public void TestGetIsotopesIMolecularFormulaDeprotonate()
        {
            IsotopePatternGenerator isogen = new IsotopePatternGenerator(.1);

            IMolecularFormula mf1 = MolecularFormulaManipulator.GetMolecularFormula("C6H12O6", builder);

            MolecularFormulaManipulator.AdjustProtonation(mf1, -1);
            IsotopePattern ip1 = isogen.GetIsotopes(mf1);

            Assert.AreEqual(1, ip1.Isotopes.Count);

            isogen = new IsotopePatternGenerator(.1);
            IMolecularFormula mf2 = MolecularFormulaManipulator.GetMolecularFormula("C6H11O6", builder);
            IsotopePattern    ip2 = isogen.GetIsotopes(mf2);

            Assert.AreEqual(1, ip2.Isotopes.Count);

            Assert.AreEqual(ip1.Isotopes[0].Mass, ip2.Isotopes[0].Mass, 0.001);
        }