How to Sorting a 2D array

for (int j = 0; j < spectrum.spectrum.GetLongLength(1); j++)
                       {
                            double mass = spectrum.spectrum[0, j];
                            double intensity = spectrum.spectrum[1, j];
                            double[] m = new double[2];
                            m[1] = mass;
                            m[0] = intensity;
                            spectrumList[j] = m;

                       }
                       double[][] orderedSpectrum = spectrumList.OrderBy(i => i[0].ToString()).ToArray();