Analytical Instrument Documents

A thermogravimetry/differential thermal analysis (TG/DTA) system is used to measure weight changes and relative temperatures of samples under programmed heat conditions. A system combining TG/DTA with mass spectrometry (MS) is called a TG-MS system, and is considered one of the best qualitative and quantitative analysis systems for inorganic materials because it can measure sample conditions, evolved gas species, and gas volume simultaneously. In this application note, we introduce the basic application of analyzing calcium oxalate using the TG-MS “STA2500 Regulus” system (NETZSCH) and the GC/QMS “JMS-Q1500GC” system (JEOL).

The phthalates used as plasticizers in polymer resins are endocrine-disrupting substances that are a risk to human health. Therefore, the use of phthalates is limited by various government agencies. In the field of electrical equipment manufacturing, diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), and di-2-ethylhexyl phthalate (DEHP) are regulated by the European Union’s Restriction of Hazardous Substances (RoHS) Directive. The use of DBP, BBP, DEHP, di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) in toys and baby care products is regulated in Europe, the United States, China, and Japan. Phthalates subject to regulation are being replaced with alternative substances. However, it is known that phthalates tend to contaminate the manufacturing process and storage areas. Some alternative materials (e.g., tris-2-ethylhexyl trimellitate [TOTM]) may contain regulated components (e.g., DEHP) as impurities. In this report, PVC cables for commercial products using alternative substances as plasticizers were analyzed by the pyrolysis/thermal desorption–gas chromatography–mass spectrometry (Py/TD-GC-MS) method described in IEC 62321-8: 2017 [1]. Any phthalates discovered were quantified, and spectral information was collected for other detected compounds.

Electron ionization (EI) is the most commonly used ionization technique in gas chromatography–mass spectrometry (GC-MS). This hard ionization technique (70eV) provides excessive energy to organic compounds that results in highly reproducible fragment ions with relatively high ion intensities. As a result, EI databases have been created that help with identifying the compounds of interest. Despite this ability to do database searches, some compounds (alkanes, alcohols, etc.) do not produce abundant molecular ions, thus making it difficult to differentiate similar compounds from each other. By contrast, photoionization (PI) is a soft ionization technique that uses a vacuum ultraviolet (VUV) light source to provide ionization energies in the range of 8–10eV. This range is optimal for the soft ionization of common organic compounds which have an ionization energy in the range of 8–11eV. This low ionization energy results in stronger molecular ion signals and less fragmentation than for EI. Combining an EI library search with PI molecular ion information can improve the accuracy of the qualitative analysis results. In this work, we report on the qualitative analysis of styrene foam (Styrofoam) before and after photodegradation, using pyrolysis (Py)-GC/MS with an EI/PI combination ion source.

Thermogravimetry (TG) is used to measure weight changes of samples under programmed heat conditions. A system combining thermogravimetry/differential thermal analysis (TG/DTA) with mass spectrometry (MS) is called a TG-MS system, and can be used for both qualitative and quantitative mass spectral analysis of evolved gas from the TG furnace. The TG-MS technique can also be used to analyze the thermal-decomposition process. This application note shows an example of comparative analysis of mechanical-pencil leads of different performances, grades, and manufacturers. These leads are made by baking a mixture of graphite and resin, and then dipping it in oil for hardness and smoothness. Since the resin is carbonized and baked out, the lead is composed of only carbon and oil. In this application note, we show TG-MS analysis results for these mechanical-pencil leads using a “STA2500 Regulus” system (NETZSCH) and a gas chromatography–quadrupole mass spectrometry (GC/QMS) “JMS-Q1500GC” system (JEOL).

The Direct Insertion Probe (DIP) option permits rapid analysis of solid or liquid samples without gas chromatography. Samples contained in a disposable glass capillary are introduced with the DIP directly into the Q1500 ion source through a vacuum lock. The DIP temperature can be programmed for fast or slow heating to desorb or pyrolyze samples for analysis. In this example, we use the DIP to detect additives in a low-density polyethylene storage bag.

Electron ionization (EI), a hard-ionization technique that generates many fragment ions, is the most widely used ionization technique in gas chromatography–mass spectrometry (GC-MS). Since EI mass spectra have good reproducibility, qualitative analysis is possible by comparing an EI mass spectrum of a sample with that of the known compound recorded in the database. However, sometimes EI mass spectra lack molecular ions, which are of key importance to molecular-weight (MW) determination and correct compound assignment. Soft ionization is a useful way to determine MW. The JEOL JMS-Q1500GC offers two soft-ionization techniques: chemical ionization (CI) and photoionization (PI). In this application note, the MW information of diethyl phthalate and n-tetradecane were estimated from measurement results using both of these soft-ionization techniques.