Development of a sequential injection–square wave voltammetry method for determination of paraquat in water samples employing the hanging mercury drop electrode

Abstract

This work describes the development and optimization of a sequential injection method to automate the determination of paraquat by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h(-1). Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of 25 mV, a potential step of 2 mV, and a flow rate of 100 µL s(-1). For a concentration range between 0.010 and 0.25 mg L(-1), the current (i(p), µA) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration (mg L(-1)): i(p) = (-20.5 ± 0.3)C (paraquat) - (0.02 ± 0.03). The limits of detection and quantification were 2.0 and 7.0 µg L(-1), respectively. The accuracy of the method was evaluated by recovery studies using spiked water samples that were also analyzed by molecular absorption spectrophotometry after reduction of paraquat with sodium dithionite in an alkaline medium. No evidence of statistically significant differences between the two methods was observed at the 95% confidence level.

Square‐Wave Voltammetry: A Review on the Recent Progress

“…In the recent years, the SW voltammetry has emerged as a viable and cheap alternative to the expensive and time-consuming techniques (such as chromatography, or spectrophotometry, for example) for the determination of inorganic and biologically important compounds. The simple working set-up, the quick time of performing the measurements, the different modes that can be applied, together with its sensitivity, make the SWV a technique of choice for quantification of important classes of compounds such as proteins [82], vitamins [83], phenols [84][85][86][87][88], benzoquinones [89], pesticides, herbicides and fungicides [90][91][92][93][94][95][96][97][98], alkaloids [99], terpenoids [100], heavy metals [101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116], and drugs [117,118]. One of the most valuable ability of SWV is its application for simultaneous determination of compounds with similar structures present in various pharmaceutical and physiological samples.…”

Simple flow injection colorimetric system for determination of paraquat in natural water

“…Potential interferences for the determination of paraquat in water such as some cations, anions and herbicides have been spiked into water containing 1 mg L À 1 of paraquat. Effects of these interferences have been investigated in the literatures [18][19][20]22,23]. Most common ions found in natural water have been reported that they did not interfere [19,20] in the determination of paraquat.…”

“…water, soil, fruit juice, human serum etc.) which comprise high performance liquid chromatography (HPLC) [7][8][9][10], electrochemistry [11][12][13][14], sensor [15,16], spectrophotometry [17][18][19][20][21], and flow based techniques [19][20][21][22][23]. Chromatography is popular technique to determine paraquat in different samples.…”

“…The blue product is not quite stable, so the method is not convenient to use in batchwise manner. Flow injection analysis systems combined with spectrophotometric [19][20][21] and voltammetric detection [22] has been developed to solve the problem that occurs in batch analysis and provide additional advantages such as improvement of sensitivity, reduction of chemical consumption and analysis time.…”

Determination of Allura Red and Tartrazine in Food Samples by Sequential Injection Analysis Combined with Voltammetric Detection at Antimony Film Electrode

“…Theu se of an eight port selection valve in SIA allows sample conditioning before the measuring step,a s well as the use of standard addition technique commonly usedi ne lectroanalyticalm ethods [17].T he present work describes the development of am ethodology to determine allurar ed and tartrazine in food samples using aSIA system with voltammetric detectiona tS bFE. …”