EN 15216:2007 – Characterization of waste – Determination of total dissolved solids (TDS) in water and eluates
1 Scope
This European standard specifies a method for the determination of total dissolved solids (TDS) in water and eluates, provided they are not volatile under the conditions specified or that they do not release water molecules from hydration. It applies to water and eluates containing more than 200 mg/l of total dissolved solids. Samples with lower amounts of dissolved solids can be analyzed by repetition of the drying step.
2 Terms and definitions
For the purposes of this document, the following term and definition applies.
2.1
total dissolved solids
TDS ρ TDS
mass of dissolved constituents per unit volume of water remaining after a specified filtering and drying process NOTE TDS is expressed in milligrams per litre.
3 Principle
The test sample is filtered and then dried in a dish to a constant mass in an oven at (105 ± 3) °C.
4 Sample storage and preparation
During storage, the laboratory sample may be subject to changes which are liable to influence the analysis result. If storage is necessary, samples shall be kept at (4 ± 2) °C.
NOTE Freezing should be avoided due to risk of formation of precipitation.
It is recommended to carry out the test immediately after sampling of the water sample or preparation of the eluate.
5 Equipment
5.1 Drying system thermostatically controlled and capable of maintaining a temperature of (105 ± 3) °C;
e.g. drying oven, infrared system.
5.2 Desiccator with an active drying agent such as silica gel.
5.3 Analytical balance with an accuracy of 1 mg or better.
5.4 Membrane filter (porosity of 0,45 µm).
5.5 Filtration apparatus.
5.6 Evaporation dish or crucible. Temperature tolerant laboratory vessel withstanding 105 °C. Suitable materials are glass, ceramic, porcelain, aluminium and other materials inert to the test portion.
6 Procedure
Filter the test sample through the membrane filter as specified in 5.4 unless it has been membrane filtered before (e. g. eluates prepared according to EN 12457).
Dry the dish, for example in the oven, at (105 ± 3) °C and weigh to the nearest 1 mg (to obtain m a ) after cooling to ambient temperature in the desiccator.
Homogenise and transfer a proper aliquot (V FB ) if necessary in stages, into the dish to ensure that not less than 20 mg and not more than 1 000 mg of dry mass, m D , remains after evaporation to dryness.
Evaporate the sample to dryness by a drying system according to 5.1 and weigh to the nearest 1 mg (to obtain m b ) after cooling to ambient temperature in the desiccator.
The mass of the dry matter, m D , shall be considered constant if, after drying for a further half-hour period, the mass obtained does not differ by more than 0,5 % of the previous value or 2 mg whichever is the greater.
Otherwise, drying shall be repeated until constant mass has been reached.
NOTE If a constant value is not obtained even after drying for a third time, record the value determined last and note this in the test report.
EN 15216:2007 – Characterization of waste – Determination of total dissolved solids (TDS) in water and eluates