Direct determination of gibberellic acid in tomato and fruit by using photochemically induced fluorescence

A simple, sensitive method for determining gibberellic acid based on photochemically induced fluorescence detection was developed to determine this plant growth regulator in a technical formulation, tomato, and fruit samples. The principle for the determination is the photochemical reactivity of the gibberellic acid, being consistent with the occurrence of photoaromatization and photochemical dimerization with loss of carbon dioxide, and with the likely formation of various fluorescent photoproducts. Six min of UV (mainly at 253.7 nm) irradiation in a solution containing 50% (v/v) methanol and buffer at pH 5 provided the best results. The calibration curve was linear over the concentration range 50-150 ng mL(-1), and the limit of detection was 1.7 ng mL(-1). The method is useful to determine gibberellic acid in samples with background fluorescence such as plum and tomato without the need for labor-intensive preparation as a result of UV irradiation suppressing the fluorescent background.