Summary
Labs worldwide have recently found that helium has been in short supply, leaving a number of labs without carrier gas. Added to this, helium prices have doubled over the past 10 years causing a number of labs to look into alternative carrier gases for GC, such as nitrogen and hydrogen. As well as lower price and unlimited availability, hydrogen has a number of potential advantages over helium, including potential for faster throughput, improved chromatography and better sample resolution.
Introduction
This application note aims to demonstrate the injection of a complex, 76-component sample diluted in Dichloromethane (DCM) using hydrogen carrier gas. One potential problem highlighted with using hydrogen carrier gas is its potential for reaction with analytes and chlorinated solvents. This study aims to show that hydrogen carrier gas produced by a Peak hydrogen generator is suitable for GC/MS analyses with the Bruker Scion-SQ. Results show that hydrogen carrier gas can be used in conjunction with DCM as a solvent and with the correct injection configuration can give improved results compared with helium as carrier gas.Experimental
0.5 µL of a 76-compound mixture (Restek Megamix cat. No. 31850) diluted in dichloromethane (DCM) was injected into a hot split/splitless inlet of a Bruker Scion SQ GC/MSD. To increase the amount of sample transferred onto the column and reduce the dwell time in the inlet, in order to reduce the potential for reaction between carrier gas and solvent, pulsed-split injection was performed for 20 seconds. Hydrogen served as the carrier gas at a rate of 1.0 mL/min.GC and MSD conditions were as follows:
MS: Bruker SCION-SQ GC-MSDMS source: 330 °C
Mass Range: m/z 45-500
2 min solvent delay, 120 ms scan time. GC: Column: BP-5MS column (20m x 0.18mm with 0.18 µm film thickness)
Oven: 45 °C (1 min hold) ramped at 30 °C/min to 310 °C (5 min. hold)
Injection: Pulsed-split injection (inlet temperature 290 °C , pressure 40 psi for 0.3 min, 70:1 split) Carrier gas: Peak Precision Trace Generator Hydrogen, 1 mL/min
Instrumentation
The sample was analysed using the Bruker Scion SQ GC/MSD, which has a lens-free ion source allowing users to easily switch between helium and hydrogen. The inert ion source requires less frequent cleaning and maintains consistent levels of sensitivity. Hydrogen was provided by the Peak Scientific Precision Trace generator, which produces hydrogen from deionised water using a proton exchange membrane (PEM) cell and purifies hydrogen to 99.9999% using a pressure swing adsorption (PSA) dryer system.>> Download the full Application Note as PDF
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