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Title

DEVELOPMENT AND VALIDATION OF A NEW MICRO EXTRACTION METHOD BASED ON TEMPERATURE ASSISTED TANDEM DISPERSIVE LIQUID-LIQUID MICRO EXTRACTION:...

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Abstract

 SAMPLE PREPARATION IS A TEDIOUS AND YET UNAVOIDABLE PROCEDURE IN ANALYTICAL CHEMISTRY [1]. THE OBJECTIVE OF THIS CHALLENGING AND CRITICAL STEP IS TO TRANSFER THE ANALYTE INTO A FORM THAT IS PRE-PURIFIED, CONCENTRATED AND COMPATIBLE WITH THE ANALYTICAL SYSTEM [2, 3]. TYPICALLY, THE SAMPLE PREPARATION STEP CONSISTS OF AN EXTRACTION PROCEDURE THAT RESULTS IN THE ISOLATION AND ENRICHMENT OF COMPONENTS OF INTEREST FROM A SAMPLE MATRIX. EXTRACTION CAN VARY IN DEGREE OF SELECTIVITY, SPEED AND CONVENIENCE AND DEPENDS NOT ONLY ON THE APPROACH AND CONDITIONS USED BUT ALSO ON THE GEOMETRIC CONFIGURATIONS OF THE EXTRACTION PHASE [4]. IN THE PRESENT STUDY, A RAPID, HIGHLY EFFICIENT, AND RELIABLE SAMPLE PREPARATION METHOD NAMED TEMPERATURE-ASSISTED TANDEM DISPERSIVE LIQUID-LIQUID MICRO EXTRACTION FOLLOWED BY GAS CHROMATOGRAPHY-NITROGEN-PHOSPHORUS DETECTION WAS DEVELOPED FOR THE EXTRACTION, PRECONCENTRATION AND DETERMINATION OF FIVE TRIAZOLE PESTICIDES (PENCONAZOLE, HEXACONAZOLE, DINICONAZOLE, TEBUCONAZOLE, AND DIFENCONAZOLE) FROM AQUEOUS SAMPLES. THIS METHOD CONSISTS OF TWO SUCCESSIVE DISPERSIVE LIQUID-LIQUID MICRO EXTRACTION TECHNIQUES WHICH THE FIRST ONE IS ASSISTED BY TEMPERATURE. INITIALLY THE TEMPERATURE OF AQUEOUS PHASE (HIGH VOLUME) IS ADJUSTED AT AN ELEVATED TEMPERATURE AND THEN A DISPERSER SOLVENT CONTAINING AN EXTRACTION SOLVENT IS RAPIDLY INJECTED INTO IT. AFTER COOLING TO ROOM TEMPERATURE THE PHASE SEPARATION IS ACCELERATED BY CENTRIFUGING. THE SEDIMENTED PHASE IS COMPLETELY REMOVED AND DISSOLVED INTO ANOTHER DISPERSER SOLVENT AND SUBJECTED TO THE SECOND MICRO EXTRACTION METHOD. VARIOUS PARAMETERS AFFECTING THE EXTRACTION EFFICIENCY SUCH AS TYPE AND VOLUME OF THE EXTRACTION AND DISPERSER SOLVENTS, TEMPERATURE, SALT ADDITION, AND PH WERE EVALUATED. UNDER THE OPTIMUM EXTRACTION CONDITIONS, THE METHOD SHOWED LOW LIMITS OF DETECTION AND QUANTIFICATION BETWEEN 0.3-2 NG L-1 AND 0.9-7 NG L-1 IN, RESPECTIVELY. ENRICHMENT FACTORS AND EXTRACTION RECOVERIES WERE IN THE RANGES OF 9715–9970 AND 97–100 %, RESPECTIVELY. THE RELATIVE STANDARD DEVIATIONS FOR THE EXTRACTION OF 25 NG L-1 OF EACH PESTICIDE WERE LESS THAN 6 % FOR INTRA-DAY (N = 6) AND INTER-DAYS (N = 4) PRECISIONS. FINALLY THE METHOD WAS SUCCESSFULLY APPLIED TO DETERMINATION OF TARGET ANALYTES IN SEVERAL SAMPLES, INCLUDING TAP, RIVER AND WELL WATERS, WASTEWATER (BEFORE AND AFTER PURIFICATION), USING THE DEVELOPED METHOD AND PENCONAZOLE WAS DETERMINED AT NG L−1 LEVEL.

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