I closed my lab book with a satisfying clap. The ancient autosampler was grinding its gears and belts to make its way to the next sample, and I glanced at the list of samples I had entered into the software. Good – everything should be just finished by the morning. In the background, the radio was playing some lively West African pop music, and I sighed contentedly as I folded my hands behind my head and leant back in the chair to wait out the clock until 10 pm. There were benefits to being the only one in the lab at a contract environmental analysis company on the late shift.
A nagging feeling arose that I was forgetting something. Slowly getting up, I shuffled over to the next room to check that no new samples had been received. “Nooooo!” I screamed in horror when I saw the dozen bottles lined up with the tag “Common anions: EPA 300.0.” A late receipt, and to add insult to injury, they were nasty samples with weird colors: the dreaded industrial wastewater.
“Right,” I thought. “Filter each one quickly; then run undiluted, at 10x, and then at 100x dilution. That should cover the concentration ranges.” I rushed through the filtration, only bursting a few syringe filters in my haste; appended the sample information into the software with only a handful of typos; and at 10 pm exactly the lab door was clicking behind me as I ran out.
Unfortunately, the next day I found that on five of the samples the concentrations were above the calibrated range even at 100x dilution, and that the acceptable hold time had passed for the samples. A different kind of sigh now emanated as I picked up the phone to have an awkward conversation.
AutoDilution is the answer to the prayers of lab rats like me, and to our companies. No more guessing of the dilution ranges necessary for a sample; no more unnecessary bulk to sample sequences trying to run multiple dilutions for every sample. If a sample is out of calibration range, the system can automatically run at a higher dilution. If it’s within range, then the next sample can be run without interruption.
Like what you are learning?
To make things really simple, Thermo Fisher Scientific offers three complementary methods of AutoDilution for its Ion Chromatography products running on Chromeleon CDS.
If you are using a system with an AS-DV autosampler (it will also work with an AS-AP autosampler), you can try AutoDilution with two injection loops. This simple setup effectively doubles the range of the concentrations you can target without any manual dilution. The system first injects each sample using a calibrated large injection loop. If the resulting concentration for a target analyte exceeds a defined range, the system will re-run the analysis using a calibrated small injection loop.
If you are using an AS-AP autosampler, you can try AutoDilution using vial-to-vial dilutions. If the system detects analyte ranges outside of a defined range, the AS-AP will create dilutions of your samples, in much the same way as you would create your own, and then inject them into the system.
Lastly, again using the AS-AP autosampler, there is Autodilution using partial loop injection. In this case, if an analyte is outside of the calibration range, the autosampler will only partially fill the injection loop. The ratio between the amount filled in the loop and the total loop volume represents the dilution.
Thermo Fisher Scientific AutoDilution for ion chromatography, whichever method you choose, will help you save labor and analysis time, while simultaneously protecting your result integrity. Just think of all those awkward conversations you can eliminate.