Ultra-Low Bleed Columns Improve Trace-Level Analysis
When measuring trace-level impurities, the sensitivity of the GC system needs to be optimized. If it is not, low-level compounds cannot be adequately distinguished from the baseline and accurate identification and quantification become difficult or impossible. Sensitivity is strongly influenced by column factors, including inertness and bleed. Rxi columns are the lowest bleed column available and improve trace-level detection by reducing background noise.
Low Bleed Rxi Columns Minimize Noise, Maximize S/N Ratios
All Rxi stationary phases are surface bonded via the interfacing deactivation layer. The deactivation layer has an important function in shielding any residual activity on the surface (Figure 1). Several types of stabilization groups can be used for minimizing stationary phase bleed (Figure 2). These stabilization groups reduce the degradation reaction of the siloxane polymers when the column is used at elevated temperatures, resulting in a much lower bleed column than other “low-bleed” columns on the market.
Figure 1: Rxi technology results in greater phase stability.
Figure 2: Structures of compounds used for the stabilization of siloxane phases.
Figure 3 shows a comparison of the degradation obtained on several commercially available stabilized 5% diphenyl polysiloxane phases. Although most commercial columns have relatively low bleed characteristics, the Rxi columns clearly show superior performance. Figure 4 shows similar results for silarylene-based columns—the Rxi column exhibits the lowest stationary phase bleed at both the column’s isothermal limit, as well as the maximum programmable temperature.
Figure 3: Rxi-5ms columns have significantly lower bleed levels, compared to other stabilized, low-bleed phases.
Figure 4: Rxi-5Sil MS columns outperform competitor columns, producing lower bleed at high temperatures.
| Column | Rxi-5Sil MS, 30 m, 0.25 mm ID, 0.25 µm (cat.# 13623) |
|---|---|
| Standard/Sample | n-tridecane in methylene chloride |
| Conc.: | 40 µg/mL |
| Injection | |
| Inj. Vol.: | 1.0 µL split (split ratio 40:1) |
| Liner: | Gooseneck Splitless (4mm) w/Wool (cat.# 22406) |
| Inj. Temp.: | 250 °C |
| Oven | |
| Oven Temp.: | 135 °C (hold 4 min) to 330 °C at 70 °C/min (hold 10 min) to 350 °C at 70 °C/min (hold 10 min) |
| Carrier Gas | He, constant flow |
| Flow Rate: | 1.4 mL/min |
| Detector | FID @ 330 °C |
|---|
In summary, Rxi columns are made using an innovative stabilizing technology that results in exceptionally low-bleed columns, which are available with the most commonly used stationary phases. Ultra-low-bleed levels improve signal-to-noise ratios by reducing background noise, making Rxi columns ideal for trace-level analyses and MS applications.