Comparison of Single-Use Funnels vs. Reusable Funnels for the Membrane Filtration Method in QC Microbiology

Reusable and single-use funnels are both viable options to perform membrane filtration in the course of quality control to ensure the microbiological safety of final products. Single-use funnels are seen as more convenient, accurate and safe in bioburden testing, while reusable ones are thought to be cheaper and less wasteful. However, the picture changes when analyzing the pros and cons more comprehensively, and with respect to a wider range of criteria, accuracy and results repeatability , total costs and waste, convenience and flexibility, and staff safety.

Accuracy and Repeatability of Bioburden Testing Results

Every test performed with single-use funnels for membrane filtration starts with a sterile product that will not introduce adventitious microorganisms, so the results generated should be the same every time. The same cannot be said of reusable funnels.

The cleaning process introduces the risk that soap residues will interfere with samples and results. Nitrate-based detergents pose a particular problem as their residues hinder microbial growth. Similarly, there is the potential that the sterilization process fails to eradicate all microorganisms, creating a further contamination risk. Wear and tear on funnels can also lead to sample bypass.

While reusable funnels can deliver accurate, repeatable results, these risks have notable but hard-to-quantify implications that make single-use products an attractive option for bioburden testing.

Operating Time

Single-use filtration units can save precious time, taking only a second to attach a funnel to a plate for set-up. Reusable funnels, on the other hand, require several steps: flaming the manifold head as well as the funnel’s base and inside, cooling with sterile water, placing the filter on the manifold head, and installing the manifold on the filter.

Costs and Waste: Reusable vs. Single-use Funnels

The operational efficiency that single-use funnels provide is one factor that offsets the extra spending on the products themselves. Another factor is reduced spending in other areas.

Facilities that use reusable funnels need autoclaves and other pieces of cleaning and sterilization equipment, so in addition to the necessary capital investment they also need to spend more on the human resources and electricity required. A boiling water bath can cost as much as EUR 1500 and EUR 20 for a liter of the alcohol used in the flaming process to ensure sterility. Putting reusable funnels through a 324-liter autoclave consumes around 18kW of electricity, adding further to the costs.

These factors also offset the perceived environmental benefits of reusable funnels. While single-use funnels may appear wasteful at first glance, they are made of recyclable materials and have no hidden environmental impacts. Manufacturers often provide information on how to recycle single-use products for sustainable waste management. Reusable funnels, in contrast, are associated with a range of hidden impacts, including the amount of energy, water and detergent needed to clean them.

Companies that factor the environmental costs of autoclaving, flaming or soaking in boiling water into their efforts to go green, rather than focus solely on reducing solid waste, stand to establish a more accurate picture of their environmental impact.

Flyer: Waste management with single-use filtration funnels

Convenience and Flexibility in Bioburden Testing

The convenience of single-use funnels is a big part of their appeal: they make membrane filtration and the transfer of the membranes to agar plates much easier to do. The single-use workflow is free from the risk of tearing and rippling of membrane filters that affects users of reusable funnels.

Another key factor is that single-use funnels eliminate cleaning and sterilization steps. A facility that normally analyzes 10 samples a day may have 12 reusable funnels. On normal days, that gives the facility the capacity to access a clean, sterilized funnel at any time. However, when the need arises to process 20 samples to a tight deadline, not enough sterilized funnels would be available. If funnels are away for cleaning or sterilization, which typically takes one or two hours, sample analyses will be delayed and downtimes the inevitable consequence.

Operator Safety During Bioburden Testing

Cleaning and sterilization pose risks to operators, most notably during the flaming process. Flaming is performed without incident the vast majority of the time, but the combination of flames and flammable fumes involved in the process has caused multiple serious safety events.

The blistering of skin is the most common such occurrence. This happens when the operator holds the funnel during flaming but does not realize the stainless steel has heated rapidly. Some operators have even burnt their arms during flaming. Flaming can also pose a fire hazard for the whole laboratory, as well as its staff.

Single-use funnels for membrane filtration in the course of bioburden testing are free from these risks. Operators simply attach a funnel to a plate and dispose of it after use, freeing them from the dangers associated with flaming and other ways of sterilizing reusable equipment.

Flyer: Improved safety of your membrane filtration workflow with single-use funnels

In a Nutshell

The accuracy, convenience, and safety of single-use funnels make these products well suited to the needs of quality control laboratories in pharmaceutical manufacturing. Choosing single-use funnels enables them to access the equipment they need when they need it, deliver accurate, repeatable results and maximize safety.

This can be achieved without incurring many of the upfront and running costs and without the environmental impacts associated with reusable funnels, making single-use products an attractive alternative for even the most cost and waste conscious of microbiological laboratories.

Watch the webinar: 6 impacts of your membrane filtration funnel choice on your workflow

EZ-Fit^® Filtration Units

Bioburden testing won’t be a burden when you use EZ-Fit^® Filtration Units. The sterilized, ready-to-use disposable filtration devices for microbial membrane filtation can streamline your workflow, save time and give you highly reliable microbial enumeration results. Filter your liquid sample, then transfer the membrane onto an agar plate or add liquid media from an ampoule to culture the captured organisms.

EZ-Fit^® pink units come with a wide range of membranes from 0.22 to 0.8 μm for maximum versatility to suit all applications. The new patented drain design speeds up processing of turbid and hard-to-filter matrices.

EZ-Fit^® blue units give you extra flexibility: after filtration, either transfer the membrane to an agar plate or add liquid media and convert the device into a Petri dish