Quantitation of thin-layer chromatograms with an Apple II computer-based videodensitometer

Area of Science:

• Analytical Chemistry
• Chromatography
• Instrumentation

Background:

• Thin-layer chromatography (TLC) is a widely used separation technique.
• Accurate quantification of separated spots is crucial for quantitative TLC.
• Existing densitometry methods can be expensive or time-consuming.

Purpose of the Study:

• To describe the development of an inexpensive, high-speed densitometer for TLC.
• To evaluate the performance and accuracy of the developed densitometer.
• To demonstrate the feasibility of using a personal computer-based system for quantitative analysis.

Main Methods:

• Construction of a densitometer using an Apple II computer, a black-and-white video camera, and an image digitizing board.
• Integration of a fast coprocessor to accelerate image acquisition and processing.
• Calibration using charred lipid standards of known weights (250-2000 ng).

Main Results:

• The system achieves rapid measurement of TLC spots in 30-40 seconds.
• High precision was demonstrated with coefficients of variation around 0.5% for 500-ng lipid spots.
• A strong second-order correlation (R=0.998) was observed between lipid spot weight and density readings.

Conclusions:

• The developed Apple II-based densitometer offers a cost-effective and high-speed solution for quantitative TLC.
• The system requires minimal electronic expertise for assembly from commercial components.
• This approach provides a reliable and accurate method for lipid quantification in TLC analysis.