Spectrophotometric determination of phosphate in river waters with molybdate and malachite green

Motomizu, Shoji; Wakimoto, Toshiaki; Tôei, Kyoji

doi:10.1039/an9830800361

Cited by 343 publications

(171 citation statements)

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“…Spectrophotometric procedures for monitoring orthophosphate include the molybdenum blue method [1,[3][4][5][6][7], the yellow vanadomolybdate complex method [8][9][10][11] and the malachite green method [12][13][14][15][16][17]. The malachite green method has been shown to enhance sensitivity by approximately 4 times when compared to the aforementioned methods [12,18].…”

Section: Introductionmentioning

confidence: 99%

Determination of phosphate using a highly sensitive paired emitter–detector diode photometric flow detector

O'Toole

Lau

Shepherd

et al. 2007

Analytica Chimica Acta

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The use of a novel inexpensive photometric device, Paired Emitter Detector Diode (PEDD) has been applied to the colorimetric determination of phosphate using the malachite green spectrophotometric method. The novel miniaturized flow detector applied within this manifold is a highly sensitive, low cost, miniaturized light emitting diode (LED) based detector. The optical flow cell was constructed from two LEDs, whereby one is the light source and the second is the light detector, with the LED light source forward biased and the LED detector reversed biased. The photocurrent generated by the LED light source discharges the junction capacitance of the detector diode from 5 V (logic 1) to 1.7 V (logic 0) and the time taken for this process to occur is measured using a simple timer circuit. * Correspondence author: Tel.: +353-1-7005404; fax: +353-1-7008002 email: dermot.diamond@dcu.ie -2 -The malachite green (MG) method employed for phosphate determination is based on the formation of a green molybdophosphoric acid complex, the intensity of which is directly related to phosphate concentration. Optimum analytical parameters such as reaction kinetics, reagent to sample concentration ratio and emitter wavelength intensity were investigated for the spectrophotometric method. Linear calibration plots that obeyed the Beer-Lambert Law were obtained for phosphate in the range of 0.02-2 µM. The dynamic range, sensitivity and limits of detection are reported.

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Section: Introductionmentioning

confidence: 99%

Determination of phosphate using a highly sensitive paired emitter–detector diode photometric flow detector

O'Toole

Lau

Shepherd

et al. 2007

Analytica Chimica Acta

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“…Mature leaf tissue (200 mg) was either extracted in 5 M H 2 SO 4 for free Pi assays (Delhaize and Randall, 1995), or digested in concentrated HNO 3 :HClO 4 (3:1) at 175°C for total phosphorus assays (Motomizu et al, 1983). Po was estimated by subtracting free Pi from total phosphorus.…”

Section: Leaf Free Phosphate and Total Phosphorus Determinationsmentioning

confidence: 99%

Reciprocal Control of Anaplerotic Phosphoenolpyruvate Carboxylase by in Vivo Monoubiquitination and Phosphorylation in Developing Proteoid Roots of Phosphate-Deficient Harsh Hakea

2013

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Accumulating evidence indicates important functions for phosphoenolpyruvate (PEP) carboxylase (PEPC) in inorganic phosphate (Pi)-starved plants. This includes controlling the production of organic acid anions (malate, citrate) that are excreted in copious amounts by proteoid roots of nonmycorrhizal species such as harsh hakea (Hakea prostrata). This, in turn, enhances the bioavailability of mineral-bound Pi by solubilizing Al 3+ , Fe 3+ , and Ca 2+ phosphates in the rhizosphere. Harsh hakea thrives in the nutrient-impoverished, ancient soils of southwestern Australia. Proteoid roots from Pi-starved harsh hakea were analyzed over 20 d of development to correlate changes in malate and citrate exudation with PEPC activity, posttranslational modifications (inhibitory monoubiquitination versus activatory phosphorylation), and kinetic/allosteric properties. Immature proteoid roots contained an equivalent ratio of monoubiquitinated 110-kD and phosphorylated 107-kD PEPC polypeptides (p110 and p107, respectively). PEPC purification, immunoblotting, and mass spectrometry indicated that p110 and p107 are subunits of a 430-kD heterotetramer and that they both originate from the same plant-type PEPC gene. Incubation with a deubiquitinating enzyme converted the p110:p107 PEPC heterotetramer of immature proteoid roots into a p107 homotetramer while significantly increasing the enzyme's activity under suboptimal but physiologically relevant assay conditions. Proteoid root maturation was paralleled by PEPC activation (e.g. reduced K m [PEP] coupled with elevated I 50 [malate and Asp] values) via in vivo deubiquitination of p110 to p107, and subsequent phosphorylation of the deubiquitinated subunits. This novel mechanism of posttranslational control is hypothesized to contribute to the massive synthesis and excretion of organic acid anions that dominates the carbon metabolism of the mature proteoid roots.

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“…Samples were digested in concentrated HNO 3 :HClO 4 (3:1) at 175°C. Total P concentration in digests was determined using the Malachite green colorimetric method (Motomizu et al, 1983).…”

Section: Measurements Of Tissue [P]mentioning

confidence: 99%

Developmental Physiology of Cluster-Root Carboxylate Synthesis and Exudation in Harsh Hakea. Expression of Phosphoenolpyruvate Carboxylase and the Alternative Oxidase

Shane¹,

Cramer²,

et al. 2004

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Harsh hakea (Hakea prostrata R.Br.) is a member of the Proteaceae family, which is highly represented on the extremely nutrientimpoverished soils in southwest Australia. When phosphorus is limiting, harsh hakea develops proteoid or cluster roots that release carboxylates that mobilize sparingly soluble phosphate in the rhizosphere. To investigate the physiology underlying the synthesis and exudation of carboxylates from cluster roots in Proteaceae, we measured O 2 consumption, CO 2 release, internal carboxylate concentrations and carboxylate exudation, and the abundance of the enzymes phosphoenolpyruvate carboxylase and alternative oxidase (AOX) over a 3-week time course of cluster-root development. Peak rates of citrate and malate exudation were observed from 12-to 13-d-old cluster roots, preceded by a reduction in cluster-root total protein levels and a reduced rate of O 2 consumption. In harsh hakea, phosphoenolpyruvate carboxylase expression was relatively constant in cluster roots, regardless of developmental stage. During cluster-root maturation, however, the expression of AOX protein increased prior to the time when citrate and malate exudation peaked. This increase in AOX protein levels is presumably needed to allow a greater flow of electrons through the mitochondrial electron transport chain in the absence of rapid ATP turnover. Citrate and isocitrate synthesis and accumulation contributed in a major way to the subsequent burst of citrate and malate exudation. Phosphorus accumulated by harsh hakea cluster roots was remobilized during senescence as part of their efficient P cycling strategy for growth on nutrient impoverished soils.In some plant species, a shortage of phosphorus induces the development of dense clusters of determinate branch roots (rootlets) that arise, en masse, from a localized region of the parent root axis. These short-lived structures have been termed proteoid roots because they were first described for Proteaceae (Purnell, 1960) but have since been found in a wide range of other species and families and are now often referred to as cluster roots . Most of our advances in cluster-root biology have been derived from studies of the crop species Lupinus albus (Fabaceae family) (Gardner et al

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Spectrophotometric determination of phosphate in river waters with molybdate and malachite green

Cited by 343 publications

References 0 publications

Determination of phosphate using a highly sensitive paired emitter–detector diode photometric flow detector

Determination of phosphate using a highly sensitive paired emitter–detector diode photometric flow detector

Reciprocal Control of Anaplerotic Phosphoenolpyruvate Carboxylase by in Vivo Monoubiquitination and Phosphorylation in Developing Proteoid Roots of Phosphate-Deficient Harsh Hakea

Developmental Physiology of Cluster-Root Carboxylate Synthesis and Exudation in Harsh Hakea. Expression of Phosphoenolpyruvate Carboxylase and the Alternative Oxidase

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