Raise your hand if you really like to extract samples and prepare them for analysis. OK, there are a few of you out there and to be honest there are some of us too. For a lot of chemists sample preparation is what needs to be done before the samples get analyzed by an instrument and the data gets processed. It is a crucial step and should never be underestimated but what if you didn’t have to extract samples for GC-MS analysis? Well that’s a question we asked and I wonder if you guess the answers we came up with, and it isn’t just pushing a banana into the injector. Over this series of posts we will go over how easy it can be to not extract a sample, just put it on the instrument for different types of samples and compounds.
The application of SPME uses a conventional Thermo Scientific TriPlus or TriPlus RSH autosampler as an in-line sample extraction and concentration technique for multi-residue pesticide analysis. This method can be used for screening and confirming on the TSQ Quantum XLS triple quadrupole mass spectrometer using selected reaction monitoring (SRM) or multi-reaction monitoring (MRM), while minimizing solvent consumption and extraction time. This technique brings Green Chemistry to the analytical laboratory.
Dry tea leaves were homogenized with a blender. One gram of sample was weighed into 20 mL VOA vials. Stock standard solutions were diluted to construct calibration curves. Standards were prepared in methanol and 10 uL of each standard was spiked into the dry tea to keep the amount of methanol consistent. A 10 uL aliquot of the internal standard solution was also added. After the addition of the standards to the dry tea, 3 mL of a 1% methanol solution saturated with NaCl was added. The vial was capped, gently swirled, and placed in the autosampler rack.
Calibration curves for most of the pesticides studied gave a linear correlation coefficient of r2 > 0.995, all above 0.99. Table 1 in the application note demonstrates that this method using the TSQ Quantum XLS is able to meet regulatory limits without the need for manual sample extraction.
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I was surprised how well this technique worked, even with high boiling point compounds. Our preliminary work was done with pesticides and PAHs that are normally tested for in drinking water. When we got a good response for benzo(a)anthracene we knew we had a method that could transfer to a method to analyze pesticides of all boiling points.
Download this application note here; Pesticides in Tea with no Extraction
If you have any questions please feel free to post a comment, we really do like talking about developing methods that work for your lab.