ASTM D4626 Practice for Calculation of Gas Chromatographic Response Factors
8. Procedure
8.1 Instrument Preparation - Install the chromatographic columns and establish the flow rates and operating temperatures as specified in the method for which calibration is being performed. Refer to Practice E260 for specific instructions. Condition the columns at their required operating temperature until a stable baseline is established at the required sensitivity.
8.2 Calibration Blends - Prepare appropriate calibration blends as described in Practice D4307. The blends should resemble as closely as possible the components and concentrations expected in the test sample to be analyzed, because response factors may not be linear over large concentration ranges.
NOTE 2 - For volume response factors, volumetric concentrations are calculated from gravimetric concentrations using component densities in accordance with Practice D4307.
8.3 Blend Analysis - Analyze each prepared blend in duplicate using chromatographic conditions and injection technique that are identical to those used for test samples.
8.4 Peak Measurements - Determine the peak height or area of each n-paraffin in the blend, excluding n-C12 diluent, using the same measurement technique that is to be used for test samples. Where electronic integration or a computer is used, the various integration parameters must be the same for analysis of the blends and for the test samples.
9. Calculation
9.1 Calculate the response factor for each n-paraffin on a mass (weight) basis as follows:
RM = M/A
where:
RM = mass (weight) response factor for a specific n-paraffin, g/unit
M = mass (weight) of a specific n-paraffin in the blend, g, and
A= area or peak height of the specific n-paraffin peak, units.
9.1.1 Calculate the mass relative response factors as follows:
NOTE 3 - For purposes of this model calculation n-heptane has been chosen as the standard reference compound.
RRM(CN) = RM(CN)/RM(C7)
where:
RRM(CN) = mass (weight) relative response factor for a n-paraffin of carbon number N
RM(CN) = mass (weight) response factor for a specific n-paraffin of carbon number N determined in 9.1, g/unit
RM(C7) = mass (weight) response factor for a n-heptane determined in 9.1, g/unit
9.2 Calculate the response factor for each n-paraffin on a volume basis as follows:
RV = V/A
where:
RV = volume response factor for a specific n-paraffin, mL/unit,
V = volume of the specific n-paraffin in the blend, mL, and
A = area or peak height of the specific n-paraffin peak, units.
9.2.1 Calculate the volume response factors as follows:
RRV(CN) = RV(CN)/RV(C7)
where:
RRV(CN) = volume relative response factor for a specific n-paraffin of carbon number N,
RV(CN) = volume response factor for a specific n-paraffin of carbon number N determined in 9.2, mL/unit, and
RV(C7) = volume response factor for n-heptane determined in 9.2, mL/unit.
10. Keywords
10.1 gas chromatography; response factor
