Automation of a Complex, Multi-Step Sample Preparation Using the Standalone Agilent 7696A WorkBench

In analytical chemistry, sample preparation can be as simple as adding a solvent or as complex as performing chemical reactions to improve the instrumental measurements that follow. While sample preparation is a critical component to any chemical measurement, chemists rarely look forward to performing this job, especially if it is complex, boring and involves handling unpleasant chemicals. As a result, manual sample preparation can be the source of many errors and poor  precision. To help reduce errors and improve precision, many manual sample preparations are done using with large amounts of chemicals and expensive volumetric glassware to make handling, dispensing, and measuring easier.

A good example of a difficult manual preparation is ASTM method D6584. This method measures the free and total glycerin content in B100 biodiesel to assure good product quality [1]. Since the various glycerins found in biodiesel are not volatile, they cannot be measured using gas chromatography (GC). Method D6584 describes a sample preparation protocol to derivatise these compounds with a trimethylsilation reagent so they can be analysed with GC. The steps for this sample preparation are complex, time consuming, and use pyridine; a toxic solvent with a distinctly unpleasant odour. This assures the unpopularity of this procedure.

The Agilent 7696A Sample Prep WorkBench is a standalone instrument specifically designed to perform automated sample preparation [1,2]. It uses two 7693A injection towers to volumetrically transfer liquids between 2-mL vials. The vials containing various chemical resources, standards and samples are housed in three 50-positions trays. The sample tray compartment houses a robotic arm to move vials, a vortex mixing station and a sample heating station.