Introducing One of the most useful components in NMR spectroscopy the application of the peak area for the quantitative analysis. Although the use of proton NMR has been applied for the determination of trace components such as the residual hydrogen in D2 O, the mixtures of dinitrotoluene, and the mixtures of drugs, its great merits have been ignored in the field of quantitative analysis because NMR method is inherently less sensitive than many other spectroscopic methods. The quantitative analysis using NMR spectroscopy, however, has been increased significantly during the last few years because of the development of new techniques including high-field NMR. Its applications are generally limited to the use of hydrogen nucleus. In our previous study, we reported that the accuracy and precision of the P-NMR methods are either comparable or superior to that of the conventional method (ASTM D 515). In a continuing study of heteronuclear NMR application in quantitative analysis, we attempted the analysis of sodium (23Na) in solution. The sodium is one of the most abundant and the most frequently analyzed elements and its analysis methods are well established. In modern laboratories, the concentration of sodium in the solution is generally analyzed by AAS or ICP methods using an external standard. These classical methods, however, could have factors, which disturb correct analysis, such as spectral, physical, chemical, and ionization interference. Thus, these matrix effects, which could repress or enhance the radiation of the element to be determined to derive considerable error, are well documented. Therefore, if the composition of sample is known, the error can be compensated by using calibrating solution through the time-consuming procedures. On the other hand, the unknown matrix sample could not be calibrated by this procedure and could produce a result containing significant error. In this study we report a new preferred alternative NMR method for the quantitative analysis of sodium in solution. Because of the natural abundance (100%) and quadrupole relaxation (I=3/2), sodium is a very amenable nucleus for NMR study. Two case studies, which are the most extreme cases containing cobalt(Co) and silver(Ag) ion in the sample, are employed to show that this NMR method is comparable or superior to that of the conventional flame or ICP method in the analysis of sodium. The representative 23 Na-NMR spectra obtained on a Bruker DRX-300 spectrometer at 79.3 MHz equipped with 10 mm broadband probe are shown in the Figure 1. A single peak (δ 3.2 ppm) shown with same intensity in all spectrum (a-g) is the peak of the 50 µg/mL sodium which is contained with 7.7 mM of Dy(TTHA) 3−at a 5 mm NMR tube and placed co-axially in a 10 mm NMR tube containing various concentrations of sodium. The complex of dysprosium used here was a shift reagent and was made by the literature procedure. This complex is widely used as a reagent to differentiate the content of intracellular and extracellular sodium in in vivo study. The spectra were collected with 0.01 s relaxation delay, 0.9 s acquisition time, and 4 k data points over a 1,500 Hz spectral width using a 90 o pulse. Because of the fast pulsing due to the quadrupole relaxation of sodium, the total acquisition time of each experiment was only about 10-60 min to get reasonable signal-to-noise ratio depe