Applications

Free white paper describes the effective use of electrochemical techniques to measure corrosion and the effectiveness of inhibitors.

Many refiners look at discounted opportunity crudes as a means to improve their margin spread. The varieties of these cheap crude oils on the market are growing in number, but they have hidden risks for the purchaser caused by factors such as high naphthenic acid and sulfur content. Sulfur compounds and naphthenic acids are among the substances that contribute to the corrosive nature of crude oils and petroleum products. This is why the risk of corrosion is increased when processing crude oils with high naphthenic acid and sulfur content. The refiner must balance the cost benefit versus the risk and the cost of corrosion control when processing these crudes. A reliable acid number determination is a crucial part of corrosion control. Guest authors Bert Thakkar, Bryce McGarvey, and Colette McGarvey of Imperial Oil and Larry Tucker and Lori Carey of Metrohm USA were involved in the development of the new ASTM Method D8045 for acid number determination. Here, they report on the method and how it came to be.

An analytic chemist in your back pocket. A forensic laboratory in a suitcase. A HazMat team in the trunk of your car. First responders need all the help they can get when faced with potentially dangerous substances. Mira DS from Metrohm Raman is a sophisticated chemical analyzer that replaces the specialist with automation. The push of a button initiates proprietary Smart Acquire routines to optimize acquisition parameters and collect the highest quality spectra. These spectra are automatically subjected to library search and Mixture Matching routines capable of identifying up to three components of a mixture. When hazardous substances are detected, the user is alerted to immediate action with color-coded warnings.

The suitability and potential of Raman spectroscopy in forensics is widely known by forensic specialists who use it in the laboratory to identify a wide variety of compounds including explosives, drugs, paints, textile fibers and inks. However, the use of laboratory-grade Raman outside the laboratory, such as for in‐situ analysis at a crime scene, was something thought possible only in forensic‐fiction until just a few years ago. Fortunately, modern portable Raman spectrometers are commercially available, and their instrumental features are comparable to Raman lab‐ spectrometers.To prove this, some extraordinarily demanding and challenging applications, in which an in‐situ standoff identification of samples might be advisable, were tested.

This Bulletin describes titrimetric methods for the determination of cadmium, free sodium hydroxide, sodium carbonate, and total cyanide. The free cyanide can be calculated from the total cyanide and the Cd content.

This Bulletin describes the potentiometric determination of lead, tin(II), and free fluoroboric acid.

As much as the many types of cement may differ from one another, the characteristic that all of them have in common is the presence of the elements calcium, magnesium, iron, aluminum and silicon.Calcium, magnesium, iron and aluminum can be determined using various indicators following digestion of the cement sample using photometric titration with the Optrode at 610 nm. The determination of silicon, on the other hand, is gravimetric.

This bulletin contains two parts. The first part gives a short theoretical overview while more details are offered in the Metrohm Monograph Conductometry. The second, practice-oriented part deals with the following subjects:Conductivity measurements in general; Determination of the cell constant; Determination of the temperature coefficient; Conductivity measurement in water samples; TDS – Total Dissolved Solids; Conductometric titrations;

This Bulletin, using practical examples, indicates how the user can achieve optimum pH measurements. As this Bulletin is intended for actual practice, the fundamentals - which can be found in numerous books and publications - are treated only briefly.

This Bulletin describes the simultaneous potentiometric titration of free boric acid and free tetrafluoroboric acid in nickel plating baths. After addition of mannitol, the formed mannitol complexes are titrated with sodium hydroxide solution. The determination is carried out directly in the plating bath sample; nickel and other metal ions do not interfere.

This Bulletin describes the fully automated determination of uranium according to the method of Davies and Gray: Uranium(VI) is reduced in concentrated phosphoric acid solution with iron(II) to form Uranium(IV). With molybdenum as a catalyst, the excess iron(II) is oxidized with nitric acid. The nitrous acid that is formed is destroyed with sulfamic acid before uranium(IV) is titrated with a potassium dichromate solution in the presence of a vanadium catalyst.

This bulletin deals with the automated determination of mixtures of HNO3, HF and H2SiF6 in the range of approximately 200-600 g/L HNO3, 50-160 g/L HF, and 0-185 g/L H2SiF6 using thermometric titration.Etch acid mixtures containing HNO3, HF and H2SiF6 from the etching of silicon substrates can be analyzed in a sequence of two determinations using the 859 Titrotherm. The first determination involves a direct titration with standard c(NaOH) = 2 mol/L, followed by a back titration with c(HCl) = 2 mol/L. This determination yields the H2SiF6 content plus a value for the combined (HNO3+HF) contents. The second determination consists of a titration with c(Al3+) = 0.5 mol/L to determine the HF content. For freshly made up mixtures of HNO3 and HF containing no H2SiF6, a linked two-titration sequence is employed. Results from the two determinations are used by tiamoTM to yield individual results for HNO3, HF and H2SiF6.

This Application Bulletin describes the determination of arsenic in water samples by anodic stripping voltammetry using the scTRACE Gold sensor. This method makes it possible to distinguish between As(total) and As(III). With a deposition time of 60 s, the limit of detection for As(total) is 0.9 µg/L, for As(III) it is 0.3 µg/L.

Abrasive machining of e.g., metal parts requires a cooling lubricant. Their purpose besides cooling and lubrication is to inhibit corrosion. Amines are added to the emulsion to keep the pH high. In the actual application, DCHA and MDCHA have to be analyzed besides other amine components and inorganic cations. To avoid oil contamination on the IC system, Inline Dialysis is applied. The detection is performed by direct conductivity detection.

Moisture in petroleum products causes several issues: corrosion and wear in pipelines and storage tanks, an increase in debris load resulting in diminished lubrication, blocked filters, or even harmful bacterial growth. As a result, increased water content can lead to infrastructure damage, higher maintenance costs, or even unwanted downtimes.Coulometric Karl Fischer titration is the method of choice for low water content in petroleum products. Using a Karl Fischer oven to vaporize the water present in the sample prior to titration not only greatly reduces matrix interferences, it can also be fully automated. This allows a reliable and cost-efficient analysis of the water content according to ASTM D6304 (Procedure B) in products such as diesel, hydraulic oil, lubricant, additive, turbine oil, and base oil.

Determination of nitrate in a nickel plating bath using anion chromatography with UV/VIS detection (205 nm).

Chrome plating is an important electroplating technique that covers metal or plastic surfaces with a thin layer of chromium for both protection and decoration purposes. The sulfate and sulfuric acid concentrations in the baths are important parameters in the coating process and require continuous monitoring. The anions in the chrome baths are separated on the Metrosep A Supp 5 - 250/4.0 column and are determined using conductivity detection in accordance with sequential suppression.

Determination of trace levels of chloride, nitrate, phosphate, and sulfate in a boiler feed water using anion chromatography with conductivity detection after chemical suppression.

Determination of chloride, nitrite, cyanate, azide, nitrate, chlorate, sulfate, thiocyanate, thiosulfate, and perchlorate in an extract of explosives using anion chromatography with conductivity detection after chemical suppression.

Clean drinking water is cited as a human right by WHO. Policies, standards, and robust and reliable analytical methods are required to safeguard water quality, and by extension, public health. US EPA Method 300.1 is the main standard method for the analysis of inorganic disinfection byproducts (oxyhalides: chlorite, chlorate, bromate) and common inorganic anions (fluoride, nitrite, bromide, nitrate, sulfate, and phosphate) as well as dichloroacetate (DCA) in drinking water. The requirement of using two injections, one for the standard anions and a second for the trace anions, reduces the sample throughput for the laboratories dramatically. Metrohm ion chromatography (IC) with suppressed conductivity detection using the highly selective Metrosep A Supp 7 column fulfills these requirements in a single-run analysis, increasing laboratory efficiency and saving money while keeping analytical quality high.

Forensic institutes examine terrorist attacks and warfare agents via trace detection analysis of the used explosives and their residuals. Of particular importance is the acquisition of «chemical fingerprints» for criminal investigation departments and governmental security agencies. Institutes for public health and environmental protection analyze such compounds that can contaminate the underlying soil and infiltrate ground water.Forensic investigation with ion chromatography (IC) using suppressed conductivity detection allows a sensitive and robust determination of anionic contaminants such as chlorate, thiosulfate, thiocyanate, and perchlorate next to the common inorganic anions over a broad concentration range.

The concentration of Sb(III) and Sb(total) in an electroless nickel bath is determined by anodic stripping voltammetry (ASV). In c(HCl) = 0.6 mol/L only Sb(III) shows a signal. In w(HCl) = 10% the Sb(total) content is determined.

Testing of in-service lubricating oils for their remaining antioxidant content is critical for capital equipment uptime as well as reducing running costs and repair expenses. Test methodologies such as RPVOT (rotating pressure vessel oxidation test) are time consuming and expensive to perform. Remaining Useful Life is a proven voltammetric method for testing the remaining active antioxidant content in minutes. Depending on the electrolyte, aromatic amine and phenolic antioxidants or hindered phenolic antioxidants can be determined.For the first time, a fully automated system is demonstrated, showing dramatically improved repeatability of data for confidence in reporting. Operator time is saved during sample preparation and irreproducible manual interpretation is eliminated via completely autonomous software processing. The user adds the sample into the vials, then the determination process of the sample series (including sample preparation and result calculations) is carried out automatically. The system is based on methods ASTM D6810, ASTM D6971, ASTM D7527, and ASTM D7590.

Electrochemical impedance spectroscopy or EIS has been used effectively to measure the polarization resistance for corrosion systems and for the determination of corrosion mechanisms.

The ASTM B825 is used to determine the corrosion and tarnish film on metal surfaces. This is achieved by using the so-called cathodic reduction method. With the help of a Metrohm Autolab PGSTAT302N and a Metrohm Autolab 1 L corrosion cell, a procedure to replicate the ASTM B825 is shown.

A corrosion inhibitor is a substance that reduces the corrosion rate of a metal. A corrosion inhibitor is usually added in a small concentration to the corrosive environment. This application note shows how Metrohm Autolab instruments can be used to check the quality of inhibitors.

Polarization resistance (Rp) can quantify the corrosion resistance of metals as an alternative to Tafel analysis. Its methodology and practical use as described in ASTM G59 are discussed.

The International Standard ISO 17463 describes the determination of the anticorrosive properties of high impedance organic protective coatings on metals. This technique uses cycles composed of electrochemical impedance spectroscopy (EIS) measurements, cathodic polarizations and potential relaxation. This application note shows the compliance of the Metrohm Autolab PGSTAT M204 and flat cell with the standard ISO 17463.

This Application Note details ASTM G61-compliant corrosion measurements performed with VIONIC powered by INTELLO using Metrohm’s ASTM-compliant corrosion cells.

Determination of trace chloride in cement and clinker by potentiometric titration with silver nitrate using the Ag-Titrode.

The automated system Basic water analysis determines conductivity, pH value, and alkalinity in all kind of water samples. The high degree of automation (e.g., automated sample addition, automated calibration as well as automated titer and cell constant determination) minimizes errors and guarantees an outstanding reproducibility.

This Application Note covers the photometric determination of calcium in cement using the Optrode (610 nm). After digestion of the cement sample, calcium is titrated with EDTA to the murexide endpoint.

This Application Note is devoted to the photometric determination of magnesium in cement using the Optrode (610 nm). After digestion of a sample aliquot, the magnesium content is determined using EDTA titration.

Basic additives are added to petroleum products to inhibit corrosion as they have a neutralizing effect on acidic compounds, which are formed as a result of degradation processes. Total base number (TBN) indicates the amount of basic additives present and thus can be used as a measure for the degradation of the petroleum product.Using an automated titration system with a photometric sensor to detect the end point ensures that the titrations are always carried out under the same conditions. This improves the precision and reliability of the results.This Application Notes describes the fully automated photometric determination of TBN in used engine oil using the Metrohm Optrode for the indication of the methyl orange endpoint (at 520 nm).

The pHe is a measure of acid strength in alcohol fuels and in ethanol. It can be used as predictor of the corrosion potential of an ethanol-based fuel. The determination of the pHe is preferred over the total acidity, because total acidity overestimates the contribution of weak acids (e.g., carbonic acid) and underestimates the contribution of strong acids (e.g., sulfuric acid). Furthermore, the acid strength is an important parameter to determine in order to reduce the risk of failing motors.This Application Note describes the determination of the pHe value using the 913 pH Meter and the EtOH Trode according to ASTM D6423, which covers denatured fuel ethanol and ethanol fuel blends.

The pHe value is an indicator for the acid strength and shows the presence of strong acids or bases in ethanol. In Europe, ethanol is used as a blending component in gasoline and needs to have a pHe value between 6.5 and 9.0.This Application Note describes a fast and accurate determination of the pHe value using the EtOH-Trode.

Denatured fuel ethanol may contain additives such as corrosion inhibitors and detergents as well as contaminants from manufacturing that can affect the acidity of produced ethanol fuel. An increased acid content in solvents could lead to a variety of problems like a shorter storage stability or chemical corrosion. Using the Optrode with phenolphthalein as indicator, the acidity is determined as acetic acid by titration with sodium hydroxide as titrant.

Corrosion of metallic components is an inherent problem for engines, because metals naturally tend to oxidize in the presence of water and/or acids. Increased acid content is indicated by a low pH value, and could lead to a variety of problems like a shorter storage life (stability) or a reduced buffer capacity of the used engine coolant or antirust.In this Application Note, engine coolants or antirust samples are dissolved in water, and the pH measurement using the Profitrode is carried out according to ASTM D1287.

Ethanol, bio-ethanol and biofuel (E85) are increasingly used as substitutes for petroleum-based fuels. During storage, they often come into contact with metallic substrates or surfaces, e.g., in barrels, tanks, or other containers. Excessive concentrations of ions in the stored fuel promotes corrosion. Monitoring the total concentration of the ions present in the fuel matrix should be the first step of an effective anti-corrosion strategy.An easy, fast, and cost-effective method to determine the total amount of ions is by measuring the electrical conductivity according to DIN 15938.

Water treatment with ozone (O3) is a common procedure for the disinfection of swimming pools. It is important that a sufficient but not excessive amount of O3 is produced to disinfect the water. Otherwise, the remaining ozone could enter the swimming water, which could irritate the respiratory system or the skin of bathers.Ozone is also used in drinking and waste water treatment because it is significantly more effective than chlorine at inactivating or killing viruses and bacteria. This application note describes a method to determine the ozone concentration in water by potentiometric titration according to DIN 38408-3.

Corrosion of metallic components is an inherent problem for engines, because metals naturally tend to oxidize in the presence of water and/or low pH value. The reserve alkalinity of engine coolants and antirusts is a measure of the buffering ability to absorb acidity. The reserve alkalinity is frequently used for quality control during production and often listed in the specifications of the coolants. A fast and accurate determination is therefore important.This Application Note describes the straightforward determination of reserve alkalinity according to ASTM D1121. Using a fully automated system allows an accurate and reliable determination due to the reduction of human errors. Furthermore, the operator is free to carry out other tasks increasing the efficiency of the laboratory.

Determination of Cr(VI) and Cr(III) in chromium baths by iodometric potentiometric titration with thiosulfate using the combined Pt electrode.

The acid number (AN) of insulating, transformer, and turbine oils is crucial to ensure safe operation, operating equipment control, and corrosion prevention. These oils generally have low AN specifications and their AN determination by manual color-indicator titration is difficult, especially when analyzing colored samples.Using a Titrator with a photometric sensor to detect the end point ensures that the titrations are always carried out under the same conditions. This greatly increases the precision and reliability of the results, which in turn results in improved monitoring for your operations.

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), pH value (EN ISO 10523, ASTM D1293, EPA 150.1), alkalinity (EN ISO 9963, ASTM D1067, EPA 310.1), Ca/Mg (ISO 6059, ASTM D1126, EPA 130.2), and chloride (ISO 9297, ASTM D512, EPA 325.3). Additionally the system transfers the required volume of sample into external titration vessels for the different analyses, reducing manual sample preparation. Furthermore, all sensors can be automatically calibrated and the titer of each titrant can also be determined.

It is widely accepted that prolonged exposure to hexavalent chromium compounds can have dire health effects. This has led to increased regulation of chromium-containing products and greater demand for technologies that can positively identify hexavalent chromium in potential matrices. These include paints, dyes, and primers, which can pose a problem for interrogation with Raman, as strongly colored materials often exhibit fluorescence when stimulated at 785 nm. Fluorescence can obscure the Raman signal and prevent positive identification. MIRA XTR DS provides all the functionality of handheld material ID with a new capability that selectively eXTRacts the Raman signal from fluorescent materials. Fluorescence rejection at 785 nm provides higher sensitivity and resolution than 1064 nm systems, as well as a much wider scope of applications amenable to Raman spectroscopy. MIRA XTR DS offers a comprehensive and versatile material ID test solution for field operations.

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Law enforcement personnel, laboratory technicians, crime scene investigators and many others face a significant challenge for identification of materials in a forensic investigation.Traditionally, technicians used multiple forms of identification in order to collect results from various forms of forensic samples. Although certain technologies are ideal for precise laboratory identification, many technologies, such as Raman spectroscopy, can be successfully used for identification of multiple forensic sample types either directly in the field or in the lab. Raman spectroscopy is classified as a Category A analytical method by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG; Version 7.1, 2016).

Silver is an important metal not only in jewelry and silverware but also in electrical conductors and contacts. The knowledge of the exact silver content in fine silver and silver alloys ensures that quality standards for jewelry and silverware are met. As for the plating industry, the knowledge of the amount of silver in silver plating baths helps to run the bath efficiently.While X-ray fluorescence (XRF) is a fast alternative to determine the silver content in fine silver and silver alloys, it can only determine the silver content of the outermost sections of the metal. In contrast, titration offers a more comprehensive solution considering the whole sample, thus preventing fraud by thick plating.This application bulletin describes the potentiometric determination of silver in fine silver and silver alloys accordingto EN ISO 11427, ISO 13756, GB/T 17823, and GB/T 18996 as well as in silver plating baths by a titration with potassium bromide or potassium chloride, respectively

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+.

Specialty chemicals have to fulfill multiple quality requirements. One of these quality parameters, which can be found in almost all certificates of analysis and specifications, is the moisture content. The standard method for the determination of moisture content is Karl Fischer titration.This method requires reproducible sample preparation, chemicals, and waste disposal. Alternatively, near-infrared spectroscopy (NIR) can be used for the determination of moisture content. With this technique, samples can be analyzed without any preparation and without using any chemicals.