Direct analysis of daughter ions

The most recent metastable defocusing technique, which is referred to as mass-analyzed ion kinetic spectroscopy (MIKES) by Beynon (77, 270, 277) and as direct analysis of daughter ions (DADI) by Maurer (278) requires the interchange of the source and collector positions in a double-focusing mass spectrometer of Nier-Johnson geometry. With... 

DADI Direct Analysis of Daughter Ion (obsolete name for MIKES)... 

MIKE, mass analyzed ion kinetic energy DADI, direct analysis of daughter ions. 

One cannot ignore the existence of multiple terms for one and the same thing sometimes just coined for commercial reasons, e g., mass-analyzed ion kinetic en-ergy spectrometry (MIKES, correct) and direct analysis of daughter ions (DADI, archaic company term). Another prominent example concerns the use of MS as an... 

Tandem mass spectrometry (i.e., MS-MS) is another technique that has recently become popular for the direct analysis of individual molecular markers in complex organic mixtures [87,505,509,578 - 583]. This technique provides a rapid method for the direct analysis of specific classes of molecular markers in whole sample extracts. In this approach the system is set up to monitor the parent ions responsible for a specific daughter ion as described above and the distribution of parent ions obtained under these conditions should provide the same information as previously obtained by GC-MS [505, 582]. Even greater specificity can be achieved by a combination of GC-MS-MS [516,584]. In view of the complexity of COM samples and the need to detect the presence of individual organic compounds or classes of compounds, it would seem that MS-MS, especially coupled with GC, would be extremely valuable in future environmental organic geochemistry studies. 

Tandem mass spectrometry (MS/MS) is a new analytical technique applied to problems in food and flavor analyses. Rapidity of analysis, a high discrimination against chemical noise, and the ability to analyze mixtures for functional groups are attributes of MS/MS that make it attractive for such problems. Sanple collection and pretreatment differ frcm methods used in GC/MS. Correct choice of an ionization method is paramount. Daughter ion MS/MS spectra are used for conpound identification via comparison with those of authentic compounds, and parent and neutral loss spectra are useful in functional group analysis. Applications to direct analysis of volatiles emitted from fruits and to spice analyses are considered. 

Figure 8.4. The SACI/MS3 spectra of the OTA daughter ion at m/z 358 (above) and of the ZAN daughter ion at m/z 303 (below). The OTA m/z 239+341 and ZAN m/z 163+189+207 signals are used for quantitative analysis. (Spectra acquired in positive-ion mode collision energy applied to the parent ion 80% of maximum value MS3 of daughter ions at 100% of maximum collision energy). (Reprinted from Rapid Communications in Mass Spectrometry 21,Flamini et al., A new sensitive and selective method for analysis of ochratoxin A in grape and wine by direct liquid chromato-graphy/surface activated chemical ionization-tandem mass spectrometry, p. 3740, Copyright 2007, with permission from John Wiley Sons, Ltd.)...

The mass spectrometry portion of the analysis was carried out by coupling a Bruker Esquire ion-trap mass spectrometer to the LC-NMR system with a 20 1 splitter. The major portion of the flow was directed to the NMR system while the minor fraction went to the mass spectrometer. The system was plumbed such that the sample reached the mass spectrometer and the UV detector at the same time. In this configuration, it is possible to use the mass spectrometer as an intelligent detector, thus allowing stop-flow experiments to be initiated on the basis of observed molecular ions or daughter ion fragments. Data were acquired with electro-spray ionization (ESI) in the positive-ion mode. 

The main advantage of MS/MS is its abihty to analyse specific target molecules directly from biological matrices without any sample preparation. One important application of MS/MS in food analysis can be the rapid screening of intact fruits or vegetables for the presence of mycotoxins or pesticides. For example intact lettuce leaves can be introduced directly into the ion source and analysed for the presence of the pesticide parathion. The CAD (methane gas) spectrum of this pesticide shows the parent ion at m/z 291 and two daughter ions at m/z 169 and m/z 154. If the peak at m/z 291 of the normal spectrum of the contaminated lettuce leaf is selected and its CAD spectrum is recorded and... 

Direct MS analysis of oligomer mixtures by FAB can be combined with the Collision Induced Dissociation (CID) technique, which is used to induce the fragmentation of selected molecular ions by means of collision with an inert gas (MS/MS). This allows one to obtain daughter ions classical MS/ MS techniques utilize the linked scanning of two or more mass analyzers to obtain product (daughter) and/or precursor (parent) ion spectra see Chapters 1 and 4. Systematic application of tandem Mass Spectrometry (MS/ MS) has produced important results in the analysis of polymeric materials by FAB. " ... 

In this mode, also known as daughter ion scanning, the mode scheme is select-dissociate-scan ( o in Kondrat symbols). For sequential instruments where mass analysis events are separated in space, the first analyzer is fixed to select intact precursor ions of a particular mIz ratio from the source, these are directed into the collision cell, which fragments the chosen ion and focuses the products into the second analyzer. The second analyzer scans the incoming stream of product ions over an appropriate mass range and produces a mass spectrum. Product ion scanning is one of the most widely used scan modes in QqQ, Q-TOF, and tandem TOF instruments. 

At each sampling period, 5 mL of solution and 50 pi of head space gas from the solution reservoir was extracted and analyzed. The solution was spiked with 50 pL of 1000 ppm benzene-D6 as a internal standard. Afterwards, the sample was shaken in a head space sampler (HP 7694E) at 70 °C for 20 minutes. The concentrations of vinyl chloride, DCE isomers, TCE, and other chlorinated products that could be daughter products of TCE were analyzed with a gas chromatograph (HP 6890) equipped with a mass selective detector (HP 5973). After the analysis of organic compounds, pH was measured and the chloride concentration in the sample was analyzed with a Capillary Ion Analyzer (Waters CIA). The 50 pi of head space gas was directly injected into a GC (HP 6890) with a HP Plot/Al203 column (50m x 0.53 mm x 15 pm) and the concentrations of methane, ethane, ethylene, and acetylene were quantified with a FID detector. 

---