Ag/AgCI, double junction reference
GLpKa - pKa, logP/D, solubility & dissolution
Please note: We have discontinued production of new GLpKa systems due to the launch of its successor, the new SiriusT3.
Service and support for existing GLpKa customers will remain available until further notice.
Overview
For 'gold standard' measurement of pKa, LogP/D, Solubility and Dissolution
- pH-metric pKa, logP and logD
- pH range of 1.8 - 12.2 (for standard titrations)
- Up to 30 samples in 24-hours
- Measurements down to 0.5mM
- Highly automated with built-in traceability and reminders
- Autosampler and single sample versions
From 1997 to 2008 GLpKa was Sirius' industry leading instrument for pKa, logP/D and solubility measurement using pH-metric technology. GLpKa has five dispenser units that deliver all necessary reagents automatically. It uses a proprietary Ag/AgCI double junction electrode for accurate pH measurement. An overhead stirrer ensures that the correct level of mixing is used for each type of assay. Temperature control is achieved using an external re-circulating water bath whilst assay temperature is monitored by a PT100 probe. Assays are designed, controlled and processed with our RefinementPro2 software.
In pH-metric methods, pKa is measured by titrating a solution of the sample in water or solvent with acid and base, and calculating the pKa from the shape of the titration curve. This method will always find the pKas of a sample, and easily copes with multiple and overlapping pKas.
LogP is also measured by a pH-metric method, based on a two-phase acid-base titration in a mixture of water and octanol. The assay delivers logP results for the neutral and ion-pair species and a pH vs. logD profile. The method works well for poorly water-soluble samples, because they tend to dissolve in the octanol phase.
Technical specification
pH electrodes
Stirrer
Overhead, variable speed
Temperature probe
PT100, allows automatic temperature compensation
Precision dispensers
Water, minimum of 2µL with 25mL syringe. Acid, base, partition solvent, minimum of 0.4µL with 5mL syringe. CoSolvent, four-installed, via 4-way valve, minimum of 0.4µL with 5mL syringe.
MultiTip dispenser
Five quartz dispenser tubes.
Probe movement
Fully automated X-Z axis
Electrode storage/calibration
Two pH7 buffer positions, one storage and one calibration
Washes
Two water washes and one special wash station provided
Single sample version
Glass temperature control vessel (external circulating bath required)
Autosampler version tray
Holds 50 samples, can be temperature controlled with external circulating bath
Purge gas
Internal flow meter, nitrogen or argon required
Partition solvents
Supports 7 including octanol and a generic solvent
CoSolvents
Supports 10 including MeOH and DMSO
Filter
Carbon scrub filter for organic vapours
Keypad
Liquid-crystal 16-line display for text and graphics, 22-buttons for numeric data entry
Keyboard
Mini keyboard for alphanumeric data entry
System standardisation
Sirius Four-Plus(TM) procedure
Sample concentration
>0.5 mM (depending on the pH range)
pH-range
1.8 - 12.2
Assay volume
Minimum 5mL, maximum 20mL
Automated
For unattended and overnight operation. Flush routines for unit readiness. Data upload. Maintenance prompts.
Services required
One mains power inlet (110 or 240 V)
Connection to the PC
Cable from GLpKa to PC serial comm port
Computer
Windows 2000 or XP
Software
GLpKa Firmware Version 1.129. RefinementPro Version 2.0.1.1
Reagent requirements
See 'pH-metric reagents' sheet
Dimensions
780 x 650 x 950mm (WxDxH)
Weight of unit
70kg
Dimensions of packed unit
1200 x 1000 x 1000mm
Weight of packed unit
120kg
Literature
Electronic copies of our GLpKa brochure and technical specifications are available for download:
> GLpKa Brochure> GLpKa Technical Specifications
New Scientific Paper Published
07.12.09
New paper from Sirius explains how our solubility measurements work, and introduces new methods for evaluating supersaturation.
New Scientific Paper Published
01.07.10
New paper - Study of pH-dependent solubility of organic bases. Revisit of Henderson-Hasselbalch relationship.
Physchem Forum 9, Barcelona
17.09.10
Sirius will exhibit at and sponsor the next Physchem Forum meeting in Barcelona