Muhamad Halimah

Method Development for Determination of Fluroxypyr in Soil

Improved methods for extraction and clean up of fluroxypyr residue in water have been established. Two methods of fluroxypyr extraction were used, namely, Direct Measurement of fluroxypyr and Concentration of fluroxypyr onto A Solid Phase Extraction (SPE) Adsorbent, followed by elution with solvent before determination of fluroxypyr. The recovery for Direct Measurement of fluroxypyr in water containing 8–100 µg L− 1, ranged from 86 to 110% with relative standard deviation of 0.7 to 2.15%. For the second method, three types of SPE were used, viz. C18, C18 end‐capped and polyvinyl dibenzene (ISOLUTE ENV +). The procedure involved concentrating the analyte from fluroxypyr‐spiked water at pH 3, followed by elution of the analyte with 4 mL of acentonitrile. The recovery of fluroxypyr from the spiked sample at 1 to 50 µg L− 1 after eluting through either C18 or C18 end‐capped ranged from 40–64% (with relative standard deviation of 0.7 to 2.15) and 41–65% (with standard deviation of 1.52 to 11.9). The use of ISOLUTE ENV +, gave better results than the C18, C18 end‐capped or the Direct Measurement Methods. The recovery and standard deviation of fluroxypyr from spiked water using ISOLUTE ENV + ranged from 91–102% and 2.5 to 5.3, respectively.

Adsorption-desorption behavior of thiram: effect of soil type, temperature and pH

1 CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(1) JANUARY-MARCH 2016 3 ULY-SEPTEMBER The present study was conducted in order to investigate the adsorption and desorption behavior of tetramethylthiuram disulfide (thiram) using the batch equilibration technique in two soil namely: Ultisols and Inceptisols. The adsorptiondesorption isotherms were expressed by the Freundlich equation. The adsorption isotherms of thiram was classified as L-type under Gile’s classification. The Freundlich’s adsorption coefficient (Kd) value for thiram in the Ultisols and Inceptisols soil were 3.78 and 2.10 mL g-1, respectively. Results indicated that soil organic matter was the main factor affecting thiram behavior in the studied soils. The calculated total percentage desorption values from the Ultisols and Inceptisols soil after the fourth desorption process were 39.2% and 51.6%, respectively. The negative Gibb’s free energy change (∆G°) values obtained suggest that thiram adsorption is an exothermic process. The effects of temperature (25, 30, and 35 °C) and soil pH (3, 7, 10) were also studied on adsorption of thiram in the test soils. Results showed that adsorption of thiram was not affected by temperature but clearly affected by soil pH.

Prediction of Hexaconazole Concentration in the Top Most Layer of Oil Palm Plantation Soil Using Exploratory Data Analysis (EDA).

Ganoderma boninense is a fungus that can affect oil palm trees and cause a serious disease called the basal stem root (BSR). This disease causes the death of more than 80% of oil palm trees midway through their economic life and hexaconazole is one of the particular fungicides that can control this fungus. Hexaconazole can be applied by the soil drenching method and it will be of interest to know the concentration of the residue in the soil after treatment with respect to time. Hence, a field study was conducted in order to determine the actual concentration of hexaconazole in soil. In the present paper, a new approach that can be used to predict the concentration of pesticides in the soil is proposed. The statistical analysis revealed that the Exploratory Data Analysis (EDA) techniques would be appropriate in this study. The EDA techniques were used to fit a robust resistant model and predict the concentration of the residue in the topmost layer of the soil.