BS EN 14107 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of phosphorous content by inductively coupled plasma (ICP) emission spectrometry
9 Procedure
9.1 Sample preparation: in order to avoid phosphorus pollution of the solutions, all sampling operations are carried out using polypropylene pipettes or automatic pipettes having disposable tips.

Weigh to within 0.001 g approximately 2.5 g (mass m in g) of sample in a 25 ml volumetric flask (volume V in ml), dilute to the mark with xylene and shake manually to homogenise.

Take two test portions per sample.

NOTE The volumetric flasks may be replaced by disposable non calibrated flasks; in this case, the dilutions of the samples are prepared and expressed in mass/mass instead of mass/volume.

9.2 Preparation of the standards: prepare calibration solutions having the following phosphorus contents: 0 mg/l, 0.5 mg/l, 1 mg/l, 2 mg/l, 4 mg/l.

The exact contents of each standards shall be calculated according to the exact concentration of phosphorus intermediate solution (see 5.6).

NOTE 1 The following procedure is given as an example:
In five 100 ml volumetric flasks, weigh 10 g of stock oil (5.3). Using graduated pipettes, transfer 0 ml, 0.5 ml, 1 ml, 2 ml, 4 ml of the 100 mg/l phosphorus solution (see 5.6). Fill up to the mark with xylene and homogenise the solutions.

WARNING - The solutions shall be freshly prepared for each series of analyses.

NOTE 2 When dilutions of the samples are expressed in % ( m/m ) (see Note in 5.6), the calibration solutions are prepared in order to be expressed in the same way.

9.3 Preparation of the appliance: since appliances stemming from diverse manufacturers have different configurations and settings, it is difficult to specify an exact procedure. Follow the manufacturer's instructions for using the instrument with organic solvents.

The choice of the instrumental parameters is determined so as to obtain the best signal/background ratio.

9.4 Measurement: the measurement of the intensity of the analytical line corresponds to the counting of the maximum of the line deducted from the counting of the background. Certain instruments are equipped with software which allows the automatic correction of the background.

9.5 Calibration: conduct the aspiration of both the blank and calibration solutions. Carry out three measurements for each of them.

Calculate for each solution the arithmetical mean of the three measurements.

Construct the calibration curve from these measurements using linear regression, by plotting the emission intensity values against the values of the respective phosphorus concentrations expressed in mg/l.

NOTE If the plot of the emission intensity values against the values of the phosphorus contents is not linear, the procedure should be inspected for errors and, if necessary, the calibration procedure should be repeated starting with clause 9.2.

9.6 Sample analysis: conduct the aspiration of the solution of the sample. Carry out the measurements in the same way as for the standards.

NOTE The drift has to be checked regularly.