Scan cycle

The electrochemical catalytic activity of various Pt-porous nanoparticles for the oxidation of methanol was shown in Figure 13. The peak mass current densities recorded after 100 scan cycles were 80mAmg Pt for those porous Pt nanoparticles. The peak mass current densities were 72, 62, 58 and 51mAmg Pt for those products formed for reaction time of 3, 5, 10, and 20min at the Pt(acac)2 HDD HDA ACA DPE molar ratio of 6 36 118 12 100, respectively. As a reference point, the catalytic activity of a commercial carbon-supported Pt... 

Chlornitrofen and nitrofen conditions for GC/MS column, cross-linked methyl silicone capillary (12 m x 0.22-mm i.d., 0.33- am film thickness) column temperature, 60 °C (1 min), 18 °C min to 265 °C inlet, transfer line and ion source temperature, 260, 200 and 200 °C, respectively He gas column head pressure, 7.5 psi injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70 eV scan rate, 0.62 s per scan cycle scanned mass range, m/z 100-400. The retention times for chlornitrofen and nitrofen were 11.8 and 11.3 min, respectively. The main ions of the mass spectrum of chlornitrofen were at m/z 317, 319 and 236. Nitrofen presented a fragmentation pattern with the main ions at m/z 283, 202 and 285. ... 

Note Scanning of a magnet is affected by hysteresis. This causes the reproducibility of mass calibration to improve after several scan cycles have passed. For best results with dual-target probes, it is therefore recommended to skip the first few scans. 

Figure 17.49 Cyclic voltammery of Co(DTB)32 + at a transparent PEDOT modified FTO. Scan speed 100 mV/s, potential referred to SCE. The smaller peak centered at about —650 mV is determined by the intrinsic polymer electroactivity. PEDOT was grown by multiple scan deposition (three scans), cycling the potential between —0.7 and +1.5 V versus SCE with a scan speed of 20mV/s. From Bignozzi et al., unpublished results.

Fig. 16.4 shows the capillary gas chromatograms obtained for a fraction. Fig. 16.4(b) shows the total ionisation chromatograms for the fraction obtained from the high resolution mass spectral data set. In general, the correlation between the total ionisation chromatogram profile and the flame ionisation detector profile is low due to both the differing relative detector responses and the consideration of scan cycle time (9.6s) with respect to chromatographic peak elution time ( 20s). 

Figure 10 illustrates the short-term dc stability of the devices (Mackenzie et al, 1983). The output characteristics of one FET are shown for 10 successive scanning cycles of VG from —10 V to +45 V and back. The gate voltage was scanned in both directions at a rate of about 0.5 V sec-1. The traces show remarkably little drift or hysteresis in fact, the maximum variation in VG is approximately 0.4 V for a given value of source-drain current. 

In cyclic voltammetry, the potential of the working electrode is scanned linearly from an initial to a vertex value, and then the scan is reversed. The electrochemical response of the target species with applied potential during the forward and reverse scans can be obtained from the scan cycle. Figure 1.14 shows... 

Figure 8.7 Cyclic voitammograms in the course of polymerization of 0.1 M pyrrole for 20 potential scan cycles in (a) 0.1M [EMIM][OTf]+ HyO, (b) 0.1 M [EMIM][OTf] + MeCN, and (c) neat [EMIM][OTf].

Li et al. [40-42] used a QTrap system to incorporate both the conventional SRM-only acquisition of parent compounds and the SRM-triggered IDA of potential metabolites within the same scan cycle during the same LC-MS/MS run in plasma sample analysis. The fast scanning capability of the LIT allowed for the IDA of metabolite MS/MS spectra <1 s/scan, in addition to the collection of adequate data points for SRM-only channels. A SRM survey scan containing 30-150 SRM channels was established by running a script in Analyst software. If the intensities in these... 

The sensitivity of this SFC-MS combination was evaluated with two standards methyl arachidate (326 Da) and tristearin (890 Da). The instrximent was tuned to "unit" resolution (10% valley definition) before the sensitivity measurements were made. Splitless injection of 800 pg of methyl arachidate produced a mass chromatogram of m/z 344, [M+NH4] , with a S/N of approximately 4. The scan range was m/z 100 to 500 with a 1 s scan cycle time. Splitless injection of 12 ng of tristearin produced a mass chromatogram of m/z 908,... 

M+NH4] ", with a S/N of approximately 5. The scan range was from m/z 500 to 1000 with a scan cycle time of 1.1 s. The tristearin result is a "worst case" result. Logistical difficulties of combining instruments from two distant sites over a short period of time precluded optimization of S/N. 

PANOA CV with different Catechol scan cycles, oxidation PANOA/Pt CV Negative shift of the oxidation peak potential and an increase in the peak current [92]... 

Figure 17.2 MIP deposition by electropolymerization using cyclic voltammetry (a) MI-PI3AA-asp-adduct/MWCNTs-PGE [inset (1) reduction peak of monomer, inset (2) oxidation peak of aspartic acid, and inset (3) oxidation peak of monomer], (b) NI-PI3AA/MWCNTS-PGE, and (c) over-oxidized MI-PI3AA/ MWCNTs-PGE [electropolymerization conditions 0.05 mM 1-asp, 0.1 mM PI3AA, 0.01 M phosphate buffer (supporting electrolyte pH 5.0), no. of scan cycles 12, potential range -1.6 to +1.6 V vs. Ag/AgCl, over-oxidation potential range -1.6 to +2.0 V, scan rate 100 mV s )]. Reproduced with permission from [60].

Figure 3.4 Cyclic voltammograms in the course of polymerization of aniline for 25 potential scan cycles. Electrol3 c solution [a) 0.5 M aniline in 1.0 M CF3SO3H + H2O (b) 1.0 M aniline in 1.0 M CF3SO3H + [EMlM][OTf]. Reprinted from Ref. [62], Copyright (2003), with permission from Elsevier.

The specimen motion required for cone-beam reconstruction is a lateral axes (x, z) translation and a vertical axis P rotation. The scanning cycle needs to be under computer control in order to synchronize mechanical movement with data acquisition. Further, the control must provide a level of accuracy that, at the very least, matches the measured resolution of the x-ray source. In practice, an encoded accuracy in lateral translation of 10,000 counts per mm and a rotational accuracy of 2000 counts per degree of revolution can be achieved with commercial components. 

Although incapable of scans that reveal the precursor ions of user-selected product ions or neutral fragments, traps can foUow fragmentations of miz selected precursor ions through several steps. Such MS experiments are discussed in Section 6.2.2. A typical scan cycle for a MS microscan is shown in Figure 6.25 for application to analysis of tetrachlorodibenzodioxin (TCDD), though this approach provides only a convenient screening technique and can not satisfy the requirements of fully validated analyses (Section 11.4.1). 

Figure 6.26 Comparison of scan cycles (and cycle times) used in operating a Paul ion trap in fuU scan MS mode, in full scan MS mode, and in MRM mode in which both precursor and fragment ions are isolated using selective injection techniques (but observation and detection of the fragment stiU requires a scan function).

The Enhanced MS mode uses Qj operated in RF-only mode so that the final Q3/T linear trap spectrum contains all ions produced in the source (down to the low m/z cutoff of Qj) this mode resembles a MS scan of operated in conventional RF/DC resolving mode except that the scan cycle time is much faster. To generate MS spectra, first generation fragment ions are produced in qj/Y from precursor ions selected by Q, and are transmitted and accumulated in Q3. p operated in hnear trap mode isolation and CID of m/z-selected first generation fragment ions are then achieved as described above for linear traps (Hager 2003). 

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