Mass spectrometry repetitive scans

Gas Chromatooraphy-Mass Spectrometry. A Finnigan MAT 4500 GC/MS/INCOS system (Finnigan MAT, San Jose, CA) was used for analysis. A 60 m X 0.32 mm i.d. DB-WAX coiumn was empioyed for the headspace samples. The oven temperature wa programmed from 50 C to 180°C at 2 C/min. A 60 m X 0.32 mm i.d. DB-1 column was used for the sample prepared by vacuum SDE. The oven temperature was programmed from 30 °C (4 min isothermal) to 210 C at 2 C/mln. HeHum was used as the carrier gas at a flow rate of 3.2 mL/min. The column outlet was Inserted directly into the ion source block. The instnjment was operated in the electron impact mode at an ionization voltage of 70 eV. The mass spectrometer was repetitively scanned from 33 to 350 m/z in a one-second cycle. 

Middleditch, B.S. Desiderio, D.M. Comparison of Selective Ion Monitoring and Repetitive Scanning ffuring Gas Chromatography-Mass Spectrometry. Anal. Chem. 1973,45, 806-808. 

Matrices (arrays) can be multidimensional three-dimensional matrices are also called tensors. Analysis of tensors is frequently called 3-way analysis. Typical example is the data from a hyphenated technique, e.g., gas chromatography-mass spectrometry (GC-MS) data one direction (way) is the mass spectrum, second direction is the chromatographic separation (time, scan), and the third direction is the samples (of different origin, repetitions, calibration series, etc.). The 3-way analyses can easily be generalized into n-way analysis including more directions. 

FIG. 4. TIC curve of urine extract in a case of multiple overdosage studied by repetitive scanning mass spectrometry. Drugs, metabolites and "artifacts identified are ... 

Direct pyrolysis-mass spectrometry (Py-MS) is applied to determine the primary structure of macromolecules and to investigate selective thermal degradation mechanisms. This technique allows the thermal decomposition products of the polymer sample to be observed directly in the ion source of the mass spectrometer, so that the evolving products are ionised and continuously detected by repetitive mass scans almost simultaneously with their formation 805917 757742. Since pyrolysis is accomplished under high vacuum, the thermal fragments are readily removed from the hot zone, and because of the low probability of molecular collisions and fast detection the occurrence of secondary reactions... 

---