Conway microdiffusion method

The potentiometric determination of cyanide using ion selective electrodes has become yet another very popular technique, because it is convenient, rapid, and sensitive method of analysis (Frant et al, 1972). Microdiffusion of biological samples containing cyanide is recommended prior to potentiometric determination. The use of a cyanide ion-selective electrode in combination with the Conway microdiffusion method for the measurement of cyanide concentrations in human red blood cells and plasma was reported with remarkable recovery of cyanide (Yagi et al, 1990). Ion chromatographic determination of sulfide and cyanide in real matrices by using pulsed amperometric detection on a silver electrode was reported by Giuriati et al. (2004). 

Separation of Sip4 by the Conway microdiffusion method is a slow process [2,3], The sample to be analysed (e.g., copper, aluminium, iron alloys, dolomite, titanium dioxide) is decomposed with acids in a polystyrene Petri dish to which hydrofluoric acid is subsequently added. The Sip4 evolved is trapped in NaOH solution, e.g., in another Petri dish placed beside. Both vessels are placed inside another, tightly closed, polystyrene vessel. To achieve quantitative separation of silicon, the reaction is carried out at 70°C for 18 h. 

The Conway microdiffusion method (2) was employed to determine the amounts of ammonia and amines resulting from irradiation of duplicate samples and subsequent dissolution in 0.006N H2S04. The Russell procedure (15) for a quantitative colorimetric determination was employed with the readings made at 628 mfi on a Beckman Spectrophotometer. 

Conway, E. J. and O Malley, E. Microdiffusion methods. Ammonia and urea using buffered absorbance (revised methods for ranges greater than 10 mu/g N). Biochem. 

Method. To die outer compartments of two Conway microdiffusion cells add 0.5 ml of dilute sulphuric acid, and to the inner comparhnents add 0.5 ml of... 

Microdiffusion methods in which ethanol is released from the sample and absorbed by an acid dichromate solution. Ethanol is oxidized to acetic acid and at the same time the yellow dichromate is reduced to green chromic ion. This technique can be carried out in a Conway dish. 

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