HPLC is a nearly universal analytical technique applied on a routine basis around the world for separation, quantitation and identification of chemical compounds by industry and academia. Approximately 130,000 conventional HPLC instruments are in use today, with another 15,000 instruments sold yearly. The majority of these instruments use a typical column diameter of 4.6 mm internal diameter (I.D.) with most analytical methods using a flow rate of 1 ml/min. If the typical HPLC is used 20 hours a week, a single conventional HPLC would require 60 L of solvent to operate and generate 60 L of mixed organic/aqueous waste per year. This translates into 8 million liters of solvent produced each year to supply mobile phase for analytical HPLC while producing the equivalent of nearly 40,000 55-gallon drums of mixed waste that must be disposed of per year.

Micro-flow HPLC, that is, liquid chromatography performed with small I.D. chromatography columns, typically 0.3 mm, and low flow rates (4 ul/min), provides a significant savings in solvent usage and mixed waste generation over conventional HPLC. Wide-scale use of micro-flow HPLC would reduce toxic waste generated by chemical researchers in academia and industry by millions of liters per year. By using a 0.3 mm I.D. column on a micro-flow HPLC and reducing the flow rate to 4.3 ul/min so that the linear velocity of the mobile phase through the column is equivalent to a conventional HPLC, a mobile phase volume savings of greater than 99% is realized. Any HPLC method that has been validated and developed over the past decades can be directly transferred to micro-flow HPLC by scaling only column I.D., flow rate, and sample volume, yielding the same separation, sensitivity and retention times, but with a significant savings in solvent usage and mixed waste generation.