Sodium borohydride-based hydride generation was automated by using programmable flow within the lab-on-valve module. Mercury vapor, generated in the reaction mixture, was extracted in a gas/liquid separator. The gas-expansion separator was miniaturized and compared with the performance of a novel gas separator that exploits the combination of Venturi effect and reduced pressure. Cold vapor atomic spectroscopy was used as a model system, with detection of mercury by absorption at 254 nm and limit of detection of 9 microg of Hg/L, using 300 microL of sample and 100 microL of borohydride. This work introduces, for the first time, sequential injection technique for hydride generation, highlights advantages of using programmable flow, and outlines means for miniaturization of assays based on spectroscopy of volatile species.

An automatically renewable microcolumn, subjected to operation by programmable flow, is presented and for the first time used for separation and quantification of biomolecules on Sepharose Protein A beads, with absorbance measurement at 280 nm and a detection limit of 6 ng mouse IgG microL(-1).

Monitoring extracellular acidification rates (ECARs) is important for the study of cellular activities, since it allows for the evaluation of factors that alter metabolic function, such as stimulants, inhibitors, toxins as well as receptor and non-receptor mediated events. While the light addressable potentiometric sensor (Cytosensor Microphysiometer) has been the principal tool for ECARs measurement in the past, this work introduces a novel method that exploits an immobilized pH indicator on the surface of microcarrier beads (Sephadex) and is probed with a fiber optic coupled spectrophotometer. Likewise, live cells under investigation were also immobilized on microcarrier beads (Cytopore). These beads are metered, transported and monitored within a microfluidic system, termed as the Lab-on-Valve (LOV). Use of carrier beads in conjunction with Bead Injection Spectrophotometry and a Lab-on-Valve module (BIS-LOV), makes ECAR measurements reliable and automated. The feasibility of the BIS-LOV approach is demonstrated measuring ECARs of the mouse hepatocyte cell line, TABX.2S, grown on Cytopore beads packed within the central channel of the LOV system. These immobilized cells were perfused in a phosphate buffer carrier solution (capacity: 1 mmol L(-1), pH 7.4). Protons extruded from 10(5) to 10(6) cells were accumulated during a stopped flow period of 220 s followed by a pH measurement, detected by changes in absorbance of the pH indicator bonded to the microcarrier beads. Addition of metabolic inhibitors (sodium azide, oxamic acid) to the carrier buffer solution can induced an increase or decrease of the basal proton extrusion rate in a very reproducible manner. Comparison of the BIS-LOV technique to the Cytosensor microphysiometer and literature confirms the validity of this novel approach, highlighting its advantages and suggesting future improvements that will make the BIS-LOV a practical tool for routine ECARs measurement.

Chromatomembrane cells (CMC) operate as unique manifolds for extraction and preconcentration procedures in computer controlled flow-injection-analysis (FIA). By coupling to an ion chromatograph and to a conductometer, respectively, instrumentation is obtained that allows the pretreatment and the detection of ozone- and ammonia-containing samples after absorption of the gaseous constituents of air inside a chromatomembrane cell. The analysis of air even in the presence of liquid aerosols is discussed.