The concentration of Fe(total) is determined in monoethylene glycol by adsorptive stripping voltammetry with 2,3-dihydroxy-naphthalene as complexing agent. The detection limit of the method is approx. 0.1 µg/L with respect to the content in the measuring vessel. If no bromate is added to the supporting electrolyte the sensitivity of the method is about 10 times lower. All reagents have to be added in the order as listed below. Fe(II) and Fe(III) give signals with the same sensitivity. All reagents typically contain iron impurities, especially the 2,3-dihydroxy-naphthalene. Therefore a subtraction of the reagent blank is recommended.

AN-V-115

Antimony in polyethylene terephthalate (PET)

Sb is determined in polyethylene terephthalate (PET) after digestion in sulfuric acid and hydrogen peroxide. The application is carried out with anodic stripping voltammetry (ASV) in hydrochloric acid.

AN-V-114

Cobalt in polyethylene terephthalate (PET)

Co is determined in polyethylene terephthalate (PET) after digestion in sulfuric acid and hydrogen peroxide. The application is carried out with adsorptive stripping voltammetry (AdSV) in ammonia buffer with dimethylglyoxime (DMG) as complexing agent.

AN-V-113

Titanium in polyethylene terephthalate (PET)

Ti is determined in polyethylene terephthalate (PET) after digestion in sulfuric acid and hydrogen peroxide. Adsorptive stripping voltammetry (AdSV) with mandelic acid as complexing agent is used for this application.

AN-V-064

Free styrene in polystyrene and mixed polymers

Determination of styrene monomers in polystyrene. Free styrene is converted to a polarographically active pseudonitrosite.

AN-V-063

Cyanide in gases resulting from the incineration of plastic insulating materials

Determination of cyanide in gases resulting from the incineration of plastic insulation materials after sample preparation by polarography

AN-V-062

4-Carboxybenzaldehyde in polyterephthalic acid

4-Carboxybenzaldehyde can be reduced directly on the DME in an solution containing ammonium

AN-V-003

Nickel, cobalt and iron in polyterephthalic acid solution

Determination of Ni, Co and Fe in a PTA solution containing HCl.

AN-V-002

Chromium, manganese and titanium in polyterephthalic acid solution

Determination of Cr, Mn and Ti in a PTA solution containing HCl.

AN-U-039

Polybrominated diphenyl ethers in polymers by UV detection, as per IEC 62321 method for RoHS testing

The determination of PBBE (tetrabromobisphenol A TBBPA, octabromobiphenyloxide OCTA and decabromobiphenyloxide
DECA) in a polymer sample was carried out with Nucleosil EC – 250 mm column, using methanol and phosphate buffer as eluent under UV detection, as per IEC 62321 method for RoHS testing.

AN-T-050

Nonionic surfactant nonylphenol ethoxylate (8 EO)

Determination of the nonionic surfactant nonylphenol ethoxylate by potentiometric titration with sodium tetraphenylborate using the NIO Surfactant Electrode.

AN-S-230

Phosphate and sulfate in polymer samples after inline dilution plus inline dialysis

Determination of phosphate and sulfate in a liquid polymer sample using anion chromatography with conductivity detection after chemical suppression.

AN-S-228

Anions in perfluorocarbon

Determination of fluoride, chloride, nitrate, sulfate and oxalate in a perfluorocarbon material using anion chromatography with conductivity detection after chemical suppression.

AN-S-130

Six anions in PVC

Determination of fluoride, chloride, nitrite, nitrate, benzoate and sulfate in PVC film using anion chromatography with conductivity detection after chemical suppression.

AN-S-122

Fluoride, glycolate, chloride and oxalate in a latex dispersion

Determination of fluoride, glycolate, chloride and oxalate in a latex dispersion using anion chromatography with conductivity detection after chemical suppression and dialysis for sample preparation.

AN-S-063

Phosphate and phosphite in poly(vinylphosphonic acid) using dialysis for sample preparation

Determination of phosphate and phosphite in poly(phosphonic acid) using anion chromatography with conductivity detection after chemical suppression and dialysis for sample preparation.

AN-R-008

Thermal stability of pure, blended, and processed PVC

The thermal stability of polyvinyl chloride (PVC) was determined using the dehydrochlorination procedure at 180 °C according to DIN 53381 part 1.

AN-N-064

Sodium dodecylsulfate (SDS) in water

Determination of sodium dodecylsulfate (SDS, sodium laurylsulfate) using anion chromatography with direct conductivity detection.

AN-N-004

Fluoride, chloride, bromide, nitrate and sulfate in organic substances after Schoeniger combustion

Determination of anions in a Schoeniger absorption solution of a test mixture without decomposition of the H₂O₂ using anion chromatography with direct conductivity detection.

AN-K-036

Water in vinyl chloride (chloroethylene)

The water content of vinyl chloride is determined according to Karl Fischer.

AN-K-035

Water in beta-caprolactam

The water content of b-caprolactam is determined according to Karl Fischer.

AN-K-034

Water in melamine

The water content of melamine is determined according to Karl Fischer in a buffered solvent mixture at 50 °C.

AN-K-023

Water in ethylene dichloride

The water content of ethylene dichloride is determined according to Karl Fischer. As the sample may contain free chlorine, which interferes with the determination, separate KF reagents have to be used.

AN-K-017

Water in expandable polystyrene

The water content of expandable polystyrene is determined according to Karl Fischer. As this product expands when heated the oven method cannot be used. The sample is first dissolved in p-xylene in order to extract the water. Then methanol is added to precipitate the sample and the water is determined in the supernatant solution by coulometric titration.

AN-K-013

Water in organic peroxides

The water content of organic peroxides is determined according to Karl Fischer using two-component reagents. To prevent any unwanted side reactions the determinations are carried out at -20 °C.

AN-K-008

Water in plastic chips

The water content of plastic chips is determined according to Karl Fischer. Because of the low water content of the sample the oven method (200 °C) and coulometric titration have to be used.

AN-K-003

Water in ammonium and potassium peroxodisulfate (persulfates)

The water content of ammonium and potassium peroxodisulphate is determined according to Karl Fischer using two-component reagents. To prevent unwanted side reactions the determinations are carried out at -20 °C. Because the potassium salt is insoluble in the solvent, a high-frequency homogenizer is used to disintegrate the salt particles.

AN-K-002

Water in methyl ethyl ketone peroxide (butanone peroxide)

The water content of methyl ethyl ketone peroxide is determined according to Karl Fischer using two-component reagents in order to prevent unwanted side reactions. (Separate solvent is used to ensure a high excess of sulphur dioxide and amine in the titration vessel.)

AN-H-054

Determination of hydrofluoric acid by aluminum titration

Determination of hydrofluoric acid in strongly acidic etching solutions (“polyetch”).

AN-H-040

Determination of HCl (ppm range) in silicone oil

Determination of low content of HCl (around 10 ppm) in silicone oil.

AN-H-039

Determination of sodium lauryl ether sulfate

Determination of sodium lauryl ether sulfate surfactants.

AN-H-013

Determination of moisture content of ultrafine solids

Determination of water in moist particulate solids such as cobalt oxyhydroxide.

AN-C-095

Methylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA) in methylpyrrolidone using Metrohm Inline Matrix Elimination

Determination of traces of methylamine, dimethylamine and trimethylamine in methylpyrrolidone using cation chromatography with direct conductivity detection.

AN-C-072

Sodium and potassium in a polyol solution

Determination of sodium and potassium in a polyol solution using cation chromatography with direct conductivity detection.

AN-C-059

Sodium, ammonium and potassium in polyethers

Determination of sodium, ammonium and potassium in polyethers using cation chromatography with direct conductivity detection.

AB-322

Fully automated potentiometric determination of the hydroxyl number (HN) according to ASTM E 1899-08 and DIN 53240-2

The presented titration system can be used for the fully automated determination of the hydroxyl number (HN) according to ASTM or DIN. The method allows, for example, the determination of polyols and oxooils without boiling under reflux or other sample preparation and is therefore a big benefit for laboratories that have to analyze a great number of these samples per day.

AB-280

Automated Karl Fischer water determination with the 774 Oven Sample Processor

In principle the 774 Oven Sample Processor can be used with all samples that release their water when heat is applied. However, the KF oven method is essential whenever direct volumetric or coulometric Karl Fischer titration is impossible because the sample contains interfering components or, due to its consistency, is difficult to place in the titration vessel.

The combination of the 774 Oven Sample Processor with coulometric Karl Fischer titration (756 or 831 KF Coulometer) is ideal for samples with a low water content. Foodstuffs, pharmaceutical products, plastics or mineral oil products can be analyzed fully automatically and extremely accurately. On the other hand, a volumetric Karl Fischer titration using a KF Titrino is to be preferred for samples with a very high water content (>50%).

In accordance with the gas extraction principle the water is driven out of the heated sample by a stream of dry carrier gas and transferred to the titration vessel, where the water is determined by KF titration.

For temperature-sensitive samples, e.g. foodstuffs, the water can be released gently at lower temperatures by simultaneous extraction with methanol. In this way it is possible to prevent any water being released by decomposition.

This Application Bulletin uses examples from the food, pharmaceutical, plastics and petrochemical industries to describe automatic Karl Fischer water determination using the 774 Oven Sample Processor and a KF Coulometer. Information concerning the combination of the Oven Sample Processor with a volumetric KF titrator is given in brackets.

AB-269

Titrimetric/potentiometric determination of ionic surfactants by two-phase titration using the Metrosensor Surfactrodes

This Bulletin describes the potentiometrically indicated «two-phase titration» of ionic surfactants in raw materials and various formulations using numerous practical examples. Two completely new designs of surfactant electrode, – the Surfactrode Resistant and Surfactrode Refill –, allow you to carry out this type of surfactant titration in s similar way to the classical «Epton titration» and with a high degree of automation.
The results obtained correlate to a high degree with those of the Epton titration. The toxic and environmentally hazardous chloroform can be replaced by alternative solvents such as ethyl isobutyl ketone or n-hexane.

AB-205

Determination of the thermal stability of PVC and related copolymers

The determination of the thermal stability of PVC in conformity with DIN 53381, Part 1, and ISO 182:1970 is described using the 679 Rancimat. The instrument allows the fully automatic and simultaneous determination of the stability and induction time. The test is suitable for monitoring manufacture and processing, for making a delivery check, for the characterization and comparison of PVC products, as well as for testing the effectiveness of heat stabilizers in molded PVC materials.

AB-200

Determination of the acid number, hydroxyl number and isocyanates in raw materials for the fabrication of plastics by automatic potentiometric titration

The determination of the acid number, the hydroxyl number and the isocyanates plays an important part in the analysis of raw materials for plastics. The present Bulletin describes the determination of these characteristic values by automatic potentiometric titration.

AB-190

Polarographic determination of 4-carboxybenzaldehyde in terephthalic acid

4-Carboxybenzaldehyde, in the following referred to as 4-CBA, can be reduced directly at the dropping mercury electrode (DME) in an ammoniacal solution. After a very simple sample preparation it is now possible to determine the concentration of 4-CBA in terephthalic acid quickly and precisely by polarography down to the lower ppm range.

AB-179

Polarographic determination of maleic and fumaric acid alone or in mixtures

Maleic and fumaric acid can be reduced electrochemically to succinic acid. In acidic solutions a differentiation of the two acids is not possible since both are reduced at the same potential. On the other hand, separation at pH 7.8...8.0 is easily possible since fumaric acid is now more difficult to reduce at the lower proton concentration (as a result of cis-trans isomerism) than maleic acid.

AB-145

Determination of low water contents in plastics using the KF oven method

In many cases it is essential to know the water content of plastics. This is of particular interest in connection with their processing or their use as insulators in electrical engineering. This Bulletin describes the coulometric determination of water according to the Karl Fischer method, which is both simple to carry out with the instruments mentioned and much less time-consuming than the other methods normally used.

AB-136

Polarographic determination of styrene in polystyrene and copolymers

This Application Bulletin describes a simple polarographic method to determine monomeric styrene in polymers. The limit of determination lies at 5 mg/L. Before the determination, styrene is converted to the electrochemically active pseudonitrosite using sodium nitrite.

AB-068

Potentiometric determination of carboxyl and amino terminal groups in polyamide fibers

Indication of the titration endpoint of the weakly alkaline or weakly acidic terminal groups in non-aqueous solution is frequently not easy. An improvement is possible by using a suitable titrant (TBAOH = tetrabutylammonium hydroxide for terminal carboxyl groups; perchloric acid for terminal amino groups).

An improvement in the evaluation can also be achieved by choosing benzyl alcohol as the solvent.

The choice of electrode combination and the measuring setup is also important. Differential potentiometry using the three-electrode technique results in a great improvement in titrations in poorly conducting solutions. Noisy signals are eliminated.

8.000.6062EN

Water determination in various plastics

The presence of excessive water in plastics adversely affects the performance of polymeric goods which is why water determination is of crucial importance. This article describes the accurate and straightforward determination of the water content using the Karl Fischer Oven Method in ten different plastic types that are not amenable to direct Karl Fischer titration. The experiments revealed that besides the determination of the oven temperature, sample preparation is one of the most important steps of the analysis, especially in case of hygroscopic plastic samples.

8.000.6047EN

Fully automated potentiometric determination of the hydroxyl number (HN) according to ASTM E 1899-08 and DIN 53240-2

Hydroxyl is an important functional group and knowledge of its content is required in many intermediate and end-use products such as polyols, resins, lacquer raw materials and fats (petroleum industry). The test method to be described determines primary and secondary hydroxyl groups. The hydroxyl number is defined as the mg of KOH equivalent to the hydroxyl content of 1 g of sample.
The most frequently described method for determining the hydroxyl number is the conversion with acetic anhydride in pyridine with subsequent titration of the acetic acid released:
H₃C-CO-O-CO-CH₃ + R-OH -> R-O-CO-CH₃ + CH₃COOH
However, this method suffers from the following drawbacks:
   - The sample must be boiled under reflux for 1 h (long reaction time and laborious, expensive sample handling)
   - The method cannot be automated
   - Small hydroxyl numbers cannot be determined exactly
   - Pyridine has to be used, which is both toxic and foul-smelling
Both standards, ASTM E 1899-08 and DIN 53240-2, offer alternative methods that do not require manual sample preparation and therefore can be fully automated:

The method suggested in ASTM E 1899-08 is based on the reaction of the hydroxyl groups attached to primary and secondary carbon atoms with excess toluene-4-sulfonyl-isocyanate (TSI) to form an acidic carbamate. The latter can then be titrated in a non-aqueous medium with the strong base tetrabutyl- ammonium hydroxide (TBAOH).

The method suggested in DIN 53240-2 is based on the catalyzed acetylation of the hydroxyl group. After hydrolysis of the intermediate, the remaining acetic acid is titrated in a non-aqueous medium with alcoholic KOH solution.

The present work demonstrates and discusses an easy way to determine the hydroxyl number according to ASTM E 1899-08 or DIN 53240-2 with a fully automated titrimetric system for a great variety of industrial oil samples.

8.000.6023EN

Determination of anionic and cationic surfactants by potentiometric two-phase titration

Compared to the classical Epton titration, potentiometrically indicated two-phase titrations using organic-solvent-resistant Surfactrodes can be easily automated and require no toxic and environmentally hazardous chloroform. Even challenging matrices such as fats and oils in bath oils and hair conditioners or strong oxidizing agents in washing powder and industrial cleaners do not interfere with the titration of the ionic surfactants. Results obtained show excellent agreement to those of the Epton titration. Irrespective of the matrix, relative standard deviations of threefold determinations are all below 2.1%. While the Surfactrode Resistant is mainly used for oil-containing formulations, the Surfactrode Refill is ideal for washing powders and soaps.
Both electrodes excel by their ruggedness and allow the rapid and precise determination of anionic and cationic surfactants.