Is it possible to improve the patch-test diagnostics for isocyanates? A stability study of petrolatum preparations of diphenylmethane-4,4'-diisocyanate and polymeric diphenylmethane diisocyanate.
We have previously shown that the concentration of diphenylmethane-4,4'-diisocyanate (4,4'-MDI) in commercial test preparations was so low that patch testing with the same was not reliable. The stability of 4,4'-MDI in petrolatum (pet.) was compared with pet. preparations of polymeric diphenylmethane diisocyanate (PMDI), which consists of a complex mixture of monomeric isomers and oligomers of MDI. Preparations of 4,4'-MDI and PMDI were stored under 3 different conditions, i.e. at room temperature, refrigerated and frozen. They were analysed continuously during 1 year with regard to the content of 4,4'-MDI, 3-ring oligomers and 4-ring oligomers using liquid chromatography-mass spectrometry. PMDI preparations kept frozen were stable for a year. All other preparations failed to fulfil the requirements of stability, i.e. +/-20% of the initial concentration. Storage in a freezer prolonged the lifetime for 4,4'-MDI. The decrease in concentration for preparations kept at room temperature and refrigerated was less rapid in PMDI preparations than in 4,4'-MDI preparations. PMDI preparations are better suited for patch testing patients exposed to MDI because they are more stable and homogeneous than 4,4'-MDI preparations. They better reflect possible allergens that workers are exposed to because products used in industry contain both monomers and oligomers.
Frick-Engfeldt
Malin
M
Department of Occupational and Environmental Dermatology, Malmö University Hospital, Lund University, S-205 02 Malmö, Sweden. malin.frick@med.lu.se
Zimerson
Erik
E
Karlsson
Daniel
D
Skarping
Gunnar
G
Isaksson
Marléne
M
Bruze
Magnus
M
D002853:Chromatography, Liquid; D003877:Dermatitis, Contact; D004355:Drug Stability; D004356:Drug Storage; D006801:Humans; D017953:Isocyanates / Q000737:chemistry*; D013058:Mass Spectrometry; D010328:Patch Tests / Q000592:standards*; D010577:Petrolatum / Q000737:chemistry*; D011140:Polyurethanes / Q000737:chemistry*; D001559:Benzhydryl Compounds
D017953:Isocyanates; D010577:Petrolatum; D011140:Polyurethanes; C087867:polymeric 4,4'-diphenylmethane diisocyanate; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds