Sample Preparation and Extraction for Organic Micropollutant Analysis

Summary

Extraction methods used to extract organic micropollutants from water or sediment samples (Gilevska et al., 2022)

Sample preparation and extraction are critical steps in achieving accurate and reliable results in organic micropollutant analysis. These contaminants, often present at extremely low concentrations, require concentration and purification techniques for effective detection. Sample preparation eliminates matrix interferences that could otherwise obscure the analytical signals of target compounds. Additionally, selective extraction from complex matrices such as water, soil, or biological tissues ensures that analytes are isolated in a form suitable for high-sensitivity and high-specificity analysis using techniques such as liquid or gas chromatography coupled with mass spectrometry. These preliminary steps maximise precision, sensitivity, and reproducibility, ensuring robust environmental and health risk assessments of organic micropollutants.

Water Sample Preparation Devices

Vacuum Filtration System

Initially, water samples are filtered through 0.45 or 0.22 µm membranes using vacuum filtration systems to remove particulate matter.

Subsequently, solid-phase extraction (SPE) is used to isolate analytes from complex water samples. SPE is based on adsorption separation, where sample components are retained on a solid phase (sorbent) according to their chemical and physical properties. Typically, a liquid sample is percolated through a cartridge or column containing the sorbent. Target compounds are adsorbed, while impurities pass through. After a washing step to remove unwanted interferences, retained analytes are eluted using an appropriate solvent. This process concentrates and purifies analytes, enhancing the sensitivity and selectivity of subsequent analyses. SPE is widely used in analytical chemistry, pharmacology, and environmental science for sample preparation before chromatography or mass spectrometry techniques.

 

 

 

 

DIONEX AutoTrace 280 Solid-Phase Extraction System

The Dionex AutoTrace 280 is an automated SPE system designed for the preparation of large-volume aqueous samples. It significantly enhances analytical precision and repeatability while reducing handling time and human error. This system utilises SPE cartridges or disks to isolate and concentrate target analytes from complex matrices, including environmental water, pharmaceuticals, and food samples. Features include continuous sampling, automatic rinsing and elution, and the ability to process up to six samples simultaneously, ensuring efficient and consistent sample preparation for subsequent chromatographic or mass spectrometric analysis.

SPE Extraction Capabilities

  • Capacity: Up to 6 samples in parallel
  • Sample volumes: 100 mL to 4 L
  • SPE cartridges: OASIS, C18, etc.
  • Target molecules: Pesticides, pharmaceuticals, metabolites
  • Preconcentration factors: x100 to x8000

Soil and Sediment Sample Extraction

MUSE Method « Modified Ultrasonic Extraction »

Ultrasound-assisted extraction is an innovative and efficient technique for extracting chemical compounds from soil and sediment samples. It operates by applying high-frequency ultrasonic waves that generate intense mechanical vibrations in the liquid medium, facilitating the release of target compounds from the solid matrix into the solvent. This technique offers several advantages, including reduced extraction time, lower solvent consumption, and improved efficiency compared to conventional methods. MUSE is particularly effective for extracting organic contaminants from soils and sediments, making it a valuable method for environmental and geochemical studies.

The QuEChERS method

The QuEChERS extraction method (Quick, Easy, Cheap, Effective, Rugged, Safe) is widely used for pesticides, organic compounds, and inorganic contaminants in soil and sediment samples. The process involves several key steps:

  1. Sample Preparation: The soil or sediment is homogenised and ground to ensure uniform distribution of target compounds.
  2. Solvent Extraction: A portion of the sample is mixed with an organic solvent, typically acetonitrile, to extract the analytes of interest.
  3. Purification Phase: Salts (e.g. magnesium sulphate) and sorbents (e.g. C18) are added to remove interferences and enhance extraction selectivity.
  4. Agitation and Centrifugation: The organic phase containing the analytes is separated for subsequent analysis, while impurities remain in the aqueous phase.

The QuEChERS method is valued for its speed, simplicity, cost-effectiveness, and robustness, making it an attractive approach for contaminant analysis in soils and sediments.

 

Characteristics of MUSE and QuEChERS Methods

  • High extraction efficiency (e.g. 77% for atrazine)
  • Detection limits in the nanogram per gram (ng/g) range
  • Extraction of 5–10 g of soil or sediment samples

For further details, see Gilevska et al., 2022.