sample to allow detection of the viable cells accordingly the percent viability can then be readily determined as can be appreciated adding substances such as detergent like compounds surfactants solvents or other compounds that affect membrane polarity membrane fluidity permeability potential gradient etc to the sample to increase the rate at which the molecule or dye enters the cells in order to speed the process other variations that are within the scope of the present invention include adding compounds that affect membrane polarity to decrease the rate of u201c leakage u201d of the converted dye from the cells further esterase enzyme inducing chemicals may be added to increase esterase activity in living cells such as naphthalene or dequalinium acetate or by environmental factors such as heat in addition compounds other than fluorescein diacetate such as calcein am may also be used to detect metabolically active live cells the stability and shelf life of the fluorescein diacetate and other chemicals may be increased by the addition of antioxidants or similar preservatives or by dissolving the fda into other solvents besides acetone or by other stabilizing methods such as lyophilization the fluorescence detection apparatus used may be designed for microscopic surface internal solution and non suspension sample formats also included within the context of the present invention is software that permits the user to interface the fluorescence instrumentation to a computer for direct calculation of percent viability and cell concentration or other data processing or recording formats addition of compounds to reduce background in the sample such as hemoglobin may be utilized rinsing the sample in a buffer solution and centrifuging or filtering or otherwise retaining the cells as they are washed.