I use microcapillary tubes (0.5 µl) to measure nectar volume in Dianthus carthusianorum flowers (= very narrow corolla tube and low nectar volume from ca 0.25 to 1 µl). The nectar volume is easy, it is calculated from the hight of nectar column in the capillary, but I can't get the nectar out of the capillary tube to measure sugar concentration with a refractometer. What is the trick? How do you get the nectar out? Or is there a better way to collect low amounts of nectar?