Copper complex colorimetric determination

The complexation of neomycin with copper results in the formation of a blue-coloured compound which has also been made the basis of a colorimetric determination of neomycin in pharmaceutical formulations . Maximum colour intensity was observed at a solution pH of 10. Further investigation showed the stoichiometry of the complex to be 1 1 in alkaline solution. 

Figure 8. Colorimetric determination of site isolation in 3-aminopropyl functionalized mesoporous silica by complexation to copper ions [22].

Clinical oncology, 18, 784 Colorimetric determination of lead(Il), 9 Copper complexes, 6, 17, 18,57,81,97, 131 Coumarin, 145, 557, 558 Crab-like synthesis of aza-crown... 

After extraction of the lead diethyldlothlocarbamate Into an organic solvent the lead can be removed by shaking with concentrated hydrochloric acid (T3), or the organic solvent evaporated and the residue dissolved In hydrochloric acid (04) followed by colorimetric determination as the dlthlzonate or by some other means. Alternatively, the lead can be determined colorlmetrlcally in dlethyldlthlocarbamate-carbon tetrachloride solution by shaking with excess copper sulfate solution to convert the lead complex Into the copper complex which Is determined at 435 mu (T3). Lead complexed with dlethylammonlum dlethyldlthlocarbamate Is usually removed by evaporating the... 

Copper(II) has often been colorimetrically determined by its intensely blue ammonia complexes. The a diagram in Figure 9-1 shows that a similar situation occurs to that for the Fe(III)-SCN complexes, namely that a constant excess NH3 concentration will be required if the color is to be proportional to the Cu(II) concentration. Even more useful, now, is the use of EDTA in the determination of metal ions. Copper ion is often titrated in ammonia buffers. Let us examine the constants to see if quantitative complexing of Cu(II) by EDTA should occur in the presence of NH3. 

Nickel also is deterrnined by a volumetric method employing ethylenediaminetetraacetic acid as a titrant. Inductively coupled plasma (ICP) is preferred to determine very low nickel values (see Trace AND RESIDUE ANALYSIS). The classical gravimetric method employing dimethylglyoxime to precipitate nickel as a red complex is used as a precise analytical technique (122). A colorimetric method employing dimethylglyoxime also is available. The classical method of electro deposition is a commonly employed technique to separate nickel in the presence of other metals, notably copper (qv). It is also used to estabhsh caUbration criteria for the spectrophotometric methods. X-ray diffraction often is used to identify nickel in crystalline form. 

Pelts and Belcher [46] have described a semi-automated method for the simultaneous determination of nitrogen and phosphorus in soil. Up to 40 samples are digested with sulphuric acid using a copper sulphate-sodium sulphate catalyst at 370°C for 2.25h in a thermostatically controlled block. Nitrogen is then determined in the 0.2-2.25% range as ammonia by automatic colorimetric analyses of the indophenol blue complex at 630nm. 

Samples of metal complexes isolated from the final solutions were subjected to microanalysis (for carbon, hydrogen, oxygen, and sulfur). Metals were determined colorimetrically by the following methods— copper as the complex formed with sodium diethyl dithiocarbamate (6) cobalt as the nitroso-R salt complex (7) nickel as the dimethylglyoxime complex (4). 

Analysis of the imine polymer can be performed by a colorimetric method which is based on the complexation reaction with copper [2], Elemental analysis serves for the determination of the nitrogen content. Potentiometric and conductometric titration is also used in analysis [3]. For quantitative routine determination, preferably in the form of the hydrochloride, refractometry is recommended. 

In view of the strong colours of many of the biguanide complexes, these have been used as colorimetric reagents, e.g. the use of phenylbiguanide for spectrophotometric determination of Fe and CN ions. A polarographic study" of a bis(biguanide)copper(II) complex gives a kinetically controlled wave prior to a two-electron transfer, followed by a diffusion controlled second wave due to the reduction of bis species in solution. 

The biuret method The bimet method is a colorimetric technique specific for proteins and peptides. Copper salts in alkaline solution form a pruple complex with substances containing two or more peptide bonds. The absorbance produced is proportional to the number of peptide bonds that are reacting and therefore to the number of protein molecules present in the reaction system. Thus, the biuret reaction with proteins is suitable for the determination of total protein by spectrophotometry (at 540-560 nm). The method is used extensively in clinical laboratories, particularly in automated analyzers in which protein concentration can be measured down to 0.1-0.15gl. The use of bovine or human serum albumin to standardize the biuret method is well established. ITigh-purity albumin contains only amino acids its nitrogen content is a constant fraction... 

Another colorimetric method for determination of traces of copper is based upon the use of bisry r/ohexanone oxalyldihydrazone. This is a selective and highly sensitive reagent for both cupric and cuprous ions. In alkaline solutions a blue complex is produced in the presence of copper which is stable for several days and is particularly suitable for absorptiometric measurement. The method first described by Nilsson has been modified by Somers and Garraway as follows ... 

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