Applications

A complete tap water analysis includes the determination of the pH value, the alkalinity and the total water hardness. Both the pH measurement and the pH titration by means of a standard pH electrode suffer from several drawbacks. First, the response time of several minutes is too long and, above all, the stirring rate significantly influences the measured pH value. Unlike these standard pH electrodes, the Aquatrode Plus with its special glass membrane guarantees rapid, correct and very precise pH measurements and pH titrations in solutions that have a low ionic strength or are weakly buffered. Total water hardness is ideally determined by a calcium ion-selective electrode (Ca ISE). In a complexometric titration, calcium and magnesium can be simultaneously determined up to a calcium/magnesium ratio of 10:1. Detection limits for both ions are in the range of 0.01 mmol/L.

This Bulletin describes the complexometric potentiometric titration of metal ions. An ion-selective copper electrode is used to indicate the endpoint of the titration. Since this electrode does not respond directly to complexing agents, the corresponding Cu complex is added to the solution. With the described electrode, it is possible to determine water hardness and to analyze metal concentrations in electroplating baths, metal salts, minerals, and ores. The following metal ions have been determined: Al3+, Ba2+, Bi3+, Ca2+, Co2+, Fe3+, Mg2+, Ni2+, Pb2+, Sr2+, and Zn2+.

This bulletin describes the determination of calcium, magnesium, and alkalinity in water by complexometric titration with EDTA as titrant. It is grouped into two parts, the potentiometric determination and the photometric determination.There are multiple definitions of the different types of water hardness. In this Application Bulletin, the following definitions are used: alkalinity, calcium hardness, magnesium hardness, total hardness, and permanent hardness. Explanations of these definitions and other expressions are provided in the Appendix.Determination of alkalinity during the photometric part is carried out in a separate acid-base titration before the complexometric titration of calcium and magnesium in water. Permanent hardness can be calculated from these values. The determination of calcium and magnesium in beverages (fruit and vegetable juices, wine) is also described.The photometric part includes the determinations of total and calcium hardness and thereby indirectly magnesium hardness using Eriochrome Black T and calconcarboxylic acid as indicators (in accordance with DIN 38406-3).

The determination of the physical and chemical parameters as electrical conductivity, pH value, p and m value (alkalinity), chloride content, the calcium and magnesium hardness, the total hardness, as well as fluoride content are necessary for evaluating the water quality. This bulletin describes how to determine the above mentioned parameters in a single analytical run.Further important parameters in water analysis are the permanganate index (PMI) and the chemical oxygen deman (COD). Therefore, this Bulletin additionally describes the fully automated determination of the PMI according to EN ISO 8467 as well as the determination of the COD according to DIN 38409-44.

This Bulletin gives a survey of standard methods from the field of water analysis. You will also find the analytical instruments required for the respective determinations and references to the corresponding Metrohm Application Bulletins and Application Notes. The following parameters are dealt with: electrical conductivity, pH value, fluoride, ammonium and Kjeldahl nitrogen, anions and cations by means of ion chromatography, heavy metals by means of voltammetry, chemical oxygen demand (COD), water hardness, free chlorine as well as a few other water constituents.

The TitrIC flex I system is used for the fully automatic analysis of water samples using direct measurement, titration, and ion chromatography. The following parameters are determined within a very short time: temperature, conductivity, pH, alkalinity, water hardness, and in parallel, the concentrations of individual anions. Further Metrohm instruments can be incorporated in the existing system at any time and used to measure additional parameters. This Application Bulletin describes in detail the installation instructions for the TitrIC flex I system.

The TitrIC flex II system is used for the fully automatic analysis of water samples using direct measurement, titration, and ion chromatography. The following parameters are determined within a very short time: temperature, conductivity, pH, acid capacity, and in parallel, the concentrations of individual anions and cations with the resulting water hardness and ion balance. Further Metrohm instruments can be incorporated in the existing system at any time and used to measure additional parameters. This Application Bulletin describes in detail the installation instructions for the TitrIC flex II system.

Beer is a popular beverage consumed by millions of people for enjoyment, despite its humble beginnings as a water purification technique in pre-modern times. Brewing beer requires large amounts of water which must adhere to strict alkalinity, hardness, and pH parameters to ensure uniformity in flavor and appearance between each batch. Alkalinity is introduced by carbonates and hydroxides in water which raise and buffer the pH. Hardness, balanced to a large degree by the alkalinity, comes from Ca and Mg ions, mainly present as hydrogen carbonates. Depending on the concentration ranges, the 2035 Process Analyzer or the 2060 Process Analyzer are ideally suited for the fully automatic execution of these important analyses, as well as additional parameters like pH or conductivity. These process analyzers can signal the plant’s distribution system to correct the water chemistry, ensuring consistent product quality. In addition to alkalinity and water hardness, numerous other parameters can also be determined (pH, conductivity, etc.).

The TitrIC flex II system is the perfect combination of titration, direct measurement, and ion chromatography for fully automated analysis of all key parameters. These include pH, conductivity, hardness, anions, cations, as well as the calculation of the ion balance: comprehensive water analysis from one system.

In this application note, a fully automated system is presented which allows the determination of several parameters according to various standards within one analysis. These include conductivity (ISO 7888, EN 27888, ASTM D1125, EPA 120.1), the pH value (EN ISO 10523, ASTM D1293, EPA 150.1), alkalinity (EN ISO 9963, ASTM D1067, EPA 310.1), and Ca/Mg content (ISO 6059, ASTM D1126, EPA 130.2). Additionally, the system transfers the required sample volume into an external titration vessel for the analysis, reducing manual sample preparation. Furthermore, all sensors can be automatically calibrated and the titer of each titrant can also be determined.