Gas Chromatography-flame Photometric Detection Research Articles

Matrix solid-phase dispersion associated to gas chromatography for the assessment in honey bee of a group of pesticides of concern in the apicultural field

A method based on matrix solid-phase dispersion (MSPD) associated to gas chromatography-flame photometric detection (GC-FPD), GC-electron capture detection (GC-ECD) and GC-mass spectrometry (GC–MS) for confirmation purposes, was developed for the determination of a representative group of twelve pesticides in honeybee with particular concern in the apicultural field (fipronil, thiamethoxam, acetamiprid, acrinathrin, metamidophos, dimetoathe, diazinon, chlorpyrifos, methidathion, profenophos, azinphos methyl and coumaphos). Factors influencing the extraction efficiency of MSPD were investigated and optimized through response surface method. The use of octadecylsilyl (C18) sorbent combined with a florisil clean-up and acetonitrile-methanol (99:1) elution was the optimal condition for the extraction of the selected pesticides. Under this condition the recovery of pesticides at the limit of quantification of the method (0.007 to 0.050 μg g−1) ranged from 68 to 102% with RSDs for within-laboratory reproducibility ≤20%. The proposed method was applied to the analysis of honeybees collected in 68 field hives from areas of great apicultural and agricultural development in central Chile. In 65% of these samples eight different pesticides were detected. Pesticides most frequently found were chlorpyrifos (34% of the samples, <0.017–0.067 μg g−1), acrinathrin (32% of the samples, <0.020–0.026 μg g−1) and diazinon (10% of the samples at values <0.015 μg g−1). The incidence of these pesticides in bees can be related to their high employ in central Chile, use to combat the varroosis in hives and hydrophobicity.

Characterization of the Major Odor-Active Compounds in Dry Jujube Cultivars by Application of Gas Chromatography-Olfactometry and Odor Activity Value.

The volatile compounds of jujube ( Ziziphus jujube Mill.) puree obtained from three cultivars, 'Jinsixiaozao' (Y1), 'Youzao' (Y2), and 'Yuzao' (Y3), were analyzed by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry, gas chromatography-flame photometric detection, and a nitrogen phosphorus detector. The results showed that a total of 37, 37, and 35 odor-active compounds were identified by GC-O in samples of Y1, Y2, and Y3, respectively. In addition, the odor activity value (OAV) was used to determine the important compounds. The results demonstrated that hexanal (OAV of 39-85), ( E)-2-octenal (OAV of 32-70), β-damascenone (OAV of 14-49), ethyl hexanoate (OAV of 22-39), 3-mercaptohexyl acetate (OAV of 17-24), and 2,5-dimethylpyrazine (OAV of 17-22) were key odor-active compounds. It is of great significance to develop high-grade jujube food by determining key odor-active compounds. Furthermore, four volatiles (hexanal, 1-octen-3-ol, 3-mercapohexyl acetate, and benzaldehyde) reduced the overall threshold value by 2.36, 1.01, 1.34, and 1.19, respectively.

GAS CHROMATOGRAPHIC DETERMINATION OF 23 ORGANOPHOSPHORUS PESTICIDES RESIDUE IN BOTTLE GUARD MATRIX

Objective: To validate in-house QuEChERS method, which scrutinizes and quantify the residue levels of some most frequently used organophosphorus pesticides and to prove a complete workflow for routine multi-residue pesticide analysis in representative bottle guard matrices and study the persistence of 23 organ phosphorus pesticides.Methods: QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction method was followed. Method validation and residue screening of bottle guard samples were conducted by GC-FPD (Gas Chromatography-Flame Photometric Detector) were used to analyse the presence of pesticides whereas confirmation of pesticides was done by GC-MS (Gas Chromatographic-Mass Spectrometer). Results: For bottle guard matrix, LOD (limit of detection) and LOQ (limit of quantification) values are lowest for phorate (0.005 mg/kg and 0.015 mg/kg) and highest for parathion-methyl (0.1 mg/kg and 0.3 mg/kg) respectively. Calibration curve, was plotted between an area of 23 pesticide standard mixture against seven different concentration levels of 0.01, 0.02, 0.05, 0.10, 0.20, 0.50, 1.00 mg/kg with regression coefficient (R2) are in the range of 0.978-0.994. The mean recovered amount at 0.05 mg/kg spikeing concentration are in the range of lowest 0.0413 mg/kg to highest 0.0467 mg/kg and relative standard deviation are in the range of lowest 2.2 to highest 8.571.Conclusion: For ensuring exposure to contaminants, especially by dietary intake, Robust analytical methods were validated for carrying out both research and monitoring programmes and thus for defining limitations and supporting enforcement of regulations.

Rapid gas chromatography with flame photometric detection of multiple organophosphorus pesticides in Salvia miltiorrhizae after ultrasonication assisted one-step extraction.

A simple and rapid gas chromatography-flame photometric detection (GC-FPD) method was developed for the determination of 12 organophosphorus pesticides (OPPs) in Salvia miltiorrhizae by using ultrasonication assisted one-step extraction (USAE) without any clean-up steps. Some crucial parameters such as type of extraction solvent were optimized to improve the method performance for trace analysis. Any clean-up steps were negligent as no interferences were detected in the GC-FPD chromatograms for sensitive detection. Under the optimized conditions, limits of detection (LODs) and quantitation (LOQs) for all pesticides were in the range of 0.001-0.002mg/kg and 0.002-0.01mg/kg and 0.002-0.01mg/kg, respectively, which were all below the regulatory maximum residue limits suggested. RSDs for method precision (intra- and inter-day variations) were lower than 6.8% in approval with international regulations. Average recovery rates for all pesticides at three fortification levels (0.5, 1.0 and 5.0mg/kg) were in the range of 71.2-101.0% with relative standard deviations (RSDs) <13%. The developed method was evaluated for its feasibility in the simultaneous pre-concentration and determination of 12 OPPs in 32 batches of real S. miltiorrhizae samples. Only one pesticide (dimethoate) out of the 12 targets was simultaneously detected in four samples at concentrations of 0.016-0.02mg/kg. Dichlorvos and omethoate were found in the same sample from Sichuan province at 0.004 and 0.027mg/kg, respectively. Malathion and monocrotophos were determined in the other two samples at 0.014 and 0.028mg/kg, respectively. All the positive samples were confirmed by LC-MS/MS. The simple, reliable and rapid USAE-GC-FPD method with many advantages over traditional techniques would be preferred for trace analysis of multiple pesticides in more complex matrices.

Validation of QuEChERS based method for determination of fenitrothion residues in tomatoes by gas chromatography–flame photometric detector: Decline pattern and risk assessment

A simple and rapid gas chromatography with flame photometric detector (GC-FPD) determination method was developed to detect residue levels and investigate the dissipation pattern and safe use of fenitrothion in tomatoes. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) using an ethyl acetate-based extraction, followed by a dispersive solid-phase extraction (d-SPE) with primary-secondary amine (PSA) and graphite carbon black (GCB) for clean up, was applied prior to GC-FPD analysis. The method showed satisfactory linearity, recovery and precision. The limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.01mg/kg, respectively. The residue levels of fenitrothion were best described by first order kinetics with a half-life of 2.2days in tomatoes. The potential health risks posed by fenitrothion were not significant, based on supervised residue trial data. The current findings could provide guidance for safe and reasonable use of fenitrothion in tomatoes and prevent health problems to consumers.

Development of Manual Shaking and Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction for Analysis of Organophosphorus Pesticides in Aqueous Samples

A novel, rapid and efficient manual shaking and ultrasound-assisted surfactant-enhanced emulsification microextraction (M-UASEME) combined with gas chromatography-flame photometric detection (GC-FPD) was developed for the extraction and determination of eight organophosphorus pesticides (OPPs) in tap water and honey samples. The main parameters that affected the extraction efficiency were investigated and optimized. Under the optimum conditions, the relative standard deviation (RSD, n = 6) ranged from 2.4 to 9.3%. Limits of detection (LOD) were varied between 0.005 and 0.05 µg L-1. Good linearity was obtained in a range of 0.5-50.0 µg L-1 for all analytes with the correlation coefficients (r) > 0.9964. Finally, the developed method was successfully applied to determine the eight pesticide residues in real samples. The recoveries of the target analytes in samples were between 82.4 and 96.7%.

Polydimethylsiloxane/metal-organic frameworks coated stir bar sorptive extraction coupled to gas chromatography-flame photometric detection for the determination of organophosphorus pesticides in environmental water samples

In this work, the metal-organic frameworks (MOFs), MIL-101-Cr-NH2 was synthesized via a direct hydrothermal method, and a polydimethylsiloxane (PDMS)/MIL-101-Cr-NH2 coated stir bar was prepared by sol-gel technique. Good reproducibility was obtained for the preparation of PDMS/MIL-101-Cr-NH2 coated stir bar with the relative standard deviations (RSDs) ranging from 3.7 to 5.2% (n=7) in one batch, and from 5.4 to 9.2% (n=7) among different batches. With the high surface area and rich benzene ring structure of MIL-101-Cr-NH2, the prepared PDMS/MIL-101-Cr-NH2 coated stir bar presented higher extraction efficiency for target organophosphorus pesticides (OPPs, including phorate, diazinon, malathion, fenthion, quinalphos and ethion) over PDMS coated stir bar. Based on it, a new method of PDMS/MIL-101-Cr-NH2 coated stir bar sorptive extraction (SBSE) coupled to gas chromatography-flame photometric detection (GC-FPD) was proposed for the determination of six OPPs in environmental water samples. The operation parameters affecting the extraction efficiency of SBSE, including extraction time, stirring rate, desorption time and ionic strength, were investigated. Under the optimal conditions, the limits of detection (S/N=3) were found to be in the range of 0.043–0.085μgL−1 for the six target OPPs, and the linear range was 0.5–100μgL−1 for malathion and 0.2–100μgL−1 for other five OPPs. The RSDs of the proposed method evaluated at 1µgL−1 for each OPP were in the range of 5.9–8.7% (intra-day, n=7) and 6.1–10.7% (inter-day, n=5), respectively. The enrichment factors were varied from 110 to 151-fold (theoretical enrichment factor was 200-fold). The proposed method was applied to the analysis of OPPs in East Lake and pond water samples with recoveries in the range of 89.3–115% and 80.0–113% for the spiked East Lake and pond water samples, respectively.

Homogeneous Liquid-Liquid Microextraction for Determination of Organophosphorus Pesticides in Environmental Water Samples Prior to Gas Chromatography-Flame Photometric Detection.

In this study, homogeneous liquid-liquid microextraction (HLLME) was developed for preconcentration and extraction of 15 organophosphorus pesticides (OPPs) from water samples coupling with gas chromatography followed by a flame photometric detector (HLLME-GC-FPD). In this method, OPPs were extracted by the homogeneous phase in a ternary solvent system (water/acetic acid/chloroform). The homogeneous solution was excluded by the addition of sodium hydroxide as a phase separator reagent and a cloudy solution was formed. After centrifugation (3 min at 5,000 rpm), the fine particles of extraction solvent (chloroform) were sedimented at the bottom of the conical test tube (10.0 ± 0.5 µL). Furthermore, 0.5 µL of the sedimented phase was injected into the GC for separation and determination of OPPs. Optimal results were obtained under the following conditions: volume of the extracting solvent (chloroform), 53 µL; volume of the consolute solvent (acetic acid), 0.76 mL and concentration of sodium hydroxide, 40% (w/v). Under the optimum conditions, the enrichment factors of (260-665), the extraction percent of 75.8-104%, the dynamic linear range of 0.03-300 µg L(-1) and the limits of detection of 0.004-0.03 µg L(-1) were obtained for the OPPs. This method was successfully applied for the extraction and determination of the OPPs in environmental water samples.

Modified QuEChERS in combination with dispersive liquid-liquid microextraction based on solidification of the floating organic droplet method for the determination of organophosphorus pesticides in milk samples.

In this work, a rapid, environment friendly and sensitive method was established for the extraction and analysis of five organophosphorus pesticides (OPPs) (chlorpyrifos, chlorpyrifos-methyl, isocarbophos, malathion and phorate) in milk samples by means of gas chromatography-flame photometric detection. The pesticides were first extracted with acetonitrile from milk samples by using the modified "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) method. No other clean-up was required after extraction. Then the above-mentioned acetonitrile extract was concentrated by using the dispersive liquid-liquid microextraction combined with solidification of floating organic droplets technique. Several factors that could influence the extraction efficiency, such as type of extraction solvent, disperser solvent, volume of extraction and disperser solvent, salt effect, sample pH, and extraction time, were investigated and optimized. As a result, 15 µL of 1-dodecanol were used as the extractant because of its lower toxicity, 300 µL methanol was chosen as dispersant and the extraction time was set to 1 min. Under the optimized conditions, good linearity was exhibited from 0.01 to 1.0 mg/L with the correlation coefficients higher than 0.9968. The limits of detection of the five OPPs were ranged in 0.1-0.3 μg/L, and the limits of quantification were at the range of 0.3-1.0 μg/L. Moreover, the recoveries of the target analytes from milk samples at spiking levels of 0.01, 0.05 and 0.1 mg/L were between 80.5 and 106.5% with the relative standard deviations varied from 3.6 to 6.3%. This method has been successfully applied to detect OPPs in real milk samples.

Efficient Oxidative Desulfurization (ODS) of Commercial Diesel with TBHP under Mild Conditions Catalyzed by Polymolybdates Supported on Al2O3

Due to the low specifications for sulfur content in diesel, a lot of research work are been conducted to develop alternative method for desulfurization. Catalytic oxidative desulfurization (Cat-ODS) has been found to be an alternative method to replace a conventional method which is hydrodesulfurization.New catalyst formulation using tert-butyl hydroperoxide polymolybdate based catalyst system was investigated in this research utilizing tert-butyl hydroperoxide (TBHP) as oxidant and dimethylformamide (DMF) as solvent for extraction. A series of polymolybdate supported alumina catalysts were prepared using wet impregnation method, ageing at ambient room temperature for 24 hours and followed by calcination process. A commercial diesel with 440 ppmw of total sulfur was employed to evaluate the elimination of sulfur compounds. Besides, the percentage of sulfur removal was measured by gas chromatography-flame photometric detector (GC-FPD). The sulfur content in commercial diesel was successfully reduced from 440 ppmw to 35 ppmw under mild condition followed by solvent extraction. From catalytic testing, Mo-Al2O3 calcined at 500°C was revealed as the most potential catalyst which gave 92% of sulfur removal.

Desulfurization of Kerosene by the Electrochemical Oxidation and Extraction Process

To meet the environmental requirements, kerosene, as the major component of jet fuel, is necessary for deep desulfurization. An electrochemical oxidation–extraction method was proposed to reduce the sulfur content in kerosene in this work. First, the electrochemical oxidation of kerosene was carried out in NaCl solution. Then, N-methyl-2-pyrrolidone (NMP) was used as an extractant to remove the oxidized organic sulfides. Gas chromatography–flame photometric detector (GC–FPD), gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, and ion chromatography were used to determine 1-heptyl mercaptan, one of the main organic sulfides in kerosene, and its products after electrochemical oxidation. The results showed that 1-heptyl mercaptan was effectively oxidized to diheptyl disulfide, 1-heptanesulfonyl chloride, and sulfate in electrochemical oxidation and removed after extraction. After electrochemical oxidation–extraction, the sulfur content of kerosene decreased from 180...

Solidification of floating organic drop microextraction combined with gas chromatography-flame photometric detection for the analysis of organophosphorus pesticides in water samples

Vortex-assisted solidification of floating organic drop microextraction combined with GC-FPD for organophosphorus pesticide analysis in water samples.

Determination of organophosphorus pesticide residues in vegetables using solid phase micro-extraction coupled with gas chromatography–flame photometric detector

An adequate and simple analytical method based on solid-phase microextraction (SPME) followed by gas chromatography–flame photometric detection (GC–FPD) for the determination of eleven organophosphorus pesticide residues (i.e., ethoprophos, sulfotep, diazinon, tolclofos-methyl, fenitrothion, chlorpyrifos, isofenphos, methidathion, ethion, triazophos, leptophos) in vegetables samples (cabbage, kale and mustard) was developed. Important parameters that influence the extraction efficiency (i.e., fibre type, extraction modes, extraction time, salt addition, desorption time and temperature) were systematically investigated. Four types of commercially available fibres (i.e., 50/30μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), 65μm polydimethylsiloxane/divinylbenzene (PDMS/DVB), 100μm polydimethylsiloxane (PDMS), and 85μm polyacrylate (PA)) were evaluated. PA fibre exhibited the best performance and was used for the rest of the studies. The optimised extraction conditions were: extraction time, 30min at room temperature; stirring speed, 1275rpm; salt content, 10% NaCl; desorption time and temperature, 11min at 260°C; and no pH adjustment of the sample extract. The method was validated over the range 0.1–100μg/L. Repeatabilities were satisfactory, ranging between 2.44% and 17.9% for all analytes. The limits of detection and quantitation ranged from 0.01 to 0.14 and 0.03 to 0.42μg/L, respectively. The method was applied to twenty local vegetable (cabbage, kale and mustard) products. Chlorpyrifos (0.22–1.68μg/kg) was the most detected pesticide in the tested samples. The obtained values are however lower than the Maximum Residue Limits (MRLs) as stipulated in the Food Act & Regulations of Malaysia.

Determination of organophosphorus flame retardants in fish by pressurized liquid extraction using aqueous solutions and solid-phase microextraction coupled with gas chromatography-flame photometric detector

A novel method was developed for the determination of organophosphorus flame retardants (PFRs) in fish. The method consists of a combination of pressurized liquid extraction (PLE) using aqueous solutions and solid-phase microextraction (SPME), followed by gas chromatography-flame photometric detector (GC-FPD). The experimental parameters that influenced extraction efficiency were systematically evaluated. The optimal responses were observed by extracting 1g of fish meat with the solution of water:acetonitrile (90:10, v/v) at 150°C for 5min and acid-washed silica gel used as lipid sorbent. The obtained extract was then analyzed by SPME coupled with GC-FPD without any additional clean-up steps. Under the optimal conditions, the proposed procedure showed a wide linear range (0.90–5000ngg−1) obtained by analyzing the spiked fish samples with increasing concentrations of PFRs and correlation coefficient (R) ranged from 0.9900 to 0.9992. The detection limits (S/N=3) were in the range of 0.010–0.208ngg−1 with standard deviations (RSDs) ranging from 2.0% to 9.0%. The intra-day and inter-day variations were less than 9.0% and 7.8%, respectively. The proposed method was successfully applied to the determination of PFRs in real fish samples with recoveries varying from 79.8% to 107.3%. The results demonstrate that the proposed method is highly effective for analyzing PFRs in fish samples.

Determination of organophosphorus pesticides in stomach contents of postmortem animals by QuEChERS and gas chromatography.

The quick, easy, cheap, effective, rugged and safe (QuEChERS) method for sample preparation was applied to determine seven organophosphorus pesticides (OPs) in stomach contents of poisoned postmortem animals. The pesticides consisted of diazinon, edifenphos, ethyl p-nitrophenyl phenylphosphonothioate, fenitrothion, monocrotophos, parathion and phosphamindon, and tested samples included stomach contents from postmortem animals of cattle, goat, dog, cat, birds, deer and rabbit. The pesticides were spiked into the samples which were found to be negative through previous pesticide poisoning analysis, and the pesticides were extracted and cleaned up based on the QuEChERS process and then they were analyzed using gas chromatography (GC)-flame photometric detector (FPD) or GC-nitrogen-phosphorus detector (NPD) with a DB-5 column. Limits of detection ranged from 0.27 to 0.41 mg/kg for the seven pesticides. The mean recoveries ranged from 80 to 99% in GC-FPD and 83 to 90% in GC-NPD. The coefficients of variation were <10% for all analytes and sample matrix combinations except for phosphamidon and edifenphos in dog stomach contents. This study demonstrated that the method using QuEChERS and GC-FPD and/or GC-NPD is very effective to analyze the OPs in the stomach contents of postmortem animals.

Composition and source of butyltins in sediments of Kaohsiung Harbor, Taiwan

Fifty-eight sediment samples were collected from the Kaohsiung Harbor (Taiwan) for analyses of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT), using gas chromatography/flame photometric detector (GC/FPD). The concentration of total butyltins (ΣBTs), sum of MBT, DBT, and TBT, varied from 3.9 to 158.5 ng Sn/g dw in sediment samples with TBT being the major component of the sediment samples, except for the vicinity of the Love River mouth where MBT was the most abundant BT compound (a proportion of over 57%). Based on the BTs concentration, distribution, composition and correlations, the sources of BTs found in harbor sediments are shipping activities, and TBT is the main pollutant; the estuary (i.e. Love River) has been the anthropogenic source of MBT from upstream inputs. Influences of TBT on aquatic organisms are evaluated using the toxicity guidelines proposed by the US EPA (US Environmental Protection Agency) and the ACCI (assessment class criterion for imposex) proposed by OSPAR (Oslo and Paris Commission). The evaluation shows that the TBT contained in the sediment at Kaohsiung Harbor is likely to have a negative influence at ACCI class C because gastropods present imposex and TBT levels are above ecotoxicological assessment criteria (EAC) limits.

Gas chromatography with flame photometric detection of 31 organophosphorus pesticide residues in Alpinia oxyphylla dried fruits

A simple, rapid and effective gas chromatography–flame photometric detection method was established for simultaneous multi-component determination of 31 organophosphorus pesticides (OPPs) residues in Alpinia oxyphylla, which is widely consumed as a traditional medicine and food in China. Sample preparation was completed in a single step without any clean-up procedure. All pesticides expressed good linear relationships between 0.004 and 1.0μg/mL with correlation coefficients higher than 0.9973. The method gave satisfactory recoveries for most pesticides. The limits of detection varied from 1 to 10ng/mL, and the limits of quantification (LOQs) were between 4 and 30ng/mL. The proposed method was successfully applied to 55 commercial samples purchased from five different areas. Five pesticide residues were detected in four (7.27%) samples. The positive samples were confirmed by gas chromatography with tandem mass spectrometry (GC–MS/MS).

&lt;b&gt;Simultaneous determination of organophosphorous insecticides in bean samples by gas chromatography - flame photometric detection

The indiscriminate use of organophosphorous pesticides (OPPs) in crops may leave residues in food and may cause poisoning in the applicators. A method was developed for the determination of five OPPs in bean samples by Gas Chromatography-Flame Photometric Detection (GC-FPD). Validation parameters comprised linearity between 0.24 and 8.56 μg g -1 ( r = 0.9985) for diazinon; 0.23 and 8.14 μg g -1 ( r = 0.9959) for methyl parathion; 0.28 and 10.25 μg g -1 ( r = 0.9987) for methyl pirimiphos; 0.52 and 18.87 μg g -1 ( r = 0.9955) for malathion; 0.86 and 13.67 μg g -1 ( r = 0.9919) for ethion. The limits of quantification (equal to those of detection) were the lowest rates of ranges mentioned above for each compound. The extraction method showed approximately 95% recovery, with CV% < 15%. Although twenty-eight bean samples obtained in the southern region of the state of Minas Gerais,Brazil, were analyzed, they failed to match any of the OPPs under analysis. The absence of OPPs in the samples could be due to the degradation that occurred between the use of OPPs and bean commercialization, levels below the detection /quantification limits and the non-use of OPPs in bean cultivation.

Study for the Revision of Analytical Method for Tris (2,3-dibromopropyl) phosphate with Restriction in Textiles

The official analytical method for tris(2,3-dibromopropyl)phosphate (TDBPP), which is banned from use in textile products by the "Act on Control of Household Products Containing Harmful Substances", requires revision. This study examined an analytical method for TDBPP by GC/MS using a capillary column. Thermal decomposition of TDBPP was observed by GC/MS measurement using capillary column, unlike in the case of gas chromatography/flame photometric detector (GC/FPD) measurement based on a direct injection method using a capillary megabore column. A quadratic curve, Y=2572X(1.416), was obtained for the calibration curve of GC/FPD in the concentration range 2.0-100 μg/mL. The detection limit was 1.0 μg/mL under S/N=3. The reproducibility for repetitive injections was satisfactory. A pretreatment method was established using methanol extraction, followed by liquid-liquid partition and purification with a florisil cartridge column. The recovery rate of this method was ～100%. TDBPP was not detected in any of the five commercial products that this study analyzed. To understand the cause of TDBPP decomposition during GC/MS (electron ionization; EI) measurement using capillary column, GC/MS (chemical ionization; CI), GC/FPD, and gas chromatography/flame ionization detector (GC/FID) measurements were conducted. It was suggested that TDBPP might thermally decompose both during GC injection, especially through a splitless injection method, and in the column or ion sources. To attempt GC/MS measurement, an injection part comprising quartz liner was used and the column length was halved (15 m); thus, only one peak could be obtained.

Magnetic solid phase extraction combined with gas chromatography-flame photometric detection for the determination of organophosphorus pesticides in juice samples

A novel method for the determination of organophosphorous pesticides (OPPs) in fresh juice samples was developed. Fe3O4 @ P (St-co-MAA) magnetic microparticles were synthesized and modified with styrene (St) and methacrylic acid (MAA) by coating St and MAA on magnetic particles and characterized by a series of techniques. The results indicated that Fe3 O4 magnetic nanoparticles (MNPs) have been successfully modified with St and MAA. Based on the prepared FeO4 @ P (St-co-MAA) magnetic microparticles, a novel method of magnetic solid phase extraction (MSPE)-gas chromatography (GC)-flame photometric detection (FPD) was developed for the determination of OPPs. The extraction/desorption conditions of MSPE were optimized, and the analytical performance was evaluated under the optimal conditions. The limits of detection (LODs, S/N = 3) for target OPPs were in the range of 0.013-0.305 μg/L with the RSDs (n = 7) ranging from 3.1% to 8.8%. The enrichment factors varied from 406 to 951. The linear ranges were over three orders of magnitudes (R2 > 0.99) and the reproducibilities were 7.4%-14.5% (n = 5). Finally, the proposed MSPE-GC-FPD method was successfully applied to the analysis of the five OPPs in fresh tomato and strawberry juice samples, with the recoveries of target OPPs in the range of 85.4%-118.9% for the spiked samples. The proposed MSPE-GC-FPD method is featured with low cost, fast separation and high enrichment factor.