Anders. Graneli

Potentiometric stripping analysis

Abstract The analytical possibilities of potentiometric stripping analysis are outlined. The technique comprises reduction of metal ions at a stationary mercury drop or thin-film electrode. The amalgamated metals are then re-oxidized with mercury(II) ions, and the time—potential behaviour of the mercury electrode is recorded. The technique is compared with d.c. and differential pulse anodic stripping analysis.

A Urea Electrode Based on the Ammonia Probe

Abstract An enzyme electrode specific for the substrate urea is described. The electrode consists of a layer of urease polymerized directly on to the surface of the gas diffusion membrane of an ammonia probe by means of glutaraldehyde. The calibration curves obtained when the electrode is allowed to measure in buffered solutions are discussed in terms of enzyme activity and pH-gradients in the membrane.

A simple automatic phototitrator for the determination of total carbonate and total alkalinity of sea water

Abstract An automatic photometric analyser based on the reversed use of a conventional motor syringe buret and modern optoelectronic components is described. The buret serves as a photometric titration vessel into which sample and reagents are selectively drawn through a set of solenoid valves. It has been applied to the photometric titration of total alkalinity and total carbonate concentration of sea water, giving precisions of 0.10% and 0.13%, respectively.

Potentiometric gas sensors for ammonia based on ion-selective electrodes for silver(I), copper(II) and mercury-(II)

Abstract Potentiometric gas sensors sensitive to ammonia were prepared with ionselective electrodes for silver(I), copper(II) or mercury(II). These electrodes measure the degree of the complexation between the metal ions and ammonia. Ammonia concentrations above 10-3.5M can be measured by these sensors. The response to changes in ammonia concentrations is rapid. The Ag+- and Cu2+-based sensors gave a response of approximately 100 mV log[NH 3 ] while the Hg2+-based sensor gave a 60 mV log [NH 3 ] response.

Successive high-precision determination of calcium and magnesium in sea water with a new probe photometer

Abstract A high-precision method for determining calcium and magnesium successively in sea water is described. The calcium end-point is evaluated with zinc—zincon as indicator, while magnesium is determined with calcon. The computerized method utilizes a new probe photometer based on modern optoelectronic components. The precision for calcium and magnesium is 0.3 ‰ and 0.4 ‰, respectively.

A microcomputer- controlled thermostat

Introduction Careful temperature control is essential for a wide variety of chemical measurements. High-precision potentiometry, for instance, requires thermostatting, since the slope of the straight line E vs log a is highly temperature dependent (E is the measured emf, log a is the logarithm of the activity of species i). The equation describing the relationship between the measured quantity and the activity of species is: