Laboratory Videos

Current Operational Videos

The use and operation of the portable X Ray fluorescence Spectrometer

X-ray fluorescence is the process in which photons emitted from an x-ray radiation source cause photoelectric fluorescence in a sample. When primary X-rays is illuminated to a sample, it excites the atoms. This causes ionization and ejecting electrons from the inner (usually K and L) energy orbitals. The ejected electrons are replaced by electrons from the higher energy orbitals. When this happens, secondary energy is released due to the decreased binding energy of the inner electron orbital compared to the outer one. The energy emitted is characteristic to the type of atom involved. Due to this characteristic transition between specific electron orbitals of an element, the resulting fluorescent X-rays can be used to quantify the elements that are present in a sample.

 

The use and operation of the Multi Purpose Analyzer Spectrometer

The Multi-Purpose Analyzer (MPA) is a Fourier-transform InfraRed (FTIR) Spectrometer that operates in the Near Infra-Red (NIR) wavebands region. The method in use is the SphereMacrosample. It has the Sample Compartment Unit that operates on the Transmission mode and the Integrating Sphere Window that operates on the diffuse Reflectance mode. The Integrating Sphere has different accessories i.e. the rotating arm that rotates the cup or wide Petri dish on the sphere window and a fixed vial mount that mounts the vial on the sphere window.

 

​​​The use and operation of InvenioS HTS-XT Spectrometer

The InvenioS HTS-XT Module is designed for measurements in diffuse reflection. When Near or Mid IR light is incident on a rough or a matte surface, two types of reflection occur: Specular reflection (i.e. the light reflects directly off the surface) and the diffuse reflection (the IR light penetrates the sample surface and is partly diffusely reflected, i.e. reflected over all angles, due to the rough surface). The optics of a diffuse reflection accessory is designed in such a way that detection of diffusely reflected light is optimized, and the detection of specular reflected light is minimized. DRIFTS (diffuse reflectance infrared fourier transform spectroscopy) is an analyzing technique in FT-IR spectroscopy that makes use of the phenomenon of diffuse reflection. The main advantage is that it enables analysis of strongly scattering and absorbing samples unlike transmission measurements and equally has high signal intensity.

 

The use and operation of the Alpha Spectrometer

The ALPHA R Module is designed for measurements in diffuse reflection. When Mid Infrared light shines on a rough or a matte surface, two types of reflection occur: specular reflection (i.e. the light reflects directly off the surface) and the diffuse reflection (the IR light penetrates the sample surface and is partly reflected, i.e. reflected over all angles, due to the rough surface). The optics of a diffuse reflection accessory is designed in such a way that detection of diffusely reflected light is optimized, and the detection of specular reflected light is minimized. DRIFTS (diffuse reflectance infrared fourier transform spectroscopy) is an analyzing technique in FTIR spectroscopy that makes use of the phenomenon of diffuse reflection. The main advantages of these techniques are they enable the analysis of strongly scattering and absorbing samples and they have high signal intensity unlike transmission measurements.

 

LDSF Soil Sample Processing Protocol

This is a step by step guide on how to process Soil samples collected using the Land Degradation Surveillance Framework (LDSF). This protocol ensures the integrity and homogeneity of the sample.

 

Fourier Transformation Mid Infrared Reflectance Spectroscopy (FT-MIR)

Mid Infrared Diffuse Reflectance Spectroscopy (MIR spectroscopy) is a rapid, high throughput method for characterizing the chemical composition of materials. A sample is illuminated and the diffuse reflected light (electromagnetic radiation) is measured in narrow wavebands. The resulting spectral signature summarizes how much energy was absorbed at each wavelength. Spectral signatures respond to soil organic and mineral composition. Analysis of specific absorption features also reveals details about the molecular structure of the sample, for example organic matter quality. MIR provides a rapid, low cost, non-destructive method of analyzing soils without use of chemicals.

 

Soil sample processing: Sieving

  • Weigh and record the whole dried soil sample to 0.1 g.
  • Mix the dry sample thoroughly while still on the drying tray. Spread the sample on a plastic sheet. Using a rolling pin, crush the sample to pass through a 2 mm sieve as you sieve and place in a separate pile (the coarse fraction).
  • Place whatever remains on the sieve back onto the plastic sheet and crush again gently. Then pass again through the 2 mm sieve. Make sure that all soil materials are crushed, but do not attempt to crush gravel and rocks.
  • Throw anything that now remains on the sieve into the coarse fraction pile.
  • The whole sample should be processed and no material should be discarded. You will remain with two fractions

 

Milling

This is done using a machine. Adjust pestle and scrapper and the pressure depending on the sample texture and set the time. Load the 1st sample to start grinding and the machine will stop automatically after the set time runs off. Clean the machine after every sample using a wet clothe and dry it with a dry clothe too. Apply ethanol and wipe using tissue paper until its dry before you load another sample.

 

NIR Sample Loading

Samples sieved through 2mm sieve are loaded into petri dishes. Each petri dish is labeled according to the sample serial number. 20g of each soil sample are loaded into the petri dishes. The petri dishes are arranged in a sequential manner in a trolley and they are transported to IR lab. For plants vials are used. When the samples are returned from the IR lab after scanning they are off-loaded by returning them into their packages and stored for archive. Petri dishes are wiped with a non-fluffy material to remove dust particles. Vials are washed with distilled water.

 

MIR Sample Loading

Samples which have been fine ground are loaded into clean aluminum micro plates and transferred to IR lab for analysis. After scanning, plates are emptied and cleaned using deionized water and a brush and dried using acetone.

 

Soil Archiving

It follows the basic library cataloging procedures for organized storage, easy and quick retrieval of samples. The samples are weighed and packed into the trays. After this the trays are shelved into the bays. All the samples are well labeled and so are the trays, shelves and bays for easy identification during retrieval. This information is stored in a database information system. The sample position can be viewed by keying in the serial number, country of origin, site name or study name into the database. The information system will give the exact position of the sample in the tray, the status (available or empty or missing) and the sample type (standard, reference or back up). After each retrieval the sample's.

 

Old Non-Operational Videos

Total Carbon, Organic Carbon, Nitrogen and Sulphur Analysis Flash Combustion Method

Soil carbon is the largest terrestrial pool of carbon and plays a key role in the global carbon cycle. Soil organic carbon is also a key determinant of soil quality, affecting cation exchange capacity, supply of nutrients to plants, water holding capacity and soil physical structure. Soil carbon is also the principle energy source for microbes and sustains soil biopersity. Soil organic nitrogen and soil organic sulphur are the predominant pools of nitrogen and sulphur in soils and their mineralization is the main supply of nitrogen and sulphur respectively for plant growth and development. Soil inorganic carbon accounts for about one third of the total carbon in soils globally and has considerable influence on the physical and chemical properties of soil.

 

Laser Diffraction Particle Size Analysis (LDPSA)

Soil particle size distribution is a key determinant of many soil functions including soil fertility, and hydraulic and mechanical behavior. Soil particle size analysis using traditional hydrometer or pipette sedimentation methods is tedious and error-prone. Laser diffraction particle size analysis is a rapid low cost technology for measuring particle sizes using light diffraction patterns. Particle size distribution can be measured in narrow size classes in dry soils, or in water using different dispersion treatments.

 

Soil Moisture

This is the extraction of water from soil using pressure extractor. Different pressure levels are applied starting from saturated soil up to dry soil at 105 degrees to achieve gravimetric water content of the soil. This helps in determining how much long soil can hold water

 

Atternberg Limit

Is described as determination of the bulk density, Atternberg limits (liquid and plastic limits) using cone penetrometer and linear shrinkage. This helps in determining compressibility, permeability, compatibility, shrink swell and shear strength of the soil.