Multi-residue analysis of PAH, PCB, and OCP optimized for organic matter of forest soil
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Analyzing organic pollutants in forest soil is challenging because they are strongly physical and chemical bound to soil organic matter (SOM). Within the framework of a forest soil inventory, an analytical protocol for the determination of polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and organochlorine pesticides (OCP) should be established and validated using one and the same extraction and cleanup procedure. The protocol should be applicable for reliable analysis of a high number of samples in a short timeframe.
Materials and methods
Two different soil samples representative for the humic layer from a typical mixed and coniferous forest soil had been used for the analysis. Three solvents of different polarity, namely cyclohexane (CH), ethylacetate (EA)/CH (1/1, v/v), and acetone (AC)/CH (2/1, v/v), and the six standard extraction techniques (pressurized liquid extraction (PLE), soxhlet extraction, fluidized bed extraction, sonication, shaking, and one-step extraction recommended for analyzing agricultural soil in Germany (VDLUFA 2008)) were compared concerning their extraction efficiency. For additional matrix separation, two different cleanup procedures (gel permeation chromatography (GPC) and solid-phase extraction (SPE) with different sorbents) were tested. Quantification was carried out using gas chromatography combined with mass spectrometry (GC–MS) and two different injection systems (split/splitless injection and programmable temperature vaporizer (PTV) injection). Labeled internal standards, added prior to extraction, were used for method evaluation.
Results and discussion
For the simultaneous extraction of PAH, PCB, and OCP from organic forest soil PLE with acetone/cyclohexane (2/1, v/v) provided the highest extraction efficiency. A two-step cleanup procedure consisting of GPC followed by SPE with silica gel was entirely sufficient for the separation of humic substances without discrimination of analytes. Recovery rates for the different extraction and cleanup steps ranged between 89% and 106%. For quantification, a GC–MS method was developed using two different injection systems and two capillary columns of different selectivity.
By comparing six standard extraction techniques for PAH, PCB, and OCP from forest soil, we obtained the highest extraction efficiency when using PLE with AC/CH (2/1). For sample injection, we achieved best results using an optimized PTV injection system as it highly reduced the breakdown of thermolabile pesticides. Using this combination of technical equipment, it is possible to determine a concentration of the analytes in the trace level range of 1–2 μg kg−1 in humic soil.
KeywordsDDT breakdown Extraction efficiency Forest soil Multi-residue analysis Organic pollutants Soil organic matter
We gratefully acknowledge the Federal Environment Agency (UBA) of Germany for financial support.
- DIN (2008) DIN 32645: chemical analysis—decision limit, detection limit and determination limit under repeatability conditions—terms, methods, evaluation. DIN, BerlinGoogle Scholar
- ISO (1995) ISO 10694: soil quality—determination of organic and total carbon after dry combustion (elementary analysis). ISO, GenevaGoogle Scholar
- ISO (2000) ISO 13877: soil quality—determination of polycyclic aromatic hydrocarbons (PAH)—method using high-performance chromatography. ISO, GenevaGoogle Scholar
- ISO (2002) ISO 10382: soil quality—determination of organochlorine pesticides and polychlorinated biphenyls—gaschromatographic method with electron capture detection. ISO, GenevaGoogle Scholar
- ISO (2005) ISO 10390: soil quality—determination of pH value. ISO, GenevaGoogle Scholar
- ISO (2006) ISO 18287: soil quality—determination of polycyclic aromatic hydrocarbons (PAH)—gas chromatographic method with mass spectrometric detection (GC–MS). ISO, GenevaGoogle Scholar
- Kickuth R (1972) Huminstoffe—ihre Chemie und Ökochemie. Chemie für Labor und Betrieb 23(11):481–486Google Scholar
- Stevenson FJ (1976) Organic matter reactions involving pesticides. Soil Sci 29:180–207Google Scholar
- UN-ECE (1998) Aarhus Protocol to the Convention on Long-range Air Pollution on Persistent Organic Pollutants, United Nations Economic and Social Council, Economic Commission for Europe (EB.AIR/1998/2). http://www.unece.org/env/lrtap/pops_h1.htm
- UNEP (2004) Stockholm Convention on Persistent Organic Pollutants. United Nations Environmental Programme. http://chm.pops.int/convention
- USEPA (1982) Priority list of the US Environmental Protection Agency. http://www.epa.gov
- USEPA (1995a) Methods for the determination of organic compounds in drinking water. US Government Printing Office: Washington DC, EPA -600/R-95/131, method rev. 3.1. pp 508.1–508.32Google Scholar
- USEPA (1995b) Methods for the determination of organic compounds in drinking water. US Government Printing Office: Washington DC, EPA -600/R-95/131, method rev. 2.0. pp 525.1–525.58Google Scholar
- VDLUFA (2008) Handbuch der landwirtschaftlichen Versuchs- und Untersuchungsmethodik. Bd. VII, 3 rd edn. VDLUFA VerlagGoogle Scholar
- Ziechmann W (1996) Huminstoffe und ihre Wirkungen. Spektrum Akademischer, HeidelbergGoogle Scholar