BS ISO 14382:2012 pdf download – Workplace atmospheres — Determination of toluene diisocyanate vapours using 1-(2-pyridyl) piperazine- coated glass fibre filters and analysis by high performance liquid chromatography with ultraviolet and fluorescence detectors
All dilutions of the stock solutions are made to arrive at the working range in 90 + 10 parts by volume ACN + DMSO. For example, a stock standard prepared in DMSO can be diluted 1→10 with pure ACN to arrive at 90 + 10 parts by volume ACN + DMSO. Any further dilutions are made with 90 + 10 parts by volume ACN + DMSO.
5.2.2 Preparation of analytical standards using pure
TDI Analytical standard solutions can also be prepared by reacting TDI (either pure 2,4-TDI or pure 2,6-TDI isomer) with 1-2PP in solution. Prepare a solution containing 1 mg/ml (0,006 mmol/l) 1-2PP by diluting 100 mg of 1-2PP to the mark with 90 + 10 parts by volume ACN + DMSO in a 100 ml volumetric flask, ISO 1042, [1] class A. Prepare a separate solution of 1 mg/ml (0,006 mmol/l) pure TDI by carefully and accurately weighing 50 mg of TDI (to three significant figures) and diluting it to the mark with 90 + 10 parts by volume ACN + DMSO in a 50 ml volumetric flask. Pipette 1 ml to 3 ml of the 1 mg/ml TDI solution into a 25 ml volumetric flask and dilute to the mark with the 1 mg/ml 1-2PP solution. Mix the solution well and allow it to react overnight. Do not use more than 3 ml of the TDI solution in order to ensure a proper excess of 1-2PP. Do not use the conversion factor in 5.2.1 to calculate the concentration of these standards. Use fresh solutions. The amount of pure TDI isomer shall be accurately known to prepare accurate standards.
5.2.3 Commercial standard solutions
Analytical standard solutions are commercially available.
5.3 Filter extraction solution
This solution is composed of 90 + 10 parts by volume ACN + DMSO.
5.4 1-2PP filter coating solution
This solution is composed of 4 mg/ml (0,025 mmol/l) 1-2PP in methylene chloride.
5.5 HPLC mobile phase
This solution is composed of 0,01 M ammonium acetate (buffered to pH 6,2 with acetic acid) in water and acetonitrile. The exact composition of the mobile phase depends on the HPLC column selected for use. The buffered ammonium acetate solution can be prepared separately and used in a solvent programmed gradient with acetonitrile.
6 Apparatus
6.1 Air sampler The air sampler consists of a three piece 37 mm polystyrene cassette with a glass fibre filter (type A/E binder free) coated with 2 mg of 1-2PP (see Figure 1).
6.1.1 Preparation of coated filters Prepare a sufficient volume of a solution containing 4 mg/ml 1-2PP in methylene chloride. The volume is based on the number of filters to be coated. Use 0,5 ml of this solution to coat each filter. Use a properly functioning fume hood to evaporate the solvent and minimize exposure of the filters to light during coating, drying, and subsequent operations. Separately place the uncoated glass fibre filters on a nickel-chromium wire grid or on the rims of 40 ml glass beakers so that only the edges of the filter are supported. Carefully, and slowly, pipette 0,5 ml of the 1-2PP solution onto the centre of the filter. This volume of solution is sufficient to fully wet the filter. Allow the methylene chloride solvent to evaporate in the hood for about 1 h. Transfer the coated filters to a clean dry container, loosely cap the container, and place the container in a vacuum desiccator equipped with a cold trap. Further dry the filters at reduced pressure for about 2 h. Analyse at least three of the coated filters for TDI after they are dry and store the remaining filters in a closed container in a freezer at −20 °C. There are various recommendations for the shelf life of these filters, however, they have been successfully used for up to 1 year after preparation when stored in a freezer until use. Do not store isocyanates, anhydrides, alcohols, carboxylic acids, or amines in the same freezer.