Adsorption/desorption of Chlorohexidine (CHX) on Flax and Cotton fibers - Literature review Example

Five different CHX concentrations with three replicates each were prepared by diluting correct portions of the mother solution (1mg/ml CHX) in 50:50 ethanol-water mixture. The concentrations used were 0.001, 0.002, 0.003, 0.004, and 0.005 mg/ml chlorhexidine. The samples were analyzed using a spectrophotometer. The transmittance and absorbance of each sample was then calculated. Table 1 shows the absorbance of each sample and the average absorbance for every concentration. Table 1. Absorbance of chlorhexidine in various concentrations.

CHX Concentration Average Absorbance Individual Absorbance mg/ml mol/L or M Sample 1 Sample 2 Sample 3 0.001 1.97845 E-06 0.039 0.038 0.04 0.039 0.002 3.9569 E-06 0.085 0.09 0.086 0.079 0.003 5.93535 E-06 0.131 0.123 0.129 0.141 0.004 7.9138 E-06 0.188 0.189 0.184 0.191 0.005 9.89225 E-06 0.23 0.232 0.224 0.233 It was observed that the values for absorbance obtained were too low compared to the ideal value of 1. Because of this, five more concentrations were prepared and tested. These concentrations were 0.011, 0.012, 0.013, 0.014, and 0.

015 mg/ml chlorhexidine. Table 2 shows the values obtained from the new set of concentrations. Table 2. Absorbance of chlorhexidine in the second set of concentrations. . The average absorbances of each sample were plotted against CHX concentration in molars (M) as illustrated in Figure 1. Figure 1. Average absorbance versus Chlorhexidine concentration with linear regression trend line and equation. The R2 value of 0.994 suggests that the relationship of CHX concentration with absorbance is very much linear and therefore follows Beer’s Law.

According to Beer’s Law, the molar absorptivity of chlorhexidine is equal to the slope of the linear equation divided by the path length in centimeters (Blauch 2009). The glass cuvettes used in the experiment has a path length of 1 cm. This means that the molar absorptivity of chlorhexidine is 52288 /M-cm. The limit of detection (LOD) is the lowest concentration that the spectrophotometer can detect while the limit of quantitation (LOQ) is the lowest concentration of CHX that the device can accurately measure.

These values were required to determine the range of the CHX concentration that can be used for the succeeding experiments. The formula for LOD and LOQ are , respectively, where y is the y-intercept of the linear equation in Figure 1 and ? is the standard deviation of the plotted points from the linear regression. The standard deviation can be computed using the formula Where is the average absorbance for concentration i and is the absorbance of concentration i according to the linear equation (ReliaSoft Corporation 2008).

Table 3 shows the values used for the computation of . Table 3. Calculated values for the determination of standard deviation. CHX Concentration (mg/ml) CHX Concentration (M) (-)2 0.011 2.1763E-05 0.4822 0.466941541 0.000233