Page 448 - Handbook of Materials Failure Analysis

446 CHAPTER 17 Application of pyrolysis

processed with Xcalibur software (ThermoQuest) and the NIST 05 mass spectral
library. In the second apparatus (2), the pyrolyzer was connected to a 7890A GC
with a series 5975C quadrupole MS (Agilent Technologies Inc., Santa Clara,
CA, USA) operated in EI mode (Figure 17.1). The fused silica GC capillary column
(60 m long, 0.25 mm I.D. with DB-5ms stationary phase, film thickness 0.25 μm;
J&W Scientific, Folsom, CA, USA) was used. Helium, grade 5.0 (Westfalen
AG) was used as a carrier gas.
The gas chromatographic conditions were as follows:

1. Programmed temperature of the capillary column from 60 °C(1min hold) at 7 °C
min 1 to 280 °C (hold to the end of analysis) and programmed pressure of helium
from 122.2 kPa (1 min hold) at 7 kPa min 1 to 212.9 kPa (hold to the end of
analysis),
2. Programmed temperature of the capillary column from 75 °C (1 min hold) at 7 °C
min 1 to 280 °C (hold to the end of analysis) and programmed pressure of helium
from 122.2 kPa (1 min hold) at 7 kPa min 1 to 212.9 kPa (hold to the end of
analysis).

The temperature of the split/splitless injector was 250 °C and the split ratio was 20:1.
The transfer line temperature was 280 °C. The MS EI ion source temperature was
kept at 230 °C.
The ionization occurred with a kinetic energy of the impacting electrons of
70 eV. The quadrupole temperature was 150 °C. Mass spectra and reconstructed
chromatograms (TIC) were obtained by automatic scanning in the mass range m/z
35-750 u. Py-GC/MS data were processed with the ChemStation software (Agilent
Technologies) and the NIST 05 mass spectral library.
The scanning electron microscopic studies were carried out using the JSM-6510
series JEOL (Germany) GmbH (Eching/Mu ¨nchen) apparatus.

2.3 DERIVATIZATION AND DIRECT GC/MS ANALYSIS
3
Micro-reaction vessels of 3 cm with solid cap and PTFE liner (Supelco, Bellefonte,
PA, USA) along with the block heater SBH 200DC (Stuart, Bibby Scientific Ltd.,
Stone, Staffordshire, UK) were used for derivatization. Approximately 100 μLof
the investigated brake fluid sample was placed in the micro-reaction vessel and
300 μL of the silylation agent N-methyl-N-(trimethylsilyl)-trifluoroacetamide
(MSTFA) was added. The sealed vessel was placed in the block heater at 70 °C
for 30 min. The resulting product was dissolved 1:1 (v/v) in methanol and 1 μLof
the solution was injected into the GC/MS apparatus for analysis. Programmed tem-
perature of the capillary column DB-5ms (30 m long, 0.25 mm I.D., 0.25 μm film
thickness) (J&W) from 60 °C (1 min hold) at 6 °C min 1 to 280 °C (hold to the
end of analysis) was used for GC separation of compounds. Helium, grade 5.0 (West-
1
falen AG) was used as a carrier gas at constant flow rate of 1 mL min . The
temperature of the split/splitless injector was 250 °C and the split ratio was 25:1.
The transfer line temperature was 280 °C. The MS EI ion source temperature was