Integration plot analysis

The primary objective of integration plot analysis is to analyze the data on influx of the test substrate from the circulating blood to the retina (i.e., blood-to-retina direction) across the BRB after intravenous administration of the test substrate. The advantage of this approach is that it allows reliable determination of the retinal uptake (i.e., clearance) of the test substrate which has a slow permeability across the BRB [28], On the other hand, due to the intravenous injection, interference by endogenous substrates and plasma-protein binding of the test substrate can produce an unseemingly low estimate of the retinal uptake. 

The apparent retinal influx clearance,. Kin,retina expressed as mL/(min g retina), of the test substrate labeled with either [3 H] or [14C] from the circulating blood to the retina is determined by integration plot analysis. In brief, rats are anesthetized, followed by injection of the test substrate (e.g., an [3H]-labeled compound, about 10 /u.Ci/head) into the femoral vein. After collection of plasma samples, rats are decapitated and the retinas removed. The retinas are dissolved in 2 N NaOH and subsequently neutralized with 2 N HC1. The radioactivity of retinal cell lysates is measured by liquid scintillation spectrometry. As an index of the retinal distribution characteristics of the radiolabeled test substrate, the apparent retina-to-plasma concentration ratio (Vd) as a function of time is used. This ratio [Vd(Q] (mL/g retina) is defined as the amount of [3H] per gram retina divided by that per milliliter plasma, calculated over the time-period of the experiment. The Kjn,retina can be described by the following relationship  

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Because tissue-specific vectors are aimed at increasing the influx of a drug into the target, assessment of unidirectional transport from the circulating plasma into the target organ is essential. In this context, integration plot analysis is a convenient in vivo method in which a tracer amount of vector is injected intravenously and the plasma (Cp) and tissue (Ct) con-... 

Figure 5.4. Schematic diagram for (a) the integration plot analysis and (h) renal processing of alkylglycoside.

Figure 2 Comparison between the uptake clearance obtained in vivo and that extrapolated from the in vitro transport study of endothelin antagonists. In vivo uptake clearance of endothelin antagonists (BQ-123, BQ-518, BQ-485, compound A) was evaluated by integration plot analysis using the plasma concentration-time profile after intravenous administration (500 nmol/kg) and the amount of drug in the liver and that excreted in the bile. In vitro hepatic uptake clearance was measured using isolated rat hepatocytes and was extrapolated to the in vivo uptake clearance assuming the well-stirred model. Source From Ref. 5.

Pump. A constant flow rate of the mobile phase is another essential condition for quantitative analysis. Especially for peak area quantification. even small variations in flow can have a disastrous effect because the recorder or integrator plots the concentration (signal intensity) versus analysis time (not versus flow rate). Therefore a variation in flow automatically influences the recorded peak area. Quantification over peak height is not so strongly influenced by fluctuations in the flow of the mobile phase. 

Finally, one can also perform a complete analysis by integrating the TPD curves, and finding sets of rates and temperatures corresponding to the same coverage. Such data can be plotted in the form of Arrhenius plots. Hoivever, this is both tedious and time-consuming, and has rarely been performed. [D.A. King, Surf. Sci. 47 (1975) 384]. 

One cm3 of the reactant/product/catalyst mixture was sampled periodically during the reaction for the transmission infrared analysis (Nicolet Magna 550 Series II infrared spectrometer with a MCT detector). The concentrations of reactants and products were obtained by multiplying integrated absorbance of each species by its molar extinction coefficient. The molar extinction coefficient was determined from the slope of a calibration curve, a plot of the peak area versus the number of moles of the reagent in the IR cell. The reaction on each catalyst was repeated and the relative error for the carbamate yield measured by IR is within 5%. 

Table 11,1.1 contains a workup of the data in terms of the above analysis. In the more general case one should be sure to use appropriate averaging techniques or graphical integration to determine both F(t) and T. When there is an abundance of data, plot it, draw a smooth curve, and integrate graphically instead of using the strictly numerical procedure employed above. 

Porod analysis is carried out in a plot In / j (st) I Fl)vs. sf. We find the number I Fi by trial-and-error and are satisfied when the linear region becomes longest. We determine the intercept Apx = nAp and the end of the Porod region, Smax (cf. Fig. 8.11). Now we can carry out the numerical integration, again add the remainder term (Apl /smax) from the analytical continuation, and obtain... 

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