http://www.legislation.gov.uk/id/uksi/1996/1342/schedule/2

SCHEDULE 2METHODS OF ANALYSIS

PART I

25d.DETERMINATION OF TRACE ELEMENTS IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY (GENERAL PROCEDURE)

EXPRESSION OF RESULTS8

The percentage of trace element (E) in the fertiliser is equal to:

E (%) = [(x s - x b) \times V \times D] / (M \times 104) .

If method (25c) has been used:

E (%) = [(x s - x b) \times V \times 2D] / (M \times 104),

where:

E is the amount of the trace element determined, expressed as a percentage of the fertiliser;
x_s is the concentration of the test solution (6.2), in μg/ml;
x_b is the concentration of the blank solution (7.1), in μg/ml;
V is the volume of the extract obtained by Method 25a or 25b, in ml;
D is the factor corresponding to the dilution carried out in (6.2);
M is the mass of the test sample taken in accordance with Method 25a or 25b in grams.

Calculation of dilution factor D:

If (a₁), (a₂), (a₃), . . ., (a_i) and (a) are the aliquot portions and (v₁), (v₂), (v₃), . . ., (v_i) and (100) are the volumes in ml corresponding to their respective dilutions, the dilution factor D will be equal to:

D = (v 1 / a 1) \times (v 2 / a 2) \times (v 3 / a 3) \times . . . \times (v i / a i) \times (100 / a) .