Mass spectrophotometers

Mounting electrodes in a bioreactor is costly, and there is an additional contamination risk for sensitive cell cultures. Some other sensors of prac ticai importance are those for dissolved oxygen and for dissolved carbon dioxide. The analysis of gas exiting from a bioreactor with an infrared unit that detects carbon dioxide or a paramagnetic unit that detects oxygen (after carbon dioxide removal) has been replaced by mass spec trophotometry. Gas chromatographic procedures coupled with a mass spectrophotometer will detect 1 the volatile components. 

The beams of reactant molecules A and B intersect in a small scattering volume V. The product molecule C is collected in the detector. The detector can be rotated around the scattering centre. Various devices may be inserted in the beam path, i.e. between reactants and scattering volume and between scattering volume and product species to measure velocity or other properties. The angular distribution of the scattered product can be measured by rotating the detector in the plane defined by two molecular beams. The mass spectrophotometer can also be set to measure a specific molecular mass so that the individual product molecules are detected. 

For the measurement of a-iduronidase activity, a novel substrate was developed that was detected by mass spectrometry. It was possible to combine this method with similar assays for Niemann-Pick type A/ , Krabbe, Gaucher, Pompe, and Fabry disease. However, separate incubation is necessary, and some additional work-up procedures are usually required to purify the sample before mass spectrophotomet-ric analysis [68]. 

A compound is known to be composed of 40.002% carbon, 8.063% hydrogen, and 53.285% oxygen. The mass spectrophotometer indicates a molecular mass about 121 u. (a) What is the empirical formula (b) What is the likely molecular formula ... 

The mass spectrometer when used as a detector for GC is the only universal detector capable of providing structural data for unknown identification. By using a mass spectrometer to monitor a single ion or few characteristic ions of an analyte, the limits of detection are improved. The term mass selective detection can refer to a mass spectrophotometer performing selected ion monitoring (SIM) as opposed to operation in the normal scanning mode. Typical limits of detection for most compounds are less than 10 "l2 g of analyte. 

D) A mass spectrophotometer would not be helpful in determining the percentages of the isotopes. 

Reverse-phase (RP)-HPLC is probably the best system for purifying triterpenoids, principally when mixtures of isomers are present [35]. Gunther and Wagner in 1996 [36] carried out the separation and quantification of active triterpenes from Centella asiatica employing an RP system with acetonitrile-water as mobile phase. Recently, Gaspar et al. [37] described the complete separation of a mixture of triterpenoid isomers from the fruit of Arbutus unedo by HPLC coupled to a mass spectrophotometer by means of a particle beam interface (HPLC-PBMS). The separation of different quassinoids from crude bark of Quassia amara was developed by Vitanyi et al. [38] using a reverse-phase HPLC-MS... 

Mass spectrometry (MS) has played an increasingly important role in drug discovery including analytical characterization of potential drug molecules and metabolic identification. A mass spectrophotometer consists of three components (1) an ionization source, (2) a mass analyzer, and (3) a detector. Mass spectral analysis requires that the analyte be introduced into the mass spectrometer as a gaseous ion. 

The dissociation pattern of I in the mass spectrophotometer showed that the isopropylidene -CHo fragmented first yielding the base peak (m/e=297), followed by cleavage of the ether linkage with the loss of the n-propyl group (-C3H0) to yield a phenol (m/e=255). This was followed by the loss of another -C3H0 to produce a biphenol (m/e=213) (Table I). 

Infrared spectra were obtained using Hitachi 260-10 and 270-30 spectrometers and a Digilab FTS-IMX FT-IR. The El (70 ev) and Cl (isobutane) mass spectra were obtained employing a JEOL JMS-D300 GC mass spectrophotometer connected with a JAI JHP-2 Curie Point Pyrolyzer (injector temperature-250"C pyrolyzer... 

The mass spectra of sandwich compounds of the type [Mcp(CHT)] (M = Zr, Nb, Mo) show the presence of M(CsH5) ions. Therefore, in the mass spectrophotometer, contraction of the cycloheptatrienyl ring and expansion of the cyclopentadienyl ring takes place. The intensity of peaks decreases in the series Zr > Nb > Mo. The presence... 

Ion implantation [15] forces ions of dopant into the silicon using a stream of high energy ions produced in a machine similar to a mass spectrophotometer. Sources of dopants for this process are elemental arsenic and phosphorus, arsine, phosphine, diborane, and some boron halides. A more detailed description of doping procedures is beyond the scope of this text and can be found elsewhere [8]. 

Generally, purification is measured by determining the enzyme specific gravity using a spectrophotometer, sodium dodecyl sulfate gel electrophoresis, isoelectric focusing, and a mass spectrophotometer. 

Various mass spectral techniques have been used in characterizing various metal-containing macromolecules. The focus will be on two techniques. The first one is the most commonly employed mass spectrophotometer setup, called high-resolution electron impact mass spectrometry (HREl-MS). The second system is the matrix-assisted laser desorption ionization (MALDl) system. Illustrative examples of these two procedures are given for the products of Group IVB metallocene dichlorides and the antibacterial drug norfloxacin, scheme 8. 

Mass spectrophotometer (MS)—good for identifying unknowns. When coupled with the GC, the MS-GC can separate and quantify solvent components. 

Infrared spectral studies were done utilizing a Mattson Instruments Galaxy 4020 FTIR employing potassium bromide pellets. All spectra were recorded at an instrument resolution of 4 cm using 32 scans. Mass spectra were obtained utihz-ing a HP Mdl. G2025A MALDI-TOF (matrix-assisted laser ionization time-of-flight) mass spectrophotometer. 

In 1977, a thermogravimetric analysis unit was successfully coupled with a mass spectrophotometer, TG-MS. More recently, a coupled programmed pyroprobe-mass spectrophotometry system, also utilising IR spectroscopy, was employed as a means of describing degradation sequences as a function of temperature. The appHcation of these tools as a means to define polymer stmcture and degradation products is described. 9 refs. 

---