Neat solution

In 1993, Linford firstly reported a quite useful method to prepare monolayers of alkyl chains by thermal hydros-ilylation of hydrogen-terminated silicon surfaces [25]. Alkyl chains are covalently bound to Si surface by Si-C bonds. This thermal hydrosilylation could be attributed to a free-radical process with 1-alkene. First, a diacyl peroxide initiator was used to produce free radicals. However, at higher temperature, only hydrogen-terminated silicon and a neat solution of 1-alkene or 1-alkyne can form Si-C linkages [26]. Furthermore, lately it is found that such Si-C covalent links can be observed even in dilute solutions of 1-alkenes [27]. In that case, the density of monolayer packing strongly depends on the reaction temperature. 

Matrix effect is a phrase normally used to describe the effect of some portion of a sample matrix that causes erroneous assay results if care is not taken to avoid the problem or correct for it by some mechanism. The most common matrix effects are those that result in ion suppression and subsequent false negative results. Ion enhancement may lead to false positive results.126 127 Several reports about matrix effects include suggestions on what can cause them and how to avoid them.126-147 While various ways to detect matrix effects have been reported, Matuszewski et al.140 described a clear way to measure the matrix effect (ME) for an analyte, recovery (RE) from the extraction procedure, and overall process efficiency (PE) of a procedure. Their method is to prepare three sets of samples and assay them using the planned HPLC/MS/MS method. The first set is the neat solution standards diluted into the mobile phase before injection to obtain the A results. The second set is the analyte spiked into the blank plasma extract (after extraction) to obtain the B results. The third set is the analyte spiked into the blank plasma before the extraction step (C results) these samples are extracted and assayed along with the two other sets. The three data sets allow for the following calculations ... 

Choquette et al. investigated the possibilities of using a series of substituted sulfamides as possible electrolyte solvents (Table 12). These compounds are polar but viscous liquids at ambient temperature, with viscosities and dielectric constants ranging between 3 and 5 mPa s and 30 and 60, respectively, depending on the alkyl substituents on amide nitrogens. The ion conductivities that could be achieved from the neat solutions of Lilm in these sulfamides are similar to that for BEG, that is, in the vicinity of 10 S cm Like BEG, it should be suitable as a polar cosolvent used in a mixed solvent system, though the less-than-satisfactory anodic stability of the sulfamide family might become a drawback that prevents their application as electrolyte solvents, because usually the polar components in an electrolyte system are responsible for the stabilization of the cathode material surface. As measured on a GC electrode, the oxidative decomposition of these compounds occurs around 4.3—4.6 V when 100 fik cm was used as the cutoff criterion, far below that for cyclic carbonate-based solvents. 

Chow, C.-E Fujii, S. Lehn, J.-M. Crystallization-driven constitutional changes of dynamic polymers in response to neat/solution conditions. Chem. Commun. 2007,42, 4363 365. 

Dynamic polymers having C=N bonds responding to changes in a neat/solution environment were reported by Lehn et al. [22]. Polymers 9-12 were synthesized by the corresponding dialdehydes and diamines in the presence of anhydrous Na SO (Fig. 8.3). The isotropic transition temperatures of polymers 9 and 10 were obtained at 72.5 and 68.4°C, respectively. Polymer 11 was not a film or solid but viscous oil with an isotropic phase at less than 40°C. In contrast, polymer 12 showed the highest isotropic transition temperature at about 160°C due to the existence of... 

Figure 8.3 Dynamic polymers responding to changes in neat/solution environment [22],...

The solution must not be allowed to evaporate to dryness dimethyltitanocene is unstable in the solid phase and could decompose with heat and gas evolution. The compound is also known to be unstable in neat solution at temperatures above 60°C. The concentration must be done at high (20 mm or less) vacuum. 

The molar volume Vi should strictly be taken as the partial molar volume which is normally unknown or the intrinsic volume of the solute species, rather than its molar volume when pure, or as a hypothetical supercooled liquid when the neat solute is a solid at the working temperature. 

The key step in their-approach was asymmetric photoisomerization of the a, 3-unsaturated (Z)-ketone precursor 103b in diethyl ( + )-Lg-tartrate. The bromide 103a obtained by N-bromo-succinimide bromination of the (Z)[8.8] precursor 64b, was converted into the a,P-unsaturated (Z)-ketone 103b by the routine synthetic procedures. Irradiation in a hexane solution with a medium pressure Hg lamp effected the photoisomerization of the (Z)-precursor 103b to afford a 1 5.5 mixture of (Z)-( )[8.8] ketones. After these preliminary experiments, a neat solution of 103 b in diethyl ( + )-Lg-tartrate was irradiated for 3 h. Preparative GLC of the resulting 1 7 mixture of (Z) and ( )[8.8] ketones produced a 38 % yield of ( )[8.8] ketone 104 enriched in the (—)-enantiomer, [a]n4 —13° (hexane). 

If online extraction techniques are used, calculation of the different types of recovery could be particularly challenging. Different approaches has been used in literature to overcome this problem, such as using an external injection valve for adding the neat solution to the extracted blank from the online extraction column just on the head of the analytical column [9,10]. Although liquid matrix can be extracted directly, a solid matrix such as tissue needs to be disrupted in... 

Usually, method-specific acceptance criteria are established for system suitability tests. For LC-MS/MS-based assay a possible general criteria for system suitability test is based on the use of at least five replicates of the neat solution concentration comparable with the closest calibration standard to LLOQ. To pass... 

Fourier Transform Infrared Spectroscopy (FT-IR) measurements were made using a Nicolet Instruments 740 FT-IR spectrometer. A horizontal attenuated toted reflectance cell equipped with a 45° zinc-selenide crystal trough wets used. Spectra of neat solutions were obtained by co-addition of 256 scans at 4 cm- resolution. 

Fig. 11 An ascorbic acid-contaminated triple quadrupole mass spectrometer affected the responses of levothyroxine (ANA), liothyronine (ANB), and 13C6-thyroxine (IS) differently when a neat solution sample was repeatedly injected, resulting in a gradual increase of analyte/IS response ratios for one analyte (ANA) while gradual decrease for the other (ANB)...

Bouzas et al. [95] developed a quantitation method for the determination of drugs of abuse (opiates, amphetamine and derivatives, cocaine, methadone and metabolites) in serum by using online extraction coupled to LC-MS/MS. The online extraction procedure described consists of an extraction column and an analytical column, which were coupled online. A PPT procedure was performed with zinc sulfate an aliquot of 0.1 M zinc sulfate in methanol was added to the serum sample in a proportion of 2 1 (v/v) to serum. Analytes were extracted by a short pentafluorophenyl silica column and separated on a longer analytical column with the same stationary phase. Recoveries of all analytes were above 80 %. The proposed procedure by Matuszewski et al. [64] was used for the evaluation of matrix effect ME(%)=B/Ax 100, where ME is the matrix effect (suppression or enhancement) and B corresponds to peak areas for standards spiked after extraction into sample extracts and A to peak areas obtained in neat solution standards. Authors compared this method to offline SPE coupled with GC-MS and results showed that LC-MS/... 

Preparation. The synthesis of alkylzinc alkoxides and aryloxides is achieved by an alkane elimination process in the simple reaction of a dialkylzinc compound, R2Zn, with one equivalent of an alcohol, R OH (equation 18). This reaction proceeds either in hydrocarbon solvents or neat solution, to give essentially quantitative yields of the desired products. The volatility of the RH side product helps to drive the equilibrium to the right. The formation of relatively strong Zn-O and C-H bonds, at the expense of breaking the O-H and a relatively weak Zn-C bond also guarantee favorable reaction energetics. 

The title compounds are usually obtain in a straightforward manner and in almost quantitative yields by alkane elimination process between a dialkylzinc compound ZnRs and the desired thiol R SH or selenol R SeH species (equation 18). This reaction works equally well in hydrocarbon solvent or neat solution. If thiocyanogen (SCN)2 is used as the reagent, then alkylzinc thiocyanate derivatives (RZnSCN) are obtained. ... 

Figure 9 Influence of the packaging on the photostability of molsidomine injection solutions (c=2mg/mL) (Suntest CPS+, window glass filter, 415 VJIrtf). ( ) neat solution, (a) packaged in brown glass ampoules, ( ) packaged in brown glass ampoules and green blisters. Source From Ret. 21.

The steps shown by rate coefficients are fast compared to the others. This is evident from the effect of solvent basicity upon the rate of rearrangement. Similar rate coefficients were obtained in the presence of diphenyl ether, dimethyl aniline, acetic acid or with neat solutions . The kinetic isotope effect data given in Table 24 provides additional support for the fact that k is high compared to the other rate coefficients. 

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