How Syringe Filtration With Integrated Prefilter Technology Improves HPLC Performance and Throughput

How Syringe Filtration with Integrated Prefilter Technology Improves HPLC Performance and Throughput Introduction In many laboratories, the need to consistently generate high-quality data means that managers, scientists, and technicians must ensure their instruments are performing optimally around the clock. Filtering samples before injection into a chromatography instrument is one of the primary ways that technicians can protect their column and instrument from unnecessary wear and excess downtime. Filtration of both the sample and mobile phase prior to analysis helps increase the lifespan of chromatography columns, reducing instrument performance and removing any particles that may interfere with the chromatogram. Sample filtration is most often conducted using syringe filters for their time-effective and easy-to-implement method. Figure 1 A Basic HPLC Configuration Of the four common causes of HPLC column failure – plugging, voids, absorbed sample, and chemical attack – plugging is the most frequently encountered by analytical chemists or analysts. Injection of samples containing particulates will eventually block the column inlet and column packing. The result: high column back pressure and shorter lifetime of the column. Figure 2 Effects of Filters on HAPLC Column Life Scientific Brief Syringe Sample Injector Column Data Recording System Detector Pump Solvent Reservoir 0 500 1000 1500 2000 2500 3000 3500 4000 0 200 400 600 800 1000 Column Backpressure, psig Number of Injections Unltered Pall Competitor 1In the Pall Analytical Technical Guide, we have shown that particulate removal through filtration can extend column life up to 52 times (Figure 2) compared to unfiltered samples. In addition to extending column life, particulate removal also protects the pump, injector, and other components from premature wear. Accurate, reproducible data depends on proper HPLC column performance. Column blockages can be prevented by filtering the mobile phase through a 0.2 μm or 0.45 μm disc filter, filtering the samples through a 0.2 μm or 0.45 μm syringe filter, such as a Pall Acrodisc One™ filter, and utilizing inline filtration within the instrument. Without filtration, particles present in the sample can cause higher system pressures, shifted retention times, poor peak shape, and separation. Difficult to Filter Samples Filters must remove extremely small particles (as small as 0.2 μm) to improve column life and data quality. In the course of daily work, laboratories perform their analyses using a wide variety of starting materials and extraction preparation methods. These differences in materials and methods can result in a wide variety of samples. Some can be filtered easily. Others can have a high number of particles or a wide distribution of particle sizes that prematurely clog the filter or increase the pressure required to filter the sample. To keep workflows running productively, analysts adopt different strategies to remove particulates. These include dilution and centrifugation. While both methodologies will increase the filter’s sample throughput, both are not without challenges and drawbacks. If analysts choose sample dilution, they risk the introduction of errors. Their glassware and technique must be accurate so the true concentration of the starting material can be calculated. If the volumes used are inaccurate, the dilution factors will be incorrect, resulting in a calculation that quantifies the starting concentration incorrectly. Another option that analysts use is sample centrifugation. During this process, the larger particles are forced to the bottom of the sample container, resulting in a cleaner supernatant. The issues with centrifugation are excessive time to process the sample, plus it will not necessarily result in a particle-free supernatant. Fine particles present in a sample require longer times at higher speeds to be pelletized and are often still suspended after centrifugation. While the process can help remove larger particles, a significant amount of particulate matter can remain suspended in the sample that can clog or slow filtration. A third and more effective option for sample processing is the use of a filter with an integrated prefilter. With a prefilter, analysts can increase their filter throughput and processing speed without having to conduct additional workflow steps. These filters utilize a fibrous depth filter over the final membrane filter. For example, in Pall’s Acrodisc® Premium Syringe Filter (PSF), the fibrous depth filter media’s high particulate-holding capacity traps and removes many of the contaminating particles before they reach the final membrane filter. With fewer particles to extract, the final membrane can process even difficult to filter samples at higher volumes and flow rates. To maximize throughput, Pall’s PSF syringe filter utilizes a GxF asymmetric glass fiber prefilter that is 40 μm on the upstream side and tapers to 1 μm on the downstream side. This construction increases throughput versus a symmetrical prefilter. It traps larger particles first, then captures smaller particles deeper in the prefilter’s structure – increasing total filter capacity. Figure 3 The Acrodisc PSF syringe filter has a serial glass fiber (GxF) prefilter to allow for maximum throughput and faster flow rates than standard glass fiber prefilter media. The multi-layered prefilter, rated from > 40 to 1 μm, more effectively traps particulates to extend filter life. Special rib design and proprietary weld ensure robust seal under high operating pressures. Free-floating prefilter prevents premature clogging. Heat sealed membrane ensures particulate retention with no chance of breakthrough. Ample headspace for filter cake to build for optimal throughput. Multi-layered prefilter traps heterogeneous particulate through out the matrix and on the surface, extending filter life.Importance of Prefiltration To determine the extent that prefiltration improves throughput and capacity, two Pall Acrodisc One syringe filter types were tested with a solution. One filter type incorporated wwPTFE membrane and the other had a GxF prefilter and wwPTFE membrane. The test solution was prepared by adding 80 mL of 0.02% latex bead solution to 5 L of water. Five filters were tested by allowing the solution to flow for 4 minutes at a pressure of 30 psi. At the end of 4 minutes, the volume of filtrate was measured in a graduated cylinder. Figure 4 Throughput comparison of latex bead solution collected after 4 minutes. Replicate 0.2 µm wwPTFE GxF/0.2 µm wwPTFE 1 130 mL 170 mL 2 135 mL 182 mL 3 142 mL 175 mL 4 144 mL 186 mL 5 138 mL 178 mL Mean 138 mL 178 mL SD 1.4 1.6 By comparing the amount of sample filtered in four minutes through each filter type, it was shown that the filter with the GxF prefilter had a higher filtration capacity and faster flow rates. The GxF prefilter increased throughput by 29% compared to the filter with only the final membrane. Conclusion Sample conditions can vary dramatically based upon the starting material and steps performed to prepare them for analysis. Some of samples can have high particle counts, be difficult to filter, and reduce HPLC instrument performance and results. There are several methods an analyst can use to process difficult to filter samples. By using a syringe filter with an integrated prefilter, throughput can be increased by 29% without the added time and risk of using dilution or centrifugation techniques. 0 50 100 150 200 0.2 µm wwPTFE GxF/0.2 µm wwPTFE Total throughput (mL) Pall 0.2 µm and GxF/0.2 µm wwPTFE Throughput Comparison Corporate Headquarters Port Washington, NY, USA +1-800-717-7255 toll free (USA) +1-516-484-5400 phone European Headquarters Fribourg, Switzerland +41 (0)26 350 53 00 phone Asia-Pacific Headquarters Singapore +65 6389 6500 phone Visit us on the Web at www.pall.com/lab Contact us at www.pall.com/contact Pall Corporation has offices and plants throughout the world. To locate the Pall office or distributor nearest you, visit www.pall.com/contact. The information provided in this literature was reviewed for accuracy at the time of publication. Product data may be subject to change without notice. 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