The laboratory is equipped with two laser particle size analyzers: a Malvern Mastersizer 3000 (a new Mastersizer model released in 2011), and Micromeritics Saturn DigiSizer 5200.
Sample preparatory equipment includes a Quantachrome Sieving Riffler, Sampletek 200 vial rotator, SPEX 8000 Ball Mill, precision analytical balances, high speed/high capacity centrifuges, shaking tables, large ovens, specialized mechanical nested-sieve shakers, and a microscope. The lab is further equipped with a Thermolyne 1400 muffle furnace (for Loss on Ignition measurements), a pressure meter (for carbonate content analysis), a pH meter, and an electrical conductivity meter. We have two chemical fumehoods with facilities for storage and disposal of chemicals.
Instruments in other labs that we have access to include a Bruker D8 Advance X-Ray Diffractometer and a Dionex ICS 1500 Ion Chromatography System.
Laser Particle Size Analysis
The laser particle size analysis (LPSA) procedure is used to determine the percentage of size-class fractions in soil or sediment samples. The procedure is based on ASTM C 1070–01 to determine particle size distribution analysis (PSDA) of alumina and quartz powders by laser light scatter (ASTM, 2000).
Based on the Mie theory of light scattering, laser diffraction measures particle size distributions by measuring the angle and intensity of light scattered as a laser beam passes through a dispersed particulate sample. Large particles scatter light at small angles and small particles scatter light at large angles. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory. The method assumes that all particles are spheres, and the reported size class percentages are volume based.
Samples may be prepared for laser particle size analysis in several ways. The two most commonly used in our lab are:
(1) External dispersion (shaking overnight in surfactant) followed by wet sieving to remove the entire sand fraction (>62.5 micrometers) and laser analysis of the fine (silt and clay) fraction only.
(2) Dry sieved to remove the coarse sand particles (>2mm, >1mm, or >0.5 mm depending on the project objectives and analyzer being used), and laser analysis of the remaining sample using internal dispersion in the laser analyzer using ultra-sonication.
Method 1 has the advantage of added resolution to the fine end by removing larger sand-sized particles, thereby reducing multiple light scatter. Method 2 has the advantage of the more of the sample entire being analyzed in a single technique. If the entire sample of interest is analyzed by laser diffraction, a mean, mode and kurtosis of the entire particle size distribution can be determined.
Malvern Mastersizer 3000
This Mastersizer 3000 is Malvern’s newest instrument that was released in 2011. It produces rapid measurements and is equipped with two different dispersion units allowing the measurement of both wet and dry samples. It is capable of analyzing samples from 3.5 mm to 0.01 micrometers.
Saturn Digisizer 5200
The Digisizer analyzes samples in a liquid medium and is capable of analyzing particles in the range of 0.05 to 1000 micrometers. It is equipped with an ultra sonic probe for internal dispersion of samples and an autosampler (MasterTech) that can be set up to run 18 samples automatically.
This instrument, housed in DAS, has a Theta-Two Theta goniometer, a Cu X-ray tube, and a Vantec position sensitive detector. It has an auto-sample changer that can hold up to 90 samples and is accompanied by specialized Bruker software and access to the ICDD (International Center for Diffraction Data) database for analysis of XRD scan data. The XRD lab also has a McCrone mill and precision balances for sample preparation.
Key Sample Preparation Apparatus
Quantachrome Sieving Riffler
We have a Quantachrome Sieving Riffler for precision subsampling for each analysis performed on a sample. The unit consists of two basic components: A cylindrical vibrating hopper which is amplitude-variable and controls the delivery rate of the sample, and a rotating sample collector which is divided into eight stainless steel compartments. Two nested sieves can be used within the hopper to remove larger particle sizes such as the gravel (>2mm) if desired.
The Sampletek Model 200 Vial Rotator
Some chemical analyses such as Fe oxide and carbonate content analysis are performed on a ground sample. Grinding homogenizes the sample allowing for very small subsamples to be used. For this we use a Sampletek Vial Rotator which uses rotational energy to break up particle aggregates over a period of 24-48 hours. The unit can accommodate nearly 100 scintillation vials at one time.