Mass spectrum low-resolution

Smith [83] classified large sets of hydrocarbon oil infrared spectral data by computer into correlation sets for individual classes of compounds. The correlation sets were then used to determine the class to which an unknown compound belongs from its mass spectral parameters. A correlation set is constructed by use of an ion-source summation, in which a low resolution mass spectrum is expressed as a set of numbers representing the contribution to the total ionisation of each of 14 ion series. The technique is particularly valuable in the examination of results from coupled gas chromatography-mass spectrometry of complex organic mixtures. 

The low resolution mass spectrum of calcitriol is shown in Figure 4 (4). The spectrum was obtained using a Varian MAT CH5 spectrometer, which was interfaced with a Varian data system 620 I. The data system accepts the output of the spectrometer, calculates the masses, compares the intensities to the base peak, and plots this information as a series of lines whose heights are proportional to the intensities. 

Figure 3 is the plotted low resolution mass spectrum of halcinonide found using an AEI Scientific Apparatus Ltd, Model 902 mass spectrometer. Spectra were collected on frequency modulated analog tape and processed on a Digital Equipment Corp., PDP-11. 

Low Resolution Mass Spectrum of Halcinonide. See text for details. 

Figure 4 shows the low resolution mass spectrum of hydralazine hydrochloride. The data were obtained with an LKB 9000S mass spectrometer, with an ionization voltage of 70 eV, source temperature 250°C. Some of the peaks may be assigned as follows C13) ... 

The low resolution mass spectrum of nalidixic is presented in Figure 1. It was obtained on a Joel JMS 01SC Mass Spectrometer at an ionization potential of 75 eV. The fragmentation pattern is presented in Figure 2. The molecular ion (m/e=232) is present at an intensity of 18% the loss of C0 gives a fragment of mass 188 which is the most abundant ion. 

The low resolution mass spectrum of pseudoephedrine hydrochloride is shown in Figure 4.5 It was obtained with a Varian MAT CH5-DF mass spectrometer. Direct probe at 80°C into the ion source was used to obtain the mass spectrum. 

Note If a peak is not present in the low-resolution mass spectrum, there is no reason why it should be detectable from the high-resolution spectrum as long as the same ionization method is employed. Instead, use of a more suitable ionization method is recommended. (And sometimes one has to accept the truth that the sample is not what it was expected to be.)... 

The low-resolution mass spectrum of Indinavir sulfate was measured using fast atom bombardment mass spectrometry on a JEOL HXl lOA mass spectrometer set at a resolution of 5000. The sample was ionized from a 5 1 dithiothreitol dithioerythritol matrix using xenon as the FAB gas. The low-resolution mass spectrum [12] ofindinavir is shown in Figure 14, while the structures of the structurally significant fragment ions are illustrated in Figure 15. 

Consider the three compounds CsHi6N2, C9H18N, C9H16O. All would give a molecular ion of m/e = 140 in tire low-resolution mass spectrum. Using the elemental exact masses in Table 11.2, the molecular exact masses are calculated ... 

Problem 13.4 The low-resolution mass spectrum of an unknown analgesic X had a molecular ion of 151. Possible molecular formulas include C7H5NO3, C8H9NO2, and C10H17N. High-resolution mass spectrometry gave an exact mass of 151.0640. What is the molecular formula of X ... 

A low-resolution mass spectrum of the neurotransmitter dopamine gave a molecular ion at m/z = 153. Two possible molecular formulas for this molecular ion are C8H11NO2 and C7H11N3O. A high-resolution mass spectrum provided an exact mass at 153.0680. Which of the possible molecular formulas is the correct one ... 

The standard low-resolution mass spectrum (Fig. 30.3) is computer generated, which allows easy comparison with known spectra in a computer database for identification. The peak at the highest mass number is the molecular ion (M ), the mass of the molecule minus an electron. The peak at RA = 100%, the base peak, is the most abundant fragment in the spectrum and the computer automatically scales the spectrum to give the most abundant ion as 100%. The mass spectrum of a compound gives the following information about its chemical structure ... 

Since the low-resolution mass spectrum produces integer values for mjz, the mass of M indicates the number of nitrogen atoms in the molecule. If mjz for M is an odd integer, there is an odd number of N atoms in the molecule and, if the value is an even number, then there is an even number of N atoms. 

The high-resolution mass spectrum shows approximately the expected isotope pattern for C o The increasing background in the low-resolution mass spectrum is not produced by the sample—such backgrounds also occur in blank measurements on uncoated stainless-steel substrates. 

The low resolution mass spectrum of diltiazem HCI shown in Figure 7 was obtained using a Finnigan 4500 mass spectrometer operated at 70 eV in the direct probe electron impact mode (15). The molecular ion of the free base is seen at m/z = 414 and the protonated free base ion is observed at m/z = 415. The fragmentation pattern (Figure 8) is consistent with the chemical struture. 

Figure 7. Low resolution mass spectrum of diltiazem hydrochloride.

Fig. 3. Low resolution mass spectrum of cyclothiazide the spectrum was obtained using a Perkin-Elmer Hitachi RMU-6D mass spectrometer...

Fig. 4 Low Resolution Mass Spectrum of Meperidine Hydrochloride, U.S.P., Wyeth Lot No. F-665901. Instrument AEI - Model MS 902...

The low resolution mass spectrum when run on a Hitachi, Perkin-Elmer RMU6 Mass Spectrometer gives two characteristic m/e peaks 263, the M+ of the free base,... 

The mass spectrum of triamcinolone acetonide was obtained from Squibb House Standard 45885-008 by direct insertion of a sample into an MS-9 double focusing mass spectrometer. Intensities were measured from the low resolution mass spectrum. Results are summarized as a bar graph (Fig. 3). The high resolution mass spec-... 

Fig. 4 Low resolution Mass Spectrum of Triamcinolone Diacetate Instrument AEI MS-9...

The low resolution mass spectrum is presesented in figure 4. The spectrum indicates the following fragmentation pattern, consistent with that obtained for fluphenazine ... 

The low-resolution mass spectrum of flu-phenazine base is represented in figure 5. ... 

Figure 5 shows the low resolution mass spectrum of primidone. This data was obtained on a Perkin-Elmer/ Hitachi RMU-6E mass spectrometer (3),... 

Scheme 61. Low-resolution mass spectrum of the linear form of cortinarin A after acetylation and permethylation. [From Tebbett and Caddy (304) by courtesy of Birkhauser Verlag, Basel.]...

Decision vectors have been published for determining the presence of heteroatoms, and the number of carbon and hydrogen atoms from low-resolution mass spectra. A sequence of appropriate vector-based decisions can determine the molecular formula of an imknown compound from its low-resolution mass spectrum alone. 20) However, the probability of obtaining the correct answer diminishes exponentially with the number of elementary decisions made. The present state of theory and practice in the application of learning machines and decision vectors to the classification of spectral data is such that the necessary reliability for longer decision chains exists only for very simple, exactly delimited classes of compounds. 

A method able to classify compounds into various functional categories from their low-resolution mass spectra, similar to the method used by Crawford and Morrison, has been recently proposed by Smith >. A large set of reference spectra is reduced to a correlation set of ion-series spectra . Smith shows that each class of compounds that is available in an archive can be characterized by a typical ion-series spectrum. To determine the class of compounds to which an unknown substance should be assigned, the intensities of the signals found in its low-resolution mass spectrum are summed in the 14 different ion series calculated according to a formula similar to that used by Crawford and Morrison. Smith uses the following equation ... 

The data submitted to the IG were the structure of 3 and its low-resolution mass spectrum, recorded at 70 eV. The input of structures and mass spectra is explained in our latest publication The way structure 3 was numbered for input is shown below (4). 

---