Inorganic nickel determination

Since the analyte is often present in quite a complex matrix comprising other elements or substances that may or may not interfere with any projected method of determination, and may indeed be quite a minor constituent of the whole sample, these considerations will effectively dominate the working details of any analytical procedure. There can therefore be no case for prescribing a single definitive method for (say) nickel that would be universally applicable to its determination in alloys see Alloys), organometallic compounds see Organometallic Complexes), inorganic salts see Ionic Bonds), or coordination compounds see Coordination Complexes), to its presence as a trace constituent see Trace Element) in maize or other plant products, or in natural waters or effluents. 

The inorganic contamination of the sediment core was assessed by a determination of selected heavy metals. According to the screening programme of the ICPR (International Commission for the Protection of the Rhine), the elements cadmium, nickel, chromium, lead, copper and zinc were analysed. The vertical concentration profiles are shown in Fig. 4 including a corresponding time scale. 

A good example of the application of this method is its use for the micro-determination of beryllium, iron, cobalt, nickel and chromium in moon dust and moon rock. Trifluoroacefylacetone and heptafluorodimethyloctanediol were used to obtain the chelates of metals in the moon samples [48]. The examples cited are indicative of the wide possibilities of this method in inorganic microanalysis. 

Nickel is often used as matrix modifier in the determinations of arsenic and selenium. Nickel stabilizes arsenic up to about 1700 K, and selenium up to about 1500 K. This is presumably due to the formation of thermally stable nickel arsenide and nickel selenide. Nickel can also be used to stabilize bismuth, antimony, and tellurium. In addition, copper, silver, molybdenum, palladium, and platinum salts have been proposed as stabilizers for these elements. Palladium and platinum are the most suitable matrix modifiers for both inorganically and organically bound tellurium. Pretreatment temperatures up to 1320 K can be used. The effect of different matrix modifiers on the determination of antimony are shown in Figure 74. Without matrix modifiers the losses of antimony begin at 1000 K. Palladium, molybdenum, and nickel are the most suitable to stabilize antimony and with these modifiers pretreatment temperatures up to about 1600 K can be used. 

Inorganic ions in biological systems can be quantified by spectrophotometric methods provided they are present at suitable concentrations (of a few micrograms per milliliter or higher) and other species in the medium exhibit little or no absorption. However, many elements including aluminum, cadmium, chromium, and nickel usually cannot be determined by UV-visible spectrophotometry, because they occur at very low concentrations in biological systems. 

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