ASSAY FOR DIBROMONITRILOPROPIONAMIDE

Abstract: A method of testing for the presence of dibromonitrilopropionamide in a sample, which comprises adding to the sample, under alkaline conditions and in the presence of magnesium ions, a phenolic or anilinic compound that generates a colour; and observing the resultant colour. The appropriate reagents may be formulated as a kit, e.g. using pyrocatechol as the phenolic compound.

Description: ASSAY FOR DIBROMONITRILOPROPIONAMIDE Field of the Invention This invention relates to an assay for the compound NC-C(Br) 2 -CON__ 2 , i.e. dibromonitrilopropionamide (DBNPA) . 5 Background of the Invention DBNPA is a biocide that is used in cooling towers, in order to control organisms such as Legionella. in paper- making, and in other aqueous environments. An object behind the invention is to monitor the level of such 10 compounds in the water. Summary of the Invention According to the present invention, a method of testing for the presence of DBNPA in a sample comprises adding to the sample, under alkaline conditions and in the 15 presence of a magnesium compound, a phenolic or anilinic compound that generates a colour; and observing the resultant colour. The invention is based on the discovery that there are many phenolic and anilinic compounds which can react with 20 DBNPA, to generate a coloured species, in the presence of magnesium ions. The novel method is both simple and effective. A kit of the essential components can be provided. Description of the Invention 25 The reaction is preferably conducted at a pH of 8.5 to 10, e.g. about 9. For this purpose, a buffer such as an alkali metal tetraborate (e.g. borax) , Tris.HCl or Tris- glycine.HCl can be used. The magnesium ions can be provided in the form of any 30 Mg compound that catalyses the reaction. MgC0 3 , as present in hard water can be used, as can MgCl 2 , MgSO A , Mg(N0 3 ) 2 and other Mg salts. Calcium, sodium, potassium and aluminium ions apparently do not catalyse the reaction. The assay may be affected by the presence of iron 35 (III) or iron (II) . If present, iron ions are therefore preferably removed, e.g. using a cation-exchange resin. The phenolic or anilinic compound can be chosen, depending on the conditions, by anyone skilled in the art. It is preferably pyrocatechol, although it may be any analogous compound, e.g. of the l,4-benzenediol/ benzenediamine/aminophenol or, preferably, 1,2- benzenediol/benzenediamine/a inophenol-type. Coloursgiven by certain suσh compounds are tabulated below: m-Phenylenediamine gives no colour, and neither does phenol, but the use of such compounds is included within the scope of this invention; a colour can be generated by the addition of an oxidising agent such as periodate. Guaiacol gives an orange colour, and isohomovanillic acid faint purple, in the presence of borax. The colour is likely to be pH-dependent, but the optimum pH can be determined simply. In use of the method according to the invention, the colour that is generated is preferably compared with a blank of the phenolic or anilinic compound. The colour can be measured by any suitable means. The following Examples illustrate the invention. Example l To aqueous DBNPA was added 10% v/v of Tris-HCl buffer, pH 9.1, containing a catalytic amount of MgCl 2 . Pyrocatechol was added in aqueous form, to a concentration of 50 μg/ml. A violet colour was allowed to develop over 5 minutes, and was read at 537 n . The colour turned yellow in acid. It also acted as an oxidation-reduction indicator, and was decolorised by SnCl 2 and K 3 Fe(CN) 6 . The reading allowed quantification of the amount of DBNPA, by comparison with a pyrocatechol-containing blank. Example 2 The following steps were conducted: 1. To a 3 ml water sample containing DBNPA, add 25 μl of 0.1 M MgCl 2 . Mix thoroughly. 2. Add 200 μl of 0.2 M Tris buffer. Mix. 3. Add 150 μl 1.5 mg/ml 0.001M catechol. Mix. 4. After 3 minutes, read the optical density at 550 nm. Example 3 The following steps were carried out: 1. Dilute 1.5 ml of sample to 3 ml with RO water. 2. Pass the diluted sample through a column containing Dowex 50W-X8 cationic resin in the lithium form. 3. Add 25 μl of 0.1M magnesium chloride to the column eluent. Mix. 4. Add 200 μl of a Tris/hydrochloric acid buffer. Mix. 5. Add 150 μl of a catechol solution. Mix. 6. After 3 minutes, read the optical density at 550 nm.

Claims: CLAIMS 1. A method of testing for the presence of dibromo- nitrilopropionamide in a sample, which comprises adding to the sample, under alkaline conditions and in the presence of magnesium ions, a phenolic or anilinic compound that can generate a colour; and observing the resultant colour. 2. A method according to claim 1, in which the compound is pyrocatechol. 3. A method according to claim 1 or claim 2, which is conducted at pH 8.5 to 10. 4. A method according to any preceding claim, which is conducted in the absence of iron ions. 5. A method according to claim 4, which additionally comprises the prior step of removing iron ions. 6. A kit, suitable for use in a method according to claim 1, comprising containers containing respectively a buffer adapted to maintain pH 8.5-10; and the phenolic or anilinic compound. 7. A kit according to claim 6 , in which the compound is pyrocatechol. 8. A kit according to claim 6 or claim 7, in which either or an additional container contains a magnesium compound.

Inventors: HILL MARTYN WILLIAM, SHARMAN DENNIS FRANK, HILL, MARTYN, WILLIAM, SHARMAN, DENNIS, FRANK
Applicants: CTS BIOCIDES LTD, CTS BIOCIDES LTD.
Application year: 1991
Main classification: G01N31
IPC codes: G01N31