Abstract: The method and apparatus for the preparation of phosphatidylcholine/dipalmitoylphosphatidic acid membranes, containing enzymes or antibodies, cast on glass microfiber or polycarbonate ultrafiltration membranes are described [cf. Anal. Chem., 1995, 67, 936; Electroanalysis (N.Y.), 1995, 7, 531, 1082]. The membranes were used in flow injection amperometric determinations of (i) substrates (e.g., acetylcholine, penicillin and urea) of hydrolytic enzymes, and (ii) antigens (e.g., thyroxine and triazine herbicides).

Abstract: This work reports on the fabrication of a mini column packed with controlled pore glass and glass wool, and its application for the on-line pre-concentration of lead with the aid of an anionic surfactant (sodium dodecyl sulphate, SDS) and AAS detection. Lead reacts with SDS in a high-ionic-strength environment, and the product is retained and pre-concentrated on a high-surface-area substrate like glass wool. The intervention of controlled pore glass increases the active surface of glasswool and prevents its accumulation into a sticky mass after wetting. Washing the mini column with a methanolic solution of HNO3, causes the retained micellar face to be eluted, and consequently the lead content can be determined with AAS. A pre-concentration factor of 50 along with a signal enhancement due to the combined presence of SDS and methanol yields a detection limit of 1.5 µg/L-1. The correlation coefficient of the calibration curve is 0.999, and the linear range 5-500 µg/L-1. The method was used for the determination of lead in water and wastewater with good results.