I want to check the different serum levels of vitamins (D, C, B12) and minerals (zinc, selenium) in two group of study. So my question is that how long can I store the serum samples for tests in -45 C. Is -45 C temp will be sufficient to store the serum for long term preservation ( about 9 month). Please any one guide me.
Hello Hamidreza Safari
You can store plasma or serum samples in -80 degree C for years. At -45 degree C serum or plasma samples can be stored to a maximum of 2-3 months. I doubt whether one could store serum or plasma samples for 9 months at -45-degree C. I would suggest you store the blood plasma or serum samples at -80 degree C if you have to store them for 9 months.
For more information on storage of biological samples you may refer to the article below.
https://www.bluechiip.com/wp-content/uploads/2018/01/Storage-of-Human-Biospecimens-Selection-of-the-Optimal-Storage-Temperature.pdf
Best.
Most minerals (analyzed using atomic absorption method) are stable (even at -20 degree). Most vitamins should be also stable if not-repeatedly thawed. One way is to test a sub-sample at the beginning and same samples analyzed after storage. You may get more information from the references cited below:
1) Kachhawa, Kamal, et al. "Study of the stability of various biochemical analytes in samples stored at different predefined storage conditions at an accredited laboratory of India." Journal of laboratory physicians 9.01 (2017): 011-015.
2) Leu, Monica, et al. "Quality assessment of 25 (OH) D, insulin, total cholesterol, triglycerides, and potassium in 40-year-old frozen serum." Epidemiology Research International 2015 (2015).
I have no experience for B12 and D, bur for Vitamin C you can stabilize the plasma (best an aliquot) with perchloric acid (5%) 1:1. Than it is stable for month, however, in our hands at -80 °C. -45 °C is an unusual temp.