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Rough Vacuum—The Essential but Overlooked Technology

Vacuum is critical to many lab processes, especially while maintaining pharmaceutical quality standards

by Agilent Technologies
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What do mass spectrometers, magnetic resonance imaging (MRI), the Large Hadron Collider (LHC), and guitar amps have in common? An utter reliance on vacuum technology.

Vacuum enables scientific progress in everything from mundane lab tasks to major discoveries in high-energy physics and deep space exploration. 

Cutaway model of a reflex klystron tube by Varian. Photo provided by Erblade

Much of the current research-enabling technology evolved from advances in the mid-20th century by the Varian brothers and their company, Varian Inc (now Agilent Technologies). Within just two decades, they invented the Klystron linear vacuum-tube amp, used in everything from TVs to radio and radar networks, the sputter ion pump that led to ultra-high vacuum, and co-invented nuclear magnetic resonance (NMR) technology. 

The ubiquity of vacuum technology is explained by the various functions vacuum serves. Vacuum is used to prevent electrical breakdown, prevent or control chemical reactions, create “clean” surfaces for deposition, dry materials, manipulate boiling point, move particles over long distances, or apply physical force.

A nuclear magnetic resonance (NMR) spectrometer in use in a chemistry lab. NMR technology is broadly used across science and medicine. Photo provided by iStock

Vacuum is used so prevalently in protocols and processes that it is largely taken for granted. And while high-vacuum instruments like electron microscopes and mass spectrometers tend to be closely monitored and carefully maintained, rough vacuum pumps receive little thought or attention—at least until something goes wrong. With so much lab work depending on them, this can be too little too late.

A day in the pharmaceutical lab

Walk through an average pharmaceutical lab on any given day, and you’re likely to see several applications of vacuum. High quality demands require multiple process steps to be carried out under vacuum, whether it’s within drug discovery, development, manufacturing, packaging, or quality control. We’ll take a whirlwind tour of some common pharma applications and the role vacuum plays.

Chemical analysis in drug discovery and development relies on countless filtration or distillation steps, as do many quality control protocols. Vacuum filtration is needed to manufacture reagents, solvents, and media, or to initiate QC protocols with sample collection or media deaeration. 

Rotary evaporators are another well-used piece of equipment, with vacuum models popular for their operational simplicity and efficiency. Labs requiring high throughput of small sample sizes are likely to add centrifugal concentrators, or vacuum centrifuges, to these protocols. The evaporation driven by reduced pressure enables low temperature processing across several applications including crystallization, concentration or extraction, helping to maintain the quality and stability of the target compounds.

Likewise, vacuum-assisted drying is used for everything from clean glassware to finished product. Water spontaneously forms films on surfaces that can drastically reduce shelf life. Drying is immensely more efficient under vacuum, speeding drying times and reducing heat-related damage and degradation. Lyophilization offers greater stability and quality retention for a wide swath of compounds and is included in numerous stages of development, including the filling and finishing stages of unstable parenterals (sterile injections) like penicillins and cephalosporins. Testing freeze-dried product for residual moisture requires a vacuum oven for loss on drying. 

Degassing is also frequently required to support quality and stability, often to limit oxidation. Vacuum is critical to releasing contaminants in the form of dissolved or trapped gasses, especially important in packaging to extend shelf-life. Packaging leaks typically require vacuum to detect, whether using traditional blue dye techniques, deflection measurement, or pressure decay protocols.

Even chores involving moving fluids and objects are frequently augmented with vacuum, especially where automated. From combining water and oil phases into an emulsion vessel for ointments to shuffling items with vacuum arms in cartoning machines, vacuum performs precision physical labor.

It’s likely that your autoclave is using vacuum as well. HPHV (high pressure high vacuum) steam sterilizers rely on vacuum to enhance steam penetration, removing air pockets and cushions from porous materials or hollow instruments.

Even high- and ultra-high-vacuum instruments rely on rough vacuum pumps to create the low-pressure environment and exhaust compression required for high vacuum pumps, which are unable to compress air to anything close to atmospheric pressure. 

Finding the right pump

With such high dependence on the vacuum units in the lab, it’s important to find the right pump for the job. Upgrading legacy pumps to a more appropriate option can save considerable time, money, and headache in the long run. Reviewing the options is the first step to understanding what’s already in the lab and what might be needed. 

Medium to low vacuum, anything from atmospheric pressure down to around 10-3 Torr, is typically generated using displacement pumps like diaphragm pumps, rotary vane pumps, piston pumps, and dry scroll pumps, or (less frequently) water aspirators or bench vacuum. Lower pressures require high vacuum pumps to capture meandering gas molecules. 

Choosing the right vacuum pump depends on several factors: the base pressure required and pump speed at operating pressure, tolerance for oil back-streaming in the process, process gas limitations, cost of ownership (initial cost plus maintenance), ease of maintenance, noise/vibration tolerance and any additional requirements by application like corrosion resistance. They should also be sized appropriately for the instrument or application. Each type of pump has a distinct efficiency curve across operating pressures, so the efficiency of pump options given a particular pressure must be considered. 

Diaphragm pumps

Diaphragm pumps use pistons, one-way valves, and deformable membranes to draw air out of one chamber and push it into another. The ultimate vacuum, or pressure capability, is limited by the inherent ‘leakiness’ of the valves, but multichambered units with sequential pumps reduce it considerably. Maintenance can grow complicated, and cost varies widely across models and features. 

Piston pumps

Piston pumps come in multiple varieties and configurations. Some use oil for sealing, while others rely on o-ring style seals. Oil-sealing models are better protected against corrosive gasses, but add to the maintenance requirements. They’re typically very noisy. Cost, maintenance, and effectiveness are highly variable between models. 

Rotary vane pumps

Oil-sealed rotary vane (RVP) pumps, sometimes called oil pumps or “vane pumps”, are still the most commonly used rough pumps across industries. They’re highly effective, producing vacuum down to pressures of 10-3 to 10-4 Torr, and often the lowest initial cost. They operate by using centrifugal force to press vanes against the sides of the chamber isolating, compressing, then venting gas. Their main drawbacks are due to the oil—the risk of sample contamination by back-streaming oil, tendency to leak, oil disposal costs, and higher maintenance demands.

Scroll pumps

Oil-free scroll pumps are a solid bet for processes that can’t tolerate oil contamination risks. While base models are slightly less effective than oil pumps, performance can be boosted with dual-stage pumps. Though initial cost is still typically higher than oil pumps, the cost of ownership is lower than both rotary vane and diaphragm pumps. Their popularity is on the rise due to greater efficiency, lower operating costs, environmental friendliness, and near silent operation.   

Mechanisms of rough vacuum pump types. Photo provided by Agilent.

Avoiding Catastrophe

Selecting the right pump is just the first step in finding reliable solutions. Pharmaceutical labs especially need to ensure uptime, availability, performance, and productivity are all maximized. These contribute, along with cost of ownership and instrument downtime, to the lifetime cost of a vacuum pump. 

Ease of maintenance on oil-free scroll pumps is demonstrated with tip seal replacement on Agilent’s IDP-3 pump. Photo provided by Agilent.

To prevent vacuum-related lab disasters, the pumps need to be properly maintained, with requirements varying by pump type. The more critical a pump is to the lab workflows, the more catastrophic a failure and subsequent downtime can be, which is reason enough to depend on trusted names in the industry. 

Agilent Vacuum, starting as Varian Inc, has partnered with major scientific institutions and installations and manufacturers of proton therapy systems around the world for decades. In addition to supporting bench work in labs spanning industries, Agilent vacuum pumps have supported and continue to support major scientific breakthroughs and medical advances, from the Large Hadron Collider at CERN to the latest deep space survey projects.

Agilent Vacuum also provides ongoing service and repair through partnership with EMSAR, a multivendor Agilent certified service for all types of vacuum pumps. They minimize downtime with local same-day turn around and 24-hour turn around on all exchange pumps and ship worldwide.

Learn more about Scroll Pumps, Dry, Quiet, Oil-Free Vacuum Pumps | Agilent.