Chromatography Analyses the Lifespan of Human Plasma

Blood plasma is a component of our blood. It is leftover when red blood cells, white blood cells and other cellular materials are removed from a blood sample. So, it could be viewed as a carrier of essential blood components - but its role in the human body is much more important than that. Outside of the body it has an essential role as a research tool in biological studies.

A recent paper published in the journal Metabolites - Effects of Long-Term Storage at −80 °C on the Human Plasma Metabolome - has looked at the effects of storage on blood plasma. How long can plasma be stored before changes affect it? The researchers used gas and liquid chromatography in their analysis and have suggested a maximum useful life span for storage of plasma samples.

Mainly water in the blood

Plasma makes up about 50% of the body’s blood volume. Mainly water - about 95% by volume - with the remaining constituents including dissolved proteins, hormones, carbon dioxide and oxygen. It carries cells and proteins around the body, but also plays an important role in helping to regulate electrolytic balance within the body and helping to prevent infection and some blood disorders.

It is easily separated from whole blood by initially centrifuging a blood sample until the heavier cells fall to the bottom of the tube allowing the plasma to be removed. Plasma is used in several medical treatments and is also transfused into patients in hospital. Fresh frozen plasma is considered so important that it is on the World Health Organization’s list of essential medicines and is stored in most hospitals as a treatment for trauma and blood loss.

Seven-year itch

But it is its role in medical research that the researchers in Europe report on in the paper in Metabolites. Plasma is one of the biological samples that are needed for high quality research studies. Its use in metabolomics research - the study of chemical processes involving metabolites and cellular processes - can help to understand disease processes and find disease biomarkers. This can then help to provide a deeper understanding of cancer and cardiovascular diseases - hopefully leading to improved diagnosis and treatment.

But many lab studies rely on whatever plasma samples they can get - the majority of plasma is needed for urgent medical use almost as soon as it has been donated. So, what is the oldest plasma samples researchers should use before the metabolites in the samples start to become unreliable or biologically change?

The team used gas and liquid chromatography to analyse samples that had been kept for up to 156 years in -80C storage. Improving chromatography’s ability to detect small changes is discussed in the article, Using Narrow Bore Columns to Enhance Sensitivity for LC-UV and LC-MS Analyses. The team found that most metabolites were stable for up to seven years when stored at -80C and they recommend frozen samples be used soon after sampling.