Методики

In the following tables, the half-wave potentials or peak potentials of 90 metal ions are listed. The half-wave potentials (listed in volts) are measured at the dropping mercury electrode (DME) at 25 °C unless indicated otherwise.

Boric acid is used in many primary circuits of nuclear power plants, in nickel plating baths, and in the production of optical glasses. Furthermore, boron compounds are found in washing powders and fertilizers. This bulletin describes the potentiometric and thermometric determination of boric acid. The determination also covers further boron compounds, when acidic digestion is applied.

This Bulletin describes potentiometric titration methods for checking sulfuric acid and chromic acid anodizing baths. In addition to the main components aluminum, sulfuric acid, and chromic acid, chloride, oxalic acid, and sulfate are determined.

Potentiometric titration is an accurate method for determining chloride content. For detailed instructions and troubleshooting tips, download our Application Bulletin.

A method is described in this Bulletin that allows molybdenum to be determined in steel and other materials containing a high iron concentration. Mo(VI) is determined at the dropping mercury electrode by catalytic polarography. The determination limit is approx. 10 μg/L Mo(VI).

In most electrolytes the peak potentials of lead and tin are so close together, that a voltammetric determination is impossible. Difficulties occur especially if one of the metals is present in excess.Method 1 describes the determination of Pb and Sn. Anodic stripping voltammetry (ASV) is used under addition of cetyltrimethylammonium bromide. This method is used when:• one is mainly interested in Pb• Pb is in excess• Sn/Pb ratio is not higher than 200:1According to method 1, Sn and Pb can be determined simultaneously if the difference in the concentrations is not too high and Cd is absent.Method 2 is applied when traces of Sn and Pb are found or interfering TI and/or Cd ions are present. This method also uses DPASV in an oxalate buffer with methylene blue addition.

Thiourea forms highly insoluble compounds with mercury. The resulting anodic waves are used for the polarographic determination of thiourea. For the analysis of very small quantities (µg/L), cathodic stripping voltammetry (CSV) is used. Differential Pulse measuring mode is used in both cases.

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.

Formaldehyde can be determined reductively at the DME. Depending on the sample composition it may be possible to determine the formaldehyde directly in the sample. If interferences occur then sample preparation may be necessary, e.g. absorption, extraction, or distillation.Two methods are described. In the first method formaldehyde is reduced directly in alkaline solution. Higher concentrations of alkaline or alkaline earth metals interfere. In such cases the second method can be applied. Formaldehyde is derivatized with hydrazine forming the hydrazone, which can be measured polarographically in acidic solution.

Determination of nickel in the absence of cobalt and other interferences.

Determination of nickel in refinery and plating solutions. When other metals capable of being complexed by EDTA are present, these will interfere and enhance the result for nickel.

Determination of nickel in solution by titration with standard disodium dimethylglyoximate.

Determination of sodium hypophosphite in electroless plating solutions.

Thermometric titration of nickel in electroless plating solution with disodium dimethylglyoximate.

Automated thermometric titration of the nickel content of electroless nickel plating solutions. The determination is suitable for fully automated titration employing a 814 Sample Processor.

Determination of boric acid in electroless plating solutions.

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

Determination of citrate and saccharin in a nickel plating bath using ion-exclusion chromatography with direct conductivity detection.

In an electroless plating bath, the consumed ingredients have to be regularly replenished to ensure an even layer of nickel-phosphorus alloy. This requires online monitoring of the active bath constituents. Parameters to be controlled are pH value (4.5–5.0) as well as nickel (NiSO4 < 10 g/L) and hypophosphite concentration (NaH2PO2: 1–12%). Other measurement options include sulfate, alkalinity, and organic additives (via CVS).

Accurate analysis of complexing agents in galvanic baths is possible with inline Raman spectroscopy. This Application Note shows an example using a 2060 Raman Analyzer.

The 2060 XRF Process Analyzer continuously monitors elemental concentrations online within zinc-nickel electroplating baths to precisely guide chemical dosing.

Determination of fluoride, chloride, and nitrate in a solution of NiSO4, ZnSO4 in sulfuric acid using anion chromatography with conductivity detection after chemical suppression.

Determination of nitrate and sulfate in sodium phosphinate (sodium hypophosphite) using anion chromatography with conductivity detection after chemical suppression.

Determination of borate and chloride with direct conductivity detection (exhausted MSM). After the introduction of the fresh MSM unit and after the eluent change, sulfate is analyzed with conductivity detection after chemical suppression.

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

Determination of hypophosphite, phosphite, and phosphate in a nickel bath using anion chromatography with conductivity detection after chemical suppression and inline cation exchange.

Determination of anionic surfactants in a nickel plating bath by potentiometric titration with TEGO®trant A100 using the «Ionic Surfactant» electrode.

This Application Note treats the photometric titration of nickel using the Optrode (520 nm). Murexide was used as the indicator and EDTA as the titrant.

Electroplating processes are used in several different industry sectors to protect the surface quality of various products against corrosion or abrasion and significantly improve their working life. It is essential to check the bath composition on a regular basis to ensure that the process is operating correctly. Typical examples of electroplating baths include alkaline degreasing baths or acidic or alkaline baths containing metals e.g. copper, nickel, or chromium, or components like chloride and cyanide. It is crucial that the chosen analysis technique fulfills high safety standards for these kinds of analyses and produces reliable results. The OMNIS Sample Robot system automatically pipettes and analyzes aggressive electroplating bath samples on different workstations, increasing the safety in the lab. This provides more reliable results in comparison to manual titration and is more time efficient as different parameters can be analyzed in parallel.

Determination of saccharin, benzamide, and o-toluenesulfonamide in a nickel electroplating bath using RP chromatography with UV detection.

The determination of iodate and iodide in used electroplating baths is a demanding task due to the high concentration of other ions. Iodate is used as a stabilizer for the bath and needs to be checked for proper electroplating. The use of a sodium chloride eluent, the Metrosep A Supp 5 - 250/4.0 column and direct UV/VIS detection permits the analysis of these samples without matrix interferences.

Lead is commonly used as stabilizer in electroless nickel plating processes. The regular and precise determination of the electrochemically active Pb(II) concentration is essential to keep the plating process running optimally under stable conditions. Differential pulse anodic stripping voltammetry can be used to determine the active lead content after dilution. The voltammetric determination has been established as a straightforward, sensitive, selective, and interference-free method for this application.

Determination of Fe and Zn in a nickel sulfate bath containing surfactants after UV digestion.

Determination of Cu in a nickel sulfate bath containing surfactants after UV digestion.

Thiourea is determined by cathodic stripping voltammetry (CSV) at the HMDE in ammonia buffer at pH 8.9. Chloride in the sample does not interfere with this determination.

The concentration of Ni in a Ni plating bath is determined by polarography in ammonia buffer pH 9.6.

The concentration of Co in a sulfamate Ni plating bath is determined by adsorptive stripping voltammetry (AdSV) inammonia buffer pH 9.6 with dimethylglyoxime (DMG) as complexing agent. All reagents have to be added in the order listed below. Special care has to be taken that the measuring solution is mixed well before the complexing agent is added. In case of precipitations of Ni-DMG further dilution of the sample is necessary.

The concentration of Cu in a Ni plating bath is determined by polarography in chloride-containing acetate buffer at pH 4.7.

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.

Electroless nickel plating is an important and well established process in the surface finishing industry. In the past, the addition of small amounts of lead has widely been used to stabilize the plating bath. With the increasing number of restrictions in recent years on the use of lead in consumber products, particularly electronics, alternative stabilizers were developed and introduced. One of the stabilizers used as lead replacement is iodate. It can be used as a single additive or in combination with bismuth or antimony. This method allows the determination of iodate directly in the plating bath sample by polarography. The method is simple and fast, however, sensitive and robust.

Electroless nickel plating is an important and well established process in the surface finishing industry. In the past the addition of small amounts of lead has widely been used to stabilize the plating bath. With the increasing number of restrictions in recent years on the use of lead in consumber products, particularly electronics, alternative stabilizers were developed and introduced. Two of the stabilizers used as lead replacement are antimony and bismuth. They can be used as a single additive or in combination with each other or iodate. This method allows the determination of antimony and bismuth directly in the plating bath sample by anodic stripping voltammetry (ASV). The method is simple and fast, however sensitive and robust

Monitoring Sb(III) stabilizer levels during electroless Ni plating is critical for high-quality coatings. Anodic stripping voltammetry offers fast, reliable Sb(III) analysis.

Electroless nickel plating ensures low-cost wear and corrosion resistance. Monitoring lead stabilizer levels in Ni plating baths is possible with the Bi drop electrode.

Electroless Ni plating offers superior surface finish and corrosion resistance. Anodic stripping voltammetry allows Bi stabilizer to be monitored in Ni plating baths.

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.