Sulphur dyes detection

Sulphur dyes can be detected by the evolution of hydrogen sulphide when treated with reducing agents. A little of the dyestuff or dyed material... 

The same technique has been employed for the purification of Food Colour Red No. 106 (Acid red). The chemical structure of the dye is shown in Fig. 3.118. The separation process was controlled by analytical RP-HPLC carried out in an ODS column (150 X 4.6 mm i.d. particle size 5 /.an). The mobile phase consisted of ACN-0.01 M TFA (27 73, v/v). The flow rate was 1 ml/min and analytes were detected at 254 nm. Equilibrated n-butanol and water were employed for CCC separation. OP was acidified with 40 mM of sulphuric acid, and 30 mM of aqueous ammonia was added to the LP. The coil was rotated at 800 rpm and LP was pumped at a flow rate of 1 ml/min. Fractions of 1 ml volume were taken from the effluent. The CCC profile of Food Colour Red No. 106 in CCC is shown... 

Separation of mono- and di-ester pyrrolizidine alkaloids has been achieved by ion-pair adsorption t.l.c., using chloride (or iodide) as the counter-ion.48 Chloranil has been used to oxidize pyrrolizidine alkaloids on t.l.c. The pyrrole derivatives that were formed were then detected with Ehrlich s reagent49 or sulphuric acid.50 Mixtures of pyrrolizidine alkaloids have been separated by h.p.l.c. on a reversed-phase styrene-divinylbenzene resin.51 In a sensitive method for the detection of pyrrolizidine alkaloids, the protonated alkaloids were complexed with aqueous methyl orange. The dye was then released from the complex and estimated spectrophotometrically.52... 

The use of diphenylamine in concentrated sulphuric acid to identify cellulose nitrate was originally used in forensic investigations in the 1930s to detect the presence of explosives on suspects hands (Gowan and Purdon, 1967). As a forensic test, wax casts were taken of the suspect s hands and the diphenylamine reagent applied to the wax. Sulphuric acid reacts with cellulose nitrate to form nitronium ions (N02 ) which then oxidize diphenylamine to form the dark blue dye, diphenylbenzidine violet. 

---