A kit comprising: a first solid composition comprising: (a) a peroxidase enzymatic catalysing agent, wherein the peroxidase enzymatic catalysing agent is selected from Lactoperoxidase, Myeloperoxidase, Eosinophil peroxidase, Urea peroxidase and plant-derived peroxidases; (b) an oxidizable substrate selected from: (i) chlorides such as sodium chloride, iodides such as potassium iodide and sodium iodide; or (ii) sodium thiocyanate, potassium thiocyanate, sodium bisulfite, sodium hydrosulfite, sodium metabisulfite, sodium nitrite, potassium nitrite, sodium hypochlorite and combinations thereof; (c) optionally at least one inert filler; and (d) a buffer system, wherein the buffer system is selected from citric acid: trisodium citrate; calcium lactate : citric acid; sodium L (+)-tartrate dehydrate: citric acid; calcium lactate : DL-malate : malic acid and Sodium L (+)- tartrate : tartaric acid a second solid composition comprising: (e) at least one oxidising agent, wherein the oxidising agent is selected from calcium peroxide, sodium peroxide, sodium percarbonate and the combination of dextrose and glucose oxidase; and (f) optionally at least one inert filler. a first solid composition comprising: (a) a peroxidase enzymatic catalysing agent, wherein the peroxidase enzymatic catalysing agent is selected from Lactoperoxidase, Myeloperoxidase, Eosinophil peroxidase, Urea peroxidase and plant-derived peroxidases; (b) an oxidizable substrate selected from: (i) chlorides such as sodium chloride, iodides such as potassium iodide and sodium iodide; or (ii) sodium thiocyanate, potassium thiocyanate, sodium bisulfite, sodium hydrosulfite, sodium metabisulfite, sodium nitrite, potassium nitrite, sodium hypochlorite and combinations thereof; (c) optionally at least one inert filler; and (d) a buffer system, wherein the buffer system is selected from citric acid: trisodium citrate; calcium lactate : citric acid; sodium L (+)-tartrate dehydrate: citric acid; calcium lactate : DL-malate : malic acid and Sodium L (+)- tartrate : tartaric acid (a) a peroxidase enzymatic catalysing agent, wherein the peroxidase enzymatic catalysing agent is selected from Lactoperoxidase, Myeloperoxidase, Eosinophil peroxidase, Urea peroxidase and plant-derived peroxidases; (b) an oxidizable substrate selected from: (i) chlorides such as sodium chloride, iodides such as potassium iodide and sodium iodide; or (ii) sodium thiocyanate, potassium thiocyanate, sodium bisulfite, sodium hydrosulfite, sodium metabisulfite, sodium nitrite, potassium nitrite, sodium hypochlorite and combinations thereof; (i) chlorides such as sodium chloride, iodides such as potassium iodide and sodium iodide; or (ii) sodium thiocyanate, potassium thiocyanate, sodium bisulfite, sodium hydrosulfite, sodium metabisulfite, sodium nitrite, potassium nitrite, sodium hypochlorite and combinations thereof; (c) optionally at least one inert filler; and (d) a buffer system, wherein the buffer system is selected from citric acid: trisodium citrate; calcium lactate : citric acid; sodium L (+)-tartrate dehydrate: citric acid; calcium lactate : DL-malate : malic acid and Sodium L (+)- tartrate : tartaric acid a second solid composition comprising: (e) at least one oxidising agent, wherein the oxidising agent is selected from calcium peroxide, sodium peroxide, sodium percarbonate and the combination of dextrose and glucose oxidase; and (f) optionally at least one inert filler. (e) at least one oxidising agent, wherein the oxidising agent is selected from calcium peroxide, sodium peroxide, sodium percarbonate and the combination of dextrose and glucose oxidase; and (f) optionally at least one inert filler. <EOS>