Cutting-out and weighing

Planimetry and cutting out and weighing of peaks makes no assumptions about the shape of the peak profile and can be used to... 

Trace each peak carefully on to another sheet of paper, cut out and weigh the area enclosed between the trace and the base line. 

The area A can be determined, e.g., by drawing a baseline and vertical lines at 141 and 159ppm and then cutting out and weighing the areas enclosed. Area A must then be corrected for SSB strengths and converted from mole fraction to weight fraction. The method summarized here follows procedures described in more detail by Hemmingson and Newman (1985) and Leary et al. (1986). 

The zones as recorded (if on an absorbance, rather than a transmittance basis) can be quantitated by measuring the area under the peaks by planimetry, triangulation, cutting out and weighing or simply counting squares or the densitometer may have an integrating facility. 

Measure the retention times. For the aspirin chromatograms, also measure the areas. The peak areas may be obtained from the height times the width at half-height for each. Alternatively, the peaks may be cut out and weighed. Or the instrument may print out the integrated areas. Using a spreadsheet, plot a calibration curve of peak area against concentration. 

The developed tapes were laid on an agar plate seeded with Neisseria catarrhalis NCIC 3622 and incubated at 37°C for 24 h. Quantitative zones of inhibition due to MM 13902 and MM 17880 were traced, cut out and weighed Rf... 

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