Testing oil content of paraffin wax
American Society for Testing and Materials (ASTM) D721-06, is the method for testing the oil in paraffin wax . The technique is slow (the process takes about 2 hours) and requires technical skills and the use of hazardous solvents. The Oil in Wax NMR method is a ratio method so the sample does not need to be weighed. Generally , the Oil in Wax NMR method can exploit two different hardware configurations to optimize for two ranges of oil content dependent on the sample and/or user requirements:
- 2% and above: rapid measurement using a standard with 10-mm diameter samples and sample pre-conditioning at low temperature (usually;5 °C).
- 0.1% to 2% oil: low detection limit measurement using an with 10-mm diameter samples and equipped with a low-maintenance , fluid-cooled temperature-regulated probe (usually ;5 °C or less).
Experience shows that different types of wax may have different physical , and consequently NMR, properties which may need to be calibrated separately.
For example, figure 1 shows the results for a set of waxes which were separated into three different calibrations depending on the oil content and wax type. The MultiQuant software is versatile. Calibrations can be optimized after the reference samples have been measured and do not have to be measured again to produce different calibrations. It is good practice to recalibrate the instrument regularly, especially if new wax products need to be measured.