Determination Of Isocyanates In Air Research Articles

Validation of Transferability of DBA Derivatization and LC–MS/MS Determination Method for Isocyanates via an Interlaboratory Comparison

An adapted method for the quantitative determination of isocyanates in air was implemented and validated in-house. The method was based on air sampling using an impinger flask containing di-n-butylamine (DBA) in toluene and a glass fibre filter in series. The DBA derivatives were determined using liquid chromatography and tandem mass spectrometry. Studied isocyanates were isophorone diisocyanate, isocyanic acid (ICA), methyl isocyanate, ethyl isocyanate, propyl isocyanate, hexamethylene diisocyanate (HDI), 2,6- and 2,4-toluene diisocyanate, 4,4'-methylene diphenyl diisocyanate (MDI), phenyl isocyanate (PhI), MDI oligomers and different HDI adducts. Monitoring of selected reactions resulted in quantifications with correlation coefficients >0.995, within-batch relative standard deviation (RSD) of repeatability was <13% for all analytes. Between-batch RSD (reproducibility) was determined for all the compounds with the exception of the adducts and oligomers and was also <13%. As an additional validation procedure, the method was evaluated by exchanging field (air) and standard samples between two laboratories. The RSDs observed by the two laboratories were comparable. The concentrations determined were between 80 and 120% of each other, depending on the analyte and the individual concentrations. The method was applied in a large field study on exposure of workers in car repair shops and industrial painters with >500 samples.

MDHS 25 Revisited; Development of MDHS 25/3, the Determination of Organic Isocyanates in Air

Isocyanates (NCO) are potent sensitizers and the largest cause of occupational asthma in the UK. Probably, MDHS 25/3 is the method most commonly used worldwide for the determination of organic NCO in air. This method uses an electrochemical (EC) detector to quantify oligo-NCO using derivatized NCO monomers as calibrants. This paper gives the results of a validation exercise using this method to quantify industrially used monomeric and oligo-NCO formulations. An expanded uncertainty of approximately 56% was found for seven formulations spiked onto two sampler types at four spiking levels. No differences were found between the analytical results obtained from spiked filters or spiked impinger/filter samplers. Also presented is work on the validation of the EC/UV ratio approach used in MDHS 25/3 to identify NCO-derived peaks. A total of 58 industrially used non-monomeric NCO formulations were studied. These formulations gave 138 peaks that were identified using MDHS 25/3 as oligo-NCO MP derivatives. One of these peaks had an EC/UV ratio outside the range given in MDHS 25/3. Work describing the use of an internal standard to improve the variability of the EC detector is reported. Finally solutions to practical problems encountered during long-term sampling using an impinger are given.

Determination of isocyanates in air

Procedures for the determination of isocyanates in air are considered, including procedures for air sampling with the subsequent analysis and on-line monitoring procedures. Only chemisorption is used for the sampling and preconcentration of isocyanates because of their high reactivity. The data on the reagents in use, the types of sampling devices, and operation conditions are surveyed. Presently, high-performance liquid chromatography is primarily used for the subsequent instrumental analysis of samples. Photometric techniques were used in early studies; more recently, thin-layer chromatography and gas chromatography were introduced. Examples of analysis using other techniques are very few. Methods of on-line monitoring of air (both instrumental techniques and rapidly developed biomonitoring, which is performed simultaneously with the analysis of polluted air) are briefly considered.

Evaluation of Chromatographic Methods for the Determination of Isocyanates in Air

Abstract Chromatographic methods for the determination of toluene diisocyanates (TDI) in air, at concentrations of 20–40μg/m3, were evaluated. Test atmospheres were generated by a gas-phase permeation principle. The GC method was based on sampling in impingers containing an acidic aqueous solution (0.4 M HC1), where the isocyanates are hydrolysed into the corresponding amines. The pentafiuoropropionic acid derivatives of the amines were analysed using glass capillary GC with thermionic detection. The HPLC methods were based on reaction with the amine reagents 9-(N-methylaminomethyl)-anthracene (1 × 10−4M in toluene) and 1-(2-methoxyphenyl)-piperazine (2 × 10−4M in toluene). The urea derivatives were determined using UV detection. The sampling efficiency for gaseous TDI with toluene as absorbing solution was 97%. Sampling efficiencies in various acidic aqueous solutions were 83–88%. The relative standard deviation for the various methods was ca. 6%. No sampling losses for TDI, due to influences of interfering substances (diethylamine, dimethylethylamine, N-methylmorpholine, DABCO, aniline, ethanol, phenol) using acidic aqueous 0.4 M HC1 were obtained. Diethylamine, N-methylmorpholine and DABCO affected the analytical results when toluene solutions of the amine reagents MAMA and MPP were used.

A highly sensitive high-performance liquid chromatographic procedure for the determination of isocyanates in air

A sensitive high-performance liquid chromatographic procedure is described to analyse hexamethylene diisocyanate (HDI), 2,4- and 2,6-toluene diisocyanate (TDI), and 4,4′-diphenylmethane diisocyanate (MDI) in air. The isocyanates are trapped on a sorbent coated with 1-(2-methoxyphenyl)piperazine (MPP). The resulting derivatives are separated using a column switching technique using either a diode array UV detector or an electrochemical detector. Working ranges are 1–5000 and 0.05–400 pmol for UV and EC detection, respectively. Virtually no breakthrough occurs if an air volume of up to 1500 l is sampled, and relative detection limits between 0.1 and 1 ng/m3 can be achieved. The procedure can be used to determine HDI and MDI in work place atmospheres and indoor air.

A Comparison of Methods for the Determination of Isocyanates in Air

Abstract Isocyanates are in widespread use in certain industries such as in the manufacture of polyurethane products, paints and elastomers. The occupational exposure limit for isocyanates corresponds to 0.3 μg of isocyanate per sample using a 15 minute sampling time. Airborne isocyanates cause a variety of respiratory problems and workplace monitoring is therefore necessary. Two methods have recently been published by the Health and Safety Executive, one colorimetric and one HPLC using both electrochemical and UV detection. This study has compared these two methods using both field samples and laboratory generated standard atmospheres over a range of concentrations relevant to test the method at occupational exposure levels. The result of the field study showed that the colorimetric method was generally being used at its limit of sensitivity. Although potentially more sensitive, HPLC did show some interference with the field samples, thus limiting its sensitivity. The laboratory study showed good correla...

Determination of isocyanates in air by liquid chromatography with fluorescence detection

Determination of isocyanates in air by liquid chromatography with fluorescence detection