ASE® is an automated solvent extraction system for solid or semisolid samples used by laboratories to prepare samples for chromatagraphic analysis. It uses liquid solvents, solvent mixtures, elevated temperatures (40–200 °C), and pressure (1500 psi) to greatly increase extraction efficiencies.
Four Key ASE Principles
The four key principles for the extraction of solid materials are:
- Increased solvent and matrix temperature will increase extraction efficiency. The increase in efficiency comes from faster diffusion rates and increased solubility.
- Like dissolves like. Use a solvent with a polarity that matches the polarity of the analytes, e.g., hexane for PAH’s or isopropanol for polymer additives.
- Particle size will influence extraction. Generally, smaller matrix particles allow more interface between the extraction solvent and the analyte on matrix. Often, grinding or lyophilizing a sample matrix can reduce particle size.
- Chemical or enzymatic pre-treatment: The matrix may be treated with an acid or base to hydrolyze the sample and make some analytes more available for extraction. In addition, pretreatment by acid hydrolysis may change the structure by removing functional groups and allow “total extraction,” as when determining total lipids from meat or other food products.
How ASE Works
ASE operates by moving the extraction solvent through an extraction cell containing the sample. The sample cell is heated by direct contact with the oven. The extraction is performed by direct contact of the sample with the hot solvent in both static and dynamic modes. When the extraction is complete, compressed nitrogen moves all of the solvent from the cell to the vial for analysis. The filtered extract is collected away from the sample matrix, ready for analysis.
Why ASE?
By using elevated temperature and pressure, ASE makes more efficient use of extraction solvents, providing lower cost per extraction. When compared to other extraction techniques, ASE provides the most efficient use of costly solvents.
This graph summarizes the results of the study done to validate ASE technology for the U.S. EPA in 1995. The bars represent the average analyte recovery using ASE relative to the conventional methods (shown as a number above each bar). This study concluded that the data generated using ASE is essentially equivalent to the conventional techniques, albeit much faster and using much less solvent. Based on this data, which represents over 1200 extractions, U.S. EPA Method 3545 was approved.
Extraction Technique Comparisons
| | Solvent Savings | Labor Savings | Walk Away Automation | EPA Methodology | Increased Productivity with In-Cell Clean-up | Acid or Alkaline Matrices | Flexible Sample Size |
| Soxhlet | | | | √ | | √ | |
| Automated Soxhlet | √ | | | √ | | √ | |
| Microwave | √ | | | √ | | √ | |
| PSE | √ | √ | | | | | |
| PLE | √ | √ | | | | | |
| ASE 100,200 and 300 | √ | √ | √ | √ | √ | | |
| ASE 150 and 350 | √ | √ | √ | √ | √ | √ | √ |
Extraction Technique Cost Comparisons
ASE provides a lower variable cost since the system requires less solvent and labor when compared to other techniques. Cost estimates include the cost for the purchase of all equipment or glassware.
| Technique | Total Cost per sample |
| Soxhlet | $23.34 |
| Automated Soxhlet | $18.62 |
| Microwave | $16.49 |
| Sonication | $21.43 |
| Accelerated Solvent Extraction | $12.26 |
Comparisons based on 50 samples/week and 2000 samples a year.
