Halogens – (Fluorine, Chlorine, Bromine, Iodine)

The halogen analytics is based on the conversion of fluorine, chlorine, bromine or iodine into an analyzable solution. For this purpose, combustion and pyrohydrolysis are used, which are done as tube, Schöniger or Wickbold combustions.

Halogens, which are contained within the combustion products are absorbed by process-depending reagents and converted into fluoride, chloride, bromide or iodide-ions. As detection methods the ICP-AES, ion-sensitive electrodes as well as titrimetric, microcoulometric, and ion-chromatographic measurements are applied.

In the ICP-AES the analyte is detected spectroscopically after exication/ionization in a plasma. The ion-sensitive electrode determines the ion concentration by voltage measurement against a reference electrode. For the titrimetric methods, we have two main approaches availabe. For chlorine and bromine as major or minor component, titrations against standards and color indicators or electrodes are applicable. For detections in the range of traces the microcoulometric titration is applied. Within the ion chromatography, fluoride, chloride, bromide or iodide-ions are separated from other ions and subsequently quantified.

S – Sulfur

For the conversion of sulfur into an analyzable form, we have various method approaches available. One option is the combustion of the sample in oxygen. Released sulfur oxides are absorbed in hydrogen peroxide solution and converted into sulfate ions. The combustion can be done as Schöniger, Wickbold or tube combustion. Alternatively, sulfur can be converted into an analyzable form after pressure digestion with oxidizing acids.

For the quantification of sulfur ICP-AES-, IR-spectroscopic as well as titrimetric and ion chromatographic methods can be applied. Within the ICP-AES, sulfur is detected spectroscopically after ionization in a plasma. The IR-spectroscopy is based on the detection of the resulting sulfur dioxide from a combustion.

For the titrimetric methods, we have two main approaches available. For sulfur as a major or minor component, the titration with barium ions and color indicator can be applied. For detections in the range of traces, the microcoulometric titration with electrolytically generated triiodine ions is used. Within the ion chromatography, sulfate is separated from other ions and subsequently quantified.

Also the XRF-spectrometry can be used to determine sulfur in some liquid matrices. After excitation of the sample by X-rays, the intensity of the resulting fluorescence radiation is analyzed.

P – Phosphorus

For the determination of phosphorus, the sample to be analyzed is converted into an analyzable solution by using high-purity reagents. Depending on the sample matrix and the expected phosphorus content, different digestion systems are available. The detection is performed by optical emission spectrometry with an inductively coupled plasma (ICP-AES). The digestion solution is transported into an argon plasma after nebulisation and the phosphorus atoms are excited to emit light. The wavelength of the emitted light is element-specific and is detected after spectral decomposition within a polychromator by using CID-technology.

O – Oxygen

A broad spectrum of methods enables us, to perform oxygen analyses on almost any matrix. For organic substances the pyrolysis is used. The oxygen compounds that are released by the thermochemical process are converted to carbon monoxide and then oxidized. The detection of oxygen is done conductometrically in the form of carbon dioxide.

Inorganic, organometallic and fluorine-, phosphorus- and silicon-containing substances can also be analyzed by pyrolysis. A special high-temperature furnace and the adding of reaction-accelerating additives enable the complete conversion of containing oxygen compounds to carbon monoxide with subsequent thermal conductivity detection.

Alternatively, inorganic, organometallic as well as boron-, fluorine- and phosphorus-containing samples can be melted in a graphite capsule by vacuum hot extraction at up to 2700°C. The oxygen content is determined by detecting the resulting carbon monoxide by infrared spectroscopy.

Especially for organometallic compounds, a combination of pyrolysis and vacuum hot extraction is possible. In this way, both volatile (e.g. from water) and stable oxygen components (e.g. from metal oxides) are detected.

Oxygen trace analyses of metals, alloys or ceramic materials can be conducted by carrier gas hot extraction. By melting the sample at up to 2700°C carbon monoxide is formed, which is detected by infrared spectroscopy. For very stable oxides, melt-forming additives are used.

N – Nitrogen

Depending on the sample matrix and nitrogen concentration, different method approaches are available. For the determination of nitrogen as a main component, the sample is combusted in oxygen. After reduction of the resulting nitrogen oxides and binding of interfering reaction gases, the nitrogen content is determined gas volumetrically or by thermal conductivity detection.

For nitrogen trace analyses either methods by chemiluminescence or carrier gas hot extraction are used, depending on the matrix.

The detection by chemiluminescence measuring cell is done after combustion of the sample and ozonization of the released nitrogen oxides.

The carrier gas hot extraction is especially applicable for metals, alloys or ceramic materials. It allows a melting of the sample with melt-forming additives at up to 2700°C. The nitrogen concentration is determined by thermal conductivity measuring cell.

Nitrogen determinations according to Kjeldahl are also possible. With this method, nitrogen is determined titrimetrically after sulfuric acid digestion and conversion of the resulting ammonium sulfate into the form of ammonia.

H – Hydrogen

To determine the hydrogen content, the sample is burned in oxygen. The combustion water formed is detected by infrared spectroscopy and converted to the hydrogen content of the sample.

For hydrogen trace analyses the carrier gas hot extraction is applied. The method is applicable e.g. for metals, alloys or ceramic materials. The hydrogen content is released by melting the sample with melt-forming additives at temperatures up to 2100°C. The detection is done by a thermal conductivity measuring cell or as water by an infrared measuring cell.

A determination of diffusible hydrogen in metals or alloys is also possible by carrier gas hot extraction.

Hydrogen in the form of water can be determined by Karl Fischer Titration

C – Carbon

The carbon analysis is based on various combustion methods in oxygen. The aim is a complete oxidation of the carbon to carbon dioxide. For this purpose, methods with temperatures of up to 1300°C are used, depending on the sample matrix. For the analysis of compounds that are difficult to combust, melt-forming or combustion-accelerating additives and variable heating times are used. The detection of the released carbon dioxide is performed conductometrically or by infrared spectroscopy.

The determination of carbon in the form of carbonate-C is also performed conductometrically after acid extraction and carbon dioxide absorption.

A distinction between inorganic (TIC) and organic (TOC) bound carbon can be done. The organic carbon (TOC) is determined as the difference between the two analyzed parameters “total carbon” (TC) and “inorganic carbon content” (TIC).