Are you Still Preparing Your GC Calibration Standards Manually?

If you are a gas chromatographer, you will surely have had to re-prepare calibrations standards and re-run a sequence due to manual mistakes. The preparation of calibration standards can be a source of errors in gas chromatography (GC) analysis, especially when done manually. The accuracy of the calibration standards is critical to the accuracy of the analytical results and any errors can lead to inaccurate data. Unfortunately, when you realize it, it is often too late to avoid a significant time sink.

For laboratories that aim to be more efficient, automation of sample handling procedures — like standard dilution — is an easy and affordable approach offering a labor-time savings opportunity. Automation doesn’t necessarily replace operators, but instead frees them up for other, more value-added, activities.

Modern robotic autosamplers like the Thermo Scientific TriPlus RSH SMART can be easily programmed to execute several sample handling operations as well as sample preparation protocols. Automated workflows can significantly reduce errors, increase reproducibility, and save time. It can also improve the quality of the results by reducing the variability of manual operations.

An example of automated sample preparation workflow combining the preparation of calibration standards with samples cleanup and on-line GC-MS/MS analysis has been used for increasing the productivity for pesticide residues analysis in food, as described in the recently released technical note TN002569.

Enhanced productivity for pesticide multi-residue analysis

Pesticides laboratories strive to meet the growing demand for high-throughput analytical methodology while achieving the required level of sensitivity, precision, and accuracy of the results. Typically, hundreds of pesticides are monitored simultaneously in numerous food matrices, in strict compliance with official regulations, and with an effort to maintain low operational costs. Manual sample preparation can be laborious and inconsistent, and streamlining such procedures is particularly challenging.

The trend for multi-residue pesticides analysis is toward faster, simpler, more generic methods of extraction with minimal — if any — cleanup to facilitate higher sample throughput. The most commonly used approach is the quick, easy, cheap, effective, rugged and safe (QuEChERS) acetonitrile extraction with dispersive solid-phase extraction (dSPE) cleanup. Despite its many benefits, this approach may result in extracts with high levels of matrix co-extractives that inevitably lead to faster contamination of gas chromatography–tandem mass spectrometry (GC-MS/MS). The reluctance to use a more effective cleanup, such as SPE in the traditional cartridge format, is most likely a consequence of the time required for manual procedures as well as for optimizing the removal of co-extractives without the loss of analytes.

The automated workflow available on the TriPlus RSH SMART autosampler includes an automated online SPE solution using miniaturized cartridges (µSPE) for effective cleanup of QuEChERS extracts for pesticide residues analysis, combined with a semi-procedural calibration setup. Figure 1 represents the steps of the workflow automatically executed by the TriPlus RSH SMART autosampler, with on-line injection into the GC-MS.

Figure 1. Calibration dilution workflow followed by μSPE clean-up and injection of the standards.

The semi-procedural calibration approach consists in preparing matrix-matched calibration standards by spiking an aliquot of a blank extract with pesticides prior to μSPE cleanup, so that any possible losses of individual pesticides during the cleanup are automatically corrected. The calibration workflow (applicable up to nine concentration levels) is automatically followed by the cleanup workflow of the samples to be quantified. The entire sequence is controlled by Chromeleon Chromatography Data System (CDS).

What is the impact of automation on laboratory efficiency?

Automating a manual workflow allows extension of unattended operations, running samples overnight or over the weekend, with significant labor savings and better use of the analyst’s time. The sample throughput can be optimized as well, thanks to the prep-ahead capability of the TriPlus RSH SMART autosampler, allowing the extract cleanup to be executed during the chromatographic run of the previous sample.

Comparing manual and automated workflow only considering the replacement of the manual cleanup of QuEChERS extracts, the estimated labor time savings for 60 samples is about 1.5 hrs. Additional manual labor time can be saved including the calibration standards preparation in the automated workflow, improving the overall efficiency of the laboratory with possible overnight operations.

Figure 2. Estimated labor time savings for clean-up of 60 samples.

Modern laboratories facing workload pressure cannot give up the benefits offered by automation. Unattended operations offer a significant labor time savings and better use of the analyst’s time. Additionally, removing manual steps, especially for calibration standards preparation, minimizes errors and avoids potential costly efforts such as batch re-run.