The invention relates to a method for calibrating volume of a transfer pipette in a liquid processing robot. The method comprises the steps of allocating a plurality of samples with preset volumes into at least one consumable; estimating the actual volume of a distributed sample, and combining a subsequent standard thought into a software interface without physical modification on the transfer pipette. The invention also relates to a method for improving the volume reproducibility of a transfer pipette in a liquid handling robot, a method for operating a transfer pipette in a liquid handling robot, a method for treating a fluid, a method for determining a liquid contained in a container and a method for determining information about a sucker in a sucker holder.