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S Seaman

Publications and source records attributed to S Seaman.

34 records · Page 2Linked to original sources
PubMed1984

On-line combination of high-performance liquid chromatography and total N-nitroso determination apparatus for the determination of N-nitrosamides and other N-nitroso compounds, and some recent data on the levels of N-nitrosoproline in foods and beverages.

A simple high-performance liquid chromatographic chemiluminescence detection method has been developed for the quantitative determination of N-nitrosamides and is based on post-column denitrosation of the compounds with hydrogen bromide-acetic acid or hydrogen iodide-acetic acid, followed by detection of the liberated NO by a chemiluminescence detector (TEATM). The method was used for the simultaneous analysis of DiazaldR, N-nitroso-N-methylurea, N-methyl-N'-nitro-N-nitrosoguandine and streptozotocin standards, and for N-methyl-N-nitrosourea extracted from model-system reaction mixtures and spiked, cured meats. The minimum detection limit of N-methyl-N-nitrosourea was about 0.5 ng. The method for the determination of N-nitrosarcosine and N-nitrosoproline in foods and beverages has been improved by replacing diazomethane with a mixture of BF3-methanol as the esterifying reagent and by simplifying the clean-up technique for purifying the prepared methyl esters. The average levels of N-nitrosoproline detected in 11 malts, 37 beers, 11 samples of fried bacon and 18 cured-meat products were found to be 24.1 micrograms/kg (5-113), 1.7 micrograms/kg (undetectable-6.0), 19.0 micrograms/kg (0.9-67.5), and 3.2 micrograms/kg (undetectable-21.6), respectively.

Amino Acids↗
PubMed1984

Volatile N-nitrosamines in baby bottle rubber nipples and pacifiers. Analysis, occurrence and migration.

A simple direct extraction method has been developed for rapid determination of volatile N-nitrosamines in rubber nipples and pacifiers. It consists of overnight extraction of the sample with dichloromethane in the presence of ascorbyl palmitate for N-nitrosation inhibition, filtration of the extract and rinsing of the samples with dichloromethane, concentration of the extract using a Kuderna-Danish concentrator, and final analysis by gas-liquid chromatography-Thermal Energy Analyser. The method gave excellent (80-100%) recoveries of various volatile N-nitrosamines that had been added to cut nipples or pacifiers at 20-80 micrograms/kg levels, and gave comparable or lower values than those obtained with another published method. The method is recommended for rapid screening purposes. A survey of 30 samples of various nipples and pacifiers indicated the presence of the following N-nitrosamines: N-nitrosodimethylamine (up to 70 micrograms/kg), N-nitrosodiethylamine (up to 88 micrograms/kg), N-nitrosodi-n-butylamine (up to 2796 micrograms/kg), N-nitrosopiperidine (up to 180 micrograms/kg), and N-nitrosomorpholine (up to 86 micrograms/kg). A more recent study, however, indicated a general decline in the levels of various volatile N-nitrosamines in these products. These N-nitrosamines were shown to migrate easily from the rubber products to liquid infant formula, orange juice and simulated human saliva.

Humans↗
PubMed1982

Gas-liquid chromatographic-thermal energy analyzer determination of N-nitrosodimethylamine in beer: collaborative study.

The GLC/TEA method for N-nitrosodimethylamine (NDMA) in beer was studied collaboratively by 13 laboratories from 7 countries. Collaborators were asked to analyze a total of 10 randomly labeled samples of beer consisting of the following duplicates: a naturally contaminated commercial beer; a beer extremely low (ca 0.1 ppb) in NDMA; and the low NDMA beer spiked with 0.5, 1.9, and 5.0 ppb NDMA. The pooled repeatability and reproducibility coefficients of variation (CV) for all samples were 17% and 27%, respectively. However, when data from 2 laboratories (outliers) were omitted, the corresponding CV values improved considerably (11% and 15%, respectively). Variance analysis showed the presence of a significant laboratory-sample interaction when all data were used for analysis, but this interaction disappeared when data from the 2 outlying laboratories were excluded. The pooled percent recovery of the overall method (omitting outliers) was 101.4 +/- 3.5. All the laboratories detected NDMA in the low NDMA beer. The method was adopted official first action.

Beer↗
PubMed1982

A rapid and sensitive method for the determination of non-volatile n-nitroso compounds in foods and human urine: recent data concerning volatile N-nitrosamines in dried foods and malt-based beverages.

Methods are described for the rapid screening of various foods for the presence of nitrosamino acids (mainly NPRO and NSAR) and of hydroxylated nitrosamines (mainly BHBN, NHPYR and NDELA). Rapid screening methods (HPLC-TEA and GC-TEA) are also described for the determination of the above mentioned nitrosamines in human urine. Recent monitoring data indicate that, in Canada, the NDMA levels in both malt and beer have decreased significantly during the last two years. Contrary to published reports, no volatile nitrosamines could be detected in vegetable oils or pasteurized milk. A new method, based on oxidation of nitrosamines and nitramines and reanalysis by GC-TEA, is described for the confirmation of low microgram/kg levels of volatile nitrosamines in foods.

Beer↗
PubMed1981

Gas-liquid chromatographic-thermal energy analyzer determination of N-nitrosodimethylamine in beer at low parts per billion level.

A gas-liquid chromatographic (GLC) procedure is described for the determination of low ppb levels of N-nitrosodimethylamine (NDMA) in beer. The sample is treated with sulfamic acid under acidic conditions followed by alkalinization with dilute KOH, distillation at atmospheric pressure, extraction of NDMA from alkaline aqueous distillate with dichloromethane, concentration of dichloromethane extract by Kuderna-Danish concentrator, and, finally determination by a GLC-thermal energy analyzer technique with N-nitrosodipropylamine (NDPA) as an internal standard. The method gave results comparable with 2 other well established methods. Recoveries of added NDMA, N-nitrosodiethylamine, and NDPA at levels ranging from 0.08 to 10 ppb were 75-112, 86-115, and 85-109%, respectively. Five replicate analyses of a beer sample gave a mean NDMA concentration (corrected for recovery) of 2.21 +/- 0.08 ppb (+/- SD). Minimum detection limit of the method is about 0.1 ppb.

Beer↗
PubMed1981

Volatile N-nitrosamines in dried foods.

An investigation was carried out to determine the levels of volatile N-nitrosamines in several dried food commodities such as malt, instant skim milk powder, infant formula containing milk powder, instant coffee, soup and soup bases, and baby cereals. The method involves vacuum distillation of the sample from 3N KOH or 1% sulfamic acid, followed by extraction of the aqueous distillate with dichloromethane. The dichloromethane extract is then washed with an acidic buffer (to remove amines), dried over anhydrous sodium sulfate, concentrated in a Kuderna-Danish concentrator, and analyzed by gas-liquid chromatography, using a thermal energy analyzer. Detection limit is 0.1-0.5 ppb. Of the samples analyzed thus far, all malts (22 samples) and instant skim milk powders (11 samples ) were positive for N-nitrosodimethylamine (NDMA); average levels were 7.4 ppb (1.3-67.0 ppb) and 0.4 ppb (0.3-0.7 ppb), respectively. Traces of NDMA and/or N-nitrosopyrrolidine were also detected in 3 of 20 dried soups and 5 of 10 instant coffees analyzed. Traces of NDMA and/or N-nitrosopiperidine (NPIP) were detected in 3 of 8 powdered instant formulas. All for baby cereal samples were negative. The identity of NDMA in 14 samples of malt and that of NDMA and NPIP in a infant formula was confirmed by gas liquid chromatography-mass spectrometry; identity of N-nitrosamines in 3 instant coffees and 1 infant formula was independently verified by high pressure liquid chromatographic analysis.

Chromatography, High Pressure Liquid↗
PubMed1980

Further studies on the occurrence of volatile and non-volatile nitrosamines in foods.

Approximately 250 samples of various foods, such as cured meat products, fried bacon, cooked-out bacon fats, baby foods containing meats, tomato products, cooked pizza, powdered and evaporated milk, mushrooms and different varieties of alcoholic beverages, were analysed by GLC-TEA for the presence of volatile nitrosamines. The levels detected in cured meat products (both cooked and uncooked) were very low, and both their incidence (at greater than 1 microgram/kg) and concentrations were much lower than those observed in a 1974 survey. The levels of N-nitrosopyrrolidine (NPYR) in fried bacon and cooked-out bacon fats were also somewhat lower than those observed at the end of 1976, but the decrease may not be significant. Traces (mean, 1.5 micrograms/kg) of N-nitrosodimethylamine (NDMA) were detected in 21 of 22 samples of beers and ales. Most of the remaining foods gave negative results, excepting the skim milk powders, which contained minute traces (mean, 0.4 micrograms/kg) of NDMA. An HPLC-TEA method was developed for the analysis of N-nitrosoproline (NPRO) and N-nitrososarcosine (NSAR) in raw and fried bacon. A study of the heat-induced decarboxylation of these nitrosamino acids suggests that these compounds are heat-labile and would not be expected to occur in fried foods at significant levels. Their presence, however, may lead to the formation of traces of NPYR and NDMA during frying at lower temperatures.

Beverages↗
PubMed1978

Recent studies in Canada on the analysis and occurrence of volatile and non-volatile N-nitroso compounds in foods.

The present paper briefly summarizes the research activities of the Food Research Laboratories, Canadian Health Protection Branch, during the past two years. Data presented indicate that traces of nitrosamines, mainly nitrosodimethylamine and nitrosodiethylamine, can occur in cheese. Several new analytical methods are presented for the determination of non-volatile nitroso compounds, such as nitrosohydroxypyrrolidine, nitrosodiethanolamine, nitrosoproline, nitrosohydroxyproline and nitrosoglyphosphate (a nitrosated herbicide). It is shown that all of the above compounds, even the very polar nitrosoglyphosphate, can be converted to volatile derivatives and then analysed by GLC-MS or by conventional GLC using a specific (such as P-photometric) detector. Traces of nitrosohydroxypyrrolidine have been detected in a few samples of cooked bacon. Contrary to previously reported findings, no significant levels of nitrosoproline were detected in the 6 samples of raw bacon analysed.

Animals↗
PubMedDate not supplied

Determination of N-nitrosodimethylamine in nonfat dry milk: collaborative study.

Ten laboratories participated in a collaborative study of a method for the determination of N-nitrosodimethylamine (NDMA) in nonfat dry milk. NDMA is eluted with dichloromethane from a mixture of Celite, acidic sulfamic acid, and nonfat dry milk (all packed in a chromatography column), concentrated in a Kuderna -Danish concentrator, and finally analyzed by a GC-thermal energy analyzer technique. Ten samples were studied: 6 were naturally contaminated (NDMA levels 0.38-3.56 ppb) and 4 were spiked with known levels (0.96 and 3.2 ppb) of NDMA. The coefficients of variation (CV) of the complete data for the naturally contaminated samples (excluding the 2 samples containing the lowest levels) were 8.5% and 22.5% for repeatability and reproducibility, respectively. The corresponding CVs for the spiked samples were 14.4% and 20.4%, respectively. The percent recoveries of the added NDMA in the spiked samples (at the 2 levels indicated above) were 101.6 +/- 3.2 (omitting 1 outlier) and 95 +/- 2.1, respectively. The method has been adopted official first action.

Animals↗