THE FORMATION OF THMS IS OF PRIME CONCERN, DUE TO THEIR PROBABLE TOXICITY TO THE AQUATIC LIFE. [4] THUS, SUCH THESE COMPOUNDS MUST BE PRECISELY DETERMINED IN THE CHLORINATED WATER EFFLUENTS OF THE POWER STATIONS. ...

HYDRIDE GENERATION (CHG) IS A WELL-ESTABLISHED TECHNIQUE FOR DETERMINATION OF TOXIC ARSENIC (AS) [1]. ELECTROCHEMICAL HYDRIDE GENERATION (ECHG) HAS BEEN INTRODUCED AS A SUITABLE ALTERNATIVE TO COMMON HYDRIDE GENERATION BY NABH4, AND HAS BEEN SHOWN, TO BE CAPABLE OF CIRCUMVENTING SOME OF THE DISADVANTAGES ASSOCIATED WITH THE NABH4-ACID REDUCING SYSTEM [2]. THIS PAPER DESCRIBES A NOVEL METHOD FOR THE QUANTITATIVE DETERMINATION OF ARSENIC IN FOOD AND ENVIRONMENTAL SAMPLES. THE METHOD IS BASED ON ELECTROCHEMICAL REDUCTION OF AS TO ARSINE (ASH3) IN AN ELECTROCHEMICAL CELL AND SUBSEQUENT REACTION OF ASH3 WITH SILVER DIETHYLDITHIOCARBAMATE TO GIVE AN ABSORBING COMPLEX AT 525 NM. THE ELECTROCHEMICAL GENERATOR CONSISTED OF A CATHODE CELL SEPARATED FROM THE ANODE CELL BY A NAFION ION EXCHANGE MEMBRANE. ARSINE IS GENERATED AT THE CATHODE AND REACTS WITH SILVER DIETHYLDITHIOCARBAMATE IN A HEADSPACE MICROFUNNEL. THE AFFECTING PARAMETERS ON THE EFFICIENCY OF THE ELECTROCHEMICAL HYDRIDE GENERATION AND THE MICROEXTRACTION STEPS HAVE BEEN EXAMINED AND OPTIMIZED. THE ANALYTICAL PERFORMANCE OF THE METHOD HAS BEEN EVALUATED UNDER OPTIMIZED OPERATING CONDITION (GRAPHITE CATHODE, 150 MA CURRENT, 0.3 M H2SO4 AS CATHOLYTE, 10 MIN FOR REACTION DURATION) AND THE ANALYTICAL FIGURES OF MERITS HAS BEEN REPORTED. AS ADVANTAGE, THE SYSTEM IS VERY FAST, EFFICIENT AND ENVIRONMENTALLY FRIENDLY FOR MONITORING TOTAL ARSENIC FOOD AND WATERS.

AROMA IS AN IMPORTANT QUALITY FACTOR IN FOODS. THE AROMA OF BEE HONEY DEPENDS ON VOLATILE FRACTION COMPOSITION, WHICH IS INFLUENCED BY NECTAR COMPOSITION AND FLORAL ORIGIN. HONEY OF UNIFLORAL ORIGIN USUALLY COMMANDS HIGHER COMMERCIAL VALUE, THUS THE FLORAL DETERMINATION AND CERTIFICATION OF UNIFLORAL HONEY PLAYS AN IMPORTANT ROLE IN QUALITY CONTROL. TWO EXTRACTION TECHNIQUES, HEADSPACE SOLID-PHASE MICROEXTRACTION (SPME) WITH A 65 MM POLYDIMETHYLSILOXANE/DIVINYLBENZENE/CARBOXEN (PDMS/DVB/CAR) FIBER AND ULTRASONIC SOLVENT EXTRACTION WAS USED TO EXTRACT VOLATILE COMPOUNDS, AND A GAS CHROMATOGRAPH EQUIPPED WITH A MASS SPECTOMETRY DETECTOR (GC/MS) WAS USED TO IDENTIFY THE VOLATILE COMPOUNDS IN HONEYS. THESE METHODS DISPLAY A VARYING DEGREE OF SELECTIVITY AND EFFECTIVENESS DEPENDING UPON THE COMPOUNDS INVOLVED AND THE EXTRACTION CONDITIONS.HONEY SAMPLES OBTAINED FROM HIVE SITES IN DIFFERENT REGIONS OF IRAN WERE ANALYZED. THE SAMPLES HAD THREE DIFFERENT BOTANICAL ORIGINS: CITRUS, THYME, MILK VETCH. ALL SAMPLES WITH THE SAME BOTANICAL ORIGIN GAVE REMARKABLY SIMILAR GC PROFILES. SOME VOLATILE COMPOUNDS WERE FOUND ONLY IN SPECIFIC FLORAL SOURCE HONEY SAMPLES AND THUS COULD BE INTERESTING FOR USE AS MARKERS, FOR EXAMPLE THYMOL AND CARVACROL FOR THYME HONEY AND LIMONENE FOR CITRUS HONEY. IN COMPARING THE TWO METHODS, ULTRASONIC SOLVENT EXTRACTION REQUIRE TOXIC ORGANIC SOLVENTS, BUT SPME METHOD CAN ELIMINATE SOLVENTS ENTIRELY. MOREOVER, SPME HAS ADVANTAGE OF BEING SIMPLE, HIGH SENSITIVITY, SMALL SAMPLE VOLUME, AND LOWER COST PER ANALYSIS. THEREFOR WE EMPHASIZE SOLID PHASE MICRO-EXTRACTION GAS CHROMATOGRAPHY TECHNIQUE TO OBTAIN FINGERPRINT GC PROFILES FOR THE PURPOSE OF CLASSIFYING UNIFLORAL HONEYS.

THE EXTRACTION EFFICIENCY OF HEADSPACE SOLID PHASE MICROEXTRACTION IS ENHANCED BY COOLING THE FIBER WHILE HEATING THE SAMPLE NAMED COLD-FIBER HEADSPACE SOLID PHASE MICROEXTRACTION (CF-HS- SPME). ...

IN THE PRESENT WORK, HEAD-SPACE SOLID-PHASE MICROEXTRACTION METHOD WAS DEVELOPED FOR THE PRECONCENTRATION AND EXTRACTION OF METHYL TERT-BUTYL ETHER. FOR THE FIRST TIME, AN IONIC LIQUID MEDIATED MULTI-WALLED CARBON NANOTUBE-POLY (DIMETHYLSILOXANE) HYBRID COATING THAT WAS PREPARED BY COVALENT FUNCTIONALIZATION OF MULTI-WALLED CARBON NANOTUBES WITH HYDROXYLTERMINATED POLY (DIMETHYLSILOXANE) USING THE SOL-GEL TECHNIQUE [1, 2], WAS USED AS SOLID-PHASE MICROEXTRACTION ADSORBENT. THIS INNOVATIVE FIBER EXHIBITED HIGH POROUS SURFACE STRUCTURE, HIGH THERMAL STABILITY (AT LEAST 320OC) AND LONG LIFESPAN (OVER 210 TIMES). POTENTIAL FACTORS AFFECTING THE EXTRACTION EFFICIENCY WERE OPTIMIZED. UNDER THE OPTIMUM CONDITIONS, THE METHOD DETECTION LIMIT (S/N=3) WAS 0.007 NG ML-1 AND LIMIT OF QUANTIFICATION (S/N=10) WAS 0.03 NG ML-1. THE CALIBRATION CURVE WAS LINEAR IN THE RANGE OF 0.03 TO 200 NG ML-1. THE RELATIVE STANDARD DEVIATION FOR ONE FIBER (REPEATABILITY, N=5) AT THREE DIFFERENT CONCENTRATIONS (0.05, 1 AND 150 NG ML-1) WERE 5.1, 4.2 AND 4.6% AND FOR THE FIBERS OBTAINED FROM DIFFERENT BATCHES (REPRODUCIBILITY, N=3) WERE 6.5, 5.9 AND 6.3%, RESPECTIVELY. THE DEVELOPED METHOD WAS SUCCESSFULLY APPLIED TO THE DETERMINATION OF METHYL TERT-BUTYL ETHER IN DIFFERENT REAL WATER SAMPLES IN THREE CONSECUTIVE DAYS. THE RELATIVE RECOVERIES FOR THE SPIKED SAMPLES WITH 0.05, 1 AND 150 NG ML-1 WERE BETWEEN 94-104%.

TWO WELL-KNOWN MICROEXTRACTION METHODS, DISPERSIVE LIQUID–LIQUID MICROEXTRACTION (DLLME) AND SOLID–PHASE MICROEXTRACTION (SPME), WERE COMBINED, RESULTING IN AS AN ENCOURAGING METHOD. THE METHOD, NAMED DLLME–SPME, WAS PERFORMED BASED ON TOTAL VAPORIZATION TECHNIQUE [1]. ....

ANTIMONY (SB (III)) IS AN EMERGING ELEMENT OF ENVIRONMENTAL CONCERN BECAUSE OF ITS ALARMING CONCENTRATION IS INCREASINGLY OBSERVED DURING THE LAST YEARS. THIS IS DUE TO THE CURRENT EXTENSIVE INDUSTRIAL USE OF ANTIMONY...