Alpha plot

Sachok, B., Stranahan, J.J., and Deming, S.N. (1981), Two-Factor Minimum Alpha Plots for the Liquid Chromatographic Separation of 2,6-Disubstituted Anilines, Anal. Chem., 53, 70-74. 

An alpha plot for a buffer (or an amino acid) shows the percentage of each component in a buffer system as a function of pH. Alpha for a given species is the percent of all the material that is present in that form. So, when alpha for the conjugate acid form is 75%, the ratio of conjugate acid to conjugate base is 75 25. Naturally, the sum of the alpha values for the conjugate acid and the conjugate base add up to 100%. 

The shape of the curves in an alpha plot is determined by the buffer equation. At low pH, most of the material is present as its conjugate acid. As the pH increases, the conjugate acid form converts to the conjugate base form. At high pH, most of the material is present in the conjugate base form. 

Let s take a look at an alpha plot for lidocaine (Figure 9.7). Lidocaine is a weak base, so a solution of lidocaine and its conjugate acid, lidocaine hydro-... 

Calculating the pH of a Buffer 248 Dilution of Buffer Solutions 251 Buffer Capacity 251 Alpha Plots 252... 

Use your Weh browser to connect to http //chemistry.brookscole.com/skoogfac/. From the Chapter Resources menu, choose Web Works. Locate the Chapter 13 section, and click on the link to the Virtual Titrator. Click on the indicated frame to invoke the Virtual Titrator Java applet and display two windows the Menu Panel and the Virtual Titrator main window. To begin, click on Acids on the main window menu bar, and select the diprotic acid o-phthalic acid. Examine the titration curve that results. Then click on Graphs/Alpha Plot vs. pH and observe the result. Click on Graphs/Alpha Plot vs. mL base. Repeat the process for several monoprotic and polyprotic acids, and note the results. 

Alpha Plots for Polyfunctlonal Acid-Base Systems. 

Titration Curves and Alpha Plots for Metal Complexforming Titrations. 

In order to get information on iiltramicropores, detailed measurements of the amount of adsorption under a relative pressure of 10" are required in other words, measurements in a very low relative pressure range are necessary. In Fig. 9b), the adsorbed amount of nitrt en is plotted against the logarithm of P/Pg for the same three activated carbon fibers to highlight the differences in adsorption at low relative pressures. To get a quantitative evaluation of micropores, the so-called alpha plot is often employed (Fig. 9c), which compares the isotherm with that one for an equivalent material having a flat surface (data fijr a carbon black are usually employed as reference). 

Fig. 11. Alpha plot of a nitrogen adsorption isotherm at 77 K on a microporous solid.

Figure 18. Alpha plot for n-paraffins, olefins and total product under steady-state conditions.

The molecular adsorption isotherm on nonporous solids can be well described by the BET theory. The deviation from the linearity of the t plot gives information on the sort of pores, the average pore size, the surface area, and the pore volume. However, the t plot analysis has the limited applicability to the microporous system due to the absence of explicit monolayer adsorption. The construction of the alpha plot does not need the monolayer capacity, so that it is applicable to microporous sohds. 

Selles-Perez, M.J., and Martin-Martinez, J.M., Classification of alpha plots obtained from nitrogen/77K adsorption isotherms of activated carbons. Fuel. 70(7). 877-882 (1991). 

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