An analytical apparatus for measuring a low concentration of a constituent in a stream at a parts per billion level is provided. A single planarizing operation is used for both the bond pad and the detector electrode. A reactant is also introduced into the chamber that reacts with residue organic compounds on the conductive element so as to remove the organic compounds from the nucleating sites to thereby permit more efficient subsequent chemical vapor deposition of conductive elements. The single piece housing including a plurality of steps.