ELECTROSPRAY AS INTERFACE IN THE COUPLING OF MICRO HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY TO INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

An electrospray nebulizer with a miniaturized spray chamber is describ ed which is suitable for coupling micro-HPLC with ICP-AES for speciati on of organometallic compounds in microlitre samples, The sensitivity and selectivity, the main characteristics of an interface in such a hy phenated technique, were established, For optimizing these features, e xperiments were tarried out without the use of a chromatographic colum n, Signal-to-background ratios and detection limits were determined by continuously feeding a test solution of metal-acetylacetonates, in me thanol-water (8 + 2, v/v), directly to the nebulizer, at a flow rate o f 10 mu l min(-1), The peak dispersion caused by the interface was mea sured by injecting various volumes of a test solution into a carrier s tream of methanol, at the same how rate, At this low liquid flow rate, the mass detection limits were, even measured by a radially viewed IC P, of the order of 10-100 pg, The time standard deviation of the peak dispersion caused by the interface was 1.25-2 s, equivalent to a volum e standard deviation of 0.2-0.3 mu l, respectively, depending on the a pplied nebulizer gas flow rate, It was found that these times were equ al to the residence times of the analytes in the gas transfer line, co nsisting of the spray chamber and connecting tubing to the ICP torch, These small dispersions allow the combination of high-performance micr o-capillary LC with ICP-AES detection.