Use of microbore high-performance liquid chromatography for the determination of caffeine, theobromine and theophylline in cocoa.
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Cacao↗
Biomedical subjects
W J Hurst
Publications and source records attributed to W J Hurst.
Analytical methods for quantitation of methylxanthines.
The methylxanthines can be determined in foods and biological systems by the chromatographic methods of TLC, GC, and HPLC. Ultraviolet spectroscopy following a separation procedure is also still used. More recently immunoassay methods have been developed. There is no single best method; the analyst must balance the features of each assay with the final requirements for data precision and reproducibility.
Animals↗
Introduction to the chemistry, isolation, and biosynthesis of methylxanthines.
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Cacao↗
High-performance liquid chromatographic determination of ochratoxin A in artificially spiked cocoa beans.
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Cacao↗
High performance liquid chromatographic analysis of cholesterol in milk.
A method was developed for analysis of cholesterol in whole milk powder and commercial liquid milk products. High performance liquid chromatography employed a nonaqueous reversed phase chromatographic system. Sample preparation was by saponification with methanolic potassium hydroxide followed by extraction with ether. Potential interfering substances were removed prior to injection by a simple clean-up procedure using a silica gel Sep-pakTM. The chromatographic system included a carbon-18 column with a hexane/isopropanol mobile phase and detection at 205 nm. Method validation and recovery studies using carbon-14 labeled cholesterol indicated excellent performance.
Animals↗
The HPLC analysis of thiamine in milk chocolate.
An HPLC method for the analysis of thiamin in milk chocolate and various chocolate products is described. Samples are extracted with H2SO4, treated with enzymes and interferences removed with a small cleanup column. The separation is effected on a monolayer reversed phase column with a post column thiochrome reaction and fluorescence detection. The method is accurate and precise.
Cacao↗
Carbohydrate composition of candy bars.
The data in Table 1 show a wide variation among products and when added to other available data provide a more complete picture of the carbohydrate composition of candy bars. Interestingly, the sucrose content of the bars in Table 1 ranges from a low of 19.12% to a high of 56.06%. Extensive use of corn syrup is clearly evident in ingrediated bar types (categories e and f). Although the higher saccharides of corn syrup were not quantitated, we think that this article adds to the knowledge of the carbohydrate composition of the best-selling candy bars, since previously only a carbohydrate by difference value was available. This report provides the health professional with an update on carbohydrate composition of a large number of candy bars.
Candy↗
High pressure liquid chromatographic determination of mono- and disaccharides in presweetened cereals: Collaborative study.
A collaborative study was conducted using a modified AOAC method (sugars in chocolate) for the determination of fructose, glucose, sucrose, and maltose in presweetened cereals by high pressure liquid chromatography (HPLC). Eight samples consisting of 6 products were analyzed in duplicate by the HPLC method and the AOAC Lane-Eynon method. The AOAC method was modified to use water-alcohol (1 + 1) and Sep-Pak C18 cartridges for sample cleanup. The HPLC results indicate precision comparable to the lane-Eynon method and the chocolate method. The modified HPLC method has been adopted official first action.
Chromatography, High Pressure Liquid↗
Liquid chromatographic determination of aflatoxins in artificially contaminated cocoa beans.
A high pressure liquid chromatographic method is described for the extraction and determination of aflatoxins in artificially contaminated cocoa beans. Aflatoxins were extracted by using a CB extraction, column cleanup, and chromatography on a reverse phase column with UV detection at 365 nm for aflatoxins B1 and G1 and fluorescence detection for aflatoxins B2 and G2 (365 nm excitation and 455 nm emission). Recoveries from artificially contaminated cocoa beans of various roast conditions ranged from 77.50 to 107.35%. CV values ranged from 4.87 for G1 to 7.66 for G2 (n = 8). The method can be used for cocoa beans ranging from no roast to a heavy roast (12 min at 400 degrees F).
Aflatoxins↗
High-performance liquid chromatographic determination of four biogenic amines in chocolate.
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Biogenic Amines↗
Ion pairing high pressure liquid chromatographic determination of amaranth in licorice products.
A high pressure liquid chromatographic method is described for the determination of amaranth (FD&C Red No. 2; Red No. 2) in licorice products. The Red No. 2 is extracted with a basic buffer solution, cleaned up on a Sep-Pak column, Chromatographed on a reverse phase column in the ion pairing mode, and detected at 254 nm. The procedure is time-conservative with accurate and precise results. Recovery data ranged from 93 to 104%, and coefficients of variation were less than 4% for standards and samples.
Amaranth Dye↗
High performance liquid chromatographic determination of carbohydrates in chocolate: collaborative study.
A collaborative study determining sucrose, glucose, fructose, maltose, and lactose in chocolate products was conducted using a previously published high performance liquid chromatographic (HPLC) method. Five samples (2 milk chocolates, 1 dark chocolate, 1 powdered mix, and 1 sirup) were analyzed in duplicate by 7 collaborators. The results indicate adequate method precision. In addition, the HPLC method allows for the simultaneous determination of 5 saccharides in chocolate products in 15 min. The method has been adopted as official first action.
Animals↗
Production of aflatoxin in cocoa beans.
Aflatoxin was produced in both non-autoclaved and autoclaved Ivory Coast cocoa beans inoculated with Aspergillus parasiticus NRRL 2999 under optimum laboratory growth conditions. Total aflatoxin levels ranged from 213 to 5597 ng/g substrate. Aflatoxin was quantitated by using high pressure liquid chromatography (HPLC). Raw, non-autoclaved cocoa beans, also inoculated with aspergilli, produced 6359 ng aflatoxin/g substrate. Variation in aflatoxin production between bean varieties was observed. Total aflatoxin levels of 10,446 and 23,076 ng/g substrate were obtained on Ivory Coast beans inoculated with A. parasiticus NRRL 2999 and NRRL 3240, respectively. Aflatoxin production on Trinidad and Malaysian beans was 28 and 65 ng aflatoxin/g substrate. These data support previously reported low level natural aflatoxin contamination in cocoa.
Aflatoxins↗
Determination of aflatoxins in peanut products using reverse phase HPLC.
A high performance liquid chromatographic (HPLC) method is described for the determination of the four major aflatoxins, B1, B2, G1 and G2, in peanut products. The aflatoxins are extracted by adapting a procedure developed by Pons (1) at the SRRC, USDA, and quantitated utilizing a new 5 mum reverse-phase column with NaCl/acetontrile/methanol mobile phase (3 + 1 + 1). The 5 mum column achieved baseline resolution of each of the four aflatoxins. Retention times and peak heights were reproducible. The procedure was successfully applied to several types of peanut products and was applicable to both roasted and unroasted peanuts, which is a decided advantage over the current CB and BF extraction methods. Additionally, it can be used for sweetened peanut matrixes with no interferences in the chromatography. The total time required for sample preparation and aflatoxin determination is less than 1.5 hours.
Aflatoxins↗
Ontogeny of the opioid growth factor, [Met5]-enkephalin, and its binding activity in the rat retina.
The endogenous opioid peptide [Met5]-enkephalin is a tonically active opioid growth factor (OGF) with an inhibitory action on DNA synthesis in the developing rat retina. In this study, the ontogeny of the spatial and temporal expression of OGF and its binding activity was examined. OGF-like immunoreactivity was detected in the retina at gestation day (E) 20, but not at E18, and was localized to ganglion cell and neuroblast layers; immunochemical reaction was no longer seen in the retina by postnatal day 6. Native OGF was further identified and characterized by high-performance liquid chromatography (HPLC) studies and immunodot assays, which revealed that [Met5]-enkephalin was present in the neonatal, but not adult, rat retina. OGF binding activity was detected as early as E18 using [125I]-[Met5]-enkephalin and in vitro receptor autoradiography. Little OGF binding activity was noted for prenatal retinas, but appreciable activity was observed from birth to postnatal day 4; no OGF binding could be detected after postnatal day 5 or in the adult. These results reveal the transient appearance of the OGF, [Met5]-enkephalin, and its receptor binding activity in the developing mammalian retina, and show that their ontogeny coincides with the timetable of DNA synthesis of retinal neuroblasts.
Animals↗
Use of o-phthaldehyde derivatives and high-pressure liquid chromatography in determining the free amino acids in cocoa beans.
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Aldehydes↗
The response of various hematologic parameters in the young bovine subjected to multiple phlebotomies.
Specific guidelines for the optimal collection of blood from calves maintained as donors do not exist. This investigation was conducted to document erythrocytic changes in calves subjected to controlled blood loss. Two groups of Holstein calves ranging in age from 2 to 5 months were compared. Six animals were designated controls and six were subjected to a series of three blood collections over an 8 day period. Each collection was roughly 50% of the total circulating blood volume (30 ml/kg of body weight). Hematologic values were compared for 18 days. All calves survived the study. There was no significant difference in circulating cortisol levels or growth rate between groups. Packed cell volumes (PCVs) for the phlebotomized group did not return to original levels during the monitoring period (initial 36%, final 26%), but were within normal limits at 30 days. All phlebotomized calves had a high reticulocyte count (0% control, 11% phlebotomized). Reticulocytes were not observed until the PCV fell below 20. HbF to HbA ratios were a sensitive and acute indicator of accelerated erythropoiesis. Variant ratios stabilized within 18 days. Other parameters compared were red cell indices, total erythrocyte count, total leukocyte count, total plasma protein, total hemoglobin values, and neutrophil to lymphocyte ratios.
Age Factors↗
Nonaqueous reverse phase liquid chromatographic analysis for cholesterol in milk chocolate.
A method using liquid chromatography was developed for the analysis of cholesterol in milk chocolate products. The method involves saponification of the sample with methanolic KOH followed by extraction with ether. Potentially interfering components are eliminated through the use of a silica Sep-Pak cleanup step before injection. The nonaqueous reverse phase LC system consists of a C18 column and an isopropanol-hexane mobile phase with direct detection at 205 nm. Recoveries of 1, 3, and 5 mg cholesterol added to 1 g sample of milk chocolate were 88.6, 102.8, and 110.1%, respectively. Studies conducted with [4-14C]-cholesterol were undertaken to further document the accuracy of the method.
Animals↗