7 Causes of Contamination of Laboratory Samples and How to Avoid Them

Laboratory Samples

As of 2023, an astounding 25,505 laboratories are operating across the United States, each conducting a multitude of tests and research every single day. The precision and accuracy of test results from these laboratories are fundamentally dependent on the integrity of the samples used. Should these samples suffer from contamination, it casts a shadow of doubt over the reliability of the test results, consequently impacting the quality of healthcare services that these laboratories can deliver. 

This blog post aims to explore the common causes of laboratory sample contamination and provide a comprehensive guide on how to circumvent them. By doing so, you can safeguard the dependability of laboratory results, a factor of crucial importance in the rapidly growing field of diagnostic and medical laboratories.

Laboratory Practice

One of the most common causes of sample contamination is poor laboratory practice. Whether it’s haphazard handling of samples or inadequate sterilization protocols, poor lab practices can swiftly introduce contaminants into your samples. Even seemingly inconsequential actions, like talking over an open sample or neglecting to change gloves, can drastically affect sample integrity.

Preventing sample contamination is a cornerstone of achieving reliable lab results. This begins with cultivating proper lab practices. Adhering to established protocols, consistently using personal protective equipment, and maintaining a clean work environment all contribute to minimizing contamination.

Storage Of Samples

Improper storage of samples is another prevalent cause of contamination. Samples stored under inappropriate conditions, such as incorrect temperature or humidity levels, can degrade or become conducive to the growth of unwanted organisms. Equally detrimental is the lack of proper labeling and organization of samples, leading to potential mix-ups and cross-contamination.

Understanding the specific storage requirements of each type of sample you work with and ensuring these conditions are met can drastically reduce the risk of contamination.

The Role Of Lab Equipment

The role of lab equipment in sample contamination can’t be overstated. Malfunctioning equipment or equipment used without proper knowledge can introduce a slew of contaminants into the samples. An example of such a vital piece of equipment is an ELISA plate washer. If not used correctly or if malfunctioning, it could either fail to remove unbound substances in the well or could contaminate the wells during the washing process, thereby interfering with assay results. Regular maintenance and calibration of lab instruments, including the ELISA plate washer, is essential to ensure they function as intended and do not become sources of contamination.

Frequent and thorough maintenance of lab equipment can also help stave off contamination. This not only entails cleaning and calibrating the equipment but also ensuring that everyone in the lab knows how to correctly use each piece of equipment. For example, the ELISA plate washer must be operated with care and regularly checked for any signs of wear or malfunction. A properly maintained and correctly used ELISA plate washer will ensure the washing steps in ELISAs are executed effectively, significantly reducing the chances of contamination.


Cross-contamination, or the transfer of substances between samples, is another key player in sample contamination. This often occurs when lab tools are not adequately cleaned between uses or when samples are placed too close together.

Preventing cross-contamination often requires strategic planning. This includes thoughtfully arranging the lab space to minimize contact between samples and always sterilizing tools and surfaces between uses.

The Lab Environment

The lab environment itself can be a source of contamination. Airborne particles, mold spores, or chemical vapors can easily find their way into open samples. Even the dust on the lab bench or the quality of the lab water can have a profound impact on sample integrity.

So controlling the lab environment is a vital part of avoiding sample contamination. Regular cleaning, using air filters, and maintaining appropriate temperature and humidity levels can help keep environmental contaminants at bay.

Reagents Use

The use of contaminated reagents or supplies can introduce unwanted substances into your samples. This is especially true when using non-sterile reagents or supplies that have not been properly stored or handled.

Regularly checking the quality of lab reagents and supplies and ensuring they’re properly stored can prevent them from becoming sources of contamination.

Human Error

Human error, while not as easily categorized as the other causes, is nevertheless a significant factor in sample contamination. Simple mistakes, lapses in judgment, or misunderstandings can all lead to unintentional contamination of samples.

Minimizing human error can be achieved through comprehensive training, clear communication, and encouraging mindfulness during lab work.


The quest for reliable laboratory results begins and ends with the integrity of the samples used. Understanding the common causes of sample contamination and how to avoid them is paramount in this endeavor. 

By implementing the preventative measures discussed here, you can help ensure your lab results accurately reflect the phenomena you’re studying rather than the unintended influence of contaminants. The key takeaway here is that contamination prevention, through diligence and adherence to proper protocols, is within your control.

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