Determination of N-nitrosodiethanolamine in cosmetic products by LC-MS-MS.

We have developed and validated in-house a liquid chromatography and mass spectrometry (LC-MS-MS) method for determination of N-nitrosodiethanolamine (NDELA) in cosmetics. The sample is diluted with water and then a C18 clean-up is performed. The average recovery of NDELA is 88.3%, range 48.3-112.7%, and the limit of detection is 22.8 microg kg-1. The repeatability is 7.6%, and the intermediate precision is 8.7%. Surveys were carried out in the Netherlands in September and October 2002 to determine the quantities of NDELA in cosmetics marketed in the Netherlands. The LC-MS-MS method was used to determine the NDELA content of 140 cosmetic products including shower gels, hair oils, shampoos and conditioners, cream and foam baths, mud baths, scrubs, creme and other soaps, and body washes. NDELA at levels ranging from 23 to 992 microg kg-1 was found in 35 cosmetic products.

Heterogeneity of human luteinizing hormone in pituitary tumor homogenates and cell incubates.

Incubation media of pituitary cells and homogenates of pituitary tumors were studied by isoelectric focusing followed by radioimmunoassay. Almost all LH-immunoreactive components detected had been observed in earlier studies on highly purified preparations. In one pituitary tumor homogenate, intact LH (LHi) was detected. The majority of LHi-components present in this tumor were relatively acidic (LH Type I) components. The corresponding beta-subunit population was in agreement with the one earlier observed for Type I LH. In all other tumor homogenates only alpha- and beta-subunits could be detected. In incubation media of pituitary cells from patients with no known endocrine disease nor a pituitary tumor highly acidic populations of alpha-subunits were detected. In only one of the incubation media significant amounts of LHi and free beta-subunits were observed. In an incubation medium of a TSH-producing pituitary tumor significant amounts of intact LH, free alpha- and beta-subunits were detected. The cell contents of this tumor contained components with lower pl-values than the medium. In general a good correlation is observed between the population of LH-components in material from individual identifiable pituitary glands and in highly purified preparations from large numbers of anonymous pituitary glands.

Heterogeneity of human luteinizing hormone. Hydrophobic interaction chromatographic fractionation of some preparations.

The heterogeneity of human luteinizing hormone was investigated with high performance hydrophobic interaction chromatography on a TSK phenyl-5PW column using an ammonium sulphate gradient. Recovery of individual subunits, expressed as immunochemical activity, was in the order of 90%. Recovery of the intact hormone was less, approximately 25%. The technique appeared to be independent of the charge heterogeneity of the individual subunits. Each component as obtained by hydrophobic interaction chromatography showed considerable charge heterogeneity when studied by subsequent isoelectric focusing. Nonetheless, all chromatography fractions derived from either subunit showed the same collection of isoelectric values, quantitatively only differences for the beta-subunits could be detected. Heterogeneity of the individual subunits was clearly demonstrated after incubation of the preparations at 37 or 56 degrees C. The heterogeneity of the beta-subunit observed after incubation at 56 degrees C was different to the heterogeneity after incubation at 37 degrees C. After incubation at 56 degrees C, an additional component, with a longer retention time, developed directly from the intact molecule. The component is unstable and is transformed to one of the components detected also after incubation at 37 degrees C. Based on these results the existence of two populations of intact LH molecules with respect to their thermal stability is hypothesized.