Spectrophotometer and pH Meter Flashcards

Flashcards for key vocabulary related to Spectrophotometry and pH Meters

Spectrophotometry

The most important instrumental method of analysis in clinical chemistry, based on the absorption of electromagnetic radiation in the visible, ultraviolet, and infrared ranges.

Spectrophotometry Analysis

The study of the frequencies of photons absorbed to provide information about the material's nature.

Types of Internal Energy Molecules Possess

Electronic, vibrational, and rotational.

Electronic transitions

Ultraviolet and visible regions.

Vibrational transitions

Near infrared and infrared regions.

Rotational transitions

Infrared and far-infrared regions.

Interaction of Radiation with Matter

Transmission, absorption, scattering, reflection, or excitation of fluorescence.

Essential Components of a Spectrophotometer

A source of radiant energy, filtering arrangement, optical system, detecting system, and readout system or display.

Common Source of Light

Tungsten lamp.

Heat Absorbing Filter

Absorbs most of the infrared radiation without seriously diminishing energy at the desired wavelength when using a tungsten lamp.

Optical Filter

A transparent medium that isolates radiation of a particular wavelength.

Requirements of an Ideal Filter

High transmittance at the desired wavelength and low transmittance at other wavelengths.

Absorption Filter

Color media such as color glasses, colored films, and solutions of colored substances.

Interference Filter

Two semi-transparent layers of silver, separated by a layer of dielectric material.

Monochromators

Optical systems providing better isolation of spectral energy than optical filters.

Dispersing Media in Monochromators

A small glass or quartz prism or a diffraction grating system.

Prism Monochromators

Isolation of different wavelengths depends on the refractive index of materials varying for different wavelengths.

Diffraction Grating

A series of parallel grooves ruled on a highly polished reflecting surface.

Holographic Grating

Superior performance in reducing stray light compared to diffraction gratings.

Optical Components

Windows, mirrors, and simple condensers.

Photosensitive Detector

Converts light energy into electrical energy for quantitative measurement of intensity.

Material for Cuvettes

Silica, glass, or perspex.

pH

A unit of measure describing the degree of acidity or alkalinity of a solution, measured on a scale of 0 to 14.

Formal Definition of pH

Negative logarithm of the hydrogen-ion activity.

H+ concentration is higher than OH-

Indicates acidity.

OH- concentration is higher than H+

Indicates basicity.

pH Measuring Electrode

Hydrogen ion sensitive glass bulb.

Reference Electrode

Output does not vary with the activity of the hydrogen ion.

Key Feature of pH-sensitive Electrode

Thin glass membrane contacting the solution to be tested.

Calomel Reference Electrode

Glass tube with a potassium chloride (KCl) electrolyte in contact with a mercuric chloride element.

Voltmeter in pH Meter

Measures the difference between the voltages of two electrodes and translates it into pH.

pH meter calibration

Compare the meter to a solution of known pH.

Buffers

Solutions with constant pH values and the ability to resist changes in pH, used to calibrate the pH meter.

Care for pH Electrode

Keep it immersed in a pH 4.00 buffer when not in use and avoid touching the membrane.