| The efficient and inexpensive methods were developed for the analysis of residues of bromoxynil in water, soil and corn. The research which has been developed was carried out from extraction, cleanup to detection three steps. In the following, the main results were summaries as following:1. Detection conditionGC, HPLC, UPLC and RRLC were developed and compared to detect bromoxynil. The results showed HPLC, UPLC and RRLC were acceptable. HPLC analyses were performed using Agilent 1100 equipped with anAgilent tunable absorbance ultraviolet detector (Agilent, Palo Alto, USA). HPLC separation was achieved using a reversed-phase column Eclipse XDB-C18, 250mm×4.6 mm i.d, 5μm particle size, maintained at 30℃with a mobile phase flow rate of 0.8 mL/min. The mobile phase consisted of methanol-water-acetic acid (60:40:0.5, v/v/v). The compounds were detected at 221 nm. The injection volume was 10μL. The detection limits were determined for bromoxynil reference substances and the linearity of the detectors checked. A series of concentrations of 0.05, 0.1, 1.0, 5.0, 10.0mg/L were detected with HPLC. The result showed the detection limit (3-fold noise of base line) of the UV detector at 221 nm was found to be 1.24ng injected for bromoxynil. The linearity was checked in the range between 1.24ng and 247.5ng injected. The regression coefficient of the UV detector was 0.9999 for bromoxynil.UPLC analyses were performed using a Waters Acquity Ultra Performance LC system with a UV detector (Waters). UPLC separation was achieved using an Acquity UPLC BEH C18 column 50 mm x 2.1 mm, i.d, 1.7μm particle size (Waters, Part No. 186002350), maintained at 50℃, with a mobile phase flow rate of 0.4 mL/min. The mobile phase consisted of methanol–0.3%formic acid (60:40, v/v); the compounds were detected at 254 nm and the injection volume was 3μL. RRLC analyses were performed using an Agilent 1200 system with a UV detector (Agilent, Palo Alto, USA). RRLC separation was achieved using a Zorbax Eclipse plus C18 column 50 mm x 4.6 mm, i.d, 1.8μm particle size (RRHT), maintained at 30℃, with a mobile phase flow rate of 1.0 mL/min. The mobile phase consisted of methanol–0.2%formic acid (60:40, v/v); the compounds were detected at 221 nm and the injection volume was 5μL.UPLC, RRLC and HPLC were developed and compared to detect bromoxynil. The results showed the retention time of bromoxynil was about 10.7min in the HPLC system, 2.3min in the UPLC system and 1.3min in the RRLC system. The UPLC system allowed shortening the analysis time up to five times and the UPLC system allowed shortening the analysis time up to nine times comparing to the conventional system. The use of UPLC allowed for powerful separation of the target analytes within a very short time of 2.3 min and the use of RRLC allowed for powerful separation of the target analytes within a very short time of 1.3 min, as compared to 10.7 min run time in the case of HPLC.UPLC and RRLC and HPLC were developed and compared to separation of bromoxynil. The results showed 2×10-5mg/mL bromoxynil could be detected with UPLC and RRLC, the peak shape was good. 5×10-5mg/mL bromoxynil could be detected with HPLC, the peak shape was bad, UPLC and RRLC had higher sensitive than HPLC.2. Determination of bromoxynil residue in waterBromoxynil in water was extracted by liquid-liquid separation, and studied different extraction times and solvents. The results showed bromoxynil in water was extracted by LLP using hexane as the extraction solvent and repeating the procedure twice. It was found that the concentration of bromoxynil in water was 0.10 -1.00 mg L-1, and that the average recovery of shaking extractions was 98.71%-111.11%.3. Determination of bromoxynil residue in soil Bromoxynil in soil was extracted by acetone: water: glacial acetic acid (80:18:2 by volume), methanol: water: glacial acetic acid (80:18:2 by volume) and acetonitrile: water: glacial acetic acid (80:18:2 by volume), the results showed extraction was undertaken using acetone: water: glacial acetic acid (80:18:2 by volume).Bromoxynil in soil was studied different solvent volume of acetone: water: glacial acetic acid (80:18:2 by volume), the results showed 100mL was acceptable.The bromoxynil internal standard was used here for recovery determination with the ultrasound-microwave extraction. The time of ultrasound bath played an important role for the extraction of bromoxynil in soil. The ultrasound time was set up 9min and 12min, the microwaves were set up 60w and 80w, two factors and two levels were intercrossed. The result showed the recoveries of bromoxynil extracted from soil by ultrasound-microwave. The result showed extraction under different times and powers were 84.2%-100.1%, the standard deviations were 6.8%-8.2%, 12min and 60w showed a better recovery compared to the other.Bromoxynil in soil was extracted by shaking, soxhlet extraction and ultrasound-microwave extraction, the three methods were used for the analysis of bromoxynil residues. Extraction was undertaken using acetone: water: glacial acetic acid (80:18:2 by volume) and the extract was cleaned up by LLP, using hexane as the extraction solvent and repeating the procedure twice. The concentration of bromoxynil in soils was 0.05 -5.00 mg/kg, and the average recoveries using soxhlet, shaking and ultrasound-microwave extraction were 90.1%-92.0%, 90.9%-100.8% and 95.6%-109.4% respectively. The relative standard deviations using these methods ranged between 0.9% and 19.2%, 4.9% and 18.4%, and 0.2% and 16.0% respectively.4. Determination of bromoxynil residue in cornExtraction by shaking was the method used for the recovery of bromoxynil from soil, and the results showed that the duration of shaking and the number of liquid-liquid partitioning steps played an important role in the extraction of bromoxynil which would also apply to the recovery of bromoxynil from corn. Recovery after 2h of shaking was higher than that after 1h, and two liquid-liquid partitioning steps proved to be more effective than one. After one liquid-liquid partitioning step, a white deposit was observed in the final solution; this deposit may have absorbed bromoxynil leading to a lower recovery, therefore acetonitrile saturated with petroleum ether was use in the second liquid-liquid partitioning step.Bromoxynil in corn was extracted by shaking, soxhlet extraction and ultrasound-microwave extraction, the results obtained using the shaking extraction technique were compared with those obtained from the two other techniques. The percentage recovery of bromoxynil using extraction by shaking was 84.8% and the standard deviation was 5.6 %. Recovery using soxhlet extraction was 50.9% and the standard deviation was 10.00% whilst that using ultrasound-microwave extraction was 59.7% and 46.5% respectively, thus establishing extraction by shaking as the most effective method of determining the bromoxynil content in corn.The addition of 0.05 -1.00 mg/kg bromoxynil to the corn samples, the average recovery of this compound using extraction by shaking was 84.8-107.3%, and the relative standard deviation ranged between 1.8% and 20.4%.Accelerated Solvent Extraction represents the application of a modern sample preparation technique which we used to study bromoxynil in corn. The result shows that the concentration of bromoxynil in corn was 0.01-1.00 mg/kg, and that the average recovery of this residue using extraction by shaking was 83.7%-90.4%. |
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