**2.6 Identification of deposits in filters of an Electrodeionization (EDI) unit for water purification in an industrial complex**

In the filters of an EDI unit some deposits have been formed causing unit clogging. The cause of the obstruction could be a phenolic epoxy paint that had been used recently. It was thought that over time some components of said paint dissolve in water and were the deposit formation cause.

A detailed analysis of the paint and the deposit was done in order to identify if the deposits formed correspond to any of its components and which component could be the cause.

The samples were analyzed by TD-GC/MS and Py-GC/MS.

**Figures 14** and **15** show the thermal desorption (at a temperature of 350°C) and the subsequent pyrolysis (at a temperature of 650°C), respectively, of the paint sample.

With the analytical conditions that were tested, benzyl alcohol, phenol and phenolic derivatives were mainly detected. These compounds are compatible with a phenolic epoxy paint. See **Tables 7** and **8**.

### **2.7 Polyethylene and polypropylene artificial weathering**

A method of analysis of Polyethylene, Polyethylene waxes and Polypropylene by thermal desorption and pyrolysis in series coupled to GC/MS was developed.

Optimal analysis conditions were sought for each matrix, testing different temperatures of thermal desorption and pyrolysis.

The objective is twofold. On the one hand, it is about obtaining information on the products that could be generated during a future biological and/or thermal

**Figure 14.** *DT-GC/MS of the paint sample (350°C).*

### **Figure 15.** *Py-GC/MS of the paint sample (650°C).*


### **Table 7.**

*Identified compounds (DT-GC/MS) with area % > 1.*


### **Table 8.**

*Identified compounds (Py-GC/MS) with area % > 1.*

degradation of polymers, and on the other hand, having information on the type of polymer and additives that they might contain.

Sample 1, sample 3 and sample 5 were a virgin polyethylene, a virgin polyethylenic wax and a virgin polypropylene sample, respectively. They were oxidized in an oven at 96°C for 28, 21 and 7 days, respectively. The corresponding oxidized samples were Samples 2, 4 and 6, respectively.

**Figure 16.** *a) DT- and b) Py-GC/MS of sample 1.*

**Figure 17.** *a) DT- and b) Py-GC/MS of sample 2.*

**Figure 18.** *a) DT- and b) Py-GC/MS of sample 3.*

**Figure 19.** *a) DT- and b) Py-GC/MS of sample 4.*

**Figure 20.** *a) DT- and b) Py-GC/MS of sample 5.*

**Figure 21.** *a) DT- and b) Py-GC/MS of sample 6.*

**Figure 22.** *Fragmentogram m/z 60 DT-GC/MS of the polyolefin samples a) 1 and b) 2.*

**Figure 23.** *Fragmentogram m/z 60 DT-GC/MS of the polyolefin samples a) 3 and b) 4.*

*Pyrolysis-GC/MS, A Powerful Analytical Tool for Additives and Polymers Characterization DOI: http://dx.doi.org/10.5772/intechopen.101623*

**Figure 24.** *Fragmentogram m/z 60 DT-GC/MS of the polyolefin samples a) 5 and b) 6.*

The six samples were analyzed by TD-GC/MS and the residual of each sample is subjected to Py-GC/MS.

The following figures show the chromatograms that were obtained for the polyolefin samples.

The Polyethylenic wax and Polyethylene pyrograms consists of serial triplets, corresponding to α, ω-alkadienes, α-alkenes and n-alkanes, respectively, in the order of increasing n + 1 carbon number in the molecule. See **Figures 16b**, **17b**, **18b** and **19b**. Identification of compounds was carried out by comparison of mass spectra with data in the NIST mass spectral library.

The pyrograms of the Polypropylene samples show branched alkenes (C4 to C13) as major components. Isobutene, 2-methyl-2-butene, 3-methyl-1-pentene, dimethylpentadienes, 2,4-dimethyl-1-heptene are the most abundant branched alkenes. See **Figures 20b** and **21b**.

In the m/z 60 fragmentograms of the oxidized Polyethylene and Polyethylenic wax samples (See **Figures 22b** and **23b**) carboxylic acids are detected. In the m/z 60 fragmentogram of the oxidized Polypropylene no carboxilic acids are detected (See **Figure 24b**). In the TIC of this sample acetone is detected. However, in the pyrograms, no carboxylic acids, aldehydes or ketones are detected.

### **3. Conclusions**

This chapter is intended for the use of both researchers and chemists who use GC/MS to analyze materials, and who need to add pyrolysis techniques to their analysis tools. Py-GC/MS is a practical, cost-effective, reliable, and flexible alternative for increasingly complex sample analyses, and can be used to analyze different kind of samples for a diversity of fields including industrial research, microbiology, forensic science, and environmental analysis.

The potential of Py-GC/MS was highlighted through different case studies, ranging from additives chemical characterization to weathered polyolefins samples.
