Abstract:

Five technological conditions for the ultrasonic-assisted extraction of chlorophyll from kelp were investigated, and the back extraction of the extract with chlorohydric acid for the displacement of magnesium ions by hydrogen ions was optimized using single factor and orthogonal array design methods. Displaced magnesium ions were assayed by atomic absorption spectrometric (AAS) method. Therefore, the content of chlorophyll in kelp could be calculated from obtained magnesium concentration data. Based on these studies, an indirect method for quantifying chlorophyll in kelp has been set up. The optimal conditions for extracting chlorophyll based on the use of an absolute ethanol/acetone mixture as the extraction solvent were found to be: solid/ liquid ratio (g/mL) 2:15 and ultrasonic power 200 W for twice extraction for 20 min each time. Chlorohydric acid concentration of 0.9 mol/L, chlorohydric acid amount of 15 mL and back extraction duration of 15 min were found optimal for the displacement of magnesium ions. The limit of detection of AAS method was 0.008 μg/mL. The average content of chlorophyll in kelp (n = 5) was 5.486 mg/g, with a relative standard deviation of 0.675% and the average spike recovery for chlorophyll was 97.7%. The developed method for chlorophyll determination has the advantages of little disturbance and high precision, sensitivity and accuracy.

Key words: kelp, chlorophyll, ultrasonic-assisted extraction, atomic absorption spectrometric method