Analysis of PAH compounds in soil with on-line coupled pressurised hot water extraction–microporous membrane liquid–liquid extraction–gas chromatography

Abstract

Pressurised hot water extraction (PHWE) was coupled on-line with microporous membrane liquid-liquid extraction (MMLLE) and gas chromatography (GC) in the analysis of polycyclic aromatic hydrocarbon (PAH) compounds in soil. The MMLLE serves as a trapping device after the PHWE. Water from PHWE is directed to the donor side of the membrane unit and the analytes are extracted to the acceptor solution on the other side of the membrane. The role of MMLLE is to clean and concentrate the extract, which is then transferred on-line to the GC via a sample loop and an on-column interface using partially concurrent solvent evaporation. Separate optimisation of MMLLE and simulations of the PHWE-MMLLE connection were carried out before the actual on-line coupling. After optimisation of the whole on-line system, the efficiencies of the PHWE-MMLLE-GC and PHWE-solid-phase trap extractions were compared. The PHWE-MMLLE-GC method allowed on-line analysis of soil samples. The method was linear, with limits of detection in the range 0.05-0.13 ng and limits of quantification 0.65-1.66 microg g(-1). Comparison of the results with those obtained by other techniques confirmed the good performance.

Extraction of Functional Substances from Agricultural Products or By-products by Subcritical Water Treatment

“…Alternative solvent-free or minimal solvent extraction methods have been attractive, including solid-phase extraction, solid-phase microextraction and microporous membrane liquid-liquid extraction. Each of these extraction methods can be either separate from or online coupled with the subcritical water apparatus (Li-Hsun et al, 2004;Kuosmanen et al, 2003;Palma et al, 2002).…”

“…Microporous membrane liquid-liquid extraction is a new technique introduced to replace solid phase extraction, which is subject to poor reproducibility because more sample matrix is extracted and, consequently, the trapping column may become blocked (Kuosmanen et al, 2003). Microporous membrane liquid-liquid extraction is used for extracting, cleaning and concentrating aqueous extracts after subcritical water treatment of various biological and environmental samples (Kuosmanen et al, 2003;Hyötyläinen et al, 2001;Shen et al, 1998).…”

“…Microporous membrane liquid-liquid extraction is used for extracting, cleaning and concentrating aqueous extracts after subcritical water treatment of various biological and environmental samples (Kuosmanen et al, 2003;Hyötyläinen et al, 2001;Shen et al, 1998). The solutes concentrated by this extraction method can be transferred on-line to a GC or HPLC for quantitative and qualitative analyses.…”

“…Alternative solvent-free or minimal solvent extraction methods have been attractive, including solid-phase extraction, solid-phase microextraction and microporous membrane liquid-liquid extraction. Each of these extraction methods can be either separate from or online coupled with the subcritical water apparatus (Li-Hsun et al, 2004;Kuosmanen et al, 2003;Palma et al, 2002).For solid-phase extraction, the aqueous extract can be passed through a cartridge or adsorbent resin, such as alkylor aryl-bonded silica (C18-trap), carbon black, polymeric absorbent (Amberlite XAD) resin, and the anion exchange resin, SAX, and the desired solutes can be eluted from the cartridge or resin by a small volume of solvent. After concentration, the solutes can be analyzed by an appropriate analytical method, such as LC-MS.…”

Modern Methods of Sample Preparation for GC Analysis

“…Several applications involving on-line coupling of SHWE with GC have been reported (e.g., [20,21]). On-line coupling of SHWE with GC is simpler than coupling of PLE, because the aqueous solubility of the analytes decreases dramatically when the water is cooled to ambient temperature.…”