Determination of Metalaxyl in Potatoes and Soil by Dispersive Solid-Phase Extraction and High-Performance Liquid Chromatography

Abstract

& A simple and sensitive high-performance liquid chromatography method with photodiode array detection combined with dispersive solid-phase extraction was developed to quantify metalaxyl residues in potatoes and soil. The limits of detection and quantification of metalaxyl were 0.0015 and 0.005 mg kg À1 . The recoveries of metalaxyl extracted from potato, potato foliage, and soil ranged from 81.53-95.50%, 90.12-94.72%, 93.16-103.0%, respectively, with relative standard deviations less than 9.74%. The method was applied to determine metalaxyl in potatoes and soil; the results showed that the dissipation rates were described by first-order kinetics. The half-lives in potato foliage and soil were 0.75 days and 5.87 days to 8.45 days, respectively. At harvest, the residue of metalaxyl in potatoes was less than 0.05 mg kg À1 following the recommended dosage at an interval of seven days from the final application. These results may be used to help establish appropriate application frequencies and harvest intervals for metalaxyl on potatoes.

The Study of the Kinetics of Metalaxyl Accumulation and Dissipation in Durian (Durio zibethinus L.) Leaf Using High-Performance Liquid Chromatography (HPLC) Technique

“…LOD and LOQ were 0.27 and 0.91 µg/mL, respectively (Table 1). Previously reported LOD and LOQ of metalaxyl detection using the HPLC technique ranged from 0.0015 to 0.015 ppm while LOQ ranged from 0.001 to 1 ppm [13][14][15][16][17]19]. The linearity, LOD, and LOQ detected in the solution and in the matrix of crude durian leaf extract were highly similar, suggesting that the matrix did not significantly interfere with the extractability of metalaxyl.…”

“…In comparison, Yang et al [13] reported that 98% of metalaxyl was degraded within three days after foliar spray application to potato plants under field conditions. Similarly, metalaxyl dissipated rapidly after one day of application and decreased 79.2-92.8% after seven days of application in pepper plants [17].…”

“…In summary, the optimized protocol for metalaxyl extraction from the durian leaf is as follows: 0.5 g cleaned leaf tissue extracted with 5 mL ethyl acetate and re-dissolved with 100% acetonitrile without further clean-up (Figure 1E). Previously reported metalaxyl extraction and preparation protocols for grape, pepper, cucumber, potato, tomato, and Swiss chard [13,14,[16][17][18]21] used larger amounts of plant tissues (10-25 g) and larger volumes of extraction solvents (40-100 mL). Moreover, the clean-up methods required specific chemical compounds and equipment.…”

“…The dissipation equation could not be determined for the soil drench application because durian seedlings died after only two time points. In comparison, the half-life of metalaxyl in other plants, such as potato, tomato, cucumber, grape, pepper, and Swiss chard, were considerably lower than in durian, ranging between 0.8-6.0 days [13,14,[16][17][18]21]. Although it is not surprising that metalaxyl half-life values in different plants were dissimilar, the reason for a much longer half-life value in durian was unclear.…”

“…To reduce the risk of metalaxyl overuse, more information about metalaxyl residue and efficacy inside durian plants is required. Analytical methods to detect metalaxyl residue in other plants had been previously reported, such as high-performance liquid chromatography (HPLC) [13][14][15][16], ultra-performance liquid chromatography (UPLC) [17], liquid chromatography tandem mass spectrometry (LC-MS/MS) [18][19][20], high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) [21], and gas chromatography (GC) [22]. The dissipation patterns of metalaxyl were studied in grape, pepper, potato, tomato, cucumber, and Swiss chard plants [13,14,16,18,21] with the half-life ranging from 0.4-6.0 days.…”