Selected-decomposition monitoring

Tandem mass spectrometry (MS-MS) is a term which covers a number of techniqnes in which one stage of mass spectrometry, not necessarily the first, is used to isolate an ion of interest and a second stage is then nsed to probe the relationship of this ion with others from which it may have been generated or which it may generate on decomposition. The two stages of mass spectrometry are related in specific ways in order to provide the desired analytical information. There are a large nnmber of different MS-MS experiments that can be carried ont [9, 10] bnt the fonr most widely nsed are (i) the prodnct-ion scan, (ii) the precnrsor-ion scan, (iii) the constant-nentral-loss scan, and (iv) selected decomposition monitoring. 

As with the Q-ToF instrument, only two types of MS-MS experiment are available with the ion-trap, i.e. the product-ion scan and selected-decomposition monitoring, as described in Sections 3.4.2.1 and 3.4.2.4, respectively. 

The MS-MS equivalent of this technique is known as selected-decomposition monitoring (SDM) or selected-reaction monitoring (SRM), in which the fragmentation of a selected precursor ion to a selected product ion is monitored. This is carried out by setting each of the stages of mass spectrometry to transmit a single ion, i.e. the precursor ion by MSi and the product ion by MS3 (see Figure 3.8 above). 

What are the potential advantages of selected-decomposition monitoring (SDM) over selected-ion monitoring (SIM) ... 

To understand the circumstances in which particular features of mass spectrometry, such as high-resolution measurements, MS-MS and cone-voltage fragmentation, selected-ion monitoring and selected-decomposition monitoring, may be nsed to address particular analytical problems. 

Quantitative methodology employing mass spectrometry usually involves selected-ion monitoring (see Section 3.5.2.1) or selected-decomposition monitoring (see Section 3.4.2.4) in which a small number of ions or decompositions of ions specific to the compound(s) of interest are monitored. It is the role of the analyst to choose these ions/decompositions, in association with chromatographic performance, to provide sensitivity and selectivity such that when incorporated into a method the required analyses may be carried out with adequate precision and accuracy. 

The advent of the time-of-flight analyser as part of an MS-MS instrument has already been noted. Its value has been compared with selected-decomposition monitoring (SDM) for the quantitative determination of Idoxifene (Figure 5.66),... 

Selected-decomposition monitoring An MS-MS scan in which the first stage of mass spectrometry is set to transmit a selected ion and the second to transmit only a selected product ion. This technique increases the selectivity of the analysis. 

Selected-reaction monitoring (See Selected-decomposition monitoring)... 

RF RIC RMM RSD S/N SDM SD SDS-PAGE spectrometry radiofrequency reconstructed ion chromatogram relative molecular mass relative standard deviation signal-to-noise ratio selected-decomposition monitoring standard deviation sodium dodecyl sulfate-polyacrylamide gel electrophoresis... 

Brown RS, Pettit K, Jones PW. 1989. A GC/GC-MS study of 2,3,7,8-TCDD using a DB-225 column and selected decomposition monitoring a quantitative tool. Chemosphere 19 171-176. 

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