Spectrophotometer vs Colorimeter: Advantages & Components Quiz

The Hehner tube is designed to add the solution to the more concentrated solution until the color of the sample and the standard solution match.

The Duboscq colorimeter is used in the visual method for determination of colored samples.

Spectrophotometer can measure both the intensity of light absorbed and transmitted through a sample.

The Beer-Lambert law is not relevant to UV/Visible Spectroscopy.

One of the advantages of using a spectrophotometer is that it cannot provide quantitative data about a sample.

One of the components of a spectrophotometer is a monochromator, used to isolate specific wavelengths of light.

A Hehner tube is primarily used to mix solutions in UV/Visible Spectroscopy.

The Variable Depth or Balancing method in UV/Visible Spectroscopy does not involve comparing light intensities of sample and standard solutions.

UV/Visible Spectroscopy is only applicable to colored samples, not colorless ones.

In Instrumental methods of UV/Visible Spectroscopy, light absorption by a sample is measured electrically.

Spectrophotometer vs Colorimeter

Spectrophotometers have a wider wavelength range and a more stable light source than colorimeters.

Components of a Spectrophotometer

Light source: emits wavelengths in the range of interest
Dispersing system (Monochromator): selects the wavelength of interest
Sample compartment (Cuvette): holds the sample
Detector: converts radiation energy to a measurable signal
Recorder (readout unit): converts the signal to data

Light Source

Requirements: intense, continuous, constant, and uniform radiation
Types: Hydrogen or Deuterium lamp (UV region), Tungsten lamp (visible region)

Monochromators

Function: selects monochromatic radiation from polychromatic radiation
Components: entrance slit, dispersing element, exit slit
Types of dispersing elements: filter, prism, grating

Colorimetry

Defined: method for quantitative analysis by measuring absorption in the visible region (400-750 nm)
Requirements for substances to be measured: colored or able to form colored solution with a reagent (chromogen)

Characteristics of Chromogen

Should be colorless
Selective (reacts with analyte only)
Reacts with the analyte quantitatively (stoichiometrically)
Rapid reaction and color development
Produces single colored product of specified λmax

Characteristics of the Color

Intensive
Stable for at least one hour
Obeys Beer-Lambert's law
Produces a clear colored solution

UV/Vis Methods in Quantitative Analysis

Visual methods: used for determination of colored samples
Instrumental methods: used for determination of colored and colorless samples

Visual Methods

Standard series method: compares test solution with a series of standards
Variable depth or balancing method: uses light intensity to match sample and standard solutions

Equipments Used in Variable Depth Method

Hehner tube: withdraws solution until the color of the sample and standard solution are matched
Duboscq colorimeter: measures the intensity of light absorbed by a sample

Test your knowledge on the components and advantages of spectrophotometers compared to colorimeters. Learn about the functions of light sources, monochromators, cuvettes, and detectors in UV/visible spectroscopy instruments.