Soluble samples can be quantitatively analyzed by various methods. As an example, the samples can be analyzed based on spectroscopic detection (e.g., UV/Vis, ELSD, etc.) or spectral detection (e.g., mass spectrometer) after performing chromatographic separation. NMR is most frequently used for the analysis of chemical structure, but it is also considered important for quantitative analysis gradually. NMR can be used for quantitative analysis because the integrated intensity of a signal is directly proportional to the number of nuclei displayed on the signal. In addition, since the sensitivities of all the protons in the spectrum are the same, there is an advantage that no extinction coefficient or verification/calibration is required for quantitative analysis.
The method most frequently used in the quantitative analysis using NMR is a method using the internal standard. In other words, it is a method in which a standard substance which knows its molecular structure and used amount is put together in a sample, and the integrated intensities of the respective signals are compared and quantitatively analyzed. This method has an advantage that the quantitative analysis is simple and accurate, but there is a disadvantage that it cannot be applied to an insoluble sample.
In the case of the insoluble sample, SSNMR (solid state NMR) can be applied, but there is a limit to the quantitative analysis using the internal standard. The reasons for this are as follows: 1) the internal standard and the sample should be uniformly mixed, but in the case of the insoluble sample, the uniform mixing is difficult; 2) the standard substance or the sample remains in the mixing tool during the mixing process and thus, accurate quantitative analysis is difficult; 3) a spinning error occurs due to nonuniform mixing; and 4) NMR peak appears broadly, and thus it is difficult to select an internal standard that can be distinguished from samples.
Recently, researches on inorganic and inorganic composite substances and inorganic substances have been actively conducted. However, since most of these substances are insoluble substances, a method of quantifying the same is required. However, in a conventional quantitative analysis of such insoluble substances, a method such as TGA or the like has been used, but there was problems that the reliability is lowered, the method of quantitative analysis is complicated, and a lot of time is required.
Therefore, the present inventors have conducted intensive studies on a method for quantitative analysis of samples, particularly a method for quantitative analysis of insoluble samples. As a result, they have found that the quantitative analysis is performed by using an external standard method that obtains NMR spectra of a sample and a standard substance and then compare them as will be described later, wherein samples can be quantitatively analyzed from information of the respective NMR spectra. The present invention has been completed on the basis of such finding.