Problem: While laboratory instruments have become faster and more automated to increase productivity, sample preparation has continued to remain a bottleneck and source of variability for most labs. The complexity and variety of samples that typically pass through labs makes this area one of the most difficult to automate.
Solution: One example of an important step forward in automating sample preparation for chromatographic analyses is Agilent Technologies’ 7696A Sample Prep Workbench (Figure 1). Many of the common preparation procedures for chromatography samples can be done by incorporating precision liquid dispensers along with mixing and heating capabilities into a stand-alone instrument such as Agilent’s new workbench. A large capacity syringe provides the capability to precisely dispense liquids into a sample vial for common operations such as internal standard addition, solvent dilution, and addition of derivatizing agents. Also, since many ASTM methods, particularly those for petroleum tests, require confirmation by weight, an optional microbalance with a five gram capacity and capable of weighing to 0.01 milligrams can be integrated into the instrument and software. A bar code reader/stirrer station that heats up to 80 °C is sufficient for most dissolution or derivatization procedures and the heater/chiller module has the ability to simultaneously heat a single 50-vial tray (25 °C - 80 °C) and cool a second 50-vial tray (40 °C - 5 °C) through energy-efficient Peltier cooling. To accommodate the in-vial chemistry strategy, it was also necessary to provide the capability to sample at any point in the vial to allow the analyst to select the correct liquid phase for transfer operations. As with any complex technology, software automation is necessary in order to reap full benefit. A highly visual “drag and drop” programming interface was developed that allows the analyst to set up and save methods within a matter of minutes (Figure 2).
- Productivity: Automated sample preparation can save ½ hour or more of analyst time per shift which translates to ≈ 550 hours labor savings per year (0.5 hrs per shift x 3 shifts per day x 365 days per year).
- Safety: Automated sample preparation typically reduces personnel exposure time to potentially toxic solvents and reagents by more than 75 percent. Reduced quantities used in small scale preparation also limit exposure and reduce risks associated with other solvent properties such as flammability. Ergonomic issues are also eliminated for labs with high pipetting requirements.
- Quality: Precision of automated sample preparation exceeds the precision achieved by multiple analysts across shifts which improves the quality and reliability of results. The repetitive nature of automation is more consistent than manual preparation which reduces the risk of analyst errors. This in turn lowers laboratory costs by reducing rework and lowers the risk of price concessions for offspec product due to lab error for the client.
- Environmental: Small scale sample preparation reduces waste volume which lowers disposal costs. Waste reduction of >50 percent is typical. This approach also supports green waste reduction initiatives such as CMA’s Responsible Care® program and ISO 14001.