Ratio recording

Whilst nothing can improve upon the disadvantage of low molar absorption coefficients, instrumental designs and improvements with ratio recording and FT-IR instruments have virtually overcome the accuracy and instrumental limitations referred to in (b) and (c) above. As a result, quantitative infrared procedures are now much more widely used and are frequently applied in quality control and materials investigations. Applications fall into several distinct groups ... 

Ratio recording, 256, 257 Rectifiers in x-ray tube power supply, 244... 

Figure 2. (A) IR spectra of CO adsorbed on the Fe-TON zeolites of different Si/Fe ratio at very low CO coverage required for the detection of the Lewis sites., (B) Difference spectra of CO adsorbed on Fe-TON of different Si/Fe ratio recorded upon the saturation of all Bronsted sites.

To measure a fluorescence excitation spectrum, a band of fluorescence from a solute in C was selected by the monochromator M2 and was received by the photomultiplier After amplification the outputs of Pi and P2 were passed to the ratio recorder, R. The frequency drum on Mi was motor-driven and as the frequency was varied the slits were adjusted so as to maintain the output of P2 approximately constant. If the contents of F were so chosen as to make the output of P2 proportional to the quantum output of Mj at all frequencies, then since Pi was proportional to ht (see eq. 2) and P2 was proportional to I0, the recorded ratio was proportional to t, i.e., the true excitation spectrum was recorded. 

D. The table below shows signal-to-noise ratios recorded in a nuclear magnetic resonance experiment. Construct graphs of... 

The composition of D-glucose has been determined over a wide range of temperature by Franks and coworkers27 and by Maple and Allerhand4 (see Table II). Both sets of data are self-consistent, but the a fi pyranose ratio recorded by Maple and Allerhand is considerably higher, for example, 39.4 0.8% of a-pyranose versus 35.5 1% at 37°. These authors added 11% of 1,4-dioxane to the solutions they used for recording the, 3C-n.m.r. 

Light Scattering. Light scattering measurements were carried out using a Beckman DK-2A ratio recording spectrophotometer. Transmission was measured at 435.8 nm (m/x) and recorded as turbidity (= log (I0/I)/l cm"1), where l is film thickness. 

Takayanagi, M., Ozima, M. (1987) Temporal variation of 3He/4He ratio recorded in deep-sea sediment cores. J. Geophys. Res., 92(B12), 12531-8. 

For all the above reasons, it is to be preferred to measure two solute properties in one detector, especially if both measurements can be performed simultaneously. An example of this is the application of dual-wavelength absorption detection in LC. The application of this technique for the purpose of selectivity optimization has been investigated by Drouen et al. [584]. For the purpose of peak assignment or recognition, ratio recording may be used. The principle of this technique is based on Beer s law and may be explained from the following equation for the absorption ratio Ra ... 

Consistently, the PIA spectra of toluene solutions containing MP-Ceo and OPVn (n = 2, 3 or 4) in a 1 1 molar ratio, recorded using selective photoexcitation of MP C60 at 528 nm (Fig. 1.28b), invariably exhibit an absorption at 1.78 eV with an associated shoulder at 1.54 eV, characteristic of MP-C6o(7i) [103]. The monomolecular decay (—AT oc Ip, p = 0.89-0.96) with lifetime 150-260 ps associated with these PIA bands supports this assignment. Furthermore, weak fullerene fluorescence at 1.73 eV (715 nm) is observed under these conditions for all three mixtures. No characteristic PIA bands of OP Vw+ radical cations or MP-Cg0 radical anions are discernible under these conditions. From these observations we conclude that electron transfer from the ground state of the OPVn molecules to the singlet or triplet excited state of MP-Cgo does not occur in toluene solution. 

Fig. 2. Far ultraviolet spectra of a-amino acids. All amino acids were in aqueous solution (2 mm quartz cells) at pH 6, except cystine (pH 3). The dibasic acids were measured as hydrochlorides and the absorbance corrected by subracting the absorbance contribution of chloride ion. Measurements were made in a Beckman DK2a extented-UV range ratio-recording spectrophotometer with continuous nitrogen flushing below 2(KK) A (Sussman and Gratzer, 1962).

Altabet, M. A., and Francois, R. (1994). Sedimentary nitrogen isotopic ratio records surface ocean nitrate utilization. Global Biogeochem. Cycles 8, 103—116. 

Unlike vanadium, REE/Fe ratios recorded in even the most recent metalliferous sediments are much higher than those in suspended hydrothermal plume particles (German et al., 1990, 1997 Sherrell et al., 1999). Further, hydrothermal sediments REE/Fe ratios increase systematically with distance away from the paleo-ridge crest (Ruhlin and Owen, 1986 Olivarez and Owen, 1989). This indicates that the REE may continue to be taken up from seawater, at and near the sediment-water interface, long after the particles settle from the plume to the seabed. Because increased uptake of dissolved REE from seawater should also be accompanied by continuing fractionation across the REE series (e.g., Rudnicki and Elderfield, 1993) reconstruction of deep-water REE patterns from preserved metalliferous sediment records remain problematic. Much more tractable, however, is the exploitation of these same sample types for isotopic reconstructions. 

Along with the silicate debris carried to the sea by rivers and wind, the calcitic hard parts manufactured by marine organisms constimte the most prominent constituent of deep-sea sediments. On high-standing open-ocean ridges and plateaus, these calcitic remains dominate. Only in the deepest portions of the ocean floor, where dissolution takes its toll, are sediments calcite-free. The foraminifera shells preserved in marine sediments are the primary carriers of paleoceano-graphic information. Mg/Ca ratios in these shells record past surface water temperatures temperature corrected 0/ 0 ratios record the volume of continental ice ratios yield information... 

Mekik F. A., Loubere P. W., and Archer D. E. (2002) Organic carbon flux and organic carbon to calcite flux ratio recorded in deep sea carbonates demonstration and a new proxy. Glob. Biogeochem. Cycles 16, 1-15. 

Simultaneous measurement of reflection and transmission, or transmission alone, can be carried out by means of a detector positioned on the opposite side of the plate (Fig. 2). Ratio-recording double-beam densitometers, which can correct for background disturbances and drift caused by fluctuations in the source and detec-... 

Figure 1 illustrates a data path in a typical ratio-recording, dispersive infrared spectrometer. The digitization of the analogue signal produced by the detector M.A. Ford, in Computer Methods in UV, Visible and IR Spectroscopy , ed. W.O. George and... 

Figure 1 Data path of a ratio-recording, dispersive IR spectrometer (Reproduced by permission from ref. 1)...

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