Two Ways to Improve Drug Discovery Speed and Productivity

Given the world-wide social and financial pressures to bring innovative new drugs to market as quickly as possible, are there simple and cost-effective ways a pharmaceutical R&D organization can do more with less?

Fortunately, there are.

One of the key tools used in the early phases of drug discovery is analytical chromatography. While this technology has been practiced for several decades, there are new technologies emerging today that facilitate the speed and simplicity of analytical purification and identification via high-pressure liquid chromatography (HPLC). Two particular developments allow researchers to separate complex samples quickly and collect more data about the target compounds.

Development 1: Small Particles – The Key to Speed

Silica with an average particle size of less than 2µm has been around for a decade, but the full benefits for HPLC have only become widely communicated in the past two years.

Evolution of Particle Size. In the 1970s, HPLC media was dominated by 10µm irregular silica with efficiencies of 45,000 plates/meter. The 1980s saw the emergence of smaller, spherical particles of 3-5µm, with increased efficiencies of 85,000-120,000 plates/meter. In the early 1990s efficiency took another leap forward with the introduction of 1.5µm spherical particles with efficiencies of 150,000 plates/meter.

In 1996, Alltech Associates Inc. (now part of Grace Davison Discovery Sciences) introduced 1.5µm spherical silica with efficiencies of more than 200,000 plates/meter – a 4.4-fold increase from the early days of chromatography.

However, it wasn’t until the introduction of ultra-high pressure LC systems in 2004 that the benefits of small, sub-2µm particles became part of mainstream conversation.

Sub-2µm Benefits. HPLC columns packed with small particles offer two main benefits – resolution and speed. By adjusting column length and particle size proportionally, you can reduce overall analysis time and increase sensitivity. For better resolution of complex samples, choose longer columns and slower flow rates. Or, for maximum speed, choose shorter columns with faster flow rates.

In other words, short columns offer speed while small particles contribute to efficiency. Combining the two dramatically reduces run times and improves HPLC throughput.

The Pressure Effect. Typically, conventional HPLC systems cannot exceed 5000psi. Using sub-2µm particles in short, large diameter columns rather than traditional column dimensions helps to stay within these pressure limits. Additionally, these dimensions offer a column volume that balances well with the system volume to maintain chromatographic peak shape and efficiency.

If even greater speed is desired, or if these large ID columns are not suitable for your MS system, then you need to make the jump to the new ultra-high pressure technologies (12,000psi) now possible with recent developments in instrumentation and column hardware. These new high performance columns and systems offer higher pressure limitations (to overcome backpressure) with reduced system volumes so smaller bore columns can be used effectively.

With an ultra-high pressure system, use sub-2µm particles in long, narrow diameter columns specifically designed to withstand high pressures.

Growth of Sub-2µm Applications. The installed base of ultra-high pressure instrument systems is increasing rapidly, but many researchers are waiting for a larger selection of ultra-high pressure columns before they convert critical methods, since security of supply of columns for this new technology is critical.

However, even with conventional pressure HPLC systems, short columns with large diameters show significant increases in resolution and speed over traditional 150mm and 250mm HPLC columns. With simple changes to your pump, system volume, and injection volume, you can enjoy the benefits of sub-2µm particles at conventional, 5000psi pressures.

There are now several sources of HPLC columns with sub-2µm silica particles, both for conventional pressures and ultra-high pressures. Grace Davison Discovery Sciences offers both – we have several 1.5µm bonded phases available in high-throughput hardware for conventional pressures, including our Rocket™ Column format and Expedite™ Column format. At conventional pressures of 5000psi these column formats can reduce run times by 70% compared to traditional dimension columns.

Grace also has recently introduced VisionHT™ Columns for ultra-high pressure systems. These columns use 1.5µm particles in new high-pressure column hardware that withstands up to 12,000psi with constant efficiencies and retention times for more than 17,000 column volumes.

Through our expertise in silica chemistry combined with specialized column hardware technologies, Grace Davison Discovery Sciences is an industry expert in HPLC column manufacturing. Grace is one of the few HPLC column suppliers with primary manufacturing capabilities for the raw 1.5µm silica, a variety of bonded phases, and column hardware design and packing methods that meet the stringent requirements of traditional as well as new instrument technologies.

Small Particles are the Key To Speed. Although the new ultra-high pressure columns and systems have significant speed and resolution advantages over conventional columns and systems, the key is the sub-2µm particle size silica. Using small particle sizes even at conventional pressures demonstrates significant speed and resolution benefits. So whether or not you decide to invest in new ultra-high pressure technologies, you can immediately improve productivity by switching to HPLC columns with sub-2µm particle size silica.

Development 2: Two detectors are better than one

Once researchers have separated their sample and isolated target compounds, they may be faced with detection challenges. The trade-offs between different detection methods can be daunting. Fortunately, there is a detection method that is nearly universal by itself, and that also complements data from ultraviolet (UV) and mass spectrometry (MS) detectors to provide more information about the target compounds, thereby accelerating sample analyses.

ELSD Technology. Although new to many chromatographers, evaporative light scattering detectors (ELSDs) have been available for more than 20 years. They were first commercialized in the early 1980s and continuous improvements in design and technology have made ELSD one of the most powerful tools in a chromatographer’s toolbox. With its low-nanogram sensitivity, ELSD has become the preferred method of detection for many difficult samples - carbohydrates, lipids, polymers, surfactants, underivatized fatty and amino acids, pharmaceuticals, and nutraceuticals. Researchers in the drug discovery arena have found ELSD to be an indispensable tool for sample characterization.

Although designs differ among manufacturers, all ELSDs follow the same general detection scheme. The sample passes through a needle and mixes with nitrogen gas to form a dispersion of droplets, which are then heated to evaporate the mobile phase. The remaining sample particles pass through a detection cell, scatter light, and generate an output signal.

ELSD Advantages. ELSDs will detect anything less volatile than the mobile phase, regardless of the compound’s optical characteristics, and with better sensitivity and baseline stability than low-wavelength UV. ELSD gives a more accurate sample mass representation than MS. Also, ELSD is gradient-compatible unlike refractive index (RI) detectors, resulting in greater flexibility and sensitivity.

Complementary Nature. While ELSD has advantages over other detection methods, it can also be used in combination with UV and MS to maximize the information collected about a sample.

Pharmaceutical formulations may contain mixtures of chromophoric and non-chromophoric compounds. ELSD will show what might be missing from your UV chromatogram, since UV detects only chromophoric compounds. Mass spectrometry can be a powerful tool for structural characterization and determining molecular weight of compound mixtures. However, MS is not well suited for quantitative analysis due to differences in ionization efficiencies for different molecules.

ELSD fills the quantitative gap as a complementary detector to UV and MS. This detector combination is especially useful in combinatorial and parallel synthesis library screening, because more complete peak information can be obtained in one run. In this configuration, the ELSD, UV and MS are operated in tandem. The MS provides structural information while the UV and ELSD provide quantitative data.

Impact on the Pharmaceutical Industry. Today, pharmaceutical researchers need rapid analysis methods for drug compounds because of increasing demands for accelerated drug development. The ELSD’s universal detection capabilities and gradient compatibility are ideal for the analysis of pharmaceutical compounds and provide many benefits over UV, RI, and MS. Using ELSD in combination with UV and MS gives maximum structural and concentration information.

Model 3300 ELSD. Grace Davison’s newest ELSD, the Model 3300, offers high sensitivity and ease of use in a compact footprint designed for today’s busy labs. The 3300 ELSD can be easily added on to an existing HPLC or MS system, and includes a driver for the Agilent ChemStation software. The scrolling chromatogram trace and intuitive software make the 3300 one of the most user-friendly ELSDs available today.

Faster separations, better detection – the recipe to do more with less

Maximize your R&D productivity in simple ways by taking advantage of new HPLC technologies. Sub-2µm particle size HPLC columns, whether at conventional pressures or ultra-high pressures, dramatically improve speed and resolution of separations. Also, combining ELSD technology with UV or MS gives you more information about your sample, allowing you to learn more from a single run. Speed, sensitivity, selectivity – all lead to a better bottom line for today’s drug development laboratories.

About Grace Davison Discovery Sciences

Since 1921, Grace has led the way in researching and refining silica's properties and capabilities in the fields of analytical, preparative, and process scale chromatography. Combining our solid position in the silica market with a full spectrum of chromatography products, Grace supports pharmaceutical research from discovery to recovery.