Application Finder

The photometric determination of nitrate is limited by the fact that the respective methods (salicylic acid, brucine, 2,6-dimethyl phenol, Nesslers reagent after reduction of nitrate to ammonium) are subject to interferences. The direct potentiometric determination using an ion-selective nitrate electrode causes problems in the presence of fairly large amounts of chloride or organic compounds with carboxyl groups. The polarographic method, on the other hand, is not only more rapid, but also practically insensitive to chemical interference, thus ensuring more accurate results. The limit of quantification depends on the matrix of the sample and is approximately 1 mg/L.

This Bulletin describes the automatic measurement of conductivity in water samples with low electrical conductivity in accordance with USP<645>. Conductivity measurement is demonstrated on the example of ultrapure water, which is used, among other things, to produce injection solutions in the pharmaceutical sector.

Heavy metals, particularly cadmium and lead, are known to be highly toxic to humans. Therefore, controlling the cadmium and lead content in drinking water is of utmost importance. In many countries, the limit in drinking water for cadmium is between 3–5 µg/L, and for lead it is between 5–15 µg/L. These trace concentrations can reliably be determined with the method described in this Application Bulletin. The determination is carried out by anodic stripping voltammetry (ASV) using the non-toxic Bi drop electrode in a slightly acidic electrolyte.

Cobalt is an essential element for humans because it is a component of vitamin B12. While small overdoses of cobalt compounds are only slightly toxic to humans, larger doses from 25–30 mg per day may lead to skin, lung, and stomach diseases, as well as liver, heart, and kidney damage, and even cancerous growths. The same is valid for nickel, which can lead to inflammation at higher concentrations. Drinking a large amount of water containing nickel can cause discomfort and nausea. In the EU the legislation specifies 0.02 mg/L as the limit value for the nickel concentration in drinking water. This concentration can be reliably determined with the method described in this Application Bulletin.

Microbore ion chromatography offers better sensitivity, shorter retention times, and consumes less eluent, increasing sample throughput and reducing running costs.

AOF (adsorbable organic fluorine) is used to screen for per- and polyfluorinated alkyl substances in aqueous matrices via pyrohydrolytic combustion and ion chromatography.

Combustion ion chromatography (CIC) measures AOX (adsorbable organically bound halogens, i.e., AOCl, AOBr, AOI) and AOF as well as CIC AOX(Cl) according to DIN 38409-59 and ISO 18127.

Tafel analysis is an important electrochemical technique used to understand reaction kinetics. By studying the Tafel slope, it reveals the rate-determining steps in electrode reactions, aiding fields like corrosion and fuel cell research. This method helps industries optimize processes and improve device performance by tailoring materials and conditions for greater efficiency.

Trace cation analysis in high purity water (sub-μg/L range) requires cation chromatography after sequential suppression and intelligent Preconcentration Technique (MiPCT). Trace cations in deionized water (DI) are determined and the method detection limit (MDL according to US EPA) as well as the limit of detection (LOD = 3 x S/N) is calculated. MDL and LOD are very similar in the lowest ng/L range for this setup with 6 mL preconcentration volume.

Copper is arguably one of the most technologically relevant metals, especially for the semiconductor industry. The deposition process used in this industry is known as the dual-damascene process and it involves the electrodeposition of copper from an acidic cupric compound, in the presence of additives.This Application Note illustrates the use of the Autolab rotating ring disc electrode (RRDE) for the study of electrodeposition of copper and the detection of the Cu+ intermediate.

The determination of heavy metal ions in a solution is one of the most successful application of electrochemistry. In this application note, anodic stripping voltammetry is used to measure the presence of two analytes, in a sample of tap water.

Differential electrochemical mass spectrometry (DEMS) is used to monitor gaseous and volatile species during electrochemical reactions in situ.

This application note demonstrates EQCM D for simultaneous mass and dissipation analysis of Ni(OH)₂ electrodeposition.

Zinc coatings are widely applied for medical devices and to protect steel against corrosion. Electrodeposition, modulated by electrochemical parameters and tailored additives such as polyethylene glycol (PEG), enables control over coating morphology, with PEG shown to delay deposition and promote smoother surfaces. This Application Note demonstrates that EQCM-D, integrated with electrochemical methods, provides detailed insight into Zn deposition and additive effects, supporting process optimization for coating performance.

PEDOT:PSS is a tunable, conductive coating whose properties depend on parameters such as counter-ion selection, secondary doping, and polymerization conditions. This Application Note demonstrates the combined use of EQCM-D, Raman spectroscopy, and electrochemical methods to monitor film growth, correlating frequency and dissipation changes across harmonics with in situ spectroscopic and electrochemical signals. The introduced probe-based EQCM-D platform enables simultaneous Raman acquisition, providing a powerful tool to design and optimize PEDOT:PSS coatings.

Determination of sodium and potassium salts of carboxylic acids in aqueous media. May be used for analysis of reagent purity.

Determination of ammonia (ammonium) in distilled water by direct potentiometry using the NH3-ISE.

Urea is not a typical analyte for ion chromatography. In combination with MS, however, IC is the method of choice for the trace analysis of urea in ultrapure water. This Application Note shows the determination of urea concentrations in the ppb range using the Metrosep C 6 - 250/4.0 column.

Determination of borate and silicate in ultrapure water using anion chromatography with direct conductivity detection.

The combination of 940 Professional IC Vario, 942 Extension Module Vario LQH and 941 Eluent Preparation Module enables process monitoring with the aid of ion chromatography. Assigned the designation ProfIC Vario 12 Anion, this combination is the anion variant of Metrohm Process IC. Intelligent preconcentration technology with matrix elimination is used for sample preparation. The use of an ELGA PURELAB® Flex 6 guarantees the supply of ultrapure water of the highest quality, particularly in cases of high numbers of samples.

Determination of 1 (3) µg/L of chloride, nitrite, bromide, nitrate, phosphate, and sulfate after direct injection using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, nitrate, and sulfate in ultrapure water after sample preconcentration using anion chromatography with conductivity detection after chemical suppression.

Determination of acetate, chloride, nitrite, nitrate, benzoate, phosphate, and sulfate using anion chromatography with conductivity detection after chemical suppression.

This Application Note demonstrates square wave voltammetry for sensitive, reproducible quantification of paracetamol using a screen-printed electrode and INTELLO.

The concentration of Fe(total) is determined in deionized water. The method is suitable for iron concentrations down to the mid µg/L range. Electrochemical deposition is not applicable for this method. A subtraction of the reagent blank is recommended. Fe(II) and Fe(III) give signals with the same sensitivity.

The concentration of Fe is determined in water samples by adsorptive stripping voltammetry with 1-nitroso-2-naphthol as complexing agent. All reagents have to be added in the order as listed below. All reagents typically contain iron impurities. Therefore a subtraction of the reagent blank is recommended. Fe(II) and Fe(III) show different sensitivities. Therefore the sample should only contain one of the iron species. Ascorbic acid (Vitamin C) can be added to the measuring solution and to the Fe(III) standard solution if both Fe(II) and Fe(III) are present in the sample to determine the concentration of total iron. A final concentration of ascorbic acid of 0.002 mol/L is suitable.

Arsenic is ubiquitous in the earth’s crust in low concentrations. Elevated levels can be found in mineral deposits and ores. Arsenic from such deposits leaches into the groundwater in the form of arsenite (AsO33–) and arsenate (AsO43–), causing its contamination. In addition to the arsenic originating from natural sources, industry and agriculture contribute to the contamination to a lower extent. The guideline value for inorganic total arsenic in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to 10 μg/L. With a limit of detection (LOD) of 0.9 μg/L, anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of arsenic. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory or alternatively in the field using the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Arsenic is ubiquitous in the earth’s crust in low concentrations. Elevated levels can be found in mineral deposits and ores. Arsenic from such deposits leaches into the groundwater in the form of arsenite (AsO33–) and arsenate (AsO43–), causing its contamination. As(III) is more toxic than As(V) and shows higher mobility in the environment. The selective determination of this species is possible using the method described in this document.With a limit of detection (LOD) of 0.3 μg/L, anodic stripping voltammetry allows speciation, i.e. the specific determination of As(III). While atomic absorption spectroscopy (AAS) (and competing methods) can only determine the total element concentration, anodic stripping voltammetry is selective to the As(III) oxidation state. The determination is carried out on the scTRACE Gold electrode.

Mercury and its compounds are toxic. The highest risk is posed by chronic poisoning with mercury compounds ingested with food. A significant part of the mercury present in the environment is of anthropogenic origin. Considerable sources are coal-fired power plants, steel, and nonferrous metal production, waste incineration plants, the chemical industry, or artisanal gold mining where the use of elemental mercury for the extraction of gold from the ore is still common. The guideline value for inorganic mercury in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to 6 μg/L.With a limit of detection (LOD) of 0.5 μg/L, anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS).While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory or alternatively in the field with the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Higher levels of copper in drinking water are usually caused by corrosive action of water leaching copper from copper pipes. While copper is an essential nutrient for the human organism, ingestion of higher concentrations have an adverse effect on human health. The current World Health Organization’s «Guidelines for Drinking-water Quality» recommend a maximum concentration of 2000 μg/L. With a limit of detection (LOD) of 0.5 μg/L, anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of copper in drinking water. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory or alternatively in the field with the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Iron is an essential element in human nutrition. It can be present in drinking water as a result of water treatment or from corrosion in the water piping system. There is no guideline value for iron in the World Health Organization’s «Guidelines for Drinking-water Quality» because typical levels usually found in drinking water are of no concern. However, there are national limit values in various countries. The European Union has set a guideline indicator value for iron of 200 μg/L. Voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of iron in drinking water. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetric determinations can be done used conventionally in the laboratory or alternatively in the field using the with 946 Portable VA Analyzer. The determination is carried out with adsorptive stripping voltammetry (AdSV) using 2,3-dihydroxynaphthalene (DHN) on the scTRACE Gold electrode.

Nickel is widely used in stainless steel production. At high enough concentrations, it is known to cause allergic reactions when in contact with skin. Drinking water may be contaminated by taps which are made from metals containing nickel. The guideline value for nickel in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to 70 μg/L. National limit values of typically lower at e. g. 20 μg/L. Cobalt usually occurs associated with nickel and can be found in smaller concentrations besides nickel. Adsorptive stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of nickel and cobalt in drinking water. While AAS (and competing methods) can only be performed in a laboratory, adsorptive stripping voltammetric determinations can be used in the laboratory or alternatively in the field with the 946 Portable VA Analyzer. The determination is carried out on a bismuth film applied to the scTRACE Gold electrode.

Bismuth is considered as a metal with a very low toxicity. In high concentrations toxic effects have been described, however. There is no guideline value for bismuth in the World Health Organization’s «Guidelines for Drinking-water Quality» because typical levels usually found in drinking water are of no concern. Anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of bismuth in drinking water. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used in the laboratory or alternatively in the field with the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Due to the toxicity and the detrimental effects of nickel and cobalt on human health, their concentrations in drinking water must be controlled. Therefore, EU the legislation specifies 20 µg/L as the limit value for nickel in drinking water. The current provisional guideline value for Ni in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to a maximum concentration of 70 µg/L. To monitor the concentrations of Ni and Co with the 884 Professional VA, a method for simultaneous determination on the glassy carbon electrode (GC-RDE) modified with a Bi film is used.

To reduce the toxic effects of cadmium on the kidneys, skeleton, and the respiratory system, as well as the neurotoxic effects of lead, the provisional guideline values in the World Health Organization’s (WHO) «Guidelines for Drinking-water Quality» are set to a maximum concentration of 3 µg/L for cadmium and 10 µg/L for lead.The powerful anodic stripping voltammetry (ASV) technique on the ex-situ mercury film modified glassy carbon electrode is more than sufficient to monitor the proposed WHO guidelines for Cd and Pb in drinking water.

No health-based guideline value exists for zinc. However, to maintain good quality municipal drinking water, the United States Environmental Protection Agency (US-EPA) set a maximum concentration of 5 mg/L as the limit value. Typical concentrations in surface and ground waters are between 10–40 μg/L Zn, with values up to 1 mg/L in tap water. Anodic stripping voltammetry (ASV) on the ex-situ mercury film modified glassy carbon electrode provides a less complex alternative to atomic absorption spectroscopy (AAS) for zinc determination in drinking water.

The guideline value for chromium in the World Health Organization’s (WHO) «Guidelines for Drinking-water Quality» is 50 µg/L. It should be noted here that chromium concentrations are often expressed as total chromium and not as chromium(III) or (VI). Chromium(VI) is responsible for changes in genetic material, and is found in significantly lower concentrations than Cr(III). Therefore an extremely sensitive method is required to monitor Cr(VI) in drinking water.The powerful adsorptive stripping voltammetry (AdSV) technique on the ex-situ mercury film modified glassy carbon electrode using DTPA as complexing agent can be used to determine such low concentrations.

EU legislation specifies 20 µg/L as the limit value for nickel in drinking water. The current provisional guideline value for Ni in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to a maximum concentration of 70 µg/L. The adsorptive stripping voltammetry (AdSV) technique performed on the ex-situ bismuth film modified Metrohm DropSens 11L screen-printed electrode (SPE) can be used to simultaneously detect concentrations as low as 0.4 µg/L for nickel and 0.2 µg/L for cobalt with a 30 s deposition time.The disposable, maintenance-free sensor can be used conventionally in the laboratory with the 884 Professional VA, or alternatively in the field with the 946 Portable VA Analyzer. This method is best suited for manual systems.

The difference between the toxic and essential levels of selenium to human health are very slight. Therefore, the current provisional guideline value for selenium(IV) in the World Health Organization’s «Guidelines for Drinking-water Quality» and in the European Drinking Water Directive is set to a maximum concentration of 10 µg/L.The anodic stripping voltammetric (ASV) technique performed on the unmodified scTRACE Gold can be used to determine concentrations as low as 0.5 µg/L selenium with a 30 s deposition time. These limits can be lowered even further by increasing the deposition time. The linear range at 30 s deposition time ends at approximately 100 μg/L. The scTRACE Gold electrode does not need extensive maintenance such as mechanical polishing. Measurements can be performed in the laboratory with the 884 Professional VA or alternatively in the field with the 946 Portable VA Analyzer. This method is suited for manual or automated systems.

Tellurium is one of the elements recently identified as technologically critical for photovoltaic conversion, quantum dots, as well as in thermoelectric technology, and has the potential to become a new emergent contaminant. Until now there is no guideline value in the World Health Organization’s «Guidelines for Drinking-water Quality» and in the European Drinking Water Directive for tellurium(IV) concentration in drinking water.To monitor the tellurium(IV) levels in drinking water, anodic stripping voltammetry (ASV) performed on the unmodified scTRACE Gold is recommended. This method allows determination of tellurium(IV) in the concentration range between 1 µg/L and 60 µg/L when using a 90 s deposition time. The scTRACE Gold electrode does not need extensive maintenance such as mechanical polishing. Measurements can be performed in the laboratory with the 884 Professional VA or alternatively in the field with the 946 Portable VA Analyzer.

«Dissolved oxygen» describes the amount of oxygen molecules (O2) which are dissolved in a liquid phase under certain conditions. In this white paper, two different methods for the analysis of dissolved oxygen, titration and direct measurement, are compared and contrasted to help analysts determine which method is more suitable for their specific applications. Here, we primarily focus on the determination of dissolved O2 in water. However, the same principle applies for other liquid phases such as non-alcoholic or alcoholic beverages.

Ion measurement can be conducted in several different ways, e.g., ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP-OES), or atom absorption spectroscopy (AAS). Each of these are well-established, widely used methods in analytical laboratories. However, the initial costs are relatively high. In contrast, ion measurement by the use of an ion-selective electrode (ISE) is a promising alternative to these costly techniques. This White Paper explains the challenges which may be encountered when applying standard addition or direct measurement, and how to overcome them in order for analysts to gain more confidence with this type of analysis.

Ion chromatography mass spectrometry (IC-MS) is a powerful tool that can handle many challenging analytical tasks which cannot be performed adequately by IC alone. IC-MS is a robust, sensitive, and selective technique used for the determination of polar contaminants like inorganic anions, organic acids, haloacetic acids, oxyhalides, or alkali and alkaline earth metals. After separation of the sample components via IC, mass selective detection guarantees peak identity with low detection limits. The inclusion of automated Metrohm Inline Sample Preparation (MISP) allows not only water samples, but also chemicals, organic solvents, or post-explosion residues to be readily analyzed without need for extensive manual laboratory work. This White Paper explains the benefits of IC-MS over IC in certain cases, the hyphenation of IC and different MS systems, as well as related norms and standards.

This White Paper presents four different «green» sensors: the scTRACE Gold, screen-printed electrodes, the glassy carbon electrode, and the Bi drop electrode from Metrohm that can be used to determine low concentrations of heavy metals in different sample matrices, such as boiler feed water, drinking water, and sea water.