Classification of soil is important for environmental control and construction purposes. Soil classification is based on several factors such as absorption, the ability to shrink or swell, water retention and permeability. Most of these factors independently correlate with the particle size of the soil. The clay fraction, the smallest fraction (0-2 micron), is indispensable in assessing soil quality. The clay fraction is measured according to for instance ISO 11277 and allows the soil to be categorized within stated classes.
The analysis is carried out in three steps:
Skalar has developed a concept to automate the second and third step in this process using a Skalar Robotic analyzer. Automation of these steps is of particular interest because they can now be carried out fully automatic and with precise timing and pick up heights.
A typical Organic Matter/Carbonates removal sequence:
After weighing, the samples are placed in a bottle. The bottles are placed in the Skalar SP50 Robotic analyzer and an amount of water is added. The bottles with sample are heated until the boiling point has been reached. A sample is boiled for 30 min. During heating and boiling every 30 min, 5 ml of hydrogen peroxide is added to remove the organic matter. Afterwards the sample is cooled down and the same process is started but now with the addition of hydro chloric acid to remove the carbonates. During the complete process water is added in intervals to avoid excessive boiling of the sample.
A typical Clay fraction analysis sequence:
The sample is transferred into a volumetric cylinder of 500/1000 ml. The system, a Skalar SP2000 robotic analyzer automatically adds Sodium pyrophosphate solution and brings the suspension to volume by adding distilled water. During a user-definable time, the sample is homogenized. After a settling period of several hours a fraction of the suspension is taken at a predefined depth from the cylinder and this fraction is transferred to an evaporation dish by the system. After drying the remainder of the sample is weighed and the Clay fraction is calculated via the software.
This procedure can also be performed unattended allowing for overnight operation. In addition, it is also possible to determine other fractions.
RoboticAccess™ is designed as a flexible and multitasking program for controlling the Skalar robotic analyzers. While analyzing the samples, already obtained results are processed and new analyses can be prepared and scheduled. An access code and password are required before operation to prevent unauthorized operation and data modification.
The application files, which contain the instructions for the analyzers to perform the specifications, are pre-set in the software by Skalar, according to (inter) national regulations or can be in accordance with user defined requirements.
Runs can be easily started by selecting the required application and simply creating a user defined sample table by dragging the racks to the analyzer. When the sample table is completed and the analysis sequence is defined, the run can be started or scheduled for another start time. All applications can be programmed to be analyzed. The status of the running analysis can be followed on the screen and the results are displayed in real-time. During the run it is possible to add priority samples or exclude samples from measurement.
Results can be printed in user defined print reports and exported to a txt, excel or LIMS. Finished runs can be archived as well as backed up and restored later.
Integrated Quality Control features assure accurate results and full compliance with required regulations. QC samples can be analyzed and Quality Control charts together with other valuable statistical information can be created. Also CLP protocols can be included, which allow automatic actions of the Robot analyzer itself if QC and CLP limits are exceeded. This guarantees the production of highly accurate results and automatic quality control on the Robotic analyzer’s performance.