The Actipix D100 detector won the Silver Editors' Award last week at the 58th Pittsburgh conference on Analytical Chemistry and Applied Spectroscopy just days after its public launch. The device allows researchers to monitor multiple separations at higher resolutions and with greater sensitivity.
The detector's higher than normal resolution enables more applications in the biopharma industry, especially with the in-line detection of proteins during the polishing stage, where the last trace impurities are removed from a purified protein.
According to Professor David Goodall, chief scientific officer at Paraytec, this application could lead to substantial cost savings in the production of biological drugs.
The detector uses a capillary as both combined lens and sample holder allowing the detector to be easily incorporated into existing capillary systems for in-line analysis.
Its spatial resolution of 70 µm is ten times better than a standard capillary UV detector. The device measures the absorbance of one wavelength of choice, with an optimal sensitivity for proteins and peptides at 190 nm. The device can be easily set up to monitor different wavelengths by switching one UV filter for another.
During a solid-phase extraction, for instance of a natural product drug from a plant, the use of such a detector allows the user to only collect the fractions needed and not collect unnecessary solvent.
"Usually in a solid phase extraction you don't know when the products are being eluted. The Actipix allows in-line detection so that you know exactly when the product is coming off and allows feedback control of the system," said Goodall.
Incorporation of the detector directly in-between a capillary liquid chromatography (LC) system and a mass spectrometer (MS) opens up new possibilities for simultaneous UV quantification and MS characterisation without the need to split the eluent from the LC system.
The detector also allows the simultaneous quantification and sizing of proteins, with the area of a peak being proportional to the amount of a compound and the band spreading, or width of a peak, giving information about the radius of the molecule.
This sizing information is calculated from the diffusion of the sample and an effect known as the Taylor dispersion, providing a simple way of measuring the size of molecules using nanolitre amounts of sample. This technique is applicable to both large and small molecules, unlike dynamic light scattering (DLS) instruments, which only work for larger molecules as they have to be large enough to scatter the incident laser light.
The detector uses an active pixel area sensor, similar to those used in mobile phones and digital cameras, which measures UV light intensity both through the sample in the capillary and the background space making absorbance measurements independent of any light source variation.
The high resolution is also critical in proteomic experiments where the analysis of the separation of complex mixtures is conducted. As the detector has a linear dynamic range of five orders of magnitude it can determine impurities down to concentrations of less than 0.01 per cent.
The signal to noise ratio is improved by using a technique known as time delayed integration, which is effectively equivalent to increasing the time constant, but does not sacrifice spatial resolution of the signal.
The detector can also be used in combination with lab-on-capillary set-ups, allowing real-time visualisation of reaction progress. As the detector is multiplexed to detect up to eight channels simultaneously, the system can be used to study parallel reaction optimisations.
This approach has a large potential in early stage drug discovery where different enzyme inhibitors can be incorporated into the capillary to test which bind most strongly to the enzyme.
Goodall mentioned that Paraytec were currently in discussions with a potential partner to develop this approach to study antibody / antigen interactions.
"Because the system has the potential to monitor the interaction between various immobilised antibodies and an analyte sample in a multiplexed format, the use of the technique in molecular diagnostics is an application we are currently exploring," continued Goodall.
The intellectual property was originally developed at the University of York by Goodall and three colleagues, with the manufacture of the instrument being conducted by the company's design and manufacturing partner GSPK Design in Knaresborough.
The company is currently developing a full range capillary spectrophotometer, which would broaden the applications of this novel technology further still.
