Eliminating Contamination in Analytical Experiments

By David Wasescha, Director of Biosafety Products

On November 09, 2020 in Articles

A key pain point for any scientist is the realization that experimental samples have become contaminated. Instead of insightful results and discussion, confusion and frustration arise. Was a sample tube improperly aliquoted? Were reagents made incorrectly? Perhaps an instrument was not properly calibrated? While sometimes the problem is easily solvable, complex multi-step experiments can result in lengthy investigational measures that progress without end in sight.

For scientists performing HPLC separations, resolving contamination issues can be especially challenging due to the sensitivity of various paired detection methods. Ultraviolet Visible Spectroscopy (UV-Vis) or extremely sensitive detection using Mass Spectrometry can identify trace analyte concentrations as low as single picograms per milliliter (pg/mL), thus demanding complete elimination of contamination from a sample to deliver accurate results.

Image: Two ‘blank’ chromatogram samples eluted and detected with liquid chromatography-triple quadrupole mass spectrometry are displayed. A true blank sample (left) and an identical blank contaminated with analyte (right) are shown.

With so many possible sources of contamination in the lab, how can you narrow down your risk? For starters, ensure that your glassware is unmistakably clean.

Labware Selection

Labware should always be evaluated prior to use. All labware should be stored in a manner that prevents ingress of dust or other contaminants that may interfere with an experiment. Glassware can be safely stored in a laboratory washer between uses, or should be stored with a lids on or in drawers. Any marring, chips, cloudiness or stains on labware should be carefully evaluated, discarding pieces that may harbor unwanted contaminants or leach material into an experiment.

For most analytical work, glass vessels are widely adopted for their reusability and broad compatibility with most chemistries – particularly mobile phases, needle rinses, and other HPLC solutions. Even glass HPLC vials may be reused after careful processing in a laboratory washer. When using plastic labware, ensure that labware material (often polypropylene) is chemically compatible with any solutions or analytes used in an experiment. Any known incompatibilities with chemicals should be reason to select different labware to eliminate potential issues with degradation of a vessel, or leaching of contaminants into precious samples. Alternatively, some plastic labware may be available with silanized coatings, which can reduce background noise and extend usable life of the consumable by improving reusability.

Washing

After using a piece of labware, thorough cleaning should commence immediately to prevent analytes and other unwanted chemicals from causing damage such as etching. Etching can leave unwanted damage, which may harbor chemicals or even obstruct visual markers such as meniscus lines on volumetric flasks. Using a laboratory glassware washer provides a fast, powerful, consistent means for processing of glassware batches, helping you keep focus on other important tasks in the laboratory.

When processing used labware in a glassware washer, it is important to identify cleaning parameters that effectively clean the pieces from your experiments. A laboratory washer should include a robust operating system that allows for program customization to reach hot temperatures, deliver pure water rinses, conductivity (cleanliness) measurement, and data storage to trace washing history in the event of a laboratory investigation. It is also imperative to select racks and inserts that are designed specifically designed for laboratory items to ensure thorough washing is not impeded. Narrow-neck items, such as volumetric flasks, should be washed on spindles to ensure delivery of water and detergent directly into the flask bodies to remove analyte and other chemical residues. Lids, caps, stir bars, and other supportive items should be processed using baskets that allow for direct contact with powerful water pressure from washer spray arms.

Careful selection of detergent and rinse aid are also key steps in reduction of contamination from labware. Laboratory grade detergents designed for automatic washers should be used because of their potency and chemical purity, with blends leaving out unnecessary chemicals that may disrupt sensitive analytical instruments. Detergents designed for residential use frequently contain agents that leave unwanted residues on washed labware. Additionally, laboratory-grade rinse aids should be used to ensure the free rinsing of any detergents used to process labware. Ensuring free-rinsing of detergent is a key step to ensuring batch cleanliness. Upon completion of washing it is important to validate batch cleaning effectiveness, which can be accomplished using techniques such as conductivity monitoring or detection of detergent residue. Regular validation should take place to monitor cleaning effectiveness through all batches.

Ensuring Consistency

With the use of a laboratory glassware washer, it is possible to soundly eliminate the risk of contamination from reusable labware. By removing risk from reusable labware, scientists can reduce environmental impact by using fewer consumables, worry less about experimental failures, and spend less time on laboratory investigations into frustrating sample contamination.

RELATED ARTICLE FORTHCOMING: Methods for Evaluating Glassware Cleanliness