , Diterpenes , Food Analysis/methods , Milk , Retinyl Esters , Spectrometry, Fluorescence , Tocopherols , Vitamin A/analysis , Vitamin E/analysis
12.
J AOAC Int ; 81(2): 453-6, 1998.
Article in English | MEDLINE | ID: mdl-9549080

ABSTRACT

A zero control reference material (ZRM) for milk and soy-based infant formula was manufactured and characterized. The ZRM was free of retinyl palmitate and all-rac-alpha-tocopheryl acetate. The composition was similar to commercially available infant formula. The ZRM provides a valuable tool to ascertain method performance.


Subject(s)
Infant Food/analysis , Animals , Chromatography, Liquid , Diterpenes , Humans , Indicators and Reagents , Infant , Milk/chemistry , Reference Standards , Retinyl Esters , Glycine max/chemistry , Spectrometry, Fluorescence , Vitamin A/analogs & derivatives , Vitamin A/analysis , Vitamin E/analysis , Vitamins/analysis
13.
J AOAC Int ; 76(6): 1276-80, 1993.
Article in English | MEDLINE | ID: mdl-8286968

ABSTRACT

A reversed-phased ion pair liquid chromatographic method developed for the simultaneous determination of thiamine (B1), riboflavin (B2), and pyridoxine (B6) in perchloric acid extracts of infant formulas was modified to include medical foods. UV detection of B1 and B2 was replaced by fluorescence detection, which resulted in improved sensitivity and specificity. B1 was detected by fluorescence after conversion to thiochrome by a postcolumn reaction with sodium hydroxide and potassium ferricyanide. The method uses a mobile phase of water, acetonitrile, hexanesulfonic acid sodium salt, ammonium hydroxide, and phosphoric acid adjusted to pH 3.6. The column is a 300 x 3.9 mm Nova Pak C18. Limits of detection were 0.05 microgram/mL for B1 and B2 and 0.01 microgram/mL for B6 by fluorescence detection. The system reproducibility was evaluated by completing 10 repetitive determinations on a medical food that gave a coefficient of variation of 5.9, 6.0, and 10.7% for B1, B2, and B6, respectively. Mean recoveries (n = 10) were 111, 96.3, and 113% for B1, B2, and B6, respectively. The results compared favorably with those by AOAC Official Methods 942.23, 940.33, and 961.15 for B1, B2, and B6, respectively.


Subject(s)
Chromatography, Liquid/methods , Food, Formulated/analysis , Pyridoxine/analysis , Riboflavin/analysis , Thiamine/analysis , Fluorescence , Sensitivity and Specificity
14.
J AOAC Int ; 76(2): 390-3, 1993.
Article in English | MEDLINE | ID: mdl-8471863

ABSTRACT

An ion exchange liquid chromatographic (LC) method using an anion exchange resin column was developed for the determination of niacin in fortified foods. Samples were extracted by autoclaving with H2SO4 (1 + 1). Florisil open column chromatography was used to remove interferences from the sample extracts. Niacin levels were quantitated by an LC system using a 250 x 4.1 mm Hamilton PRP-X100 column, a mobile phase of 2% glacial acetic acid in water, and UV detection at 254 nm. The limit of detection was 0.11 micrograms niacin/mL, and the standard curve was linear from 0.24 to 0.80 micrograms niacin/mL. The system reproducibility was evaluated by completing 10 repetitive analyses on an infant formula and a macaroni product, which gave an average CV of 2.7%. Mean recovery (+/- standard deviation) was 99.8 +/- 7.7 (n = 15). The results compared favorably with those by the AOAC microbiological method.


Subject(s)
Food, Fortified/analysis , Magnesium Silicates , Niacin/analysis , Chromatography, Ion Exchange/methods , Chromatography, Ion Exchange/standards , Niacin/standards , Reference Standards , Silicic Acid
15.
J Assoc Off Anal Chem ; 73(2): 318-9, 1990.
Article in English | MEDLINE | ID: mdl-2324040

ABSTRACT

Recently, hypoglycin A (HG-A), a natural toxin, was detected in canned ackee fruit. To determine the source of contamination, the HG-A content in the ackee fruit components (aril, seeds, and husks) at various stages of ripeness was determined by a method using an amino acid analyzer. HG-A concentrations in the unripe ackee fruit components were 939, 711, and 41.6 mg/100 g of seed, aril, and husk components, respectively. Analysis of the ripe fruit components showed that HG-A in the seed decreased to 269 mg/100 g and remained unchanged in the husk while the concentrations in the edible ripe aril decreased below the detection limit of 1.2 mg/100 g.


Subject(s)
Cyclopropanes/analysis , Fruit/analysis , Hypoglycins/analysis , Amino Acids/analysis
16.
J Assoc Off Anal Chem ; 72(2): 374-7, 1989.
Article in English | MEDLINE | ID: mdl-2708289

ABSTRACT

An ion-exchange chromatographic method was developed to determine hypoglycin A (HG-A) levels in canned ackee fruit by using an amino acid analyzer. HG-A was extracted by homogenizing the sample in 80% alcohol. An isocratic buffer system, consisting of 30% sodium citrate buffer (pH 3.15) and 70% sodium chloride-sodium acetate buffer (pH 7.40) was used to obtain baseline separation between HG-A and the other amino acids. The system can detect HG-A levels as low as 4.8 micrograms/mL. HG-A levels in the edible portion of fruit in 6 cans ranged from 11.0 to 66.5 mg HG-A/can. Recoveries by standard addition averaged 102.5%.


Subject(s)
Cyclopropanes/analysis , Food Preservation , Fruit/analysis , Hypoglycins/analysis , Amino Acids/analysis , Chromatography, Ion Exchange , Magnetic Resonance Spectroscopy
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