Helium is the most common carrier gas in GC/MS systems, and it is also an important strategic resource. Under the current environment, the price of helium continues to rise, which has also caused “helium anxiety” for users of GC/MS systems. In June 2022, Agilent will simultaneously release a variety of GC/MS systems globally, including the single quadrupole GC/MS system 5977C, the triple quadrupole GC/MS system 7000E and 7010C. The new products launched by Agilent have also brought “disruptive” innovations: the development and launch of a new ion source (HydroInert, hydrogen inert ion source) that uses hydrogen as the carrier gas for GCMS.
The special physical and chemical properties of hydrogen not only help to improve the chromatographic behavior, but also in Agilent’s innovative and proprietary technology JetClean has been proven to be used to reduce the cleaning needs of the ion source, reducing the cleaning frequency by up to 90%【1】 . Hydrogen as a carrier gas redefines the performance of the GC/MS system, creating more room for system improvement in terms of analysis speed, resolution, peak shape, and stability. Spectral results for hydrogen as a GCMS carrier gas are already provided in the new version of the polycyclic aromatic hydrocarbon test standard AfPS GS 2019:01 PAK published by the German Consumer Product Safety Commission (Ausschuss für Produktsicherheit, AfPS). The future of the GC-MS system has come, and the future is coming. Let’s take polycyclic aromatic hydrocarbons as an example to experience the changes brought about by hydrogen as a carrier gas.
HJ 805-2016 stipulates the determination method of polycyclic aromatic hydrocarbons in soil and sediment. The heating program lasts for 28 minutes. First, let’s look at the spectrum analyzed by hydrogen in the same heating program:
Compared with the spectrum provided in the HJ 805 standard, the most direct improvement is shorter analysis time and better peak shape. At the same time, we can’t help but have two problems:
- Under the premise of maintaining the separation requirements, how fast can hydrogen be used as a carrier gas?
- Excluding other chromatographic factors such as chromatographic columns, how much change can be brought about by only considering hydrogen as a single variable of carrier gas?
To answer these two questions, we compared the temperature program and the exact same column. The figure below shows the spectral results using HP-5ms UI (20 m, 0.18 mm, 0.18 µm) helium and hydrogen as the carrier gas. The heating program is 80°C for 1 min, 20°C/min to 300°C for 5 min. Based on benzo[g,h,i]perylene, which has the longest retention time, the analysis time was shortened from 28 minutes in the standard method to 13 minutes, and the efficiency was more than doubled!
Due to some degree of ion interference from indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene, complete baseline separation is usually required to avoid impact on quantitation. Let’s take a closer look at their resolution and peak shape. Obviously, under the same chromatographic conditions, hydrogen as a carrier gas has better resolution, symmetrical and sharper peaks, and the analysis time is significantly shortened.
In addition to the improvement of chromatographic behavior, polycyclic aromatic hydrocarbons can achieve an extremely wide linear range under the action of hydrogen, and the calibration curve of perylene is still linear in the range of 1.0 ppb~50 ppm over four orders of magnitude.
A 8890-5977C GC-MS equipped with a hydrogen inert ion source (HydroInert) was used to perform stability tests on soil samples with complex matrices [2], and the spiked concentration of 27 PAHs was 100 ppb. During the 100-injection test, there was no need for inlet or column maintenance, and results remained stable throughout.
The future has come. Agilent HydroInert makes it feasible to use hydrogen as the carrier gas of the GC/MS system, and it has been verified that it is significantly better than helium as the carrier gas in terms of resolution, peak shape, and analysis speed. Effect. It even shows great potential in more dimensions such as sensitivity, repeatability, stability, linear range, and keeping the ion source clean. All of this not only eliminates “helium anxiety”, reduces costs and increases efficiency, but also changes and subverts our perception of the performance of GC-MS. At the same time, hydrogen has been introduced as a carrier gas standard internationally, and domestic users have also taken steps to explore. At this new node of innovation and change, choosing to change will undoubtedly bring a series of challenges, but it will undoubtedly benefit GCMS analysts a lot.