What is turbidity?
Turbidity is defined as the optical property of a liquid caused by light absorption and scattering. Turbidity is normally determined by visual judgement by the human eye. This subjective method is causing large variations and errors and in addition to this, it is a time consuming, inefficient and costly method.
Automatic turbidity determination
The TURBITRONIC is a combination of turbidity detection, temperature control and stirring speed control, thus offering all conditions for reproducible measurements.
The turbidity detection system consists of an infrared photocell with a maximum spectral sensitivity at 900 nm. The overall measuring range is 10 – 1000 NTU, but partial ranges can be selected by individual calibration with a turbidity standard. The smallest difference between min. and max. range is 10 NTU.
The sample under test can be heated up or cooled down by an integrated Peltier heating/cooling system. The overall temperature range is –5°C to +80°C. In order to guarantee a homogeneous temperature distribution, the sample under test is stirred by a magnetic stirring bar that is inserted into the glass test tube. By electronic stirring speed control, the stirring speed can
be varied from 200 to 1000 rpm depending on the viscosity of the sample.
Standardization of laboratory test method
It is commonly accepted that cloudpoint measurement is the best technique to obtain quantitative data on phase transitions in water solutions of non-ionic surfactants.
Compared with laboratory instruments with visual determination, the precision of cloudpoint measurements have greatly been improved by the infrared light optical method of the TURBITRONIC turbidity analyzer.
This method complies with the DIN/EN 1890 and ISO 0607 standards and improves the precision, repeatability, reproducibility and effectiveness of this test method.
The practical use has been proven both by interlaboratory tests to include the use of various operators (repeatability) and intralaboratory test to include variability between several laboratories in Germany.
The instrument functions and test conditions documentation comply with Good Laboratory Practice (GLP).
Analysis of test results
Compared to the uncertainties of the visual test method, the TURBITRONIC is a new, valuable instrument both for the development of new formulations and for quality assurance applications.
The test method is providing accurate results as samples can be tested under controlled conditions. Particularly in cases where the interval from initial to full turbidity is extending over several degrees Celcius, considerable differences may arise with other test methods.
In addition to the cloud point temperature values, which are automatically stored with the date and time of the test, additional data can be obtained by turbidity monitoring. This can be achieved by optional PC application software. In the standard version, the test results can be printed out in A4 format on a standard office printer that can be connected to the parallel printer
port of the instrument.
Technical Specification
-
Programmable temperature, stirring speed and turbidity level, program memories for specific test procedures
-
Integrated data printer, serial interface RS232 standard
|
