Determination of gibberellic acid by sequential injection analysis using a potentiometric detector based on Mn(III)-porphyrin with improved characteristics

Abstract

Descreve-se a determinação de ácido giberélico em promotores de crescimento usados na agricultura, por análise de injecção sequencial e detecção potentiométrica. , declive de -64,5 ± 1,6 mV/dec e melhores coeficientes de selectividade potenciométrica (log K pot ) do que os obtidos com eléctrodos convencionais. Na análise de amostras comercializadas em Portugal obtiveram-se desvios padrão de 0,01 e 0,4 (n= 4) e um ritmo de amostragem de 30 amostras/hora. This work describes the determination of gibberellic acid in growth promoters formulations used in agriculture by sequential injection analysis and potentiometric detection. The potentiometric detectors with improved characteristics used a PVC membrane prepared with Mn(III)tetraphenylporphyrin-Cl as electroactive specie. Different membranes formulated with several ionic additives were compared in order to select the most suitable one concerning slope, response time, reproducibility and selectivity. A membrane containing 6 wt% of manganese tetraphenylporphyrin-Cl [(Mn(TPP)Cl], 27 wt% of PVC, 66 wt% of dibutylphthalate (DBP), as mediator solvent, and 1 wt% of sodium tetraphenylborate, as anionic additive, was chosen for analytical applications. When coupled to a SIA system the tubular electrode presented a linear range between 5×10 -4 mol L -1 and 8×10 -3 mol L -1 , a slope of -64.5 ± 1.6 mV/dec and lower potentiometric selectivity coefficients (log K pot ) than those obtained with the conventional electrodes. Standard deviation of 0.01 and 0.4 (n= 4) and a sampling rate of 30 samples/hour were obtained in the analysis of real samples.

Direct Determination of Gibberellic Acid in Tomato and Fruit by Using Photochemically Induced Fluorescence

“…This has promoted the use of various extraction procedures including liquid-phase and solid-phase extraction to purify phytohormones from plants prior to their determination. Also, gibberellic acid has been determined by using a variety of techniques including liquid chromatography − in addition to spectrophotometry, fluorimetry, and sequential injection analysis with potentiometric detection. − …”

Optimised separation procedures for the simultaneous assay of three plant hormones in liquid biofertilisers

“…Accurate analysis of trace quantities of hormones in complex samples requires sophisticated analytical techniques. Several analytical techniques have been used for the determination of plant hormones, including spectrophotometry (Berrios et al, 2004;Ehmann 1977), capillary electrophoresis (CE) (Liu et al, 2003), gas chromatography-mass spectrometry (GC-MS) (Perrine et al, 2004;Edlund et al, 1995;Muller et al, 2002;Rachev et al, 1997), thin-layer chromatography (TLC) (Liu et al, 1996), liquid chromatographymass spectrometry (LC-MS) (Durgbanshi et al, 2005;Zhou et al, 2003), 2D-high performance liquid chromatography (2D-HPLC) (Dobrev et al, 2005) and sequential injection analysis (SIA) (Santos et al, 2004). Nowadays, reversed phase high performance liquid chromatography (RP-HPLC) (Kelen et al, 2004;Ross et al, 2004) is the most preferable method for the separation and determination of the plant hormones.…”