should be at least 1 cm preferably 2 5 cm for this the nonreacting portion 4 of the matrix as a rule contains no detection reagents however it is also possible for one or more components of the reagent system of reagent zone 5 to be present in this portion of the test strip the liquids used for impregnation consist of the reagents required for the desired detection reaction which are dissolved in a suitable solvent surfactants are as a rule also added in order to improve wettability an impregnating solution for glucose detection contains for example the components described in the first example an impregnation solution of sodium nitroprusside magnesium sulphate and phosphate buffer is used for the detection of ketones the detection of bilirubin can be carried out for example with the aid of an impregnating solution of a 2 5 dichlorophenyl diazonium salt in 0 1n hydrochloric acid one carrier matrix can also be impregnated several times in succession by the impregnating process according to the invention the components of the impregnations previously carried out are not thereby extracted it is also possible for the impregnating liquid to contain other auxiliaries such as for example water soluble polymers such additives are of interest above all if the reagents of the individual impregnations are to remain separated within the matrix especially in the case of multiple impregnations for example the detection reaction actually desired can in this manner be carried out after another reaction in which interfering components are to be eliminated the process according to the inventions is also outstandingly suitable for the production.