Data Acquisition Rate

Operating parameters that affect the rate of acquisition of data points in SIM and MRM modes are the switching time (an intrinsic property of the analyzer) and the dwell time per SIM or MRM channel (specified m/z value for 

In the final reckoning it is the total data acquisition time that must be considered when ensuring at least 10 data points are acquired across a chromatographic peak when using ion beam instruments in SIM or MRM mode  

While the concept of duty cycle also applies to ion traps, if an attempt is made to produce a similar simple relationship the situation becomes immediately more complicated as a result of the need for such instruments to deal with the implications of space charge effects. For example, only a limited total number of ions (analyte plus matrix) can be accumulated in a trap at any one time, so the number of microscans (fill-scanout cycles. Section 6.4.5), which must be accumulated and averaged to provide adequate ion statistics for the analyte ions, is highly variable depending on the analyte matrix ratio. If selective ejection techniques (Section 6.4.5) are used to eliminate 

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The data acquisition rate is generally set so that the sample spacing of the sonic log (the distance between two acquired data points) ranges from 6 in. to 1 ft based on the anticipated drilling rate of penetration (ROP). 

The full-scan mode is needed to achieve completely the full potential of fast GC/MS. Software programs, such as the automated mass deconvolution and identification system (AMDIS), have been developed to utilize the orthogonal nature of GC and MS separations to provide automatically chromatographic peaks with background-subtracted mass spectra despite an incomplete separation of a complex mixture. Such programs in combination with fast MS data acquisition rates have led to very fast GC/MS analyses. 

Applications The diversity of MS/MS instrumentation offers considerable opportunities for polymer/addit-ive analysis. The best geometry for a particular application depends on a number of factors, including mass resolution in the first and third stages, mass range, sensitivity, available collision energy, the type of information required, data acquisition rate, etc. Polymer science applications of MS/MS comprise ... 

If the LC part is optimized to deliver peaks in a shorter time or more peaks in the same time when compared to a conventional method, we must consider the system s ability to handle data. Because the speed optimization described above will produce much narrower peaks, widths below 1 sec can be achieved easily. However, the data acquisition rate and data filtering steps must be considered. 

To identify a compound, five data points per peak may be sufficient. Quantitation may require at least 10 data points across a peak. Many of today s laboratories still house standard detectors (UV, ELSD, fluorescence, etc.) with maximum data acquisition rates at or below 20 Hz. Many conventional LC/MS methods acquire data at rates of 5 Hz or less. As shown in Figure 3.8, this is not sufficient for modem speed optimized chromatography. Obviously, selecting the wrong data acquisition rate will nullify all attempts to optimize chromatography. 

Careful setting of the scan range is recommended. The narrower the scan range, the higher the number of data points per peak. This is not necessarily a linear relation it can depend on the MS. If a large mass range and fast data acquisition rate are required, a time-of-flight (ToF) MS would be... 

MS operated at 20 to 40 Hz data acquisition rates in centroid or profile mode and at a mass range of 900 amu. The resulting cycle times varied from 49 to 62.22 The longest system overhead time was 21 sec and the shortest was 8 sec—a difference of 260 percent Translated into throughput, the difference equals almost 400 samples per day ... 

However, signal also depends on detector data acquisition rate noise increases with increased detection acquisition rate. Since GCxGC peaks are narrow, necessitating higher detection frequencies, S/N ratio improvements are not as great as might be initially anticipated. 

AED combined with GC x GC was first reported by van Stee et al. [21 ] for element-selective detection in petrochemical samples. The AED used in this study had a maximum data acquisition rate of 10 Hz, which when applied to the detection of GCxGC peaks of base width of 100-300 ms, will not achieve the required minimum of 5-10 data points per peak. In order to meet this criterion, peak widths need to be broader, with necessary widths of400-1- ms required. Deliberate broadening of second... 

It should be noted that regardless of the CDS used, a data-acquisition rate that is too low will produce a peak that is impossible to integrate accurately. There must be enough data points to define the peak accurately. It is always safer to have too many points across a peak than too few, provided that the noise generated by the A/D is sufficiently lower than the detector noise generated by the chromatographic system. 

Examined factors were voltage, buffer or electrolyte concentration, " buffer or electrolyte pH, chiral selector concentration, capillary temperature, detection wavelength and its bandwidth, reference wavelength and its bandwidth, peak width, threshold, data acquisition rate, filter and its peak width, and surfactant... 

Certainly, the inherent lack of depth resolution of the BMP techniques minimizes the utility of sputter profiling combined with BMP analysis. However, gross comparisons of the exterior versus interior composition can be obtained by recording X-ray spectra before and after a minimum of several thousand angstroms of material are sputtered from the particle surface (13,44). Similarly, BSCA is not very suitable when used in conjunction with sputter profiling for reasons that include a) data acquisition rates are very slow, b) potential chemical information is lost since sputtering may alter the chemical forms of the elements present, and c) individual particles cannot be depth profiled (11, 14, 26). 

Most of the traditional HPLC detectors can be applied to LCxLC analyses the choice of the detectors used in comprehensive HPLC setup depends above all on the nature of the analyzed compounds and the LC mode used. Usually, only one detector is installed after the second-dimension column, while monitoring of the first-dimension separation can be performed during the optimization of the method. Detectors for microHPLC can be necessary if microbore columns are used. Operating the second dimension in fast mode results in narrow peaks, which require fast detectors that permit a high data acquisition rate to ensure a proper reconstruction of the second-dimension chromatograms. 

PDA detectors can be operated at rapid data acquisition rates (up to 40 Hz) and are the most common used. Quadrupole MS systems are capable of supplying sufficient spectra for peak. For reliable component assignment, of course, TOF-MS systems possessing higher scan speed can be used. 

It is important to ensure that the data collection rate is fast enough for peaks with low retention times in order to ensure good reproducibility of all peak parameters. For modern instrumentation, this is generally not a problem for example, FID detectors are typically able to achieve a data acquisition rate of 50-250 Hz using the standard instrument configuration. 

The result of our effort to develop the best possible detector for MES is as follows. Our detector has a resolution of approximately 2 KeV (fwhm) at 15 KeV as shown in Figure 6. There is virtually no deterioration in performance over a period of several months. The overall efficiency of the detector when used for MES with 14-KeV y-radiation is such that a 0.001-inch thick sample of stainless steel type 302 (natural isotopic abundance) gives a spectrum with the peak height some 400% of the base line, Figure 7. (For comparison, when we started we were quite content with 50%.) With our 10-mc Co-57 source, the data acquisition rate in the peak is approximately 500 counts/min. This means that in a matter of a minute or less one obtains a recognizable spectrum. As a bonus, the observance of 6-KeV x-rays yields an effect of approximately 50% of the baseline. To accomplish this, we interpose a plastic filter between the source and the sample to absorb most of the 6-KeV radiation from the source (which does not contribute to the effect but is elastically... 

We next develop a method to estimate the data acquisition rate necessary to measure a first-order rate coefficient to a specified accuracy. The probability distribution of the signal pulses in time (with no background) is given by... 

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