Application of Dried Blood Spot Cards combined with liquid chromatography-tandem mass spectrometry to determine eight fat-soluble micronutrients in human blood

The analysis of the fat-soluble vitamins A and E and lipid micronutrients in blood, such as carotenoids, is an important parameter to monitor the micronutrient status in humans. Although the potential of dried blood spot (DBS) cards, the use of this technique for blood sampling and subsequent analysis of these fat-soluble micro nutrients has been poorly or not studied. An analytical method based on DBS cards (FTA (R) DMPK-A) combined with liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) has been developed and validated for the determination of carotenoids (lutein, zeaxanthin, beta-cryptoxanthin and beta-carotene), tocopherols (alpha-tocopherol, gamma-tocopherol and delta-tocopherol) and all-trans-retinol in human blood. Under optimum DBS card extraction conditions, the extraction recoveries of the studied compounds were higher than 72%, the sample matrix effect lower than 17%, and the detection limits at hundred nM concentration levels. The developed method was applied to the analysis of human blood, and the concentration ranges obtained fell within the expected ranges previously reported in healthy adults. Moreover, the influence of hematocrit effect was investigated in a range of 25-55% in order to compare the obtained results to those reported in the literature for the analysis of plasma samples. This method represents an improvement over current techniques reported in the literature due to the use of a non-invasive blood collection method, and moreover, this methodology was for the first time 1) validated for the analysis of all-trans-retinol, tocopherols and carotenoids, and 2) applied for the determination of tocopherols in human blood samples.