Neat samples

IR spectra can be recorded on a sample regardless of its physical state—solid liquid gas or dissolved m some solvent The spectrum m Eigure 13 31 was taken on the neat sample meaning the pure liquid A drop or two of hexane was placed between two sodium chloride disks through which the IR beam is passed Solids may be dis solved m a suitable solvent such as carbon tetrachloride or chloroform More commonly though a solid sample is mixed with potassium bromide and the mixture pressed into a thin wafer which is placed m the path of the IR beam... 

Chemically, nitrosamines are considered to be quite stable compounds and are difficult to destroy cmce they are formed. Reducing or destroying preformed nitrosamines in pesticides offers special challenge, as they occur in trace amounts which require specific selective treatment without effecting the composition of the principal product. Experimental laboratory work revealed that reactions suitable for mass quantities of reactants, that is neat samples, are not necessarily analagous to micro reactions for the reduction of a given trace nitrosamine contaminant or impurity. 

Diethylamino)trimethylstannane is a colorless liquid which boils at 36°/6 mm. The compound is quickly hydrolyzed by moisture. The proton nuclear magnetic resonance spectrum of a neat sample shows a CH3—Sn resonance at 9.92 r with HChs—Sn119 splitting of 56.5 cycles and HCh,—Sn117 splitting of 54.0 cycles. The ethyl resonance consists of a triplet at 9.10 r... 

The stannyl hydride 30, in contrast, showed nonequivalence of the geminal methyls for the neat sample up to 222 °C. Furthermore, no noticeable line broadening was observed in DMSO-dioxane at 160 °C. Thus, it may be concluded that the hydride 30 is configurationally stable while the chloride 29 is not. 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

Get a disposable pipet and a little rubber bulb and construct a narrow medicine dropper. Use this to transfer your sample to the NMR tube. Don t fill it much higher than about 3-4 cm. Without any solvent, this is called, of course, a neat sample. 

Monitoring the polymerization of each substrate provided an informative picture of the effect of both substituents and of isomer distribution on the curing process. We first addressed the question of the relative rates of substrate isomerization and polymerization. We found that, for the parent monomer (PN and PX), the rate of isomerization greatly exceeds the rate of polymerization. Under conditions where PN and PX are fully equilibrated (195°C/15 hrs or 250 /l hr) there is still less than 20% polymer formation in the neat sample. We conclude that for PN or PX the composition of the mixture undergoing polymerization is essentially independent of the starting isomer. The observation that fully cured samples of either PN or PX show identical and C NMR spectra and indistinguishable SEC analyses, is consistent with this contention. 

While exo/endo isomerization of the substituted monomers had been found to be comparable to that of the parent monomer, polymerization of the substituted monomers was much faster. Under the conditions indicated above for <20% polymer formation in neat samples of PN or PX, both the phenyl and carbomethoxy monomers show >80% polymer formation. This greatly complicates any attempt to dissect isomerization from polymerization in these neat samples. Nevertheless, we were able to establish that, in the lower temperature (195 C) polymerization, the isomeric mixture undergoing polymerization was the same (for the carbomethoxy system) whether we started from CBN or from CVN (195 , 1 hr 71% VN, 23% VX, 6% BN + BX). A similar result was obtained by comparing the polymerization of < >VN and <)>BN. 

To further understand the action of the hydroxide ions on the primer properties, weight gain tests were undertaken on various, commercially available adhesives. We attempted to prepare neat samples of ten types of adhesive agents (ie top coats and primers) which had been recommended by the manufacturers as suitable for marine applications. The neat samples were prepared with the use of a commercial adjustable wet film applicator supplied by the Paul Gardner Company. This applicator will lay films up to 0.25inches... 

Figures 3-4 are representative of the range of results on the weight gain tests. The range of results was dramatic. Table II Includes a tabulation of the volume changes observed in the six adhesives. Some of the neat samples showed extreme increases in...

Polavarapu et al. (60) have obtained FTIR-VCD (1625-600 cm ) for neat samples of the three substituted a-phenylethanes, 10, X = NH2, OH, NCO. In (-F)-a-phenylethylamine, seven VCD bands are observed, all with positive sign. Features near 1370 and 1200 cm were identified as possibly useful probes for the configuration of similar analogs. 

UV cut-off the wavelength at which the optical density of a 1-cm-thick neat sample is unity as measured against air. 

Relatively few examples of the stereospecificity of P-C-F couplings exist in the literature but the general features are similar to that found for P-C-H couplings. It is observed for instance, that in the neat sample of... 

Rotations were determined on neat samples specific rotations are for material of the Indicated e.e. 

Cyclic allenes undergo head-to-head cyclodimerization to give tricyclic 1,2-alkylidenccyclobu-tanes. Unsaturated cyclic allenes represent molecules with increased strain and often dimerize spontaneously. Whereas cyclonona-1,2-diene (28) requires heating of a neat sample to 138°C,38 the tetraene 31 has a half-life of 10 minutes at 0°C.39 The more strained cycloocta-l,2,4,6-te-traene (34) could not be isolated and only the dimeric cyclobutane 35 was formed on thermolysis of the tosylhydrazone precursor 33.40... 

The cycloadditions of nonactivated allenes require neat samples heated to temperatures of 150-220°C in sealed tubes for extended periods of time. The regiochemistry of the major cycloadducts can be predicted from the most stable diradicals formed upon initial bonding of the sp carbon in the allene, as exemplified for cycloadducts 2,5 4,6 5,6 67 and 7.7... 

In structures such as 2,6-di-r-butylphenol, in which steric hindrance prevents hydrogen bonding, no bonded hydroxyl band is observed, not even in spectra of neat samples. 

The absorption ranges of the various types of alcohols appear in Table 3.2, below. These values are for neat samples of the alcohols. 

In a discussion of these effects, it is customary to refer to the absorption frequency of a neat sample of a saturated aliphatic ketone, 1715 cm-1, as normal. For example, acetone and cyclohexanone absorb at... 

The absorption frequency observed for a neat sample is increased when absorption is observed in nonpolar solvents. Polar solvents reduce the frequency of absorption. The overall range of solvent effects does not exceed 25 cm-1. 

Intermolecular hydrogen bonding between a ketone and a hydroxylic solvent such as methanol causes a slight decrease in the absorption frequency of the carbonyl group. For example, a neat sample of ethyl methyl ketone absorbs at 1715 cm-1, whereas a 10% solution of the ketone in methanol absorbs at 1706 cm-1. 

Nitroso Compounds Primary and secondary aliphatic C-nitroso compounds are usually unstable and rearrange to oximes or dimerize. Tertiary and aromatic nitroso compounds are reasonably stable, existing as monomers in the gaseous phase or in dilute solution and as dimers in neat samples. Monomeric, tertiary, aliphatic nitroso compounds show N=0 absorption in the 1585-1539 cm1 region aromatic monomers absorb between 1511 and 1495 cm-1. 

Nonaqueous Liquid Wastes Protocol. Nonaqueous liquid wastes were defined to include samples that range from water-soluble organic liquids to immiscible oils. Only a limited amount of data are available on the applicability of this protocol (Figure 4) to compounds other than oils or petroleum products. This medium differs from other environmental media because mutagenic materials are often concentrated in organic liquids. Therefore, this protocol incorporates dilution steps rather than the concentration techniques used in the other media protocols. This protocol is also unique because of the opportunity to test neat samples or samples diluted with DMSO rather than sample components isolated with an absorbent or extracted with a solvent. For this reason, samples treated with this protocol should contain polar compounds and/or volatile compounds that would be lost when the other protocols are used. 

An even more dramatic example of the potential lack of selectivity afforded to the Norrish II reactions of ketones by supposedly very ordered systems than that described in the 76 systems is provided by neat samples of the mesomorphic alkanophenones (81) [278]. These molecules are capable of existing in nematic and smectic B mesophases (see Figure 16) as shown in Scheme 42. The instability of the monotropic smectic B phase of 81a and smectic B phase of 81b did not allow their photoreactions to be examined these smectic phases became solids soon after the initiation of irradiation. 

Attenuated total internal reflection (ATR) probes offer several advantages over other probe types. ATR is a phenomenon that relies on a difference in the index of refraction of a crystal and that of the solution with which it is in contact to prevent light from escaping the crystal. Only the evanescent wave of the light interacts with the solution layer at the crystal face. The result is an optical pathlength of only a few microns. Typical designs make use of faceted crystals or hemispheres (see Figure 6.1). The most common ATR material in the UV-vis is sapphire. In rare cases, fused silica may be used. ATR allows spectra to be taken of neat samples with optical density (OD) of 500-1000... 

A neat sample of this material, prepared as part of a study of thermal decomposition of arylcycloalkanepercarboxylates, spontaneously exothermed to explosion. One would expect it to have been one of the more stable of those studied. It is recommended that neat samples of such compounds be kept cold and handled with caution and protective equipment. 

A related matrix effect of considerable analytical interest is the enhancement in absolute ion yield sometimes observed under conditions of high dilution in a solid matrix (22). Comparison of the SIMS spectrum of a neat pyrilium salt with that of the same salt diluted 1000-fold in NH Cl shows that the intact cation signal is observed in about three times greater abundance for the NH Cl-diluted sample. The threefold increase is observed even when the absolute amount of salt analyzed in the dilute sample is one thousand times less than that in the neat sample. An additional aspect of this experiment is the persistence of the enhanced signal. Ion bombardment yields products for one day in the NH Cl matrix, but for only about one hour in the neat sample under identical conditions. Effective desorption of ammonium chloride, which entrains analyte, is one way of accounting for these observations. 

In the above equation, D is the dilution expressed in volumes of diluent per volume of neat sample, V0 and V 2 are the molar volumes in liters per mole of the neso and a middle group, repectively, R is the overall mole ratio [T]/[Q] and all bracketed concentrations are measured in terms of mole fractions of the total building units. 

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