Determination of mercury by multisyringe flow injection system with cold-vapor atomic absorption spectrometry.

A new software-controlled time-based multisyringe flow injection system for mercury determination by cold-vapor atomic absorption spectrometry is proposed. Precise known volumes of sample, reducing agent (1.1% SnCl2 in 3% HCl) and carrier (3% HCl) are dispensed into a gas-liquid separation cell with a multisyringe burette coupled with one three-way solenoid valve. An argon flow delivers the reduced mercury to the spectrometer. The optimization of the system was carried out testing reaction coils and gas-liquid separators of different design as well as changing parameters, such as sample and reagents volumes, reagent concentrations and carrier gas flow rate, among others. The analytical curves were obtained within the range 50-5000 ng L(-1). The detection limit (3sigma(b)/S) achieved is 5 ng L(-1). The relative standard deviation (R.S.D.) was 1.4%, evaluated from 16 successive injections of 250 ng L(-1) Hg standard solution. The injection and sample throughput per hour were 44 and 11, respectively. This technique was validated by means of solid and water reference materials with good agreement with the certified values and was successfully applied to fish samples.

Monitoring of total Hg in the river Elbe: FIA-device for on-line digestion.

The development of an apparatus for the on-line sampling, digestion and quantification of total mercury in surface water is described. Detection and quantification is done by flow injection cold vapor atomic absorption spectroscopy (FI-CVAAS). Three digestion methods were tested, chemical, microwave and UV. The influence of the digestion parameters (digestion method, digestion time, microwave power, concentration of oxidation solution) on the recovery of mercury in water of the river Elbe have been investigated. Mercury can be determined almost quantitatively (recovery rate > 85%) with some digestion procedures described. The best results were reached by UV digestion. The technique is fast, simple to handle and robust. Each complete analysis only take four minutes. The working range is 10 to 1000 ng/L. The measuring arrangement has been applied successfully in a governmental monitoring station at Schnackenburg/Elbe, Germany.

On-line determination of mercury in river water at the German monitoring station Schnackenburg/Elbe.

A monitor is described which provides the on-line determination of mercury in river water at concentrations from 20 to 1000 ng/L. The measurement includes an on-line digestion with Br-/BrO3- and UV-radiation. Each determination is controlled by an on-line addition of 50 and 100 ng/L mercury carried out by pre-dilution of a 500 and 1000 ng/L stock solution using sequential injection analysis (SIA). One cycle of analysis takes 20 min and results in nine signals. A five days stand-alone operation has been performed successfully. Details are also published at web page: "http/www.rzbd.fh-hamburg.de/-prmercol".

Flow system device for the on-line determination of total mercury in seawater.

The instrumental set-up for the on-line sampling, digestion and quantification of total mercury in seawater is described. Based on a flow system and cold vapour atomic absorption spectrometry (CVAAS) detection limit was improved by a gold amalgam preconcentration to 0.5 ng l(-1). The manifold design was optimized by the variation of the gas flow, length of reaction coils, shape and material of the gas-liquid separator and flow rate of the reductant. A calibration following the equations p=0.039c+0.0813 (p, peak area; c, concentration) and a correlation coefficient of r=0.9996 was obtained. The relative standard deviation of three measurements of 0.5 ng l(-1) Hg(2+) was 3.8%. The long-time (12 h) reproducibility was 6.2% RSD (n=25) of 0.5 ng l(-1) Hg(2+). With a recovery rate >90% mercury can be determined after on-line UV digestion. For a complete analysis, 6 min is required. The technique is fast, simple to handle and robust. The apparatus is designed for the use on research vessels under sea conditions.

New injection technique for flow injection atomic absorption spectrometry using tubing clamp valves.

Flow injection devices for atomic absorption spectrometry usually are equipped with a sixport-valve consisting of two PTFE-cylinders. This kind of valve can be substituted by an arrangement of tubing clamp valves. The advantages and limits of this new injection technique for flow injection atomic absorption spectrometry are discussed.

Ion exchange micro columns for on-line preconcentration of heavy metalsII. On-line break-through test for zinc, cadmium and lead.

An on-line break-through test for zinc, cadmium and lead has been carried out by means of a flow-through cell and computerized potentiometric stripping analysis. This test has been applied to seventeen ion-exchange materials and enabled within a short time a predecision about the suitability of a resin for a special preconcentration problem. For the determination of the three trace elements in drinking water five ion exchangers are found to be appropriate without restriction and eight resins with some restrictions (not suitable for all three elements, weak matrix influences).