How to Streamline Your Sample Preparation Workflow
Sample preparation is critical to chromatography analysis; the objective is to have a sample injected on to the chromatography system that is representative, reproducible, and homogenous. In Ron Majors’ book “Sample Preparation Fundamentals for Chromatography,” published by Agilent Technologies in 2013, he describes sample preparation as follows:
“The aim of sample preparation is to provide a sample aliquot that (a) is relatively free of interferences, (b) will not damage the column or instrument and (c) is compatible with the intended analytical method. In chromatography, the sample solvent should dissolve in the HPLC mobile phase or be injectable into a GC column without affecting sample retention or resolution, the stationary phase itself, and without interfering with detection. It is further desirable to concentrate the analytes and/or derivatize them for improved detection or better separation.”
In speaking with customers over my twenty (plus) year career, reproducibility is extremely important, as it is needed to have confidence in lab results. Streamlining sample preparation workflow can improve reproducibility. Herein, we will discuss ways to streamline your sample preparation workflow by utilizing solid phase extraction and collecting the final eluate in either autosampler vials or 96 well plates.
In typical Solid Phase Extraction (SPE) Methods the SPE cartridge is conditioned, sample is added, impurities are washed to waste, then the sample of interest is eluted with solvent. All of these steps require either the use of a vacuum manifold or a positive pressure manifold. From there, the eluate is typically evaporated to dryness and reconstituted into the initial mobile phase conditions (for HPLC analysis).
In solid phase extraction, sample preparation instrumentation is essential to success. As mentioned, In SPE, a vacuum manifold or positive pressure manifold is required. A major problem with conventional vacuum manifolds occurs as wells can run dry at different rates while the manifold pulls liquid through the SPE plate (or cartridges), allowing a free flow path for vacuum through the dry ports. In turn, this slows the flow in the remaining wells. The result is variation in column processing times, thus contributing to irreproducible analyte recoveries. In contrast, our positive pressure manifolds have restricted-flow gas ports. These ports create superior flow control such that even if 95 out of 96 wells (47 out of 48 ports) are empty, dry, or wet, the remaining single port will receive normal pressure to allow easy processing. Our positive pressure manifolds are an efficient solution to viscous samples. Vacuum manifolds often cannot provide adequate processing power, since the maximum pressure is limited to less than atmospheric pressure (approx. 15 PSI). The positive pressure manifold allows for gas pressures up to the supplied line pressure (typically 60-75 PSI), thus supplying greater motive force for viscous sample flow. Adjusting the pressure up or down produces a column flow response that is smooth and immediate. Therefore, when interested in streamlining your solid phase extraction workflow, we always recommend the use of our Positive Pressure Manifolds for reproducibly consistent results.
Another way to streamline the workflow is by using the Cerex Concentrator/Evaporator with our Positive Pressure Manifold. When using autosampler vials for chromatographic analysis, you can use our 48 Position Positive Pressure manifold to elute your sample directly into your autosampler vials, using our collection rack for autosampler vials. This autosampler vial rack can then be placed directly into our 48 Position Concentrator/Evaporator. This process reduces sample transfer and helps streamline your sample preparation workflow.
We can also streamline working in 96 well plates, as well, by using the Cerex 96 well plates positive pressure manifold with our Porvair Concentrators/Evaporators for 96 well plates.
Our 48 Position Positive Pressure Manifold and Evaporators comes with many different rack options. Call Chrom Tech today to discuss how to streamline your sample preparation workflow; there may be other applications/considerations, as some liquid handling systems can be customized to utilize our racks and further streamline your sample preparation workflow.