Iris Chardon

Since the end of 2011, Iris Chardon (1987) works as a research assistant within the Netherlands Institute of Ecology.

One of her main drivers is “development”. She gets satisfaction from developing and/or optimizing analytical methods, and from gaining and transferring knowledge, thereby contributing to the development of others. Besides that, she is involved in research projects.

In February 2019, she started as a research assistant within the TTW project ‘SmartResidue’, together with Paul Bodelier, Stijn van den Bergh, Gerard Korthals and Wietse de Boer. The project aims to lower the greenhouse gas emission by turning agricultural soils into sinks of methane after application of bio-based residues. The mechanisms of this residue stimulated methane uptake will be investigated and field trials will be performed to optimize the effect and to engineer residues and their mode of application for optimal performance in agricultural practice. Iris her tasks will include field screenings, microbiological work, chemical and physical analyses and molecular assays.

Before she started working in the ‘SmartResidue’ project, her main responsibilities were the chemical analyses of soil, sediment and plant samples, which she performed mostly for the departments Microbial Ecology and Terrestrial Ecology. She advised (PhD-) students and (postdoctoral) researchers about the choice of the analyses and she gave them instructions for performing extractions or destructions. Afterwards, she analyzed the samples with ICP-OES, a TOC-analyser, LC-MSMS, AutoAnalyser or with an Element Analyser. She processed the data and reported them to the scientist. Furthermore, she analyzed data of unknown volatile organic compounds (VOC’s) measured with GC-QTOF.

Feel free to visit her LinkedIn page for more information about her curriculum vitae.

ICP-OES

Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) is a technique that can be used for multi (trace)-element determinations in solution. By introduction of the sample to a radio-frequency inductively coupled plasma with a temperature of approx. 5000K a lot of atoms and ions become excited, and the number of photons that is emitted during transition to a lower energy level is measured with an emission spectrophotometer.

Available methods:

- Measuring Al, Co, Cu, Fe, K, Mg, Mn, Na, Ni, P, S and Zn in 0,01M CaCl₂-soil extracts to get an indication of metal phytoavailability in soil. This method is also used for measuring the same elements in pore- and surface waters.
- Elemental profiling of plant material after a microwave-assisted digestion with HNO₃ and H₂O₂.

TOC-analyser

This analyser can determine the Total Carbon (TC), the Total Inorganic Carbon (TIC) and the Non-Purgeable Organic Carbon (NPOC) fraction in liquids. The sample is combusted and/or acidified, and the CO₂ that is formed is measured with a Non-Dispersive InfraRed (NDIR) dectector. An extra Total Nitrogen module is added to the apparatus at the NIOO. In this module, ozone is added to the NO that comes out of the TOC-analyser. NO₂* is formed, and the number of photons that is emitted during transition to a lower energy level is measured.

Different applications:

- Surface waters
- Soil extracts

- Water Soluble Carbon (WSC)
- Hot Water extractable Carbon (HWC)
- Chloroform fumigation + K₂SO₄ extraction for determination of living soil microbial biomass

- Microbial cultures or algae suspensions

LC-MSMS

With this technique, the components present in a sample are separated by liquid chromatograpy. Ionization takes place, and the component of interest (precursor ion) is filtered from the mixture. Thereafter, the precursor ion is fragmented and the product ions generated by fragmentation are detected by a mass spectrometer. 

LC-MSMS is used for measuring ergosterol. This is an important sterol in the membrane of almost all fungi, which accomplishes the same function as cholesterol in animals. Because it is not commonly produced by other organisms (with the exception of e.g. certain green algae and protozoa), ergosterol concentrations can be used to quantify fungal biomass in soil or organic matter. Ergosterol is present in two forms: free and esterified with fatty acids. At NIOO we use two different extraction methods, depending on the organic matter content of the sample.

AutoAnalyser

An AutoAnalyser (a.k.a. Segmented Flow Analyser (SFA) or Continuous Flow Analyser (CFA)) can measure different compounds colorimetrically at the same time, and in the same sample. The liquid sample is mixed with reagents automatically, a color reaction takes place and the sample is brought to a colorimeter. Air bubbles are introduced to the sample flow to segment each sample into discrete packets, to avoid cross contamination. In this way, up to 60 samples per hour can be measured. At the NIOO we measure NO₃, NO₂ , NH₄ and/or PO₄ in soil extracts, plant destruction residues or (pore-) water samples. Commonly used extractants are KCl, CaCl₂ and NaHCO₃.

Element Analyser

With the Element Analyser we have at NIOO, the total amount of carbon and nitrogen in solid-phase biological sample material can be measured according to the micro-Dumas method. The ground sample is weighed and wrapped into a small tin-foil capsule. This small package is brought into a combustion reactor together with an amount of pure oxygen, were it is burned quickly at ± 1800 °C. The inert carrier gas helium leads the oxidation products through a reduction tube were the excess of oxygen gas is removed and the different nitrogen oxides are reduced to elemental nitrogen. After that, a gas trap removes water vapor from the sample. The clean sample gases pass through a gas chromatography column to separate the N₂ and CO₂, and in the end, a thermal conductivity detector (TCD) quantifies the elements C and N.

Data analysis of unknown Volatile Organic Carbons (VOC’s) determined with GC-QTOF

Volatile organic carbons (VOC’s) play an important role in the communication between plants, insects and microorganisms. They can serve as a defense against enemies or as a signal that food is within easy reach. For studying these interactions, the VOC’s are collected and measured with GC-QTOF.  First, a capillary gas chromatography column separates the VOC’s. Then ionization takes place, and the VOC’s undergo a collisional induced fragmentation by acceleration against nitrogen gas. The formed fragments enter a Time of Flight (TOF), where electrical pulses send them up in a flight tube. The time that it subsequently takes for the particle to fall down and to reach a detector corresponds to a certain mass-to-charge (m/z) ratio. Identification of the VOC’s is done by comparing the spectrum of fragments (m/z ratios) with libraries. Since there are still many unknown VOC’s and overlap of spectra also occurs, data analyses has to be done with care.

Mass spectrum (intensity vs. mass-to-charge ratio) of (±)-α-Pinene, a volatile organic compound of the terpene class.