the present invention provides a new device for use in measuring lead levels in biological and environmental samples . using square wave coulometry and colloidal gold particles impregnated on carbon electrodes , the present invention provides a rapid , reliable , portable and inexpensive means of detecting low lead levels . the colloidal gold modified electrodes have microelectrode array characteristics and produce significantly higher stripping detection signals for lead than are produced at bulk gold electrode surfaces . the method is effective in determining levels of lead down to at least 5 μg / dl in blood samples as small as 10 μl .