Malvern MPT-2, User Manual, Page: 10 / 85

Chapter 1 Introduction and hardware
Page 1-4 MAN 0318
The software can be set up so that measurements are made under a number of sam-
ple conditions. The sample is stirred, using the stirrer attachment

, pumped
through the flow cell and then measured at each of these conditions. In this way the
effects of adding various amounts of these titrants on the zeta potential, size or
intensity can be investigated. This method is known as a titration measurement.
A pH probe  continually monitors the pH of the sample, while a temperature
controller in the optical unit maintains the sample at a selected temperature.
A pinch valve  integrated into the Zetasizer Nano basin moulding pinches the
tubing and ensures that fluid is stationary during measurements.
Once the measurement sequence is complete, the sample and titrants can be
flushed from the system. The sample and titrant containers, if required, are
replaced with ones containing flush fluid. The fluid is then circulated through the
system to a waste container.
Vacuum degasser
The Vacuum degasser is a high-efficiency in-line module that removes dissolved
gasses from solvents used in flowing systems, and more specifically from the
titrants used in the MPT-2 Multi-purpose titrator. Its design assures reliable con-
tinuous operation and the highest level of continuous performance available with-
out the need for helium degassing. Up to 3 titrant lines may be degassed
simultaneously by one unit.
Internally, the titrant flows through a short length of Teflon AF® tubing which is
located in a vacuum chamber. Within this chamber a partial vacuum is maintained
by a constantly running, low RPM (revolutions per minute) vacuum pump.

Dissolved gasses migrate across the tubing wall under a concentration gradient
produced by the vacuum as the titrant flows within the coil.

Gasses removed are expelled, and the chamber is maintained at a constant, pre-
set vacuum level by varying the vacuum pump speed as needed.
An additional port in the vacuum pump continually flushes the pump head with a
small "bleed" of air to remove any titrant vapours which may enter the pump from
the vacuum chamber. This air bleed eliminates the need for any solenoid valves
within the system. This patented design results in zero vacuum "hysteresis".
Control of the Titrator
The MPT-2 titrator can be controlled by two methods - both via the Zetasizer
Nano application software:

Automatically, as part of measurement protocol when controlled through a
Standard Operating Procedure (SOP). The software tells the user what they
need to do as the measurement progresses.
MAN0318-4.0 - MPT-2 Autotitrator-Degasser.book Page 4 Tuesday, September 4, 2012 12:15 PM