Flow injection mass spectrometr

The chromatographic and mass spectrometric choices facing the analyst in coupling SFC and MS successfully, namely injection method column type of flow restrictor and mass spectrometer ionisation method and type of vacuum system, have been described [398]. In SFC-MS coupling, the restrictor plays a major role, as the expansion behaviour to a large extent determines the overall performance of the SFC-MS system and defines the range of applications. 

Catalytic tests were conducted in a pulse microreactor coupled to a quadrupole mass spectrometer. Samples were dried in situ in flowing helium at 773 K for four hours and, thereafter, sequential propane pulses were injected at 703 K with mass-spectrometric analysis of the products.The main text can start here. 

Tandem mass spectrometric methods have demonstrated superb specificity because of their ability to isolate analytes selectively in the presence of endogenous interferences. Attempts to further increase sample throughput led to the idea of using LC/MS/MS without the LC. Traditional chromatographic separations were replaced with flow injection analysis (FLA) or nanoelectrospray infusion techniques. The MS-based columnless methods attracted a lot of attention because of their inherent fast cycle times and no need for LC method development. 

Bayliss and co-workers [10] combined ultra-high flow rates, parallel LC columns, a multiplex electrospray source, and mass spectrometric detection for the rapid determination of pharmaceuticals in plasma using four narrow bore (50 mm x 1 mm, 30 pm Oasis HLB) or capillary (50 mm x 0.18 mm, 25 pm Oasis HLB) HPLC columns with large particle sizes (to avoid high system back-pressure) in parallel with a multiple probe injector and a MUX MS interface. Small sample aliquots were injected directly into the system without sample pre-treatment procedure, obtaining very low limits of quantification (from 1 to 5 ng/mL). 

Calibration and quantification procedures are easier in LA-ICP-MS compared to other solid-state mass spectrometric techniques because the laser ablation and the ICP ion source operate at normal pressure and the laser ablation of solid samples and ionization of analytes are separated in space and time. Therefore the advantage of solution calibration in ICP-MS can be applied in this solid-state analytical technique. The introduction of solution based calibration, which is only possible in LA-ICP-MS, was an innovative step in the development of this sensitive mass spectrometric technique. A number of different calibration approaches using aqueous standard solutions in the dual gas flow technique have been discussed by various authors.74 75 In the dual gas flow injection technique , the nebulized standard solution and the laser ablated sample material are mixed in the -piece and the two gas flows from the nebulizer (e.g. ultrasonic nebulizer) and laser ablation chamber are added. Using solution based calibration with the addition of a standard solution, Leach et alP determined minor elements in steel reference materials with a relative accuracy of a few %. In comparison to the so-called dual gas flow technique proposed in the literature, where the argon flow rates through the nebulizer and ablation cell add up to 11 min-1 (e.g. 0.451 min-1 and... 

Online trace enrichment by flow injection using a microcolumn of activated alumina and mass spectrometric determination of uranium in mineral, river and sea water is relevant for analyzing small sample volumes.80 Flow injection with online preconcentration using solid... 

CE detection is similar to detectors in, and include absorbance, fluorescence, electrochemical, and mass spectrometric detectors. The capillary can also be filled with a gel, which eliminates the electroosmotic flow. Separation is accomplished as in conventional gel electrophoresis but the capillary allows higher resolution, greater sensitivity, and on-line detection. In CE, low picogram amounts of analytes can be detected using glass fiber optics. However, this does not mean low limits of detection since only a few nanoliters can be injected. 

FAB and LSIMS are matrix-mediated desorption techniques that use energetic particle bombardment to simultaneously ionize samples like carotenoids and transfer them to the gas phase for mass spectrometric analysis. Molecular ions and/or protonated molecules are usually abundant and fragmentation is minimal. Tandem mass spectrometry with collision-induced dissociation (CID) may be used to produce abundant structurally significant fragment ions from molecular ion precursors (formed using FAB or any suitable ionization technique) for additional characterization and identification of chlorophylls and their derivatives. Continuous-flow FAB/LSIMS may be interfaced to an HPLC system for high-throughput flow-injection analysis or on-line LC/MS. 

Thompson, J. J. and Houk, R. S., Inductively coupled plasma mass spectrometric detection for multielement flow injection analysis and elemental speciation by reversed phase liquid chromatography, Anal. Chem., 58, 2541-2548, 1986. 

Various workers [32-34] have discussed mass spectrometric and other methods for the determination of plutonium in soils. Plutonium in soils has been quantified using 238plutonium as a yield tracer. Hollenbach et al. [36] used flow injection preconcentration for the determination of 230Th, 234 U, 239Pu and 240Pu in soils. Detection limits were improved by a factor of about 20, and greater freedom from interference was observed with the flow injection system compared to direct aspiration. 

In summary, LC-MS offers excellent sensitivity for many classes of pharmaceutical compounds. Due to the fact that MS is becoming more routine (i.e., it is essentially another detector), LC-MS should be the first consideration for all cleaning verification assays that are less than 0.1 pg/swab. In the citations outlined above, LC-MS has been shown to offer excellent sensitivity and specificity for the analytes of interest. The mass spectrometric conditions can be optimized in a flow injection mode to allow for rapid method development. All LC-MS analytical methods were validated in a way consistent with the requirements outlined in Table 15.3. The applications cited utilized LC-MS because of the sensitivity requirements of the safety acceptance limits however, if the molecule of interest poses unique detection challenges such as a poor chromophote, LC-MS should be considered for assays at the level of 1.0 ig/unit area, or less. Above 1.0 xg/unit area there may be more attractive options for these swab determinations. 

Only recently, flow injection has been used as an interface to the first on-line application of flow cytometry [480]. Gorlach et al. [137] used flow injection for high throughput mass spectrometric mapping. 

There have been great advances in mass spectrom-etric instrumentation over the past decade. All of the instruments described above are rugged and available for routine use. While these are not the only tandem mass spectrometric systems available, when used together, they provide a powerful complement for metabolite characterization experiments. A flow chart illustrating the complementary nature and effective utilization of these various MS/MS techniques is shown in Fig. 1. The most effective use of these instruments involves setting up the front end of the systems identically. All systems should be fitted with the same LC and injection system and the mass spectrometers should be set up in parallel with a radio flow detector. In this manner, samples can be easily moved from one... 

The remainder of the chapter discusses microdialysis coupled to mass spectrometric detection to both on-line and off-line methods, with an emphasis on analysis of drugs. Applications of microdialysis/mass spectrometry to gas chro-matography (GC), liquid chromatography (LC), and flow injection into the mass spectrometer are discussed. In particular, approaches to overcome problems with introduction of high-ionic-strength dialysate into the mass spectrometer are described. 

Using capillary LC/microelectrospray no additional sample cleanup was necessary before triple-quadrapole mass spectrometric detection [12]. The small volumes of dialysate injected did not affect the sensitivity of the mass spectrometer. The development of microelectrospray and nanoelectrospray interfaces has made the coupling of micro and capillary LC to mass spectrometry much more feasible. Thus, the low flow rates associated with capillary and micro LC make ESI well suited for this approach. 

Two sets of experiments were also carried out by means of a previously described temperature-programmed reaction (TPR) apparatus, equipped with a mass spectrometric (MS) detector [13] and operated isothermally (200°C) in the pulse mode. In the first set some 2 pi pulses of HEP were injected in the flowing carrier gas (ultrapirre helium, > 99.9999 vol%) just before the catalyst bed (50 mg of Y84). The second set of experiments was carried out on another fi esh batch of the same catalyst under exactly the same conditions, but after poisoning the catalyst surface by some pulses of CO2. 

Another current trend that is well underway is the use of more specific analytical instrumentation that allows less extensive sample preparation. The development of mass spectrometric techniques, particularly tandem MS linked to a HPLC or flow injection system, has allowed the specific and sensitive analysis of simple extracts of biological samples (68,70-72). A similar HPLC with UV detection would require significantly more extensive sample preparation effort and, importantly, more method development time. Currently, the bulk of the HPLC-MS efforts have been applied to the analysis of drugs and metabolites in biological samples. Kristiansen et al. (73) have also applied flow-injection tandem mass spectrometry to measure sulfonamide antibiotics in meat and blood using a very simple ethyl acetate extraction step. This important technique will surely find many more applications in the future. 

Geerdink, R. B., Wilfried Niessen, M. A., and Udo, A. Th., Brinkman, Mass spectrometric confirmation criterion for product-ion spectra generated in flow injection analysis. Environmental application, J. Chromatogr. A., 910, 291-300, 2001. 

CoEDO AG, Dorado MT, Ruiz J, Escudero M and Rubio JC (1996) Evaluation of flow injection sample to standard addition method for the inductively coupled plasma mass spectrometric determination of aluminium in biological tissues. J Mass Spectrom 31 427-432. 

Figure 1.7 Chromatogram of iodate and iodide in seawater by nonsuppressed 1C with inductively coupled plasma mass spectrometric detection. The main speoiation of iodine in seawater, iodate (IO3) and iodide (l ), could be determined simultaneously. Conditions column, Agilent G3154A/101 (150 X 4.6 mm inner diameter) column temperature = 20°C injection volume = 10(il mobile phase, 20.0mmol 1 of NH4NO3 at pH 5.6 flow rate = 1.0ml min The ICP-MS conditions flow rate of plasma gas (Ar) = 151 min flow rate of auxiliary gas (Ar) = 1.01- min flow rate of oarrier gas (Ar) = 1.151- min sampling depth = 7.5mm integration time = 1 s dwell time = 0.5s. The 2 1 was seleoted for deteotion by single-ion monitoring mode. Reprinted from Chen etal., (2007) with permission from Elsevier.

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