Tablet powder containing 100mg of promazine hydrochloride is ground to a paste  with 10 ml of 2 M HCl. The paste is then diluted with 300 ml of water, shaken for  15 min and finally made up to 500 ml. A portion of the extract is filtered. Then,  5 ml of the filtrate is taken and diluted to 200 ml with 0.1 M HCl.  – Absorbance reading=0.855 is read at a wavelength wavelength of 251 nm  – a (1%, 1 cm) value of promazine.HCl at 251 nm=950  – Stated content of promazine.HCl per tablet=60 mg  – Weight of 24 tablets=1.500g  – Weight of tablet powder taken for assay=180 mg expected content in tablet taken is:   172.8 mg 1000mg 100 mg 100g   Concentration in diluted tablet extract is:   0.1g/mL 0.9 g/100ml 1.11 g/mL 0.9 mg/100ml       Concentration in original  tablet extract is:   36g/mL 36 mg/100ml 19.38 mg/100ml 16.15 mg/mL     Amount of  promazine.HCl in original extract is:   172.8mg 180mg/100ml 96.90mg 180mg     percentage of stated content 99.1 % 96% 80.75mg/100ml 104.2%

Suppose that a solution has an absorbance of 0.250 at a wavelength of 450 nm.  If the concentration of the solution is 22 μM, what is the value of the molar absorptivity?  The data were taken with a standard 1-cm cuvette. molar absorptivity in (L cm^−1 mol^-1):

SPECTROPHOTOMETRY Two groups in a BIO 120 lab extracted a blue-violet pigment from mayana plant which was to be used as a natural dye for Philippine textiles. To determine the concentration of the pigment isolated, each group made a standard curve using commercially available indigo dye in dimethylsulfoxide (DMSO). The following data were obtained by the two groups: Table 4. Absorbance readings of standard solutions of varying concentrations of indigo dye in DMSO. Pure DMSO 0.115 Standard solutions (ppm) Group 1 Data Group 2 Data 0.2 0.398 0.224 0.4 0.563 0.437 0.6 0.732 0.603 0.8 0.833 0.811 1.0 1.008 0.966 1. Show the constructed standard curves of the two groups with proper figure titles. 2. Which of the two groups generated a better standard curve? Justify your answer by providing the R? value for each data set. 3. The extracted pigment has an absorbance of 0.983. When a 0.2 mL-aliquot of the extract was diluted to 1.0 mL, the absorbance of the diluted solution was found to be…

In the determination of lead content in a solid food sample, 1 g of the solid food sample was extracted with 10 mL of solvent and then diluted to a final volume of 50 mL. A calibration plot of lead standards was obtained from the standard solutions of 1 to 50 ug/mL and it gave a linear regression line of y = 0.025x + 0.004. The wavelength for lead analysis is 283.3 nm. The absorbance value for the extract was 0.302 arbitrary units. Calculate the percentage of Pb in 1 g of the solid food sample.