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The new PT scheme "Diisocyanates on filters" serves as a quality assurance measure for the analyses of diisocyanates relevant to occupational health and safety.
Since it is not possible to evaporate diisocyanates in the test gas stream, air samples are simulated by spiking filters with diisocyanates. The spiking process is performed using an electronic pipette. After spiking and drying, the spiked and dried filters are sent to the participants.
An initial comparative measurement was conducted in 2024. Based on the promising results, a test PT scheme is now offered for the first time.
The filters will be spiked with the following substances:
| Diisocyanate | CAS Number |
| Diphenylmethane 4,4‘-diisocyanate (4,4‘-MDI) | 101-68-8 |
| Hexamethylene 1,6-diisocyanate (HDI) | 822-06-0 |
| Isophorone diisocyanate (IPDI) (isomeric mixtures) | 4098-71-9 |
| Naphthylene 1,5-diisocyanate (NDI) | 3173-72-6 |
| Tolulene 2,4-diisocyanate (2,4-TDI) | 584-84-9 |
| Tolulene 2,6-diisocyanate (2,6-TDI) | 91-08-7 |
The concentrations to be measured depend on the German occupational limit values (AGW1) of the substances. They will lie for each substance in the range of 1/10 to two times the AGW[1] value which results to 1.5 to 45 µL per analyte per filter. In total this PT scheme will consist of four samples, three for all analytes except NDI and one additional sample only spiked with NDI.
Choice of sample carriers (one type):
IFA-filter (glass fibre filter, diameter 37 mm, impregnated with 1-(2-methoxyphenyl)piperazine (1,2-MP) and acetonitrile), own fabrication
Supelco Orbo 80 filter (glass fibre filter, diameter 37 mm, impregnated with 1-(2-pyridyl)piperazine (1,2-PP) and acetonitrile), Prod. No. 20812-U
Each participant will receive a sample kit with ten filters (one type) comprising of:
two filters per sample loaded with all analytes except NDI (six samples in total)
two filters only spiked with NDI
two blind value filters
Analysis according to the IFA-Folder 7670 [1] is recommended. The corresponding international methods [2, 3] may also apply.
1 The German acronym AGW stands for Arbeitsplatzgrenzwert (Occupational Exposure Limit value - OEL). For carcinogenic substances and substances without AGW the database GESTIS - International limit values for chemical agents (www.dguv.de/ifa/gestis-limit-values) is used.
[1] Isocyanate – Monomere Diisocyanate, Totalkonzentration reaktiver Isocyanatgruppen (TRIG) und Polyisocyanatgehalt (Kennzahl 7670) In: IFA-Arbeitsmappe Messung von Gefahrstoffen. Lieferung: 01/2020.
[3] ISO 16702: Workplace air quality – Determination of total organic isocyanate groups in air using 1-(2-methoxyphenyl)piperazine and liquid chromatography. Geneva 2007.
