In blood collection tubes with additives and gels may be contain substances which can interfere with chromatographic separation and analysis. For this reason it is necessary to know possible interferences of the additives and separations gels before performing HPLC and or LCMSMS analysis.

In the study of the University Hospital Basel six different types of tubes from two different manufacturers were tested.

First 3 ml of physiologic sodium chloride (NaCl 0.9%) was added to each tube. In a second step 3 ml serum were added. After inverting the tubes eight times manually, they were agitated for thirty minutes. At this time it was unknown if there would be a significant if there would be a significant mixing between the gel on the one hand and the sodium chloride and or the serum on the other hand. Afterwards the tubes had been run on a Remedi (Biorad) HPLC system for General Unknown Screening (GUS) analysis. Furthermore this material was analysed with HPLC methods (determination of Tricyclic Antidepressants) and with LCMS/MS (GUS). As the baseline marker sodium chloride was used. The reason is that it has no interfering potential with the methods carried out in this study. For chromatographic routine analyses usually serum is used. 

Blood samples from the clinical chemistry routine analysis in the same tubes as mentioned above were analysed with chromatographic methods in a third study. In this trial the gel penetrates the blood during the centrifugation step. Therefore stronger interferences were expected. 

The study concludes that on the methods used the gel in blood sampling tubes has a medium to strong interference potential. In generals unknown analysis such as Remedi and LCMS main mass the interference may lead to false interpretations. Furthermore it can lead to false quantitative analysis in commercial available HPLC methods (TCA analysis) when only UV detection is used (without spectre analysis, ?DAD?). Therefore for chromatographic methods gel tubes and tubes with additives (LCMS) should not be used.

Source: Fatiga, M., Scholer, A. & Muser, L. (2006). Study of possible Interferences by Additives and Gel Separators in Blood Sampling Tubes on Chromatographic Methods. Clinical Chemical Laboratory. University Hospital Basel