Carr method

Table 6 Properties of bulk solids to determine flowability with the Carr method ...

Venkatesh P K, Dean A M, Cohen M H and Carr R W 1999 Master equation analysis of intermolecular energy transfer in multiple-well, multiple-channel unimolecular reactions. II. Numerical methods and application to the mechanism of the C. + O2 reaction J. Chem. Phys. Ill 8313... 

Vitha, M. F. Carr, P. W. A Laboratory Exercise in Statistical Analysis of Data, /. Chem. Educ. 1997, 74, 998-1000. Students determine the average weight of vitamin E pills using several different methods (one at a time, in sets of ten pills, and in sets of 100 pills). The data collected by the class are pooled together, plotted as histograms, and compared with results predicted by a normal distribution. The histograms and standard deviations for the pooled data also show the effect of sample size on the standard error of the mean. 

Nimura, Y. Carr, M. R. Reduction of the Relative Error in the Standard Additions Method, Analyst 1990, 115, 1589-1595. The following paper discusses the importance of weighting experimental data when using linear regression Karolczak, M. To Weight or Not to Weight An Analyst s Dilemma, Curr. Separations 1995, 13, 98-104. 

Spectroscopic methods such as uv and fluorescence have rehed on the polyene chromophore of vitamin A as a basis for analysis. Indirectly, the classical Carr-Price colorimetric test also exploits this feature and measures the amount of a transient blue complex at 620 nm which is formed when vitamin A is dehydrated in the presence of Lewis acids. For uv measurements of retinol, retinyl acetate, and retinyl palmitate, analysis is done at 325 nm. More sensitive measurements can be obtained by fluorescence. Excitation is done at 325 nm and emission at 470 nm. Although useful, all of these methods suffer from the fact that the method is not specific and any compound which has spectral characteristics similar to vitamin A will assay like the vitamin... 

Wang, X., Stoll, D.R., Carr, P.W., Schoenmakers, P.J. (2006). A graphical method for understanding the kinetics of peak capacity production in gradient hquid chromatography. J. Chromatogr. A 1125, 177-181. 

Others have examined the necessary parameters that should be optimized to make the two-dimensional separation operate within the context of the columns that are chosen for the unique separation applications that are being developed. This is true for most of the applications shown in this book. However, one of the common themes here is that it is often necessary to slow down the first-dimension separation system in a 2DLC system. If one does not slow down the first dimension, another approach is to speed up the second dimension so that the whole analysis is not gated by the time of the second dimension. Recently, this has been the motivation behind the very fast second-dimension systems, such as Carr and coworker s fast gradient reversed-phase liquid chromatography (RPLC) second dimension systems, which operate at elevated temperatures (Stoll et al., 2006, 2007). Having a fast second dimension makes CE an attractive technique, especially with fast gating methods, which are discussed in Chapter 5. However, these are specialized for specific applications and may require method development techniques specific to CE. 

Other applications that utilize different types of reversed-phase columns in both dimensions have been advocated by Carr (Stoll et al., 2006) for metabolomics work in small-molecule separations. These stationary phases include a pentafluorophenyl-propyl stationary phase in the first dimension and a carbon-coated zirconia material stationary phase in the second dimension. A common mistake in 2D method development is to mismatch the solvent system the two solvent systems must be miscible as discussed below. 

Hussam, A., Carr, P.W. (1985) Rapid and precise method for the measurement of vapor/liquid equilibria by headspace gas chromatography. Anal. Chem. 57, 793-801. 

In recent years the compressibility index Ci( has become a simple, fast, and popular method of predicting powder flow characteristics [40,42-44,51,52]. Carr [42-44] proposed its use as an indirect measure of bulk density, size and shape,... 

Some LC/MS users adhere to isocratic separation because of the myths around gradient elution (it is complex to develop and transfer between instruments and laboratories, it is inherently slower than isocratic methods because of re-equilibration, and other reasons summarized by Carr and Schelling6). A researcher may have a very good reason to use an isocratic method, for example, for a well defined mixture containing only a few compounds. The isocratic method would certainly not be useful in an open access LC/MS system processing varying samples from injection to injection. 

CPMG Carr-Purcell-Meiboom-Gil 1 spin-echo method To suppress signals with short relaxation time (e.g., protein signals) Small molecules can be detected and quantified in the presence of proteins... 

Huddleston, M.J. Bean, M.F. Carr, S.A. Colli sional Fragmentation of Glycopep-tides hy ESI LC/MS and LC/MS/MS Methods for Selective Detection of Glyco-peptides in Protein Digests. Amd. Chem. 1993,65, 877-884. 

Methods for measuring Ti and T2 are discussed in Chapter 5 of reference 21. Suffice it to say here that understanding the method for measuring T2 (the Carr-Purcell pulse sequence or spin-echo method) becomes important for discussing two-dimensional NMR spectra. When spin-spin coupling is present, a modulation of spin echoes is produced, and it is this fact that is important in 2-D NMR spectroscopy. Nuclear relaxation rates and mechanisms become important when discussing the effect of paramagnetic metal centers on NMR spectroscopy. 

Sadek, P.C., Carr, P.W., Doherty, R.M., Kamlet, M.J., Taft, R.W., and Abraham, M.H. Study of retention processes inreversed-phase high-performance liquid chromatography by the use of the solvatochromic comparison method. Anal. Chem., 57(14) 2971-2978, 1985. 

Bruner, L.H., Carr, G.J. and Curren, R.D. (2002) An investigation of new toxicity test method performance in validation studies 3. sensitivity and specificity are not independent of prevalence or distribution... 

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