Gas chromatographic-thermal energy analysis method for determination of volatile N-nitrosamines in baby bottle rubber nipples: collaborative study.

A collaborative study was conducted on the U.S. Food and Drug Administration (FDA) dichloromethane extraction method for determining volatile N-nitrosamines in baby bottle rubber nipples. Following dichloromethane extraction, N-nitrosamines were determined by gas chromatography-thermal energy analysis. Six pairs of blind duplicate rubber nipple samples representing 6 lots were analyzed by 11 collaborating laboratories. All samples were portions taken from equilibrated composites of cut-up rubber nipples obtained from manufacturers in the United States. Recoveries of the internal standard (N-nitrosodipropylamine) at approximately 20 ppb ranged from 10 to 120%. Reproducibility relative standard deviations (RSDx) were between 35 and 45% for N-nitrosamine levels from 10 to 20 ppb. However, when data from laboratories with recoveries less than 75% were excluded (this is now specified in the method), RSDx values were between 11 and 32% for N-nitrosamine levels from 6 to 26 ppb. Values were consistent with or better than those reported for other analytical techniques designed to quantitate trace contaminants at the low ppb level, e.g., aflatoxin in foods. The method has been adopted official first action for the quantitation of volatile N-nitrosamines in baby bottle rubber nipples.