Diablo Analytical, Inc.

	Two of the more commonly used polymer additives, Irganox 1076 and 1010, are phenolic primary antioxidants used to provide long-term thermal stability to the end product. They are widely used in polyolefins such as polyethylene, polypropylene, polybutene, and copolymers such as polyurethane. Analysis of 1076 and 1010 is difficult because each is highly resistant to conventional extraction and has a very low vapor pressure. It is not unusual for a laboratory to use HPLC or LC-MS for these two additives. Note that both additives have the exact same phenolic group in the ratio of 4:1.

	This application note details a GC-MS-based analytical method for the qualitative and quantitative determination of Irganox 1076 and 1010 in polyethylene.

	Irganox 1076 can be thermally desorbed from polyethylene at 320 °C. The mass spectrum has a base peak of 

 530-representing the molecular ion. Both 1076 and 1010 have an ester linkage which can be thermally hydrolyzed and methylated using tetramethylammonium hydroxide (TMAH). The derivatized product is the same for both 1010 and 1076; the mass spectra of the derivatized additives are also identical and exhibit large peaks at 

 291 and 306. The stoichiometric ratio of the derivatized product compound for Irganox 1010 is 4:1 compared to Irganox 1076. Reactive pyrolysis alone cannot be used to differentiate Irganox 1076 and 1010. See Figure 1.

 Both 1076 and 1010 have an ester linkage which can be thermally hydrolyzed and methylated using tetramethylammonium hydroxide (TMAH). Reactive pyrolysis alone cannot be used to differentiate Irganox 1076 and 1010.

	
	It is a relatively straight forward process to identify and quantitate both Irganox 1010 and 1076 in polyethylene. Analysis of the sample using reactive pyrolysis (RxPy) yields the total ppm of the two additives. A second analysis of the sample using thermal desorption quantitates the Irganox 1076. Subtracting the two numbers is all that is necessary to find the amount of Irganox 1010:

1010 & 1076 (RxPy) total – 1076 (TD) = 1010 amount. 

	Example shown in Table I for the PE unknown sample where the calculated amount of 1010 is 1406 ppm.

	Complex samples can rarely be fully characterized using a single analytical technique; consequently, the analyst must analyze the sample a number of times using different analytical tools. This work clearly illustrates the value of having a chromatographic system that can be configured to perform multiple analytical techniques. The EGA/PY-3030 Multi-shot Pyrolyzer from Frontier Laboratories can be used to characterize a sample using evolved gas analysis, pyrolysis, multi-zone thermal desorption, and reactive pyrolysis. Both liquid and solid samples can be analyzed directly; conventional sample prep regimes are unnecessary. More complete information regarding this analysis is contained in a technical brief from the authors.

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This application note details a GC-MS-based analytical method for the qualitative and quantitative determination of Irganox 1076 and 1010 in polyethylene.

Characterization and Determination of Irganox 1076 and 1010 in Polyethylene Using Thermal Desorption and Reactive Pyrolysis-GC-MS

The Diablo 5000A Real-Time Gas Analyzer (RTGA) is a real-time chemical measurement tool for continuous process improvement. It is ideal for applications where fast chemical analysis is required, such as monitoring process transients and dynamic continuous reactions. The 5000A RTGA can be used for fuel cell gas analysis, syngas monitoring, catalyst research, monitoring of volatile solvent residues, pharmaceutical reactor headspace monitoring, and many other applications.

	Reliable chemical and engineering information is critical for rapid process development. Often, common sensors are either simple or slow, and they provide limited information. The result is nearly blind operation and slow development progress.  The Diablo 5000A RTGA-MS allows the process stream to be seen in real-time and provides quantitative data with reliable mass information. The result is visualization.

	Process development experiments can often be performed more rapidly with reduced quantities of reagents and materials such as catalysts with a higher efficiency process test device. This reduces the requirements for rare or costly catalysts during screening, reduces consumption of chemicals and related potential hazards. However, as experimental time is reduced, the ability to follow the process in real-time becomes even more critical. For modern experiments, the measurement systems need to be designed as an integral part of the experiment. The experiment shown in Figure 1 begins with a monitoring of the starting materials. Then at about 9 min, the catalyst is placed in-line and the composition of the process stream changes in seconds. But the process returns to the original reagent conditions after only 5 min of catalyst exposure. The RTGA allows this to be followed with high data acquisition rates in real-time. Thus, the process can be visualized on a time basis with the detail of mass information as it changes on the seconds time scale.

					Figure 1: Real-time monitoring of starting materials, addition of catalyst at 9 min showing reaction products; catalyst lasts only about 5 min.

	The RTGA is designed to allow real-time measurements on a quantitative basis. Simpler and lower-cost designs would only result in rough trend monitoring. The RTGA interface (Figure 2) has been designed to control or account for fluctuations in sample pressure, present the correct concentration range to the very sensitive mass spectrometer (MS), and connect real world pressures to the vacuum world of MS. Poor instrument designs with excessive system drift will confuse process results. The RTGA is also very flexible and easy to adapt to different experiments that might present a wide requirement for mass range, scan speeds, matrix omission, real-time calibration, and calculations.

					Figure 2: RTGA interface design to MS. Shows process stream sampling to detection by Agilent MSD.

	Fast, flexible, rugged real-time response to process changes are benefits of the Diablo 5000A RTGA direct-to-MS design. However because this system uses the 5977B Agilent MSD, quick and easy conversion for GC–MS applications can be achieved by adding an Agilent 7890B GC for additional system flexibility.

	The RTGA-MS, based on the proven Agilent MSD platform, is designed to be robust and stable for engineering research and development environments. The system can be configured to measure masses from hydrogen to heavier vaporizable organic molecules. This system allows rapid process development due to the use of reliable information and visualization in real-time. Gone are the clumsy estimation-based trend monitoring tools of the past. The capability to acquire quantitative mass information by MS is powerful and provides quick, reliable knowledge about the process stream.

The Diablo 5000A RTGA-MS allows the process stream to be seen in real-time and provides quantitative data with reliable mass information. The result is visualization.

Diablo Analytical, Inc.

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Characterization and Determination of Irganox 1076 and 1010 in Polyethylene Using Thermal Desorption and Reactive Pyrolysis-GC-MS

Visualize Your Process Streams in Real-Time with MS for Rapid Process Development