ASTM D5827 Standard Test Method for Analysis of Engine Coolant for Chloride and Other Anions by Ion Chromatography
10. Procedure
10.1 Set the ion chromatograph up in accordance with the manufacturer's instructions.

10.2 Equilibrate the system by pumping eluant for 15 to 30 min, until a stable baseline is obtained. Sample preparation is usually performed by 99 + 1 (v/v) dilution with eluant.

10.3 Flush the injection loop with 2 to 3 mL ofsample using a 10-mL disposable plastic syringe fitted with a 0.2-µm syringe filter.

10.4 Start the chromatographic run in accordance with the manufacturer's instructions.

10.5 At least one duplicate and one fortified coolant sample must be analyzed with each batch of ten or fewer samples. Results must be recorded in the laboratory manual. The fortified sample is to be prepared by addition of a mixed analyte mid-range standard. Addition of 100 µL of fortification standard solution to 10 mL of prepared sample in eluant will not dilute the sample appreciably.

11. Calculation
11.1 Integrate the peak area for determination of the concentrations. Plot the peak area against concentration. A linear calibration curve is generated for each analyte of interest. Calibration is in the concentration range of interest and must have a linear least squares correlation coefficient of 0.9990 or greater (see Fig. 3).

11.2 The concentration of analyte is given by the concentration read from the calibration curve multiplied by the dilution factor used.

11.3 Relative percent difference (RPD) of duplicate runs:

A = concentration found in Analysis Run 1, and
B = concentration found in Analysis Run 2.
Results must be within 20 %.

11.4 Spike (fortified) recovery as percent:

A = concentration found in analysis of fortified sample,
B = concentration found in analysis of sample, and
C = concentration of analyte added to sample.
Spike recovery must be within a 80 to 120 % range.