Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 160

chloride with chloramine-T and this cleaves the pyridine ring of nicotinamide (Von
Braun reaction), giving a product which has a strong blue fluorescence in alkaline
medium.

Quinone monoxime benzensulphonote ester
Cyanide has been determined by redox and substitution reactions. The reactions of
cyanide with quinone monoxime benzenesulphonate ester [259,260] are highly selective.
This reagent reacts specifically with cyanide. Other anions such as sulphide and
thiocyanate, which interfere in most tests for cyanide, do not interfere in these
determinations.
Guilbault and Kramer [261] have proposed a specific method for the determination of
cyanide based on its reaction with quinone monoxime benzenesulphonate ester, giving a
green fluorescent compound. In a later paper these authors reported the reaction of
cyanide with several quinones and quinone derivatives: p -benzoquinone, N-
chlorobenzoquinoneimine and substituted quinone monoxime benzenesulphonate esters
and ethers. All of these compounds react specifically with cyanide to give fluorescent
products. The proposed reaction of cyanide with p-benzoquinone is

In general, all of the products have approximately the same excitation and emission
wavelengths, 440 and 500nm, respectively. Substitution on the quinone ring decreases the
fluorescence of the product and the rate of reaction. The order of fluorescence intensity
and the rate of reaction increase in the following order of solvents used: dioxane<ethyl
formate

<2-methoxyethanol<methanol<acetonitrile<dimethylformamide< dimethyl

sulphoxide. This parallels the order of the dielectric constants of the solvents.

Quinoline-8-ol-5 sulphonic acid
The better sensitivity of fluorometric methods versus colorimetric methods can be
observed in the determination of cyanide with quinoline-8-ol-5-sulphonic acid [262]. The
colorimetric method is sensitive to 1µg mL −1 of cyanide whereas the sensitivity of the
fluorometric method is 0.02µg mL −1 of cyanide.

2', 7'-di(acetoxymercuri) fluorescein
Using 2 ′ ,7 ′ -di(acetoxymercuri) fluorescein, two methods for the determination of cyanide
have been proposed [263].

Enzymatic methods
Cyanide can be determined by the inhibitory action over the enzymatic activity of the
hydraluronidase enzymatic system. One method involves the hydrolysis of the non-
fluorescent indoxyl acetate (i) which measures the enzymic activity of hyaluronidase
through the formation of the highly fluorescent indigo white (iii) [264].