Single-drop microextraction for the analysis of organophosphorous insecticides in water (original) (raw)
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Journal of Chromatography A, 1998
Solid-phase microextraction (SPME) is a relatively new technique that appears as a convenient and efficient extraction method in contrast with more complex techniques used for pesticide residue analysis based on liquid-liquid and solid-phase extraction. This extraction procedure involves the absorption of analytes into a polymeric film coated onto a fine silica fiber directly dipped in the aqueous sample. An SPME procedure for the determination of 12 organophosphorus pesticides in clean environmental water samples at low ng / ml concentration level has been developed by optimising variables involved in extraction and desorption. The absorption equilibrium has been estimated by mathematical treatment of the process using an expression that describes experimental absorption time profiles. The method was evaluated according to the reproducibility, linearity range and limits of detection using two different fiber coatings: 100 mm polydimethylsiloxane and 85 mm polyacrylate. The limits of detection obtained using nitrogen-phosphorus detection ranged between 0.01 and 0.2 ng / ml with relative standard deviations lower than 15% at the 1 ng / ml level. The method showed good linearity between 0.1 and 10 ng / ml with regression coefficients ranging between 0.97 and 0.999. Determination of organophosphorus pesticides in water samples in concentration below 0.1 ng / ml can be easily carried out with this fast, economic and solvent-free SPME procedure.
2020
In this paper, the technique of continuous sample drop flow microextraction (CSDF-ME) is developed by the addition of a narrow-necked conical vessel. In the developed technique, an organic solvent denser than water is used for the extraction of organophosphorus pesticides (OPPs) from fruit juice and river water, followed by analysis with GC-MS. Eight milliliters of the sample solution is pumped at 0.5 mL min −1 flow rate into 12.0 μL extraction solvent (chloroform) and placed in the narrow-necked conical vessel for extraction and pre-concentration processes. Under optimal condition, the enrichment factor (EF) and linearity are found to be in the range of 102–380 and 500.0 μg L −1 with correlation coefficient greater than 0.98, respectively. The detection limit is in the range of 0.3–1.0 μg L −1 and LOQ ranged from 2.0–5.0 μg L −1 . The relative standard division (RSD) of six replicate measurements for three different concentrations (i.e., 15.0, 50.0, 150.0 μg L −1 ) is 3.8–8.4%, 2.6...
Journal of Separation Science, 2011
Dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography and mass spectrometry (GC-MS) was applied to the determination of six organophosphorous pesticides (OPPs) in water samples. The analytes included in this study were prophos, diazinon, chlorpyrifos methyl, methyl parathion, fenchlorphos and chlorpyrifos. Several extraction and dispersion solvents were tested for dispersive liquid-liquid microextraction of these analytes and the best results were obtained using chloroform as extraction solvent and 2-propanol as dispersion solvent. Calibration curves of the analytes in water samples were constructed in the concentration range from 100 to 1100 ng/L for prophos, diazinon and methyl parathion and in the range from 100 to 1000 ng/L for chlorpyrifos methyl, fenchlorphos and chlorpyrifos. Limits of detection (LODs) were in the range of 1.5-9.1 ng/L and limits of quantification (LOQs) were in the range of 5.1-30.3 ng/L, below the maximum admissible level for drinking water. Relative standard deviations (RSDs) were between 6.5 and 10.1% in the concentration range of 100-1000 ng/L. The relative recoveries (%RRs) of tap, well and irrigation water samples fortified at 800 ng/L were in the range of 46.1-129.4%, with a larger matrix effect being detected in tap water.
Headspace solid phase microextraction in the determination of pesticides in water
Headspace solid phase microextraction (HS-SPME) was optimized for the analysis of pesticides with gas chromatography electron capture detection (GC-ECD) and high-resolution mass spectrometry. Factors influencing the extraction efficiency such as fiber type, extraction mode and temperature, effect of ionic strength, stirring and extraction time were evaluated. The lowest pesticide concentrations that could be detected in spiked aliquots after HS-SPME-GC-ECD ranged from 0.0005 to 0.0032 μg L − 1 . Consequently hexachlorobenzene, trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected in water samples after HS-SPME at concentrations ranging from 2.4 to 61.4 μg L − 1 that are much higher than the 0.1 μg L − 1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C 18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. Precision for both methods was satisfactory with relative standard deviations less than 20%. This work demonstrated the superiority of HS-SPME as a sample clean-up and pre-concentration technique for pesticides in water samples as well as the need to identify and control point sources of pesticides.
Microchimica Acta, 2012
We have developed a new method for single-drop microextraction (SDME) for the preconcentration of organochlorine pesticides (OCP) from complex matrices. It is based on the use of a silicone ring at the tip of the syringe. A 5 μL drop of n-hexane is applied to an aqueous extract containing the OCP and found to be adequate to preconcentrate the OCPs prior to analysis by GC in combination with tandem mass spectrometry. Fourteen OCP were determined using this technique in combination with programmable temperature vaporization. It is shown to have many advantages over traditional split/splitless injection. The effects of kind of organic solvent, exposure time, agitation and organic drop volume were optimized. Relative recoveries range from 59 to 117 %, with repeatabilities of <15 % (coefficient of variation) were achieved. The limits of detection range from 0.002 to 0.150 μg kg −1. The method was applied to the preconcentration of OCPs in fresh strawberry, strawberry jam, and soil.
The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC– MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.
Journal of Chromatography A, 1999
A solid-phase microextraction (SPME)-GC procedure has been developed for the analysis of four selected pesticides (propanil, acetochlor, myclobutanil and fenoxycarb) in water samples. Mass spectrometry (MS) was used and two different instruments, a quadrupole MS system and an ion trap operating in the MS-MS mode, were compared. A Carbowaxdivinylbenzene SPME fiber was used. The performances of the two GC-MS instruments were comparable in terms of linearity (in the range of 0.1-10 mg / l in water samples) and sensitivity (limits of detection were in the low ng / l range); the quadrupole MS instrument gave better precision than the ion trap MS-MS system, but generally the relative standard deviations for replicates were acceptable for both instruments (,15%). Specificity with these two instruments was comparable in the analysis of ground water samples. Recovery tests were made to assess the applicability of the SPME procedure in the quantitative analysis of contaminated groundwaters.