MOLSPIN pH/AUTO-TITRATION

This high precision dual input device is designed to be driven by an IBM pc or compatible computer. It has two ranges; a low range of 300 millivolts and a high range of 1000 millivolts. The electrical connections to the pH electrodes and the associated measuring system are completely isolated from the computer connections.

There is an output that will drive a digitally operated syringe, (such as the Molspin DSI). With extra software (SUPERQUAD) the ph meter becomes a powerful automatic titrator.

The program SUPERQUAD is one of the most powerful PC-based programs for calculating acid dissociation constants and metal complex stability constants and the Molspin pH meter software is designed to work in conjunction with it. SUPERQUAD can be purchased with the pH meter.

The power and flexibility of the Molspin pH meter can be readily extended because the controlling software is held on disk and can be modified as required. Customised software can be written on a contract basis provided the requirements are specified precisely.

Auto-titration:

The titration option provides the most powerful facilities. Auto-titrations can be performed using 1 or 2 electrodes with measurements in either mV or pH (or one of each). The total volume to be delivered and increment size are under user-control, as are the time delay and expected electrode stability between additions. The user can skip a reading or terminate a titration at any time. Progress of a titration is monitored in both tabular (volume - pH/mV) and graphical form.

When a titration is complete it can be saved to disk (using either text or SUPERQUAD format) and the titration curves can be examined and end-points calculated.

End point determination. One electrode, in pH. (total volume 0.022ml) Titration in progress. 2 electrodes, both in mV, (Total volume 0.08 ml))

Digital output:

Specification

Input bias current: less than 2. 10 -13 A.

Input bias current change with temperature: less than 3.10-14 A/K

Input resistance: greater than 5. 10 +14 ohms

Input capacitance: less than 5.10-10 F.

The meter floats to better than 108 ohms with respect to earth.

The error in gain (linearity) is better than 2 parts in 10 +4.

Zero point drift: less than 20 uV.K-1.

Change of gain with temperature: better than 10-4 /K

Resolution: better than 10 microvolts (300 millivolt range).

Resolution: better than 30 microvolts (1000 millivolt range).

Resolution of ph: better than 0.002 in ph.

Temperature measurement: platinum resistance probe, accurate to better than 0.2 degrees Celsius.

Temperature resolution: better than 0.05 degrees Celsius.

Note: There are no physical preset controls, all adjustments are done by computer program and can be set by the user.

Computer requirements:

The computer requirements are met by the entry level IBM PS/1. This computer has 640k of RAM, a serial card and a VGA/HGA graphics card.

The program SUPERQUAD is one of the most powerful PC-based programs for calculating acid dissociation constants and metal complex stability constants and the Molspin pH meter software is designed to work in conjunction with it. SUPERQUAD can be purchased with the pH meter.

The power and flexibility of the Molspin pH meter can be readily extended because the controlling software is held on disk and can be modified as required. Customised software can be written on a contract basis provided the requirements are specified precisely.