Ensuring samples maintain their original state from collection to analysis is critical to generating accurate and reliable results. When sample integrity is compromised, results can be distorted and undermine research conclusions, quality control, or even regulatory compliance.
It is not always possible to conduct an analysis as soon as a sample is collected. Therefore, a series of measures concerning handling, transportation, and storage are needed to protect the sample from factors that can alter its state, such as degradation and contamination.
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Key Aspects of Sample Integrity
Sample integrity includes processes and conditions that preserve a sample's original state. Maintaining sample integrity involves taking precautions to prevent sample contamination or degradation.
Environmental factors can alter the sample's composition. For instance, some chemicals degrade when exposed to UV light, while volatile compounds may evaporate if the sample is exposed to high temperatures.
Sample contamination (e.g., by dust or other materials) can jeopardize the validity of subsequent analyses. Improper sample handling, the use of unsterile containers, or cross-contamination from other samples can also affect the analysis results.
Over time, chemical or biological changes (e.g., pH, oxidation, microbial growth) can cause the samples to degrade. For example, biological samples like blood or tissue require refrigeration to slow enzymatic activities and preserve their state.
Errors in Chemical Analysis
Methods to Ensure Sample Integrity
Sampling procedures should be performed meticulously, using the right equipment and tools. Controlled environments play an important role in maintaining sample stability, and adhering to standardized protocols is essential.
Storage conditions can significantly impact samples, ultimately affecting data results, reproducibility, and reliability. Refrigeration, freezing, and the use of inert atmospheres (e.g., nitrogen flushing) help maintain sample integrity.
Storing samples at -80 °C is a very common practice used to prevent degradation. For volatile or reactive compounds, specialized storage solutions such as sealed glass containers are often necessary.
Generally, using sterile, tamper-evident containers minimizes contamination risks. Containers need to provide protection from light, air, and moisture and should not interact with the sample.
Chemical agents may also be used to stabilize samples. For instance, sodium thiosulfate is added during microbiological water quality testing to destroy chlorine before samples are transported to the lab. This ensures that results accurately reflect the water quality at sample collection.1
Maintaining a chain of custody also helps preserve sample integrity. Procedures aim to maintain a documented record of every stage of the sample’s journey, from collection to analysis.2 Records of who handled the sample and environmental conditions during transportation ensure traceability and accountability.
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Applications and Implications
Sample integrity is crucial in industries such as pharmaceuticals, food production, and materials testing. Pharmaceutical products undergo rigorous testing to ensure active ingredient concentrations are accurate and free from contaminants. If sample integrity is compromised, there is a risk of product recalls, regulatory violations, or consumer harm.
Maintaining sample integrity is paramount in environmental studies. For the analysis of heavy metals in water, samples need to be stored in acid-washed containers and kept at low temperatures to prevent metal adsorption onto container walls.
Sample integrity directly impacts clinical diagnostics and biomedical research. For example, RNA samples require freezing to preserve molecular structures critical for genetic analysis.3
Compromised blood or tissue samples can lead to incorrect diagnoses or inaccurate research conclusions. Hence, there are guidelines and procedures to preserve the integrity of samples and strengthen the quality of test results produced by clinical laboratories.4
Commercial Relevance
Laboratories often need to comply with accreditation and certification standards to ensure they meet industry-recognized quality and safety criteria. Examples include good laboratory practices (GLP), good manufacturing practices (GMP), and good clinical practices (GCP).
Standards such as ISO 17025 and guidelines from agencies like the FDA ensure that analytical results are reliable and trustworthy. ISO 17025 is an international standard that discusses the requirements for testing and calibration laboratories that want to ensure the accuracy and reliability of their results.
Compliance with ISO 17025 demonstrates a laboratory's commitment to quality, and since test reports can be accepted from one country to another without the need for further testing, it helps facilitate cooperation between laboratories and other bodies.5
The FDA also establishes guidelines and compliance programs that address sample integrity for several types of applications and procedures. Examples include 21 CFR 211.94: Drug product containers and closures, 21 CFR 211.113(b): Control of microbiological contamination, or the investigations operations manual (IOM).6
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Challenges and Future Directions
Preserving sample integrity requires a combination of meticulous protocols and adaptive methodologies. Sampling in remote locations often does not allow immediate access to controlled environments, increasing the risk of degradation during transport. In addition, the high costs associated with preservation technologies can be a barrier, particularly for smaller laboratories.
Emerging technologies aim to overcome these challenges by including real-time monitoring devices, such as sensors integrated into storage containers, to alert users of environmental changes. Advancements in cryopreservation and molecular stabilizers hold promise for preserving highly sensitive samples.
Standardization of protocols and consistent methodologies across laboratories, disciplines, and countries is also crucial because it allows for the comparison of different studies' data and provides reliability and validity within the scientific community.
Conclusion
Maintaining sample integrity in chemical analysis helps ensure accurate results that reflect the true nature of the sample. Across various fields, compromised integrity can lead to flawed data and research conclusions, as well as hindering regulatory compliance.
Innovations in sample preservation, tracking, and monitoring will play a critical role in overcoming current challenges. Moreover, by adhering to best practices and adopting new technologies, laboratories can protect the reliability and reproducibility of their analytical results.
References
- Murray, A. L., Kumpel, E., Peletz, R., Khush, R. S. & Lantagne, D. S. (2018). The effect of sodium thiosulfate dechlorination on fecal indicator bacteria enumeration: laboratory and field data. J Water Health, 16, 70-77.10.2166/wh.2017.077.
- D’anna, T., Puntarello, M., Cannella, G., Scalzo, G., Buscemi, R., Zerbo, S. & Argo, A. (2023). The Chain of Custody in the Era of Modern Forensics: From the Classic Procedures for Gathering Evidence to the New Challenges Related to Digital Data. Healthcare, 11, 634. Available: https://www.mdpi.com/2227-9032/11/5/634
- Najafi, M. (2014). RNA Preservation and Stabilization. Biochem Physiol, 03, 126.10.4172/2168-9652.1000126. Available: https://www.omicsonline.org/open-access-pdfs/rna-preservation-and-stabilization-2168-9652.1000126.pdf
- Joshi, R. K., Sarangi, S. C., Mohapatra, S., Mallick, S. & Datta, S. K. (2023). A Comparative Review of ICMR, WHO, and EMA Guidelines for Good Clinical Laboratory Practices. J Lab Physicians, 15, 179-186.10.1055/s-0042-1757237.
- Huber, L. 2009. Understanding and Implementing ISO/IEC 17025. 5990-4540EN. Available: https://www.demarcheiso17025.com/document/Understanding%20and%20Implementing%20ISO17025.pdf.
- 2024. 2024 Investigations Operations Manual (IOM) [Online]. Available: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/inspection-references/investigations-operations-manual [Accessed 01/12/2024 2024].
Further Reading