Sirius GLpKa - automated pKa, logP, logD and Solubility measurement

Service and support for existing GLpKa customers will remain available until further notice.

Overview

For 'gold standard' measurement of pK_a, LogP/D, Solubility and Dissolution

pH-metric pK_a, 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 pK_a, 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, pK_a is measured by titrating a solution of the sample in water or solvent with acid and base, and calculating the pK_a 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

Ag/AgCI, double junction reference

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

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.