Sequential measurement

A) and (10 A), while the low intensity ion beam (10 to 10 A) is measured simultaneously in the low-level detector. A second sequence shifts all masses to monitor U in the ion counting channel relative to U. A comparison of the two sequential measurements using different collector configurations provides an... 

Quasi-multidimensional information as shown in Fig. 3.9 (right side) can be obtained in different ways, mostly by sequential measurements, for example ... 

Hollow-cathode lamps are currently available for over sixty elements. Several multi-element lamps have been constructed and are useful for routine determinations, but they have proved to be of doubtful performance up to now. More successful with regard to multi-element analysis have been computer controlled automated systems, which enable a programme of sequential measurements to be made with instrumental parameters being adjusted to the optimum for each element to be measured. 

So how does the IRMS get its stability Collector slits are several times the width of the ion beams. This gives a flat-topped peak shape (Fig 6) which makes the ion current intensive to drift. The main source of drift is temperature variation which both affects the electronic components used for mass selection and caused expansion and contraction of mechanical parts. Simultaneous measurement of ion beams using a double or triple collector is more precise than sequential measurement by mass scanning with a single detector. Finally, frequent comparison of sample gas under identical conditions also contributes to stability. Ion beam stability is more important than resolution for isotopic measurements. 

This estimate is not acceptable. Since measurements f, /2, and fo were used in step 1 and they gave a good estimate, the gross error is in either measurement /4 or f or both. Now, applying the combined approach, we delete sequentially measurements f 4 and f5 from the adjustment. 

FIGURE 9.20 An illustration of the optical path for an ICP instrument that utilizes a monochromator for the sequential measurement of spectral lines. 

Pharmacokinetic concentration-time curves for a drug and ifs mefabolifes are used to identify primary exposure metrics such as AUC, or which are not time-dependent unlike the sequential measurements of concentration over time. A peak plasma concentration of a drug is often associated with a PD response, especially with an adverse event. There can be large inter-individual variability in the time-to-peak concentration, and closely spaced sampling times are often critical to determining the peak plasma concentration accurately in individual patients because of differences in demographics, disease states, and food effects, if any. All these elements are clearly spelled out in the protocols written to conduct these studies. 

Case III - Analyte Detection (A - random). One of the most reliable modes of simple (single) analyte detection obtains when y, B and A are each measured (observed) for every sample processed. Such is often the case, for example, in radiocarbon dating where the age of each unknown artifact is estimated from sequential measurements of the sample, the background, and the radiocarbon dating standard. Thus,... 

Reproducibility of elution activity of Au-195m. The reproducibility of the eluted Au-195m activity was evaluated from 81 sequential measurements obtained on-line from the intravenous tubing utilized for patient injections. The... 

There is a commercially available instrument for HR-CS AAS in which a flame, a graphite furnace, or a CVG system are used to carry out atomization. The instrument has a double monochromator with a prism premonochromator and a high-resolution echelle monochromator, which allows a wavelength from 189 to 900 nm to be used in a sequential measurement mode.19... 

The installation of the sensors can be (1) remote head system (continuous measurement, continuous readout), (2) multiple head system (continuous measurement, sequential readout), and (3) tube sampling system (sequential measurement, continuous readout). Multiple head systems are used where at... 

Count the sample every two or three days for 2 weeks to confirm the 8.02-day half-life. Record sequential measurements, as in Data Table 10.1. Plot a decay curve of In net count rate vs. time. Checking the decay curve also serves as a means of determining if there are any radioactive contaminants in the sample. 

CE-MRA also allows repetitive measurements to follow the passage of contrast bolus. Reduction in the number of slices and of in-plane resolution admits sequential measurements with a temporal resolution ofless than 1 s (Krings and Hans 2004). In combination with high resolution measurements, thus dynamic processes in arteriovenous shunts or for instance in steal phenomena can be studied (Fig. 5.7). 

Figure 5. Visible laser stability. The laser power fluctuations using a 488 nm (blue) and 568 nm (red) lasers were determined using a 10x objective and a Chroma red slide. The fluorescence was sequentially measured every 30 sec (400 times) for total time duration of 3.33 hrs. The variation of the peak to peak using 488 nm or 568 nm excitation was approximately 25%. The fluctuating power intensity line suggests that the system scanning and detection devices are yielding large power fluctuations that will affect the illumination of the sample. The Acousto Optical Transmission Filter (AOTF) is probably contributing to this 488-568 nm sinusoidal pattern.

Both Q and SF mass spectrometers are scanning (sequential) analyzers and multiisotope analysis can be achieved at the expense of the measurement sensitivity and precision. The sequential measurement of m/z at different points within a time-dependent concentration proble of a transient signal can result in peak distortions and quantisation errors commonly referred to as spectral skew. The alternative is TOF-MS which features the ability to produce a complete atomic mass spectrum in less than 50 xs and thus allows very brief transient signals to be recorded with high bdelity. This is especially useful in the on-line isotope ratio determination. However, a 10-fold loss in sensitivity of a TOF-ICP-MS instrument in comparison with the latest Q instruments often creates an obstacle for the wider application of TOF-ICP-MS as a detector in the CE of metallobiomolecules in biological samples. 

A coulometric titration method was introduced for sequential determination of sulfite, thiosulfate and ascorbic acid (1) in solutions containing sulfite-thiosulfate or sulfite-ascorbic acid couples. Formaldehyde or acetaldehyde can be used to mask the sulfite component. Two sequential measurements of coulometric time, one for both components in the mixture and one for the sample solution in which sulfite is masked, can be used to determine the concentrations of sutfite-thiosulfate and sulfite-ascorbic acid couples. The method is linear for 0.5-60 p,M 1 in the presence of 0.44-13 (xM sulfite, with RSD 0.1-4% and current efficiency of ca 98.0%. The method can be used for determination of the presence of sulfite and 1 in real sample matrices such as mineral waters and vitamin C tablets . 

After rapid intravenous injection, sequentially measured plasma levels may follow a pattern similar to that shown by the solid circles in Figure 3.8. For most drugs, the elimination phase is reached when the data points fall on the line marked " S." The distribution phase occurs prior to that time. In this case, the curve contains two exponential phases and can be described by the following sum-of-exponentials data equation ... 

CMIN [2]. By sequentially measuring these substances before and after CM exposure and by using antagonists of these vasoactive substances (misoprostol, bosentan, ace-inhibitors, a-blockers, etc.) [53, 56-60] the degree of involvement for each of these potential mediators in the process of developing CMIN has been investigated. To date, only endothelin and adenosine have been shown to play a role as important mediators in CMIN [58, 59, 61]. 

Sequential measurement of impedance by Fourier analysis provides good accuracy for stationary systems. The sequence of ftequencies can be arbitrarily selected, and therefore frequency intervals of A///, considered to be the most economical use of frequencies, can be employed. Because the measurements at each frequency are independent of each other, frequencies foimd to be inconsistent with the Kramers-Kronig relations can be deleted. 

Readout Noise. As defined in Section 4.2.5, readout noise is the standard deviation of sequential measurements of a constant number of electrons. Readout noise is generally determined by successive readouts of a dark detector with very short integration time. 

There are obvious limitations in terms of choice of biofluid for instance, urine might not be as appropriate as cerebrospinal fluid for studying neuropathology. There is also the potential for confusion with mixed-toxicity drugs that, for example, affect both liver and kidney, as the biomarkers of toxicity will be a complex combination that relates to both sites and possibly to the multiple mechanisms. However, this offset by the fact that mixed toxicities often have different timescales and such effects can therefore be deconvoluted by making repeated sequential measurements in individual animals. 

Fig. 14.25 Automated evaluation of a Ni porphyrin44 (a) Differential pulse voltammograms (DPVs) recorded for different NO concentrations (b) Peak current measured from DPVs for five NO concentrations recorded in 22 sequential measurements in a microtiter plate (c) Resulting calibration plot (n = 22)...

Mapping involves the sequential measurement of the spectra of adjacent regions of a sample. This is achieved by moving each region of that sample into the beam focus of a microscope after the spectrum of the previous region has been measured the measurement is then repeated until the entire region of interest has been covered. 

Van der Poll T, Malefyt RW, Coyle SM, Lowry SF. Antiinflammatory cytokine responses during chnical sepsis and experimental endotoxemia Sequential measurements of plasma soluble interleukin (IL)-1 receptor type II, IL-10, IL-13. J Infect Dis 1997 175 118-122. 

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