Plasma analyses

From the analytical point of view, plasma emission can be divided into several time domains. The simplified approach to plasma time history is that soon after plasma initiation, continuum and ionic spectra are seen. The continuum is the white light from the plasma that contains little spectroscopic information and the ions result from electrons ejected by neutral atoms. As the plasma decays, these are followed by spectra from neutral atoms, and eventually simple molecules formed from the recombination of atoms. Throughout the temporal history, one observes a diminishing continuum spectral background due to recombination of free electrons with ions. Actually the situation is more complicated and rich of information starting from delay of 1 ns and after the actual plasma termination. 

The first stage is actually characterized by a broad emission originating from the Bremsstrahlung of the free electrons and electron-ion recombination and it has duration of a few hundred nanoseconds. Weak lines show up on the strong continuum and they are mostly identified as ionic lines of the plume constituents. This time domain was considered as not suitable for analytical applications and minimum delay time of 100-500 ns was recommended to remove the Bremsstrahlung. 

Besides, triple ionization was found in emission spectra of a laser-induced zirconium plasma at early times after plasma formation in the short UV spectral range from 190 to 240 nm (Gaft et al. 2013). Many lines from highly ionized Zr ions, such as Zr IV at 216.4 and 228.7 nm and Zr III at 194.1, 194.7, 193.1, 196.3, 196.6, 197.5, 199.0, 200.3, 200.8, 202.8, 203.6, 205.7, 206.1, 207.1, 208.6, 210.2, 211.4, 217.6, and 219.1 nm have been found in the plasma under ambient and vacuum conditions (Fig. 6.3). These lines could be detected in both single-pulse and double-pulse modes. 

The third time domain, from 100 ns to 30 ps, is characterized by an emission spectrum, where narrow atomic lines dominate corresponding to the elements present in the plume and the line strength is proportional to the atomic concentration. This time regime lasts for tens microseconds, where in its early stage ionic 

4 ps after plasma pliune creation by 1.06 pm laser pulse 

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Optical emision spectra nowadays are simply measured using a fiber optic cable that directs the plasma light to a monochromator, which is coupled to a photodetector. By rotating the prism in the monochromator a wavelength scan of the emitted light can be obtained. Alternatively, an optical multichannel analyzer can be used to record (parts of) an emission spectrum simultaneously, allowing for much faster acquisition. A spectrometer resolution of about 0.1 nm is needed to identify species. 

Quantitative analysis of emission spectra is difficult. As a first assumption the emission intensity from a species is proportional to its concentration, but the pro- 

Optical emission is a result of electron impact excitation or dissociation, or ion impact. As an example, the SiH radical is formed by electron impact on silane, which yields an excited or superexcited silane molecule (e + SiHa SiH -t-e ). The excess energy in SiH is released into the fragments SiH SiH -I-H2 + H. The excited SiH fragments spontaneously release their excess energy by emitting a photon at a wavelength around 414 nm. the bluish color of the silane discharge. In addition, the emission lines from Si. H, and H have also been observed at 288, 656, and 602 nm, respectively. 

Matsuda and Hata [287] have argued that the species that are detectable using OES only form a very small part ( 0.1%) of the total amount of species present in typical silane deposition conditions. From the emission intensities of Si and SiH the number density of these excited states was estimated to be between 10 and 10 cm , on the basis of their optical transition probabilities. These values are much lower than radical densities. lO cm . Hence, these species are not considered to partake in the deposition. However, a clear correlation between the emission intensity of Si and SiH and the deposition rate has been observed [288]. From this it can be concluded that the emission intensity of Si and SiH is proportional to the concentration of deposition precursors. As the Si and SiH excited species are generated via a one-electron impact process, the deposition precursors are also generated via that process [123]. Hence, for the characterization of deposition, discharge information from OES experiments can be used when these common generation mechanisms exist [286]. 

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M. D. Hester, Gas Plasma Analysis Using an Emission Spectrometer, AUiedSignal Inc., Kansas City, Mo., Jan. 1990, p. KCP-613-4169. 

NURMI T, ADLERCREUTZ H (1999) Sensitive HPEC method for profiling phytoestrogens using coulometric array detection application to plasma analysis, Analytical Biochemistry, 274, 110-17. 

Plasma analysis is essential in order to compare plasma parameters with simulated or calculated parameters. From the optical emission of the plasma one may infer pathways of chemical reactions in the plasma. Electrical measurements with electrostatic probes are able to verify the electrical properties of the plasma. Further, mass spectrometry on neutrals, radicals, and ions, either present in or coming out of the plasma, will elucidate even more of the chemistry involved, and will shed at least some light on the relation between plasma and material properties. Together with ellipsometry experiments, all these plasma analysis techniques provide a basis for the model of deposition. 

Plasma analysis reveals information on the products of chemical processes, and can be used to good effect as a feedback to plasma modeling. The role of ions has been thoroughly illustrated, and the important result that ion bombardment with moderate energy is beneficial for material quality has been quantified. 

The antiradical capacity of proteins is thought to be an important component of the total antioxidant capacity of blood plasma. Analysis of the ACW of blood plasma showed, that under normal conditions, its main components are the UA and ASC. The rest of the total antiradical capacity (ACR), which can be... 

Hsieh Y. et al., 2003. Direct plasma analysis of drug compounds using monolithic column liquid chromatography and tandem mass spectrometry. Anal Chem 75 1812. 

Hsieh Y., 2004. Using mass spectrometry for drug metabolism studies, in Direct Plasma Analysis Systems, Korfmacher, W.A., Ed., Boca Raton, FL, CRC Press, Chap. 5. 

Zang X. et al., 2005. A novel online solid-phase extraction approach integrated with a monolithic column and tandem mass spectrometry for direct plasma analysis of multiple drugs and metabolites. Rapid Commun Mass Spectrom 19 3259. 

Table 5.1 Inductively coupled plasma analysis of Heck reaction filtrates. (Reproduced from ref. 13, with permission.)...

An internal standard should always be used for every analysis carried out. This is an amino acid that is known to be absent from the sample under investigation. For instance in blood plasma analysis either of the non-physio-logical amino acids, nor-leucine or a-amino-/3-guanidinobutyric acid, may be used. This should be added in a known amount to the sample prior to any sample pre-treatment (for example, removal of protein). 

Thoi peutic of drug monitoring, pit lls in plasma analysis. 218... 

The presence of Pr in apatite samples, up to 424.4 ppm in the blue apatite sample, was confirmed by induced-coupled plasma analysis (Table 1.3). The luminescence spectrum of apatite with a broad gate width of 9 ms is shown in Fig. 4.2a where the delay time of500 ns is used in order to quench the short-lived luminescence of Ce + and Eu +. The broad yellow band is connected with Mn " " luminescence, while the narrow lines at 485 and 579 nm are usually ascribed to Dy and the fines at 604 and 652 nm, to Sm +. Only those luminescence centers are detected by steady-state spectroscopy. Nevertheless, with a shorter gate width of 100 ps, when the relative contribution of the short lived centers is larger, the characteristic fines of Sm " at 652 nm and Dy + at 579 nm disappear while the fines at 485 and 607 nm remain (Fig. 4.2b). It is known that such luminescence is characteristic of Pr in apatite, which was proved by the study of synthetic apatite artificially activated by Pr (Gaft et al. 1997a Gaft... 

Johnson DW (2005) Ketosteroid profiling using Girard T derivatives and electrospray ionization tandem mass spectrometry direct plasma analysis of androstenedione, 17-hydroxypro-gesterone and cortisol. Rapid Commun Mass Spectrom 19 193-200... 

Although the advantages associated with online plasma extraction are attractive, care must be taken to monitor the recovery of dmg-related material during the extraction process. Unlike quantitative plasma analysis, where poor recovery only affects the limit of quantitation, the recovery of all drug-related components in metabolite profiling studies must be high in order to ensure that the quantitative data are meaningful. 

A sensitive and rapid chromatographic procedure using a selective analytical detection method (electrospray ionization-mass spectrometry in SIM mode) in combination with a simple and efficient sample preparation step was presented for the determination of zaleplon in human plasma. The separation of the analyte, IS, and possible endogenous compounds are accomplished on a Phenomenex Lima 5-/rm C8(2) column (250 mm x 4.6 mm i.d.) with methanol-water (75 25, v/v) as the mobile phase. To optimize the mass detection of zaleplon, several parameters such as ionization mode, fragmentor voltage, m/z ratios of ions monitored, type of organic modifier, and eluent additive in the mobile phase are discussed. Each analysis takes less than 6 min. The calibration curve of zaleplon in the range of 0.1-60.0 ng/ml in plasma is linear with a correlation coefficient of >0.9992, and the detection limit (S/N = 3) is 0.1 ng/ml. The within- and between-day variations (RSD) in the zaleplon plasma analysis are less than 2.4% (n = 15) and 4.7% (n = 15), respectively. The application of this method is demonstrated for the analysis of zeleplon plasma samples [14]. 

II.Q.2 Plasma Analysis of Benazepril Using Gas Chromatography with Mass-Selective Detection (GC-MSD) 633... 

PACKAGE CODE ( Plasma Analysis, Chemical Kinetics, And generator Efficiency) ARI-RR-177, February 1980, Aerodyne Research, Inc., Bedford, MA 01730 (available from NTIS,... 

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