Solvent analysis

Storage tanks on a chemical production plant

On this page, you will find information on:

  • Impurity analysis in solvents: Trace metals, anions and cations, and acid/hydroxyl/saponification number
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Solvent analysis in compliance with standards

Standards

There are many international standards relating to the quality control of solvents.

Click on the link below to find an overview of some standards and the analytical solutions provided by Metrohm.

> Go to the standards overview


Water in organic solvents

Organic solvents are highly lipophilic. This characteristic allows them to dissolve oils, fats, resins, rubber, and plastics. They find widespread application in paints, coatings, adhesives, and detergents. Additionally, they are indispensable in the production of cosmetics, agrochemical products, polymers, and rubbers, to name but a few.

In spite of environmental concerns and potential health hazards, organic solvents (hydrocarbon, chlorinated, oxygenated as well as nitrogen- and sulfur-containing) are still widely used because of their unparalleled performance.

Amber bottles containing solvents

In organic solvents, the most common solvent – water – is the most frequently found impurity. It interferes with many reactions, which is why the determination of the water content is crucial. Karl Fischer titration is a reliable, accurate, and widely recognized method for this purpose. Metrohm offers an extensive product portfolio as well as a wide range of applications.

> Learn more about Metrohm Karl Fischer titration

Methylcyclohexane

Methylcyclohexane is a cycloaliphatic hydrocarbon that is less volatile than cyclohexane because of an additional methyl group. Its solubility lies between that of aliphatic and aromatic hydrocarbons. It is an ideal solvent for fats, oils, bitumen, rubber, and nonpolar resins.

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Ethylene dichloride

For most organic compounds, chlorinated solvents have a better dissolving power than their nonchlorinated counterparts. Although the use of chlorinated solvents is declining because of environmental concerns, they are still of crucial importance in certain industries. Ethylene dichloride, one of the most stable chlorinated hydrocarbons, for example, is used for making vinyl chloride and numerous chlorinated polymers.

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Piperidine

Piperidine and its derivatives are important solvents and building blocks used in the production of numerous drugs and other fine chemicals.

Karl Fischer titration allows you to determine the water content in these solvents accurately and easily.

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Further applications and products

More solvents …

Karl Fischer titration is capable of determining water also in harsh production environments. Download the poster to read more about atline water determination in acetonitrile, phenol, methanol, and isopropanol.

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Automation …

Water determination by Karl Fischer titration can be easily automated to improve repeatability and precision of results and reduce the time and work required for the determination.

Read the poster on automated KF titration Read more about automation for KF titration

NIR spectroscopy for water determination …

As an alternative to Karl Fischer titration, NIR spectroscopy can also be applied for determining water in solvents. This method delivers results in virtually no time and does not require any sample preparation. Here, the purity of a chlorinated solvent mixture is monitored in terms of water and methanol impurities.

Go to the application Learn more about NIR spectroscopy

Monitoring impurities in solvents

Trace metals with voltammetry

884 Professional VA voltammetry system

In the chemical industry, solvents are used in large amounts and in a multitude of processes. Particularly for mediating and moderating chemical reactions, high-purity solvents are required. Trace metal contaminations such as iron, zinc, and lead can be sensitively and accurately determined using stripping voltammetry at the Hanging Mercury Drop Electrode (HMDE).

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Anions and cations with ion chromatography

For simultaneous anion and cation determination, ion chromatography is ideally suited, whether you want to determine anions in dipolar aprotic solvents such as N,N-dimethylacetamide or in hydrophobic apolar toluene.

> Learn more about ion chromatography

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Acid, hydroxyl, and saponification number and metal content by titration

Acidity in solvents can have various causes. It may originate in residual acidity from the manufacturing process or point to degradation reactions taking place during transport and storage, for example.

The acidity is expressed as the total acid number (TAN, or acid value, AV) in mg KOH per g sample. The TAN is determined by titration, a convenient, reliable, and rapid method that is stipulated in numerous international standards. Similarly, titration is the method of choice for determining a whole range of important quality parameters for solvents and paints, from the purity of esters or the hydroxyl, bromine, and saponification number to the metal content of liquid paint driers.

> Learn more about titration

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Solvent recovery/recycling

If spent solvents are to be disposed of after use, halogenated solvents have to be treated separately to ensure proper disposal. Instead of going through the tedious, costly, and environmentally harmful disposal process, the chemical industry is relying on solvent recovery, involving collection, purification, and reuse of spent solvent.

To keep production processes efficient and avoid side reactions, chemicals manufacturers have to ensure that the recovered solvents are of sufficient purity for their intended purpose.

Metrohm offers various analytical techniques relating to solvent characterization and qualification:

  • Combustion (pyrohydrolytic) Ion Chromatography to determine halogens and sulfur
  • NIRS analyzers to measure methanol and water levels

Halogens and sulfur in solvents

Combustion IC

Determination of the halogen content in residual solvents is required to separate halogenated solvents from non-halogenated solvents and to ensure proper disposal procedures in accordance with regulatory bodies.

Combustion Ion Chromatography is a reliable method for the determination of halogens. In this method, the halogens are released from the sample by combustion (pyrohydrolysis), and the gaseous components of interest are transferred into an absorption solution and determined by ion chromatography.

> Learn more about Combustion Ion Chromatography

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Water and methanol in solvents

Spectroscopy is an excellent option for solvent purity monitoring after recovery. In an exemplary application, Metrohm shows how NIR spectroscopy can help you to monitor the two most common impurities in methylene chloride: methanol and water.

NIR spectroscopy requires no sample preparation, yields fast results, and can be set up with inline sampling.

> Learn more about NIR spectroscopy

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Further applications and products

Solvent identification with Raman spectroscopy

You can identify organic solvents, e.g., methanol, ethanol, isopropanol, tetrahydrofuran, acetonitrile, and others, within seconds with the Mira M-1 handheld Raman analyzer.

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