ISO 17735:2019 pdf free download – Workplace atmospheres一 Determination of total isocyanate groups in air using 1-(9-anthracenylmethylpiperazine (MAP) reagent and liquid chromatography.
5.5.4 Post-column acid mobile phase
Dilute 35 ml of 85 % mass fraction phosphoric acid to 350 ml final volume with water. Mix this dilute phosphoric acid with 650 ml acetonitrile. Filter the solution through a 0,45 um nylon filter. Degas the mobile phase prior to use either by vacuum degassing or by helium sparging. Experience shows that the acid mobile phase is stable for six months if evaporation is prevented.
6 Apparatus
6.1 General
The following list of apparatus are used for the procedures below, as well as for the procedures in Clause 7 and for the preceding procedures in Clause 5: chromatographic column (150 mm x 2,0 mm 5 um C8 high purity silica), guard column (4 mm x 2,0 mm C8 Octyl, MOS), IOM sampler (stainless steel), liquid chromatographic system (autosampler, column oven, fluorescence detector, post-column pump, pumping system capable of gradient elution, vacuum degasser, and variable wavelength UV/ visible absorbance detector), microlitre syringe, midget impinger (graduated receiver and tapered inlet tube), portable flowmeter, rotary evaporator, sampling pump, SPE vacuum manifold, sonicator, vacuum filtration apparatus.
6.2 Sampler
6.2.1 General
The choice of sampler depends on the chemical and physical properties of the airborne isocyanateLl4l. If little is known about the physical and chemical nature of the isocyanates in the atmosphere, then the sampler should consist of a midget impinger followed by a MAP impregnated filter (see ISO/TR 17737). If the isocyanate is present only as vapour, either a MAP-coated filter or a midget impinger may be used. If isocyanate species are present in particles < 2 urn in diameter (condensation or combustion aerosol), then filters should be used. If isocyanate is present in particles > 2 p.m (e.g. spray painting), the recommended choice of impinger or filter depends on the reactivity of the aerosol. Typically, aerosols containing aliphatic isocyanates react relatively slowly and can be collected using a MAP-impregnated filter as described in Reference. Aerosols > 2 p.m containing aromatic isocyanates, such as those generated by MDI spray operations, frequently react fast and shall be collected using an impinger. If both particles < 2 p.m and relatively fast-curing particles> 2 p.m are present, then the recommended sampler consists of an impinger followed by a MAP-coated filter.
6.2.2 Filters
The filter material should be glass fibre (binder-free) and the filter should allow no more than 5 % mass fraction breakthrough of the aerosol being sampled. The choice of filter size and filter holder (opaque holders are preferred if available) is primarily dependent on the physical state of the isocyanate. Vapour and relatively small aerosol can be collected efficiently with any of the common filter samplers (e.g. open- or closed-face 37 mm polystyrene cassettes, 13 mm polypropylene filter holders). For relatively large aerosol (>20 um), a sampler designed to collect the inhalable fraction [e.g. that developed by the Institute of Occupational Medicine (IOM), UKI is recommended. Because isocyanates are strong sensitizers, it is appropriate to measure isocyanate in particles that will be deposited anywhere in the respiratory tract, i.e. the inhalable fraction.
6.2.3 Midget impingers
A midget impinger consists of a graduated receiver and a tapered inlet tube. The two parts should be matched so that the distance between the inlet and the receiver bottom is 1 mm to 2 mm. Non-spill impingers are commercially available.