Phosphite Determination in Fertilizers after Online Sequential Sample Preparation in a Flow Injection System

Abstract

A flow injection spectrophotometric system is proposed for phosphite determination in fertilizers by the molybdenum blue method after the processing of each sample two times on-line without and with an oxidizing step. The flow system was designed to add sulfuric acid or permanganate solutions alternately into the system by simply displacing the injector-commutator from one resting position to another, allowing the determination of phosphate and total phosphate, respectively. The concentration of phosphite is obtained then by difference between the two measurents. The influence of flow rates, sample volume, and dimension of flow line connecting the injector-commutator to the main analytical channel was evaluated. The proposed method was applied to phosphite determination in commercial liquid fertilizers. Results obtained with the proposed FIA system were not statistically different from those obtained by titrimetry at the 95% confidence level. In addition, recoveries within 94 and 100% of spiked fertilizers were found. The relative standard deviation (n = 12) related to the phosphite-converted-phosphate peak alone was </=3.5% for 800 mg L(-1) P (phoshite) solution. Precision due to the differences of total phosphate and phosphate was 1.1% for 10 mg L(-1) P (phosphate) + 3000 mg L(-1) P (phosphite) solution. The sampling rate was calculated as 15 determinations per hour, and the reagent consumption was about 6.3 mg of KMnO4, 200 mg of (NH4)6Mo7O24.4H2O, and 40 mg of ascorbic acid per measurement.

Direct Determination of Phosphite in Fertilizers by Amperometric Titration

“…All samples were also analyzed by spectrophotometry (10). Other analytical characteristics such as reagent and sample consumption also were evaluated.…”

“…Among analytical techniques usually employed for phosphorus determination are atomic absorption spectrometryAAS , inductively coupled plasma optical emission spectrometryICP OES , gravimetry , , spectrophotometry − , amperometry , , and titrimetry .…”

“…A flow-injection spectrophotometric procedure already had been proposed for phosphite determination using the molybdenum blue method (9). The automated spectrophotometric flow injection analysis system with online sample treatment allowed the sequential determination of phosphite and phosphate (10). Electrochemical studies on the behavior of phosphorous acid on palladium surfaces showed a catalytic effect for oxidation of phosphite to phosphate (15).…”

UiO‐66/GO Composites with Improved Electrochemical Properties for Effective Detection of Phosphite(P(III)) in Phosphate(P(V)) Buffer Solutions

“…[2] Therefore, phosphite is also an important nutrient carrier to support the growth of algae, [3] and it has been found in drinking water, lakes, and industrial waste-water. [4] At present, traditional analytical techniques such as spectrophotometry, [5] as well as chromatography including ion chromatography, [6] and highperformance liquid chromatography, [7] are mainly used for the determination of phosphite. These methods exhibit their excellent performance except for cost and time for pretreatment of samples.…”

Highly Selective Fluorescent Sensing of Phosphite through Recovery of Poisoned Nickel Oxide Nanozyme

“…A full analysis of phosphorus would require quantification of not only its total amount but also its speciation. To date, phosphite has been mainly identified using traditional analytical techniques such as ion chromatography, , nuclear magnetic resonance spectroscopy, spectrophotometry, gas chromatography, and high-performance liquid chromatography . However, their excellent performance is at the expense of cost, time, and lengthy procedures for preconcentration or pretreatment of samples.…”