Indigo detection

Analysis. Indium can be detected to 0.01 ppm by spectroscopic analysis, using its characteristic lines in the indigo blue region, at wavelengths 4511.36, 4101.76, 3256.09, and 3093.36 nm. Procedures for the quantitative deterrnination of indium in ores, compounds, alloys, and for the analysis of impurities in indium metal are covered thoroughly in the Hterature (6). 

Wood, S.,et ah, Erythrosine is a potential photosensitizer for the photodynamic therapy of oral plaque biofihns, J. Antimicrob. Chemother., 57, 680, 2006. Hurlstone, D.P., et ah. Indigo carmine-assisted high-magnification chromoscopic colonoscopy for the detection and characterisation of intraepithelial neoplasia in ulcerative colitis a prospective evaluation. Endoscopy, 37,1186, 2005. 

Indigo is considered as one of the most important dyes. Its preparations are usually analysed by HPLC with UV-Vis [46,60] or APCI MS detection. [61,62] Separation of the colouring components of indigo extracted with DMSO is usually performed with the use of a Cl 8 column. Spectrophotometric detection of blue indigotin is performed at 617 nm, red indirubin at 540 nm, and brown isoindigo at 365 and 490 nm. As mobile phases, mixtures of methanol or acetonitrile and water with the addition of TFA or formic acid are used to ensure compatibility with the requirements of the APCI source. 

Finally, two ancient textiles of the sixteenth and seventeenth century were studied. The presence of molecular ion at m/z 263 and fragment ions at m/z 235 and m/z 247 demonstrate that indigo was used (Figure 15.7). No mordant-related peaks were detected. Lee et al. explain that indigo has so strong an affinity with the fibres that it could be used without mordant. 

Both HPLC and GC-MS were employed for the separation, identification and quantitation of the decomposition products of indigo and indigo carmine. The chemical structures of the dyes are shown in Fig. 3.73. Carboxylic acids were preconcentrated before HPLC analysis either by ion-exchange SPE or by solid-phase microextraction. HPLC measurements were performed in a Sarasep column (300 X 7.8 mm i.d.) using 5 mM H2S04 at a flow rate of 0.7 ml/min. Analytes were detected at 215 nm. The main intermediates formed during the photocatalytic decomposition are compiled in Table 3.26. The results demonstrated that... 

MAIN INTERMEDIATE PRODUCTS DETECTED DURING PHOTOCATALYTIC DEGRADATION OF INDIGO CARMINE AND INDIGO... 

Indium produces characteristic lines in the indigo-hlue region and may be detected by spectroscopic analysis. iVt trace concentrations In may be determined by lame-AA, fumace-AA, ICP-AES, x-ray fluorescence, or neutron activation analysis. 

Dyestuffs of plant origin include indigo blue, used to dye jeans. A poison of detective novel fame is strychnine, obtained from the plant resin curare (Box 1.6). 

Analysis. The colorimetric method for In is capable of a detection limit of 20 ppb. Indium or an In compound in the flame gives an indigo blue color (451.1 nm). This photon line allows for the spectrophotometric determination ofinby AAS (atomic absorption flame spectroscopy). The method is sensitive to about 300 ppb. With ETAAS, this limit drops to 10 ppb, as it does with ICPAES. ICPMS drops the limit to 0.01 ppb. Alizarin detects In, as well as Al, but the reaction with Al can be masked by addition of F to a spot test. The limit of detection is about 1 ppm. 

The detection and determination ot the perchlorates.—The perchlorates give no precipitates with silver nitrate or barium chloride soln. cone. soln. give a white crystalline precipitate with potassium chloride. Unlike all the other oxy-acids of chlorine, a soln. of indigo is not decolorized by perchloric acid, even after the addition of hydrochloric acid and they do not give the explosive chlorine dioxide when warmed with sulphuric acid unlike the chlorates, the perchlorates are not reduced by the copper-zinc couple, or sulphur dioxide. Perchloric acid can be titrated with —iV-alkali, using phenolphthalein as indicator. The perchlorates can be converted into chlorides by heat and the chlorides determined volumetrically or gravimetrically they can be reduced to chloride by titanous sulphate 28 and titration of the excess of titanous sulphate with standard permanganate they can be fused with zinc chloride and the amount of chlorine liberated can be measured in terms of the iodine set free from a soln. of potassium iodide and they can be... 

Detection of Indigo Carmine and Artificial Organic Dyestuffs. 

Also by oxidising the carmine solution with permanganate for the determination of the mdigotin, many artificial organic dyes may be detected thus, pure indigo carmine solution remains yellow, whereas it may be bluish, violet, grey or reddish in presence of artificial organic dyes. 

Simultaneous detection of indigo and sodium dithionite for control of dyeing processes... 

The aim of an indigo sensor is to keep the leuco-indigo concentration in the solution at a constant value. In the past, different methods were developed for detection of the indigo and sodium dithionite concentration, but up to now with limited success. The sodium dithionite concentration can be determined by volumetric titration with iodine2 22 or with K3[Fe(CN)6]23. The endpoint detection of these titrations can be done visually22,24"25 or... 

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