A screening procedure for total N-nitroso contaminants in personal care products: results of collaborative studies undertaken by a CTPA Working Group.

Synopsis A modified procedure for the determination of total N-nitroso compounds in personal care products was evaluated in collaborative studies organized through the UK Cosmetic Toiletry and Perfumery Association (CTPA). The method offers a true 'totals'determination in that a solution of the whole sample is analysed. Samples are dissolved/suspended in water or aqueous THF, and nitrite/nitrite ester interferences are removed by prior treatment with sulphamic acid. The treated test solution is denitrosated in a single reaction with HBr/acetic acid, in refluxing n-propyl acetate, and 'total'N-nitroso compounds are determined in a chemiluminescence reaction of the released nitric oxide with ozone. The use of a propyl acetate denitrosation solvent and of higher concentrations of HBr have improved both the sensitivity (routine limit of determination at 10 mugkg(-1)) and water tolerance of the method. The method was shown to recover N-nitrosamines quantitatively, and to be sufficiently repeatable and reproducible to be used as a screening technique for N-nitroso compounds in personal care products.

Study of the fate of Bronopol and the effects of antioxidants on N-nitrosamine formation in shampoos and skin creams.

Synopsis The role of antioxidants in preventing nitrosamine (N-nitroso diethanolamine) formation in shampoos and skin creams and the levels of Bronopol (2-bromo, 2-nitropropane-1, 3-diol) addition in relation to the resultant levels of N-nitroso compounds have been studied. The addition of 0.05% BHT, alpha-tocopherol or ascorbate was effective in preventing nitrosamine formation (limit of determination: 2.5 mug kg(-1)) in products preserved with 0.01% Bronopol. At 0.05% Bronopol, 0.2% of all three antioxidants was effective in preventing nitrosamine formation but at 0.1% Bronopol only alpha-tocopherol was effective. Levels of Bronopol found in shampoo formulations stored for 2 weeks at 37 degrees C with initial concentrations of 0.005-0.1% were reduced by 64-86%, independent of the initial concentration. The levels in skin creams stored for extended periods at ambient temperature with 0.01% Bronopol initially were reduced by, on average, 60%. High nitrite levels (NO(2) (-)) were found in formulations containing 0.01% Bronopol but no antioxidants (200-250 mg kg(-1)). Detected levels of nitrite in skin cream formulations were greater than could be formed by stoichiometric decomposition of Bronopol. In formulations with both Bronopol and antioxidants the levels of nitrite were considerably reduced. When alpha-tocopherol rather than BHT or ascorbate was the antioxidant then the nitrite levels were appreciably higher but formation of N-nitroso diethanolamine was no greater. High nitrite levels correlated with the formation of detectable levels of N-nitroso compounds in the absence of antioxidants.

The determination of N-nitrosodiethanolamine (NDELA) at trace levels in shampoos and skin creams by a simple, rapid colorimetric method.

Synopsis A technique is described for the rapid determination of N-nitrosodiethanolamine (NDELA) in shampoos, skin creams and similar products based on aqueous extraction, partition into ethyl acetate and colorimetric determination using the Eisenbrand-Preussman cleavage reaction. Recoveries of NDELA added at levels of 5-100 mug kg(-1) to a range of shampoo and cream types ranged from 90-101%. The limit of determination for the method is 2.5 mug kg(-1). Observations on the application of a thermal energy analyser linked to a gas chromatograph are also reported. Application of the technique to a survey of a wide range of shampoo and skin cream types showed that levels of total N-nitroso compounds were less than 30 mug kg(-1) in < 90% of samples and, in many cases, less than 2.5 mug kg-1.

Determination of organochlorine insecticide residues in fatty foodstuffs using a clean-up technique based on a single column of activated alumina.

A method is described for the extraction and clean-up of fatty foods prior to the determination of organochlorine insecticides and related compounds. Clean-up is based on the use of a single 22-g column of activity-4 alumina and the method is capable of routinely determining cyclodienes, BHC isomers and HCB at the 5-10 microgram/kg level and DDT-type compounds at 20-30 microgram/kg level.

Studies on the effect of feeding nitrite and secondary amines to Wistar rats.

1. When 1 000 mg/l sodium nitrite are added to drinking-water, nitrosamines are formed in the stomachs of Wistar rats at levels greater than the background only if the concentrations of added DMA or pyrrolidine exceed 1 000 mg/kg. Once this concentration is exceeded there is a rapid increase in nitrosamine formation up to 2 000 mg/kg added amine; however, for pyrrolidine, the rate of increase of NPy decreases when the dietary level of amine exceeds 2 000 mg/kg. This threshold level of 1 000 mg/kg amine is one which is rarely reached in normal human dietary patterns. 2. Due to the presence of this threshold it is unrealistic to extrapolate from high experimental dietary concentrations of secondary amines to those found in practice when considering nitrosamine formation in vivo. 3.The concentration of dietary amine has a greater influence on nitrosamine formation in the stomachs of rats than does the concentration of nitrite in drinking-water (up to 1 000 mg/l). This finding is in contradiction to the current kinetic theory of nitrosamine formation, in which formation is predicted to be proportional to the square of the nitrite concentration.