Methodology for determination of nitrogen content in nitrocellulose
View Patent ↗In at least one embodiment, the invention is directed to a method of determining the nitrogen content in nitrocellulose by High Performance Liquid Chromatography (HPLC). It is within the scope of the invention for the sample of nitrocellulose to be unstable nitrocellulose, unrefined nitrocellulose, or refined nitrocellulose. The sample of nitrocellulose can wet or dry. A sample of nitrocellulose that is wet can be in acid or in water. Before HPLC, the sample is dissolved in a suitable solvent. The nitrogen content of the sample is determined by comparing the retention time of the sample to a graph of retention time to amount of nitrogen due to the linear correlation of retention time and percent nitrogen substitution.
1. A method comprising
subjecting a sample of nitrocellulose to HPLC; and
determining the nitrogen content of the sample of nitrocellulose as a function of HPLC retention time of the sample of nitrocellulose.
2. The method of claim 1 , wherein the nitrocellulose is selected from the group consisting of refined nitrocellulose, unstable nitrocellulose, or unrefined nitrocellulose.
3. The method of claim 2 , wherein the nitrocellulose is wet.
4. The method of claim 1 , wherein the sample of nitrocellulose is dissolved in a solvent is selected from the group consisting of 1,2-dimethoxyethane, acetone, ethyl acetate, tetrahydrofuran, butyl acetate, acetone/water, 2-butanone, acetonitrile, and any combination thereof.
5. The method of claim 1 , the HPLC being reversed phase HPLC.
6. The method of claim 5 , the reversed phase HPLC using a column having as its stationary phase a silica treated to provide C 6-30 alkyl groups on the surface thereof.
7. The method of claim 5 , the reversed phase HPLC using a polar solvent system.
8. The method of claim 7 , the HPLC solvent system is a gradient solvent system changing over a time period in which HPLC is performed.
9. The method of claim 7 , the HPLC solvent system being an acetonitrile/water solvent system.
10. The method of claim 9 , wherein the ratio of acetonitrile to water is changed over a time period in which the HPLC is performed.
11. The method of claim 10 , the ratio changes as a linear gradient of 85/15 (v/v) acetonitrile/water to 100% acetonitrile over said time period.
12. The method of claim 7 , the HPLC solvent system being a 1,2-dimethoxyethane water solvent system.
13. The method of claim 7 , the HPLC solvent system being an acetone/water solvent system.
14. The method of claim 1 , further comprising correlating the HPLC retention time of the sample of nitrocellulose to nitrogen content of the sample of nitrocellulose to a graph of nitrogen content and HPLC retention time of reference samples of nitrocellulose.
15. The method of claim 14 , wherein the nitrogen content of the reference samples of nitrocellulose is determined by ferrous sulfate titration.
16. The method of claim 14 , wherein the nitrogen content of reference samples of nitrocellulose is determined by MIL-STD-286C method 109.11.1.
17. The method of claim 1 , the HPLC generating a chromatogram, the chromatogram comprising at least one peak, the at least one peak having a peak maximum, the peak maximum having a HPLC retention time, the HPLC retention time being used to determine the nitrogen content of the sample of nitrocellulose.
18. The method of claim 17 , wherein a non-uniformity of an average nitrogen content of the sample of nitrocellulose can be determined by a deviation from an even distribution about the peak maximum.
19. The method of claim 17 , the at least one peak having a peak width, the peak width providing an estimated measure of a distribution of the nitrogen content of the sample of nitrocellulose.
20. A method of analyzing nitrogen content of a sample of nitrocellulose comprising:
HPLC analysis of the sample of nitrocellulose, the HPLC analysis generating a chromatogram, the chromatogram comprising at least one peak with a peak maximum, the peak maximum having a retention time; and
correlating the retention time of the peak maximum to the nitrogen content of the sample of nitrocellulose by comparing the retention time of the peak maximum to a graph of retention time and nitrogen content of reference samples of nitrocellulose.