Figure 8 & 9: Possible installation in the preparation of pharmaceutical water.
or by a programmable timer. The applied
solutions are not subject to pharmaceutical
guide lines and can be produced by the operators themselves. The substances can be
purchased from the local chemical distributor as long as they comply with the quality
requirements for an analysis.
SIMPLE GRAB SAMPLING
An extra benefit of the operating process
is the possibility of examining grab samples
with the instrument. The sample is drawn
through the instrument by a peristaltic pump,
regardless of whether it is an SST sample, a
functional test (see 4. 2), or a grab sample.
Grab samples are easily connected and can
be measured immediately by the press of a
button. As long as the grab sample measurement mode is active, the signal outpoints of
the last value is held to avoid a false alarm.
After the grab sample measurement mode
is over, the instrument is rinsed for a set
time before the signal points are released to
The focus of the development of the TOC-
The prevailing UV lamps have a life expec-
tancy of 6 months in instruments with direct
UV-oxidation. Every lamp exchange requires
an SST, which means a minimum of two tests
a year. Many operators also use the certified
SST solutions more often than the required
validation interval, even up to monthly checks.
This involves considerable costs and is logistically very time consuming.
The automatic functional test of the AMI-
Line-TOC can effectively simplify this routine.
The process is similar to the established SST.
Highly concentrated solutions (Sucrose and
Benzoquinone) are used, which last up to 3
months. The solutions are diluted at the time
of the test with sample water by an integrated
peristaltic pump. Both stock solutions are
measured one immediately after the other.
Conclusions can be made about the functions
and the conditions of the instrument by the
degree of recovery. The basic function of the
instrument can be easily proved without intervention or external modification. The operator
has the ability to examine the instrument regularly online, reducing the number of expensive and elaborate tests.
The functional test is activated manually
no clear correlation between TOC-content
With such applications, a TOC-conductivity (^)-model can be constructed
by the production of calibration solutions
which cover the concentration range of
the relevant components. The temperature
dependency of the conductivity of the samples only needs to be taken in consideration
when the calibration and the online-monitoring are made at different temperatures.
The AMI-Line-TOC stabilizes the sample
temperature, not just with online-monitoring
but also with a calibration at 42-43°C. In
order to allow readings with deviating temperatures, the conductivity values ^in and ^
out are converted to 25°C.
A constant temperature performance
is assumed over the entire measurement
range with a linear compensation. With a
normal setting of 2% per degree Celsius,
this approximation is generally recognized
and approved. This value can be manually
The calibration in linear mode occurs
through the measurement of an exactly
defined sample solution (Sucrose 1ppm).
Based on the measurement result, the
instrument calculates the effective slope,
which it displays. From experience, the values are in the range of 0.150 to 0.3.
LOCATION OF MEASUREMENT
The standard sampling points in pharmaceutical plants are after the distillation, in
the storage tank, at the inlet and the outlet
of the loops and at the extraction point.
THE FUNCTIONAL TEST AS AN AIDE
Instruments that are installed in pharmaceutical applications must pass an SST
(System Suitability Test) according to the
authoritative pharmacopeia (USP 643 / EP
2. 2. 24). The specifications of the test solution in these monographs are described in
If the test is carried out in plants which
produce according to the USP guidelines,
the solutions have to be produced with
USP certified reagents. Due to the extreme
dilution, the storage life of these solutions
is limited to only a few weeks. An SST is the
only possibility to check a TOC instrument