Phase plus, measured

Another classification of detector is the bulk-property detector, one that measures a change in some overall property of the system of mobile phase plus sample. The most commonly used bulk-property detector is the refractive-index (RI) detector. The RI detector, the closest thing to a universal detector in lc, monitors the difference between the refractive index of the effluent from the column and pure solvent. These detectors are not very good for detection of materials at low concentrations. Moreover, they are sensitive to fluctuations in temperature. 

A critical requirement for the success of receptor models for atmospheric particles Is that the compositions of particles from all major sources in an area be accurately known. Chemical element balances (CEBs) of 130 samples taken In Washington, D.C. and analyzed for 40 elements yielded nearly the same source strengths when 28 elements are used In the least-squares fit as when only nine carefully chosen elements are used. Certain elements are important to the stability of CEB fits (Na, Ca, V, Mn, As and Pb) and should be measured carefully In particles from sources. For three of the nine elements (Al, Fe and Zn), other elements can serve as surrogates (many lithophlles for Al and Fe, Sb and Cd for Zn). Measurements on many more sources of each Important type should be done In order that trends can be observed that will allow one to predict compositions of particles from unmeasured sources. Instack measurements should Include collections of at least two size fractions of particles plus vapor-phase species. Measurements of at least 20 elements plus some classes of carbonaceous material should be made. 

Flowsheet Testing. Na2C03 scrub waste solutions were prepared by extracting measured amounts of U(VI) and Pu(IV) into dodecane solutions containing 0.02 M - 0.04 M HDBP and 0.0067 M -0.0134 M H2MBP. The resultant organic phase plus precipitates were then slurried with the required amount of Na2C03 until all the precipitate dissolved. 

Some filled-bulb thermometers take account of the pressure increase in the capillary stream. This increase is due to the vapor-pressure rise of the liquid phase plus the rise due to the compression of the gas. A relatively high pressure may hence occur. Bending the capillary tube is sometimes used, and the tube straightens to a degree as the pressure rises. The amount of straightening can be calibrated with a pointer on a dial to measure the temperature. 

It measures the difference in refractive index between the mobile phase and the mobile phase plus sample. 

From isotherm measurements, usually earried out on small quantities of adsorbent, the methane uptake per unit mass of adsorbent is obtained. Sinee storage in a fixed volnme is dependent on the uptake per unit volume of adsorbent and not on the uptake per unit mass of adsorbent, it is neeessary to eonvert the mass uptake to a volume uptake. In this way an estimate of the possible storage capacity of an adsorbent can be made. To do this, the mass uptake has to be multiplied by the density of the adsorbent. Ihis density, for a powdered or granular material, should be the packing (bulk) density of the adsorbent, or the piece density if the adsorbent is in the form of a monolith. Thus a carbon adsorbent which adsorbs 150 mg methane per gram at 3.5 MPa and has a packed density of 0.50 g/ml, would store 75 g methane per liter plus any methane which is in the gas phase in the void or macropore volume. This can be multiplied by 1.5 to convert to the more popular unit, V/V. 

Fig. 12 Magnetic phase diagram of [Fe(Cp )2][Ni(a-tpdt)2]. Boundaries detected by different measurements M(T) (open triangles) M(H) (crosses) %(T)(open circles) and %"(H) (open squares and plus signs)...

The extraliposomal ammonium ion concentration [(NH4)jJ yj ] was measured as ammonia with the ammonia electrode at pH 13.5. Under these conditions, all ammonium ions are converted to ammonia and no leakage of intraliposomal ammonium ion occurred during the measurement. For measurements of total ammonium ion plus ammonia present in both intraliposome aqueous phase and external medium ammonia [(NH4)jJ g4i y +(NH4)Jpg j ] the liposomes were sonicated under acidic conditions (pH 1.5-2.0) using the Transonic 460/H bath sonicator in sealed vials for 45 minutes. Then, in order to convert ammonium ion to ammonia, NaOH was added to bring the pH to... 

Over platinum black, -hexane gives 2- and 3-methylpentanes, methylcyclopentane, and benzene. Actual concentrations are compared in Fig. 2 with equilibrium ones as a function of hydrogen pressure. Unreacted n-hexane is ignored since it would not be able to equilibrate with all its products. Realistic values are obtained if methylcyclopentane plus isomers are compared with the amount of benzene. These, however, correspond to much higher effective hydrogen concentrations than measured in the gas phase (31). 

Near the surfactant region the crystalline or lamellar phase is found. This is the region one finds in hand soaps. The ordinary hand soap is mainly the salt of fatty acid (coconut oil fatty acids or mixtures [85%] plus water [15%] and some salts. X-ray analyses have shown that the crystalline structure consists of a layer of soap separated by a water layer (with salts). The hand soap is produced by extruding under high pressure. This process aligns the lamellar crystalline structure lengthwise. If the degree of expansion versus temperature is measured, the expansion will be found... 

There are two ways to collect FLIM data freqnency-domain or time-domain data acqnisition (Alcala et al. 1985 Jameson et al. 1984). Briefly, in freqnency domain FLIM, the fluorescence lifetime is determined by its different phase relative to a freqnency modulated excitation signal nsing a fast Fourier transform algorithm. This method requires a frequency synthesizer phase-locked to the repetition freqnency of the laser to drive an RF power amplifier that modulates the amplification of the detector photomultiplier at the master frequency plus an additional cross-correlation freqnency. In contrast, time-domain FLIM directly measures t using a photon connting PMT and card. 

In addition, for solid samples or peptides in nonaqueous solvents, the amide II (primarily in-plane NH deformation mixed with C—N stretch, -1500-1530 cm-1) and the amide A (NH stretch, -3300 cm-1 but quite broad) bands are also useful added diagnostics of secondary structure 5,15-17 Due to their relatively broader profiles and complicated by their somewhat weaker intensities, the frequency shifts of these two bands with change in secondary structure are less dramatic than for the amide I yet for oriented samples their polarization properties remain useful 18 Additionally, the amide A and amide II bands are highly sensitive to deuteration effects. Thus, they can be diagnostic of the degree of exchange for a peptide and consequently act as a measure of protected or buried residues as compared to those fully exposed to solvent 9,19,20 Amide A measurements are not useful in aqueous solution due to overlap with very intense water transitions, but amide II measurements can usefully be measured under such conditions 5,19,20 The amide III (opposite-phase NH deformation plus C—N stretch combination) is very weak in the IR and is mixed with other local modes, but has nonetheless been the focus of a few protein-based studies 5,21-26 Finally, other amide modes (IV-VII) have been identified at lower frequencies, but have been the subject of relatively few studies in peptides 5-8,18,27,28 ... 

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