Abstract: A method and apparatus for non-invasive extraction and/or detection of chemicals such as heavy metals, drugs such as cocaine and analytes such as blood glucose has been developed. A patch or hydrogel containing a reagent such as N-methyl pyrrole, or a similar compound, is used to extract the chemical or analyte to be measured through the skin or hair. This method is most useful for detecting analytes which are generally present in relatively constant blood concentrations. The method is particularly useful for the detection of heavy metals such as lead, lithium, copper, iron, and has been demonstrated to be useful with drugs such as cocaine and acetominaphen, and metabolic analytes like blood glucose. In the preferred embodiment, the method involves the use of the water miscible solvent N-methyl pyrrolidone (NMP) in an aqueous solution which is incorporated into an adsorbent pad or hydrogel.