Chapter 19, Problem 19.1P

Interpretation Introduction

Interpretation:

Single and double beam spectrophotometers have to be distinguished and manner they measure transmittance has to be explained along with sources of error.

Concept Introduction:

Various components of spectrophotometer include light source that is usually tungsten or a deuterium lamp enables absorption of light by sample. Then a monochromator that essentially selects one particular wavelength and allows it to pass across sample cuvette, beam chopper splits incident light beam path amongst reference cell and sample cell; analyte within sample absorbs light. And a reference solution has same solvent that is found in analyte sample cuvette, the detector transforms photons into specific electrical response that is further enhanced by amplifier and data is displayed.

Explanation of Solution

Single beam spectrophotometer has a separate mount for blank cuvette before the test run.

In double beam spectrophotometer, blank solution or reference solvent can be mounted along with test sample in a separate cuvette. In this spectrophotometer, the monochromatic light is allowed to alternatively pass across each cuvette and this reduces the time and effort required to perform the measurements unlike the single beam spectrophotometer.

Sources of error are minimized since light acts as constant source for each measurement unlike detector response drift error that leads to sources of error in single beam spectrophotometer.