High pressure liquid chromatographic method for indole in shrimp: development of method and collaborative study

Area of Science:

• Analytical Chemistry
• Food Science
• Chromatography

Background:

• Indole is a key compound affecting the flavor and quality of shrimp.
• Accurate determination of indole levels is crucial for food safety and quality control.
• Existing methods like AOAC gas-liquid chromatography (GLC) require validation with newer techniques.

Purpose of the Study:

• To compare the accuracy and precision of a high-performance liquid chromatography (HPLC) method with spectrofluorometric and AOAC-GLC methods for indole determination in shrimp.
• To validate a new HPLC method for routine indole analysis in shrimp.
• To establish an official method for indole quantification in shrimp.

Main Methods:

• High-performance liquid chromatography (HPLC) using an octadecylsilane reverse phase column and fluorescence detection.
• Spectrofluorometric method involving solvent extraction and fluorescence measurement.
• AOAC gas-liquid chromatography (GLC) method (18.075-18.078) as a reference standard.

Main Results:

• The HPLC method demonstrated high recoveries (averaging 102-104%) and the lowest coefficient of variation (10%) at tested indole levels.
• Spectrofluorometric method showed variable recoveries (0-255%) and a high coefficient of variation (64%).
• AOAC-GLC method provided acceptable recoveries (96-101%) but with a higher coefficient of variation (20%) compared to HPLC.

Conclusions:

• The HPLC method is accurate, precise, and reliable for determining indole in shrimp.
• The HPLC method significantly outperforms the spectrofluorometric method and is more precise than the AOAC-GLC method.
• The HPLC method was adopted as the official first action for indole analysis in shrimp exceeding 1 microgram/100 g.