Malachite green complexes, with

Phosphomolybdate - Malachite Green complex with absorbance at 620 nm... 

Numerous spectrophotometric methods are based on the formation of ion-associates of the anionic iodide complex (CdL or Cdls ) [52-55] and bromide (CdBr4 ) [56] complexes with basic dyes. In the old flotation-spectrophotometric method (e = 1.3-10 ) [52], Crystal Violet is used, DIPE as floating solvent and acetone for dissolution of the floated compound. Other dyes that have been used in association with the cadmium iodide complex include Rhodamine 6G [57], Malachite Green (extraction with benzene) [53,54], and a basic azo dye [55]. 

The anionic zinc-thiocyanate complex forms ion-pairs with basic dyes, extractable by e.g., benzene or CCI4 [68]. Use has been made of Rhodamine B [69], Victoria Blue B [70], or Malachite Green [89], with e values within (5-12)-10 [71]. 

Phosphomolybdate forms strong ion association complexes with basic dyes at low pH. For example, the sensitivity of a method based on spectrophotometric determination of the 12-MPA-malachite Green complex [84,85] was approximately 30 times that of a reduced phosphomolybdate determination. Other dyes used for this purpose include Saffranin, brilliant green, Fuchsine red, methylene blue, methyl violet, and Rhodamine B [5]. Surfactants such as polyvinyl alcohol are frequently used to avoid precipitation of the ion association complex. 

A proper identification of the active enzyme-substrate complex requires accurate correlations of the kinetics of the complex with the over-all activity. With this method, many obscure aspects of the enzyme action are more readily understood for example, the loss of activity due to the formation of inactive forms of the enzyme can be directly measured as a decrease in the concentration of the active enzyme-substrate compound. For simultaneous measurements, a single-beam spectrophotometer for recording the enzyme-substrate compound kinetics at 405 mu and a platinum microelectrode are satisfactory. A double-beam spectrophotometer may be used with the second beam set at 230 m i for recording the hydrogen peroxide kinetics, at 268 m/i for recording ascorbic acid kinetics, or at 610 mu for recording malachite green kinetics with peroxidase. If a doublebeam spectrophotometer is not available, the enzyme-substrate kinetics may be recorded in one experiment and the over-all activity in a duplicate experiment. Some examples of these types of studies are included. 

Molybdates are used in a variety of industries. Sodium molybdate is used for the synthesis of pigments such as molybdate chrome orange, which is a homogeneous mixture of lead molybdate, lead chromate and lead sulphate. This use is likely to decline because of concerns about health hazards associated with lead, but phosphomolybdates and phosphotungstomolybdates are used to complex certain dyestuffs to produce pigments. A few of the best-known of these are Malachite Green, Rhodamine Band Methyl Violet, also used as indicators in analytical chemistry. 

Catalysts have been used to make end points detectable these have been reviewed by Mottola. In such systems the titrant reacts rapidly with the substance titrated, but excess reagent reacts only slowly with an indicator in the absence of an appropriate catalyst. For example, small amounts of complexing agents such as EDTA can be determined by titration with Mn(II). With malachite green as indicator in the presence of periodate, the excess Mn(II) catalyzes the indicator oxidation. 

Absorption and fluorescence spectra of 7-aminocoumarin derivatives have been recorded and the photophysics of coumarin inclusion complexes with 0- and y-cyclodextrins investigated. Solvent effects on the photophysical behaviour of pyrrolocoumarin derivatives are similar to those on the psorolens . Vibronic exciton bands and the absorption spectra of Eosin Y dimers have been analysed theoretically and compared with experimental data. Picosecond spectroscopic studies have been made on the ionic photodissociation dynamics of malachite green leucocyanide . The lowest state produces ions within 0.1 to 0.5 ns whilst for higher states 6-13 ps are sufficient for the development of charge separation. The photophysics of crystal violet in a series of n-... 

The anionic complex of Sb(III) with mandelic acid forms with Malachite Green an associate which is extractable into chlorobenzene from weakly acid solutions (e = 6.T10 ) [54]. Mandelic acid and other organic reagents have been applied for the joint determination of Sb(ffl) and Sb(V) [55,56]. 

Besides the Methylene Blue, other spectrophotometric methods, based on ion-associates of anionic boron complexes with basic dyes are used. Extractable associates with BF4 are obtained with Nile Blue A (formula 4.32) [7,36,37], Capri Blue (formula 4.31) [38], Malachite Green (formula 4.26, with Me instead of Et), Chrompyrazole II (CHCI3, e = 6.7-10 at 595 nm) [40], etc. 

In addition to BF4 , other anionic boron complexes, also forming ion-associates with basic dyes, have been applied to determine boron, namely 2,4-dinitro-1,8-naphthalenediol and Brilliant Green (formula 4.26) (toluene, e = 1.0-10 at 637 nm [41 3], 2,6-dihydroxy-benzoic acid, and Malachite Green (chlorobenzene, e = 9.5-10 [5], 2,3-dihydroxy-naphthalene and Crystal Violet (benzene, e = 8.8-10 [44]), mandelic acid, and Malachite Green (benzene, e = 6.5-10 ) [45,46], pyrocatechol derivatives, and Ethyl Violet (toluene, e = 1.05-10 [47,48]. The ion-pair of the salicylate complex of boron with ferroin has also been proposed (CHCI3) [49]. 

Cadion has been used in determining cadmium in industrial fluids (in zinc production) [20,83], and in soils [84]. The ion associate of cadmium iodide complex with Malachite Green has been used for determining Cd in fertilizers [85], and industrial fluids (in zinc production) with Crystal Violet for determining Cd in food products and in waste waters [86]. 

Spectrophotometric methods based on ion associates with basic dyes are very sensitive. The Co-thiocyanate complex was associated with Malachite Green (CCI4 -i- cyclohexane), (e = 8.6-10 ) [61], Turquoise Blue (triphenylmethane dye) (toluene -1- DMF) [62], and 6-nitrodimethyline-carbocyanine [63,64]. The anionic complex of Co with chloro-oxine [65] associated with Rhodamine 6G was extracted with benzene. The complex of Co with 2-nitroso-l-hydroxynaphthalene-4-sulphonic acid was extracted into CHCI3 as the associate with a basic azo dye (e = 1.66-10 at 566 nm) [66]. 

Methods based on extraction of Ge(IV) complexes with 3,5-dinitropyrocatechol or 4-nitropyrocatechol, associated with Brilliant Green (CCI4, e =1.4-10 ), Nile Blue A (CHCI3, e =1.3-10 ), and Methylene Blue (benzene, e =1.0-10 ), have been recommended [45,46]. The anionic complex of Ge with Alizarin Complexone, associated with Rhodamine 6G, is the basis of a sensitive method (e = 2.9-10 ) [1,2]. In another very sensitive method, use has been made of tetrabromofluorescein and Rhodamine 6G [47]. Ge is determined after extraction (with chlorobenzene) with mandelic acid and Malachite Green (e = 1.33-10 ) [48]. 

The bromide complex of indium gives extractable ion-associates with the xanthene basic dyes Rhodamine B [49] and triphenylmethane dyes. Brilliant Green [50,51], and Crystal Violet [52], extractable into non-polar solvents. The related dye. Malachite Green, has been used to form an associate with tetra-iodoindate, extractable with benzene, hexane, and CCI4 [53]. 

Sensitive methods for lead include a number based on ion-associates formed by the anionic iodide-lead complex and the basic dyes, such as Malachite Green (benzene, e = 8.0-10 ) (58,59], Brilliant Green (59], Ethyl Violet [59], fuchsin (formula 27.1) (extraction with benzene-cyclohexane from 0.2 M H2SO4, e = 2.0-10 at 560 nm [60], and cyanine dyes [61]. In the method involving the antipyiine dye Chrompyrazole I (formula 23.1), the pseudo-solution formed is stabilized with the non-ionic surfactant OP-10 [62]. 

There exist methods based on extraction of the bromide-lead complex with basic dyes, such as Malachite Green [59,63], Victoria Blue 4R (59], and Butylrhodamine B (benzene, e = 6.2-10 ] [64,65]. 

Pb has been also determined by the FIA technique, after conversion in a picolinic acid complex which is then associated with Malachite Green [66],... 

Mercury(II) forms anionic complexes with F, Br, and CF ions, which react with basic dyes to give ion-associates extractable into organic solvents. Sensitive extractive spectro-photometric methods for determining mercury are based on such reactions with the following dyes Crystal Violet (e = O-IO -IO-IO ) [43 6], Malachite Green and Methyl... 

Many other basic dyes besides Methyl Violet have been used in sensitive extraction-spectrophotometric methods for the determination of Ta as the anionic complex TaFe [92]. Mention may be made of Crystal Violet (formula 4.27) (e = 8.5-10" ) [91-93], Brilliant Green (e = 1.2-10 ) [94,95], Malachite Green [96,97], Methyl Green (e = 1.2-10 ) [98], Rhodamine 6G and butylrhodamine B [99], Methylene Blue (e = 9.1-10" ) [98], Nile Blue A [100], Capri Blue (e = I.TIO ) [101], and Victoria Blue B [102]. Ion-associates with these dyes are extractable from acid solutions into benzene, toluene, CHClj, xylene, or dichloroethane. 

Methods for Pd determination based on ion-associates with basic dyes are often very sensitive. In extraction-spectrophotometric methods, thiocyanate [84-89], chloride, and bromide [84] anionic complexes of palladium are associated with Brilliant Green [84], Malachite Green [85,88], Rhodamine B (e = 9.0-10 ) (86), Rhodamine 6G [89], and Methylene Blue [87]. In flotation-spectrophotometric methods, ion-associates formed by the... 

Besides the Rhodamine 6G-SnCl2 flotation-spectrophotometric method described above, similar methods using other basic dyes, e.g., Victoria Blue B, Victoria Blue 4R, Capri Blue [41], Crystal Violet (e = 2.1-10 ) [42], or Nile Blue A [43], have been proposed. An ion-associate of the chloride platinum complex with Methyl Green has been extracted with a mixture of 1,2-dichloroethane and CCI4 (e = 1.45-10 ) [44]. The ion-associate of the Pt-thiocyanate complex with Malachite Green has been extracted with benzene [45], and a thiocyanate- or iodide- Pt complex associated with Crystal Violet has been extracted into xylene or toluene [46]. 

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