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
(nephellometric turbidity units).
The
sample under test can be heated up or cooled down by an
integrated Peltier heating/cooling system. The overall
temperature range is –15°C to +90°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.
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
-
Optional
data printer, serial interface RS232 standard
|
