Evaluating Phthalate Contaminant Migration Using Thermal Desorption–Gas Chromatography–Mass Spectrometry (TD–GC–MS)

This study describes a methodology for evaluating regulatory levels of phthalate contamination. By collecting experimental data on short-term phthalate migration using thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS), the migration of di(2-ethylhexyl) phthalate (DEHP) from polyvinyl chloride (PVC) to polyethylene (PE) was found to be expressed by the Fickian approximation model, which was originally proposed for solid (PVC)/liquid (solvent) migration of phthalates. Consequently, good data correlation was obtained using the Fickian approximation model with a diffusion coefficient of 4.2 × 10−12 cm2/s for solid (PVC)/ solid (PE) migration of DEHP at 25 °C. Results showed that temporary contact with plasticized polymers under a normal, foreseeable condition may not pose an immediate risk of being contaminated by phthalates at regulatory levels. However, as phthalates are small organic molecules designed to be dispersed in a variety of polymers as plasticizers at a high compounding ratio, the risk of migration-related contamination can be high in comparison with other additives, especially under high temperatures. With these considerations in mind, the methodology for examining regulatory levels of phthalate contamination using TD–GC–MS has been successfully demonstrated from the viewpoint of its applicability to solid (PVC)/solid (PE) migration of phthalates.

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A New Method for Workplace Monitoring of Airborne Diacetyl and 2,3-Pentanedione Using Thermal Desorption Tubes and Gas Chromatography-Mass Spectrometry

Annals of Work Exposures and Health ◽

10.1093/annweh/wxz014 ◽

2019 ◽

Vol 63 (4) ◽

pp. 407-414

Author(s):

Ian Pengelly ◽

Veronica M Brown

Keyword(s):

Mass Spectrometry ◽

Gas Chromatography ◽

Thermal Desorption ◽

Passive Sampling ◽

New Method ◽

Gas Chromatography Mass Spectrometry ◽

Short Term ◽

Chromatography Mass Spectrometry ◽

Exposure Limit ◽

Workplace Monitoring

Abstract Diacetyl is a potentially harmful chemical that is used as an artificial flavouring in the food industry and may also be generated during processing of some natural products including coffee. In Europe, an 8-h time weighted average occupational exposure limit (TWA-OEL) of 20 ppb has been adopted for diacetyl, together with a short-term exposure limit (STEL) of 100 ppb. A sensitive new measurement method for diacetyl, and the related compound 2,3-pentanedione has been developed and evaluated. The new method uses Tenax TA sorbent tubes as the sampling media with analysis by thermal desorption (TD) and gas chromatography-mass spectrometry (GC-MS). The sample tubes are suitable for both active (pumped) and passive (diffusive) sampling. Diacetyl is stable on the sample tubes for at least 3 months but 2,3-pentanedione requires analysis within a month. Sample recovery is unaffected by changes in relative humidity and the presence of acetic acid. For short-term sampling, active sampling is recommended. The safe sampling volume for diacetyl is 3 litres which, at a flow rate of 100 ml min−1, equates to a maximum recommended sampling time of 30 min. For long-term samples, in particular collection of personal samples, passive sampling is recommended. Diffusive uptake rates have been determined for both diacetyl and 2,3-pentanedione on Tenax TA tubes fitted with standard diffusion heads over sampling periods of 1 to 8 h. Analytical limits of detection are approximately 0.2 ng for diacetyl and 0.1 ng for 2,3-pentanedione. These values equate to airborne concentrations of around 0.04 ppb of diacetyl and 0.02 ppb of 2,3-pentanedione for a 1.5-litre active sample and 0.3 ppb of diacetyl and 0.1 ppb of 2,3-pentanedione for an 8-h passive sample. In the case of passive sampling, this limit of detection is less than 1/50th of the new European TWA-OEL for diacetyl of 20 ppb. The method can also be used to identify the presence of other volatile organic compounds at sub-ppm concentrations.

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