Polarographic methods were used to determine glyphosate, morfamquat and diquat in natural waters.

A method based on electrophoresis analysed glyphosate. In this method an electrospray condensation nucleation light scalloping detector was coupled with capillary electrophoresis. An N-acetyl trimethyl-ammonia bromide prerinsing capillary electrode method was employed to reduce the separation time and the adsorption of glyphosphate on the capillary electrophoresis electrode. The protocol consisted of 15 minutes prerinsing of the capillaries and 5 minutes with ammonium nitrate buffer at pH 2.8 before analysis with N-acetyl trimethyl-ammonia bromide solution. The resultant capillary linear wall coating lasted up to 10 hours without bleeding to interfere with the electrospray condensation nucleation light scattering detector signal. Calibration dates were linear over two orders of magnitudes, with an instrumental detection limit of 60 μg L?1 and a method detection limit of 200 μg L?1.

In this technique a mixture of lipophilic surfactant, water, and oil are used to stabilize the system thermodynamically. Compared with other methods, small-size and monodisperse polymeric nanoparticles (≤10 nm) can be obtained through this method. In brief, cetyl trimethyl ammonia bromide solution is prepared in an organic solvent, to which an active ingredient and chitosan solution are added, followed by addition of cross-linking agent under agitation. The evaporation of organic solvent resulted into a dry and translucent water-soluble pellet. To precipitate the surfactant, salt is added to this mixture and then centrifuged. The supernatant is collected, which contains active substance–loaded nanoparticles and later separated by dialysis. Through this method, immobilization of enzymes and encapsulation of oligonucleotides have been reported. Due to the requirement of large quantity of organic solvent and tedious procedure, its usage is limited.

Bromine, resulting from the charged Zn–Br2 battery, is dissolved in a nonaqueous phase electrolyte contained in the aqueous electrolyte. The bromine can be stored as a complex species with quaternary ammonium cations contained in the electrolyte and forming tetramethyl ammonia bromide-bromine, N-ethyl-N-methyl-morpholinium bromide-bromine, trioctyl methyl ammonium chloride-bromine, and polymeric salts such as polydiallyldimethyl ammonia bromide. The quaternary ammonium salts form a high-density emulsion containing bromine and this is separated from the aqueous electrolyte, containing lower amounts of bromine, as a dense liquid. This phase generally contains both a miscible organic solvent and the quaternary ammonium polybromide salt. These methods are a convenient way to contain and store bromine, allow low rates of self-discharge, reduce the reactivity and vapor pressure of bromine, improve safety, and diminish bromine traveling toward the negative electrode where it can be reduced at the zinc electrode. A porous or ionic separator between the positive and the negative electrode also partially prevents the transport of bromine to the zinc electrolyte compartment. The bromine emulsion circulates through the cell with the aqueous electrolyte and is separated by gravity in the storage tank. As a result, the electrolyte contains an aqueous phase with diluted bromine and a phase rich in polybromine. Most of the bromine-rich phase sits at the bottom of a second internal reservoir, contained in a larger reservoir for this electrolyte. In some systems, the positive electrolyte containing bromine enters the cell at the top and leaves from the bottom manifold. This avoids the accumulation of the bromine-rich phase in the bottom of the cell.

One of the problems with the Zn–Br2 battery is the rate of self-discharge caused by the migration of bromine into the zinc electrode compartment. Concentrations of up to 2 mol dm?3 of bromine can be dissolved in an aqueous electrolyte during charge and an ion-exchange membrane is required to reduce bromine transport. If an ion-exchange membrane is not available, the common strategy is to use the quaternary ammonia bromide salt in the bromine electrolyte to reduce bromine migration. The salt absorbs most of the bromine generated during the charge cycle to leave an aqueous solution of approximately 0.1 mol dm?3 concentration and offers the possibility of using a microporous separator. An alternative option when a microporous separator is used is to add propionitrile (PN) as a solvent for the bromine generated during charge. Propionitrile is immiscible in water and helps to decrease the self-discharge rate. An example of a Zn–Br2 cell based on PN–water electrolytes consists of a flat titanium negative electrode (zinc) of 16 cm2 surface area. For the positive electrode (bromine), two different materials were tested: spot-welded platinum gauze to titanium plate and a plastic-bonded carbon electrode. A microporous plastic 0.6 mm in thickness separated the two electrodes forming the negative and positive electrolyte compartments. The gap between each electrode and the separator was 0.7 mm. The electrolyte volumetric flow rate in both compartments was 2 cm3 s?1 and the cell was charged and discharged at a constant current of 25 mA cm?2 at 298 K. It was found that the PN electrolyte containing bromine leaked to the zinc electrode compartment and reduced the overall energy efficiency of the cell to around 38%. However, high energy efficiencies of 66% could be obtained when the plastic separator was interleaved between two filter paper discs. The combination of PN, a separator, and a quaternary ammonia bromide salt increased the overall energy efficiency to 93%. The disadvantages of using PN are its low conductivity, in comparison with the aqueous phase together with its toxicity and flammability. Some advantages of PN addition to the electrolyte include a lower viscosity and a low-energy pumping requirement.