Biomedical subjects
Publications and source records attributed to S Fregert.
A case of allergic contact dermatitis to the rubber additive material ethylene thiourea (ETU) is presented. Testing for cross-sensitivity gave a positive reaction to the fungicide Maneb, manganous ethylenebisdithiocarbamate, but this reaction was probably due to ETU which was detected in Maneb by thin-layer chromatography. Different sources of ETU are reported.
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Allergic contact dermatitis from not fully cured epoxy resin in nasal canulae is reported. Patch testing and chemical analysis utilizing the actual batch are stressed.
19 photo substances were studied by thin-layer chromatography (TLC) as fresh solutions, and during storage under various conditions. Chlorhexidine was excluded as it is sparingly soluble and only used in commercial products as a derivative. Trichlorocarbanilide was the only substance shown to be impure from the start. Only benzocaine, buclosamide, chlorhexidine acetate and chlorhexidine gluconate remained unchanged to the naked eye, and in TLC. The other substances were changed in colour and/or in their TLC-pattern. As extraction method is described which makes it possible to use TLC for the examination of substances in petrolatum preparations. UV-absorption spectra have also been examined for all the substances.
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28 patients reacting to a PVC adhesive tape used in routine patch testing gave positive reactions to diphenylthiourea (DPTU) and to phenylisothiocyanate (PITC) in low concentrations. DPTU is a heat stabilizer in the PVC and is partly decomposed to PITC. The two substances were found in another type of PVC. Thioureas giving isothiocyanates are also used in certain types of rubber. Isothiocyanates are present in plants, mainly of the Cruciferae family, and are also formed from thiuram sulfides and thiocarbamates. The connection between isothiocyanates derived from different sources should be investigated.
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A certain amount of chromate can be added to calcium aluminate and calcium aluminate ferrite, 2 compounds present in clinker, without being extractable with water. Solutions of sulfate and the chemically related selenate and molybdate can extract about 2/3 of the added chromate. Also a certain amount of molybdate can be added to calcium aluminate without being extractable with water. About 2/3 of the added molybdate can be extracted with solutions of sulfate, selenate and chromate. Chromate present in clinker can partly be extracted with solutions of sulfate, selenate and molybdate. The present results indicate that chromate is partly present in crystals of calcium aluminate and calcium aluminate ferrite and that the correlation between chromate and sulfate in cement is due to an equilibrium between these two compounds inside and outside the crystals. The results also indicate that chromate, sulfate, selenate and molybdate can substitute each other. As cement always contains gypsum, which is partly water soluble, the possibility to make chromatefree cement is limited.
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