| abstract |
A method for the determination of an ion in an aqueous liquid in which the ion passes into a phase which is immiscible with the aqueous liquid and as a result a pH indicator which is present there undergoes a colour change which can be used for the determination of an ion; in order to increase the sensitivity of the measurement a compound of formula I, II or III is added to the miscible phase; the compounds (I), (II) and (III) being as follows: in which one of R1 to R4 is, alkyl, alkoxy or aralkyl and the others of R1 to R4 are the same or different and selected from nitro, halo, cyano, alkylsulfonyl or alkyl substituted with halogen; in which R5 to R9 are as defined for R1 to R4 or if R5 and R6 represent vitro groups, R8 and R9 can also denote hydrogen; in which R10, R11, R12, R13, R14 are the same or different and each denotes hydrogen, nitro, halo, cyano, alkylsulfonyl or alkyl substituted with halogen. |