ANEX II

IV. DETERMINATION OF TOTAL NITROGEN CONTENT

9. MODIFIED PROCEDURES
9.1. Use a block digestion apparatus fitted with cylindrical flasks, instead of the digestion apparatus and the Kjeldahl flasks described in 5.5. and 5.1. In this case to identify potential trouble, each spot has to be checked individually (6.7.).
9.2. Use of steam distillation instead of direct heating of the flasks (6.4.). When the apparatus does not allow the use of distilled water, care should be taken that the water does not contain acid or alkaline volatiles.

9.3. A test portion of 1 g of milk (semi-macro Kjeldahl) can be used instead of 5 g (6.1.) provided:
the amounts of the reagents used for mineralization (6.1.): H2SO4, CuSO4 · 5 H2O, K2SO4, are reduced to the same ratio (1/5).
the total digestion time (6.2.) is reduced to 75 minutes.
the amount of sodium hydroxide solution (6.3.) is reduced to the same ratio (1/5).
an acid standard solution (4.7.) of lower concentration (0,02 to 0,03 mol/l) has to be used.
Note: Using one or more of these options is acceptable only if the repeatability value (8.2.1.) and the two accuracy tests results (6.7.) are in accordance with the requirements given in this method.