Small Molecule Sample Preparation
Automation of small molecule sample preparation processes on a liquid handling workstation offers many advantages, allowing a diverse range of analytes and laboratory protocols to be accommodated, increasing versatility and analytical flexibility. Typically, throughput is enhanced considerably, with one liquid handling system able to prepare sufficient samples for up to 10 mass spectrometry systems on a daily basis. Additionally, the adoption of built-in security features, such as sample tracking, satisfies even the most stringent quality requirements.
Laboratories working in the small molecule field generally analyze large numbers of blood, urine, plasma, and serum samples, with the choice of sample preparation method dependent on the matrix, analyte of interest, and the sensitivity required. For example, solid phase extraction (SPE) is a popular means of purifying and concentrating samples prior to liquid chromatography-mass spectrometry (LC-MS) analysis. However, when performed manually, it is cumbersome, time consuming, and prone to errors, resulting in reduced productivity. Compared to manual SPE, automation offers significant benefits, enabling parallel extractions to be performed in 96-well plates, increasing speed of preparation and sample throughput for maximal productivity.
Liquid-liquid extraction (LLE) is another popular purification technique which, although effective, can show variability in results according to the operator when performed manually. It also exposes users to large volumes of organic solvents. Automated LLE provides fast, robust analyte purification and quantification, increasing operator safety by reducing exposure to organic solvents.
For the analysis of blood, plasma, and serum, a protein precipitation step is generally also necessary to remove the proteins that would otherwise prevent MS detection of the analyte, while some conjugated compounds may exhibit poor ionization efficiencies and require enzymatic hydrolysis prior to analysis; when performed manually, both these techniques involve a great deal of laborious pipetting. Similarly, the straightforward "dilute and shoot" technique—sample dilution and addition of an internal standard—requires numerous serial dilutions, increasing the likelihood of introducing manual errors and inconsistencies. These simple pipetting tasks can be carried out reliably and consistently, irrespective of the operator, using automated liquid handling.
Other crucial considerations are the flexibility and versatility of the workstation; laboratories must plan for the future, anticipating the changing demands of the marketplace. Today’s liquid handling workstations can be designed to perform a single extraction technique in high throughput, or a combination of techniques. This enables laboratories to future-proof their investment by specifying not only the sample preparation method currently in use, but also those likely to be required as new applications are introduced.