Introduction - Determination of Anions in Natural and Treated Waters - page 40

chloride, iodide, nitrate and thiocyanate. Also formate, bromate, bromide,
chromate, dichromate, chloride, chlorate, iodate and iodide.
Potable waters: phosphate.
Waste waters: ethylene diamine tetracetate.
Sewage effluents: phosphate.
Trade effluents:

Aqueous
precipitation:

fluoride, polythionate and thiosulphate.

There has, in recent years, been a growing interest in applying high performance liquid
chromatography which is not subject to this temperature limitation, to the determination
of the not only volatile compounds, such as aliphatic and polyaromatic hydrocarbons,
saturated and unsaturated aliphatic and polyaromatic hydrocarbons, saturated and
unsaturated aliphatic halogen compounds, haloforms and some esters, phenols and others
but also non-volatile components of water.
Modern high performance liquid chromatography has been developed to a very high
level of performance by the introduction of selective stationary phases of small particle
sizes, resulting in efficient columns with large plate numbers per litre.
There are several types of chromatographic columns used in high performance liquid
chromatography.
Four basic types of elution system are used in high performance liquid
chromatography. This is illustrated below by the systems offered by LKB, Sweden.

The isocratic system
This consists of a solvent delivery for isocratic reversed-phase and gel filtration
chromatography. The isocratic system (Fig. 1.3) provides an economic first step into high
performance liquid chromatography techniques. The system is built around a high
performance, dual-piston, pulse-free pump providing precision flow from 0.01 to 5mL
min −1 .
Any of the following detectors can be used with this system:

• fixed wavelength ultraviolet detector (LKB Unicord 2510);
• variable ultra violet-visible (190-600nm);
• wavelength monitor (LKB 2151);
• rapid diode array spectral detector (LKB 2140);
• refractive index detector (LKB 2142);
• electrochemical detector (LKB 2143);
• wavescan EG software (LKB 2146).

Basic gradient system
This is a simple upgrade of the isocratic system with the facility for gradient elution
techniques and greater functionality (Fig. 1.3(b)). The basic system provides for manual
operating gradient techniques such as reversed-phase, ion exchange and hydrophobic
interaction chromato-graphy. Any of the detectors listed above under the isocratic system
can be used.