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Lab Instrumentation: Overview

The laboratory is equipped with two laser particle size analyzers: A Malvern Mastersizer 3000 and a Micrometrics Saturn Digisizer 5200. The lab is also equipped with an Accumet pH Meter 915, Accumet Excel XL30 Conductivity Meter, Thermolyne 1400 Muffle Furnace, Ro-Tap Sieve Shaker, a tensimeter, and more. Sample prepatory equipment includes a Quantachrome Sieving Riffler, Sampletek 200 Vial Rotator, SPEX 8000 Ball Mill, Gilson Performer III, precision analytical balances, high speed/high capacity centrifuges, shaking tables, large ovens, a microscope, and more.

The lab is also equipped with two chemical fume hoods 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 (XRD) 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, as well as water-sediment mixtures. 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 undergoing laser particle size analysis can be prepared in several ways. The two most commonly used in our lab are:

  1. External dispersion (shaking overnight in a surfactant), followed by wet sieving to remove the entire sand fraction (>62.5 μm) and laser analysis of the fine (silt and clay) fraction only.
  2. Dry sieved to remove the coarse sand particles (>2mm, >1mm, or >0.5mm 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 having more of an entire sample 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.

Instrumentation

Malvern Mastersizer 3000

The 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 3.5mm to 0.01 μm.
MalvernMastersizer3000

Saturn DigiSizer 5200

The DigiSizer analyzes samples within a liquid medium and is capable of analyzing particles from 0.05 to 1,000 μm. It is equipped with an ultrasonic probe for internal dispersion of samples and an autosampler (MasterTech) that can be set up to run 18 samples automatically.

DigiSizer

Tensimeter for Carbonate Content

A tensimeter is used to determine the carbonate content of a sample. The tensimeter measures the pressure created by the production of CO2. CO2 is created when reacting HCL with CaCO3. A set of pure CaCO3 standards can be used to create a calibration curve. The carbonate content of a sample can then be determined based on the weight and pressure of the sample and this calibration curve. (Evangelou et al, 1984; Horvath et al, 2005; Sherrod et al, 2002; Wagner et al, 1998).
CaCO3Meter

Thermolyne 1400 Muffle Furnace for Loss on Ignition

The Thermolyne 1400 Muffle Furnace is used to determine organic matter content. Organic matter content is determined using the loss on ignition method (LOI). The percent weight of organic matter in a soil or sediment sample is measured based on removal of organic matter under high temperature (400° C) for 1 hour (Storer, 1984; Powell, 1989).

FurnaceLOI

Accumet pH Meter 915

The pH of a sample is determined by using the Accumet pH Meter 915. This meter is calibrated prior to each use using pH buffering solutions as well as lab standards with known pH values.

pHMeter

Accumet Excel XL30 Conductivity Meter

Total soluble salts are estimated from electrical conductivity (EC) of aqueous soil extracts. A soil-water extract of 1:5 is used in conjunction with a conductivity bridge to estimate the total amount of soluble salts. The meter is calibrated prior to each use using KCl solutions with known cell constants as well as lab standards with known values.

ECMeter 

IEC Centra GP8 and Eppendorf 5702 Centrifuges

The lab is equipped with two centrifuges. These centrifuges can hold multiple sample sizes. Centrifuging is used in sample preparation for multiple analyses including carbonate removal for PSDA, and electrical conductivity.

Centrifuges 

Ro-Tap Sieve Shaker

The lab is equipped with a Ro-Tap Sieve Shaker for stacked sieve analysis, with a large suite of sieve sizes.

 RoTapSieves

Gilson Performer III Sieve Shaker

The lab has two Gilson Performer III Sieve Shakers used for sample preparation (PSDA) as well as for stacked sieve analysis of smaller quantity samples.

 GilsonSieves

Inductively Coupled Plasma Machine (ICP)

The ICP machine is used for elemental analysis. The machine is capable of detecting elements at trace concentrations, and is able to scan for multiple elements simultaneously.
ICPMachine 

X-Ray Diffraction

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.
 

Quantachrome Sieving Riffler

The lab has a Quantachrome Sieving Riffler for precision subsampling for each analysis performed on a sample. Obtaining a representative subsample from splitting is critical for data interpretation. 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 gravel (>2mm) if desired.
 

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 a time.
 

Analytical Balances

The lab contains multiple analytical balances capable of measuring to an accuracy of 0.0001 g.
 

Shake Tables

The lab is equipped with two shake tables used for sample preparation of multiple analyses including PSDA and LPSA.