Soil Contaminant Analysis

Evaluating soil nutrients and contaminants

Soil analysis is routine testing for both research and farm communities. Understanding the nutrient components in soil as well as testing biosolids (often used as fertilizers) and plants are necessary in order to determine how much fertilizer is needed. The levels of pesticides and contaminating metals are also routinely evaluated.

Soil analysis features

Application note

This application note presents data on nitrogen determination in soil and plant reference materials with different nitrogen concentrations to demonstrate the performance of the system using argon as an alternative carrier gas and show the reproducibility of the results obtained.

Application note

This application note evaluates the effectiveness of a system that combines the Atomx nitrogen purge option with the Helium Saver Module for VOC analysis using U.S. EPA method 8260C. Purge and trap coupled with GC-MS enables the greatest potential selectivity and sensitivity for analysis.


Organic contaminants in soil

Organic contaminants encompass a wide array of compounds determined as harmful or detrimental to human and environmental health. Many of these compounds are human-made chemicals that are used and produced in industrial, manufacturing and agricultural activities. Due to the potentially drastic impact of contamination and high susceptibility of soil to pollution accumulation such as agricultural runoff of pesticides, this environmental matrix is routinely analyzed for the presence of xenobiotic compounds. Exposure to contaminated soil has the potential to directly affect human health through either direct contact or indirect contamination of ground and surface water systems.

Regulatory bodies attempt to streamline the cost of known contaminant compliance monitoring by regulating them as groups with similar health effects, co-occurrence, common analytical methods, and common treatment or control practices. In addition to known contaminants, unknown compounds pose a serious threat to environmental protection and create a growing challenge across the globe.

To analyze soil for the presence of a vast assortment of compound classes and meet regulatory requirements a robust strategy is needed that employs various analytical techniques. Workflows that support sample preparation and analysis for different soil types have to be considered in order to successfully extract, identify and quantitate compounds. Extraction approaches typically include solvent exchange, solid phase extraction (SPE), accelerated solvent extraction (ASE) and/or microwave extraction methods. Chromatographic separations and Mass spectrometry techniques provide the bulk of identification and quantitation data for these compounds in environmental matrices. Common analytical methods for analyzing organic contaminants in soil include GC, HPLC, IC, GC-MS, IC-MS and LC-MS. The Thermo Fisher Scientific environmental analysis portfolio provides tailored systems for all of these routine chromatographic and mass spectrometry techniques with comprehensive workflows that enable laboratories to effectively and efficiently meet today's organic contaminant regulations and prepare for the evolving needs of tomorrow.

See an example of volatile organic contaminant analysis using EPA Method 8260C and PAH analysis.

Also, see a workflow for pesticide analysis using ASE-GC-MS.

Instruments and consumables used for organic contaminant analysis:

LC and LC-MS

Routine HPLC Vanquish Flex UHPLC System
Routine / research LCMS low level and high matrix TSQ Endura Triple Quadrupole Mass Spectrometer
Targeted / untargeted and unknown research applications accurate mass requirements Q Exactive Hybrid Quadrupole-Orbitrap Mass Spectrometer

LC and LC-MS Sample prep

SPE HyperSep Hypercarb SPE Cartridges

GC and GC-MS

Routine SA GC TRACE 1300 Gas Chromatograph
Routine GCMS spec ISQ LT Single Quadrupole GC-MS System
Routine GCMS low level and high matrix TSQ 8000 Evo Triple Quadrupole GC-MS/MS
Targeted / untargeted and unknown research applications accurate mass requirements Q Exactive GC Orbitrap GC-MS/MS

Nutrient analysis

At least 17 nutrients are essential for plant growth. Some are macronutrients (existing in larger amounts), such as nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, while others are micronutrients, including boron, copper, iron, manganese, and molybdenum, and others. It is critically important to know the quantity of available nutrient in both soil and compost (such as biosolids) so the right kind and amount of fertilizer can be applied. Overuse or lack of nutrients will reduce plant growth potential, and leads to resource waste and even contamination of soils. For soil and compost nutrient analysis, multiple routine parameters need to be measured with different technologies.

Soil macronutrient testing

Element analyzers

Macronutrients are necessary to measure for identification of soil quality. They can be quantified by element analyzers using combustion to convert the elements to gaseous form and further separated by gas chromatography.

  • Nitrogen—nitrogen in soils is important for the evaluation and calculation of the amount of fertilizer to be added for plant growth. Nitrogen content quantitation is critical for determination of the quality of various types of crops for feeding and processing, as well as for N-cycle and N-fixation monitoring in agricultural and environmental research.
  • Total carbon, total organic carbon and CHNSdue to the heterogeneity of the material used for compost, accurate control of parameters such as nitrogen, total carbon, total organic carbon (TOC) and sulfur content in recycled waste is a key factor for ensuring high quality fertilizer.
  • Sulfur—like carbon and nitrogen, sulfur is also an essential component of living being through uptake and synthesis of several amino acids: cysteine, cystine and methionine. The deficiency of sulfur has a negative influence in the growth of vegetable crops. In addition, the levels of sulfur detected in leaves and pine needles are also an indicator of environmental pollution.

All of these analyses can be performed by the following instruments:

MAS Plus autosampler  FlashSmart NC/Soil Analyzer

Nutrient analysis

In addition to element analyzers, discrete analyzers can also be used for potassium and phosphorus analysis. Different from the element analyzers that determine the nutrients by the property of the elements, the discrete analyzers use specific chemical reactions from nutrients and certain chemicals to generate colors that can be detected by discrete analyzers. Besides testing the soil, discrete analyzers are also used for drinking water and wastewater analysis.

View the case study for fertilizer analysis.

Mineral analysis

The growth of plants needs mineral elements. These mineral nutrients are micronutrients as they are required in very small amount (often in the ppm level). The mineral elements are metal elements and often are analyzed by ICP-OES.

The mineral nutrients have to be extracted from the soils before they are analyzed. There are multiple extraction methods, such as DTPA-TEA, HCL solution, Mehlich-1, Mehlich-3, and total digestion (EPA 3050B, 3051A, and 3052 Method). Depending on the requirement, different extraction methods can be used.

Mineral analysis can be performed using the following instruments:

Microwave digestion system (from CEM) → CETAC AutosamplersiCAP 7600 ICP-OES Analyzer


Heavy metal analysis

In addition to the mineral metal elements, toxic heavy metals in soils, such as arsenic (metalloid), cadmium, lead, and mercury, can also be analyzed using the same technology, or a more sensitive cold vapor atomic absorption spectrometer, cold vapor atomic fluorescence spectrometer, or ICP-MS technology. Quantifying these elements is required for biosolids used as fertilizer and the soil screening by the U.S. EPA. It is necessary to keep these toxic metals at really low levels to keep the soil and plants away from contaminants and prevent us from eating polluted food.

Multiple technologies have been used for heavy metal analysis based on chromatography, spectroscopy, and electrochemistry.

ICP-OES and ICP-MS

When using ICP-MS for soil sample analysis, it is important to keep in mind the limitation of the ICP-MS for total dissolved solid (TDS). Typical ICP-MS can handle less than 0.2% TDS. However, with argon gas dilution or autodilution techniques, tolerance to high matrix is improved for ICP-MS analysis.

Instruments for ICP-MS analysis of toxic heavy metals:

CETAC AutosamplersiCAP RQ ICP-MS

Hexavelent chromium (Cr (VI)) is also a toxic species from different industries such as chemical and leather tanning industries. It is regulated in California in drinking water and soil.

The U.S. EPA has approved:

  • Ion chromatography analysis of Cr (VI) in Method 218.7 for drinking water
  • Ion chromatography analysis of Cr (VI) in ground water and industrial wastewater in SW846 Method 7199
  • The EPA SW846 Method 3060A for extraction of Cr (VI) from soil

We also developed ion chromatography method using accelerated solvent extraction (ASE) to prepare the samples and further quantify Cr (VI) by ion chromatography via post-column derivatization. Download poster note 70729.

Instruments for Cr (VI) determination in soil:

Dionex ASE 350 Accelerated Solvent ExtractorDionex ICS-5000+ Hybrid HPIC SystemDionex Chromeleon 7.2 Chromatography Data System

X-ray fluorescence (XRF) analyzers

Portable XRF is a powerful tool to detect heavy metal elements in soil. Analyzing up to 25 metals at one time, the XRF analyzers can analyze soil samples on the spot without the need of sample digestion. The EPA SW846 Method 6200 uses XRF for metal analysis in solid waste and soil analysis. However, the method's low detection limit is usually higher than the regulatory level for most analytes regulated in RCRA (Resource Conservation and Recovery Act). It is used as a confirmatory method for atomic absorption technologies (such as ICP-OES and ICP-MS) in determination of metals. Nevertheless, the instrument is a great tool for on-site screening and quality control applications.

Not only is XRF used for heavy metal analysis, other elements such as S, P, Al, Mg, Si, and U, can also be analyzed.

To see how XRF analyzers can be used to detect toxic metals & contaminants, visit the XRF Soil Contaminant Analysis page.


ASE soil sample cleanup

Sorbents and post extraction clean-up cartridges can be used to cleanup unwanted interferences. 

  • In-cell extractions, using the sorbents of choice, remove interferences and allow for complete automation of extraction and post-extraction cleanup steps. This option reduces overall costs and preparation time, and increases sample throughput.
  • Post-extraction clean-up cartridges provide a choice of sorbents to clean-up the extracts while reducing the likelihood of solvent interactions with the sorbents at elevated temperature and pressure.
Remove water in your soil samples

Thermo Scientific Dionex ASE Prep MAP Dispersant and Sorbent is a unique polymer designed to remove moisture and increase extraction efficiencies from wet samples including soils and food products. This unique formulation allows moisture removal up to 5 g of water per gram of polymer (at room temperature) under a variety of ionic strength conditions and using accelerated solvent extraction conditions. The polymer is a free flowing white granular material that can be easily mixed with the Thermo Scientific Dionex ASE Prep DE (diatomaceous earth) dispersant in a 1:1 ratio and used for improved moisture removal under accelerated solvent extraction conditions.

Improve cleanup of soil extracts for pesticide analysis

This is a selective normal-phase sorbent used to remove polar interferences and concentrating pesticides, alcohols, aldehydes, amines, herbicides, PCBs, ketones, nitro compounds, organic acids, and phenols from extracts prior to GC or GC-MS analysis. The Thermo Scientific Dionex ASE Prep Florisil cartridge is specially processed to give consistent results when used for column cleanup and separation of chlorinated pesticide residues prior to quantification by GC and is recommended for cleanup of soil extracts for pesticide analysis.

Remove water in your soil samples

Thermo Scientific Dionex ASE Prep MAP Dispersant and Sorbent is a unique polymer designed to remove moisture and increase extraction efficiencies from wet samples including soils and food products. This unique formulation allows moisture removal up to 5 g of water per gram of polymer (at room temperature) under a variety of ionic strength conditions and using accelerated solvent extraction conditions. The polymer is a free flowing white granular material that can be easily mixed with the Thermo Scientific Dionex ASE Prep DE (diatomaceous earth) dispersant in a 1:1 ratio and used for improved moisture removal under accelerated solvent extraction conditions.

Improve cleanup of soil extracts for pesticide analysis

This is a selective normal-phase sorbent used to remove polar interferences and concentrating pesticides, alcohols, aldehydes, amines, herbicides, PCBs, ketones, nitro compounds, organic acids, and phenols from extracts prior to GC or GC-MS analysis. The Thermo Scientific Dionex ASE Prep Florisil cartridge is specially processed to give consistent results when used for column cleanup and separation of chlorinated pesticide residues prior to quantification by GC and is recommended for cleanup of soil extracts for pesticide analysis.

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