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Biomedical subjects

D C Havery

Publications and source records attributed to D C Havery.

At least 19 recordsLinked to original sources
PubMed1989

HPLC analysis of N-nitrosamino acids and N-nitrosodipeptides N-terminal in proline.

An attempt has been made to develop conditions for the analysis of some N-nitrosamino acids and N-nitrosodipeptides N-thermal in proline by means of high performance liquid chromatography with thermal energy detector (HPLC-TEA). Two HPLC columns have been tested; cyano and amine chemically bonded columns. Although both of them give positive results baseline separation all of the compounds investigated takes place only on the amine column. On the cyano column two of the compounds remains unresolved and two other are not completely separated. Increasing the temperature of the HPLC columns to 90 degrees C and 100 degrees C for the cyano and amine columns respectively dramatically increase their efficiency due to the syn and anti isomers merging.

Amino Acids↗
PubMed1985

Reduction in levels of volatile N-nitrosamines in rubber nipples for babies' bottles.

Levels of volatile N-nitrosamines were determined in 189 samples of rubber nipples for babies' bottles. Domestic (US-manufactured) and imported rubber nipples for consumer and hospital use were analysed to determine compliance with the US Food and Drug Administration's action level of 60 ppb (b = 10(9] for total volatile N-nitrosamines. Only one sample was found to be in violation of the action level; it contained a total of 137 ppb N-nitrosamines.

Bottle Feeding↗
PubMed1984

Nonvolatile N-nitrosamine investigations: methods for the determination of N-nitrosoamino acids and preliminary results of the development of a method for the determination of N-nitrosodipeptides N-terminal in proline.

The development of a rapid method for the determination of N-nitrosoamino acids is reported. Preliminary recoveries of N-nitrosoamino acids in ham fortified with 20 micrograms/kg generally ranged from 70 to 100%. The synthesis and instrumental characterization of four N-nitrosodipeptides N-terminal in proline from nitrite in aqueous acid solution are reported. Electron ionization-mass spectroscopy and infra-red spectroscopy strongly support the conclusion that only the amine nitrogen, and not the amide nitrogen at the peptide bond, is nitrosated. High-performance liquid chromatographic conditions are described for the separation of the synthesized N-nitrosodipeptides.

Amino Acids↗
PubMed1983

Survey of baby bottle rubber nipples for volatile N-nitrosamines.

A local market survey of 27 baby bottle rubber nipples for volatile N-nitrosamines was conducted. N-Nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, and N-nitrosopiperidine were found at levels up to 387 ppb. All 4 nitrosamines migrated from the rubber nipples into water, milk, and infant formula when sterilized together in a manner typical of that used in the home. The source of the nitrosamines is the chemical accelerators and stabilizers added to raw rubber during the vulcanization process.

Animals↗
PubMed1982

Estimation of volatile N-nitrosamines in rubber nipples for babies' bottles.

A method is described for the estimation of volatile N-nitrosamines in the rubber nipples of babies' bottles. In a study of rubber nipples from one manufacturer, N-nitrosodimethylamine, N-nitrosodiethylamine and N-nitrosopiperidine were determined by gas chromatography, using a thermal energy analyser, and their presence was confirmed by mass spectrometry with average levels of individual nitrosamines ranging from 22 to 281 ppb. When the nipples were sterilized in a conventional sterilizer together with milk or infant formula the three nitrosamines migrated into the milk or formula. Storing a bottle of milk with a rubber nipple inverted in it for 2 hr at room temperature or overnight in a refrigerator after sterilization resulted in an 8-13% average increase in the nitrosamine levels migrating into the milk. On repeated sterilization of a single nipple, the quantities of nitrosamines migrating into milk from rubber nipples declined steadily, but after seven sterilizations, nitrosamines were still readily detectable in the milk. Nitrosamine levels were higher in rubber nipples after sterilization, indicating the presence of nitrosamine precursors in the nipples. No nitrosamines were found in raw, uncured rubber. Chemical accelerators and stabilizers added during the vulcanization process are the source of the amine precursors in rubber nipples.

Bottle Feeding↗
PubMed1982

Volatile N-nitrosamines in direct flame dried processed foods.

The presence of N-nitrosodimethylamine (NDMA) in malt and malt beverages has been linked to the direct flame drying of malt. Similar drying procedures are used in the preparation of a variety of foods, such as non-fat dry milk, soy proteins and dried cheeses. A survey of some of these processed foods for volatile N-nitrosamines has shown that low levels of NDMA are present, along with N-nitrosomorpholine in one sample of soy protein isolate. This paper describes the procedures used for the analysis of a variety of processed dried foods for volatile nitrosamines and reports the results obtained.

Animals↗
PubMed1981

Rapid method for estimation of N-nitrosodimethylamine in malt beverages.

A new, rapid column elution method is described for the estimation of N-nitrosodimethylamine in malt beverages. Recoveries for N-nitrosodimethylamine and N-nitrosodipropylamine fortified at 5 ppb averaged 90 and 91%, respectively. A study of 20 different malt beverages showed that the results obtained with this method compared favorably with those obtained by a direct distillation procedure.

Beer↗
PubMed1981

Determination and confirmation of N-nitrosodimethylamine in beer.

A qualitative method has been developed for the confirmation of N-nitrosodimethylamine (NDMA) in beer by capillary gas chromatography-mass spectrometry (GC/MS) from full mass scans after quantitation, using a gas chromatograph interfaced to a thermal energy analyzer (GC/TEA). The GC/MS method has a lower limit of confirmation of 5 ppb. In a survey of 22 imported and 42 domestic beers, NDMA was found in 60 samples by GC/TEA at levels up to 7.7 ppb, and was confirmed by GC/MS in 5 samples.

Beer↗
PubMed1980

Determination of volatile N-nitrosamines in foodstuffs: I. A new clean-up technique for confirmation by II. A continued survey of foods and beverages.

A clean-up technique has been developed which enables MS confirmation of the identity of a nitrosamine from a sample extract obtained by the mineral oil distillation method. A survey of fried bacons using this technique has confirmed the presence of NPYR at levels of 7-26 micrograms/kg in six of nine samples. NDMA has been found by GC-TEA in 62 of 64 beer samples. Five of the higher levels (from 5.8-7.7 micrograms/kg) have been confirmed by MS, following a direct distillation technique. A survey of 106 market samples of poultry products, Chinese foods and herring meals for volatile nitrosamines was conducted. GC-TEA analyses indicated low levels of several nitrosamines in these samples (less than or equal to 11 micrograms/kg), with the exception of two herring meal samples in which NDMA was confirmed by MS at 2.5 and 2.7 mg/kg.

Animals↗
PubMed1978

Survey of cured meat products for volatile N-nitrosamines: comparison of two analytical methods.

A survey of 106 cured meat samples for 14 volatile N-nitrosamines has been completed. N-Nitrosopyrrolidine has been confirmed in fried bacon at levels ranging from 5 to 75 ppb. Unconfirmed trace levels of N-nitrosodimethylamine have been observed in a variety of cured meat products. The comparison of the multidetection GLC-MS method with the mineral oil distillation TEA method for the determination of volatile N-nitrosamines in foods shows good agreement between the analytical methods, especially at the 10 ppb level, and excellent agreement between the GLC and TEA analyses of an identical sample extract.

Animals↗
PubMed1978

Survey of cured meat products for volatile N-nitrosamines: comparison of two analytical methods.

A survey has been completed of 106 cured meat samples for 14 volatile N-nitrosamines. N-Nitrosopyrrolidine has been confirmed in fried bacon at levels ranging from 5 to 75 ppb. Unconfirmed trace levels of N-nitrosodimethylamine have been observed in a variety of cured meat products. The comparison of the multidetection gas-liquid chromatographic (GLC)-mass spectrometric method with the mineral oil distillation-thermal energy analyzer (TEA) method for the determination of volatile N-nitrosamines in foods shows good agreement between the analytical methods, especially at the 10 ppb level, and excellent agreement between the GLC and TEA analyses of an identical sample extracts.

Animals↗
PubMed1978

Trend in levels of N-nitrosopyrrolidine in fried bacon.

Commercially purchased bacon has been periodically analyzed since 1971 for N-nitrosopyrrolidine in the fried product. The downward trend in the concentration of N-nitrosopyrrolidine that has been observed is partially explained by the use of reduced levels of nitrite and increased levels of ascorbate in bacon curing mixtures.

Animals↗
PubMed1977

Survey of finfish and shellfish for volatile N-nitrosamines.

A variety of finfish and shellfish obtained on the local retail market were analyzed for 14 volatile N-nitrosamines by using a gas-liquid chromatographic method demonstrated to be sensitive to 10 ppb (microng/kg). A total of 78 samples (fresh, frozen, and canned), representing 26 varieties of fish, were analyzed. No nitrosamines were found.

Animals↗
PubMed1976

Survey of food products for volatile N-nitrosamines.

A variety of food products containing nitrite were analyzed for 14 volatile N-nitrosamines by using a method demonstrated to be sensitive to 10 ppb. A total of 121 food samples were screened for volatile N-nitrosamine content. N-Nitrosopyrrolidine was confirmed in fried bacon at levels up to 139 ppb. N-Dimethylnitrosamine, N-nitrosopyrrolidine, and N-nitrosopiperidine were also confirmed in spice-cure mixtures at levels ranging from 50 to 2000 ppb.

Dimethylnitrosamine↗