Determination of TBC Linearity and Carry-over in 1,3-Butadiene with the DVLS Butadiene Analyzer

Polymerization-grade 1,3-Butadiene contains polymerization inhibitors to prevent spontaneous auto-polymerization during storage and transport. 

The prescribed inhibitor for 1,3-Butadiene is para-tert-butyl catechol (TBC). 

Current method ASTM D1157 determines TBC traces in 1,3-Butadiene with a detection limit of 50 mg/kg, requiring evaporation of large volumes of Butadiene.

Due to its chemical structure, TBC has low solubility in non-polar hydrocarbon streams and tends to adsorb onto active surfaces. 

To provide a safe and accurate alternative to D1157 Da Vinci Laboratory Solutions B.V. (DVLS) developed the DVLS Butadiene Analyzer containing a Liquefied Gas Injector (LGI). 

This Application Note reports on the tests of TBC linearity and carry-over in 1,3-Butadiene with the DVLS Butadiene Analyzer.

Experimental

The DVLS Butadiene Analyzer is configured on an Agilent 8890 GC equipped with a DVLS Liquefied Gas Injector (LGI) and DVLS Pressure Station. 

The LGI injects the sample directly from the gas cylinder into the DVLS Programmable Temperature Inlet (PTI), followed by a separation on a capillary column and detection using a Flame Ionization Detector (FID). 

This sampling approach eliminates the need for evaporation and prevents analyst exposure to 1,3-Butadiene.

A stock solution containing 3.2% TBC in Methanol was prepared. 

Known amounts of this stock were diluted with Pentane in a copper strip cylinder as shown in Table 1. 

The standards shown in Table 1 were injected in triplicate. To check for carry-over, blank Pentane was injected after the standard 6 (containing 142 mg/kg) was injected. 

Finally, a sample was analyzed to determine the detection limit and repeatability.

Results

Figure 2 shows a chromatogram of a TBC standard in Pentane, Figure 3 displays the analysis of the TBC standard at 23.4 mg/kg concentration level along with the blank Pentane injected after standard 6 containing the highest concentration. 

The blank chromatogram seen in Figure 3 does not show a quantifiable trace of the TBC introduced during the previous analysis. 

This shows the system does not have any carry-over for this compound, even at high concentrations. 

Figure 4 shows a linear regression of the injected TBC concentrations plotted against the corresponding peak areas from Table 1.

The results of the linear regression in Figure 4 demonstrate that the TBC analysis shows excellent linearity over a broad concentration range.

Table 2 lists the repeatability with a relative standard deviation (RSD) below 5% for TBC and a limit of detection (LOQ) below 1 mg/kg.

Conclusion

The DVLS Butadiene Analyzer is a GC system equipped with a Liquefied Gas Injector, designed for determining inhibitors such as TBC. 

Tests on TBC linearity and carry-over in Pentane showed a consistent linear response across the tested concentration range, with no carry-over effects. 

Detection limits were below 1 mg/kg, and relative standard deviations remained under 5%. 

These results indicate that the DVLS Butadiene Analyzer is a safer and more reliable alternative to the ASTM D1157 method, offering improved performance in terms of sensitivity and reproducibility.