Gas Chromatography With Flame Photometric Detection Research Articles

Characterization of the Key Aroma Compounds in Three Truffle Varieties from China by Flavoromics Approach.

The volatile compounds of three different fresh-picked truffle varieties (Tuber sinensis, T1, Tuber sinoalbidum, T2 and Tuber sinoexcavatum, T3) were extracted by headspace solid-phase microextraction (HS-SPME). Separation and identification of volatile components and sulfur compounds were investigated by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC–MS) and gas chromatography with flame photometric detection (GC-FPD). The results showed that 44, 43 and 44 volatile compounds were detected in T1, T2 and T3 samples, respectively. In addition, 9, 10 and 9 sulfur compounds were identified in three samples by GC-FPD, respectively. Combining physicochemical and sensory properties, T1 presented fatty, green and rotten cabbage odor; T2 exhibited mushroom, sulfuric and musty odor notes; T3 had nutty, floral and roasted potato odor. Dimethyl sulfide, 3-methylbutanal, dimethyl disulfide, 3-octanone, bis(methylthio) methane, octanal, 1-octen-3-one, 1-octen-3-ol and benzeneacetaldehyde played indispensable roles in the overall aroma of three truffles. Finally, based on quantitative concentration in T1, odorous compounds (OAV) > 1 were mixed to recombine aroma, demonstrating that these key aroma compounds based on OAV can successfully recombine pretty similar aroma of each variety.

Application of a magnetic graphene nanocomposite for organophosphorus pesticide extraction in environmental water samples

A novel magnetic nanocomposite was prepared and applied for the extraction of organophosphorus pesticide residue (malathion, chlorpyrifos, isocarbophos, fenamiphos, profenofos) in environmental water by magnetic solid phase extraction. The magnetic nanocomposite was synthesized by coating Fe3O4 with silicon dioxide and then bonding with graphene oxide under the catalytic action of hydrazine hydrate. A residue analysis method for the determination of organophosphorus pesticides in environmental water was established via magnetic solid phase extraction with the nanocomposite as the sorbent, followed by gas chromatography with flame photometric detection (GC-FPD). Various experimental parameters affect extraction efficiency and must be optimized, such as the sorbent amount, the type and volume of desorption solvent, desorption time, desorption step, salt concentration and pH. Under the optimum conditions, a linear response was achieved for malathion and chlorpyrifos in the concentration range of 0.05 mg L−1–5 mg L−1. Other organophosphorus pesticides were quantified in a concentration range of 0.1 mg L−1–5 mg L−1, and the coefficient of correlations were between 0.996 and 1 for this method. The method was used to determine organophosphorus pesticides in river water and groundwater. The average recoveries ranged from 90.2% to 102.9%, with low relative standard deviations (RSD), and the limits of detection (LOD) were between 0.016 mg L−1 to 0.033 mg L−1 at a signal to noise ratio of 3. The method was efficient for the residue analysis of organophosphorus pesticides in water with easy operation, high sensitivity, and good precision.

Determination of propineb and its metabolites propylenethiourea and propylenediamine in banana and soil using gas chromatography with flame photometric detection and LC–MS/MS analysis

ABSTRACTA sensitive and specific method for the determination of propineb and its metabolites, propylenethiourea (PTU) and propylenediamine (PDA), using gas chromatography with flame photometric detection (GC-FPD) and LC–MS/MS was developed and validated. Propineb and its metabolite residue dynamics in supervised field trials under Good Agricultural Practice (GAP) conditions in banana and soil were studied. Recovery of propineb (as CS2), PDA and PTU ranged from 75.3 to 115.4% with RSD (n = 5) of 1.3–11.1%. The limit of quantification (LOQ) of CS2, PDA and PTU ranged from 0.005 to 0.01 mg kg−1, and the limit of detection (LOD) ranged from 0.0015 to 0.0033 mg kg−1. Dissipation experiments showed that the half-life of propineb in banana and soil ranged from 4.4 to 13.3 days. PTU was found in banana with a half-life of 31.5–69.3 days, while levels of PDA were less than 0.01 mg kg−1 in banana and soil. It has been suggested that PTU is the major metabolite of propineb in banana. The method was demonstrated to be reliable and sensitive for the routine monitoring of propineb and its metabolites in banana and soil. It also serves as a reference for the detection and monitoring of dithiocarbamates (DTCs) residues and the evaluation of their metabolic pathway.

New Study Concerning the Biodegradation of Dimethoate, Chlorpyrifos and Chlorfenvinphos in some Medicinal Plants

Herbal drugs are widely used in pharmaceutical industry due to their beneficial effects on human health. The current research was carried out to evaluate the organic pollutant degradation in the flower part of the plant after a foliar application of pesticides. Also, based on the fact that selected pesticides are highly toxic to bees, it is important to monitor the removal rate of the pollutant. Under laboratory conditions, the marigold and French flowers (Calendula Officinalis and Tagetes Patula) were spiked with a mix of organophosphorus insecticide, dimethoate, chlorpyrifos and chlorfenvinphos, where the first two substances are still used on Romanian territory. The samples were extracted at different time moments over 300 min after sprayed treatment in order to evaluate the concentration in flower. The analytes were quantified by using gas chromatography with flame photometric detection (GC-FPD) technique. The developed method ensures the quality and comparability of analytical results, with a good sensitivity in determining the analytes over the concentration range 5-250 �g/L.

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.

Degradability of Treated Ethion Insecticide by TiO2 Photocatalysis.

Ethion, an insecticide, is widely used with fruit and vegetable crops. This research studied the reduction and oxidative degradation of standard ethion by TiO2 photocatalysis. A standard ethion solution (1 mg L(-1)) was treated with different concentrations of TiO2 powder (5, 10, 20, 40 and 60 mg mL(-1)) for 0, 15, 30, 45 and 60 min. The amount of ethion residue was detected by gas chromatography with flame photometric detection (GC-FPD) and the concentration of anions produced as major degradation products was determined by Ion Chromatography (IC). The TiO2 photocatalysis efficiently reduced ethion concentrations, with the highest degradation rate occurring within the first 15 min of reaction. The reaction produced sulphate and phosphate anions. The TiO2photocatalysis reduced 1 mg L(-1) ethion to 0.18 mg L(-1) when treated with 60 mg mL(-1) TiO2 powder for 60 min. The lethal concentration (LC50) of standard ethion was also estimated and compared to the treated ethion. All treatments, especially 60 mg mL(-1) TiO2 powder, markedly detoxified ethion, as tested with brine shrimp (Artemia salina L.), with an LC50 value of 765.8 mg mL(-1), compared to the control of 1.01 mg mL(-1).

Development and validation of a shipboard system for measuring high-resolution vertical profiles of aqueous dimethylsulfide concentrations using chemical ionisation mass spectrometry

Environmental context Dimethylsulfide, a trace gas produced by oceanic plankton, is a key chemical species in the global cycles of sulfur and aerosols, with implications that span marine ecology to climate regulation. Knowledge of what governs dimethylsulfide production in the surface ocean depends on our ability to measure concentration changes over time and depth. We describe a sampling and analytical system that provides continuous shipboard measurements of dimethylsulfide concentrations in high-resolution vertical profiles. Abstract A sampling and analytical system has been developed for shipboard measurements of high-resolution vertical profiles of the marine trace gas dimethylsulfide (DMS). The system consists of a tube attached to a conductivity–temperature–depth (CTD) probe with a peristaltic pump on deck that delivers seawater to a membrane equilibrator and atmospheric pressure chemical ionisation mass spectrometer (Eq-APCIMS). This allows profiling of DMS concentrations to a depth of 50m, with a depth resolution of 1.3–2m and a detection limit of nearly 0.1nmolL–1. The seawater is also plumbed to allow parallel operation of additional continuous instruments, and simultaneous collection of discrete samples for complementary analyses. A valve alternates delivery of seawater from the vertical profiler and the ship’s underway intake, thereby providing high-resolution measurements in both the vertical and horizontal dimensions. Tests conducted on various cruises in the Mediterranean Sea, Atlantic, Indian, and Pacific Oceans show good agreement between the Eq-APCIMS measurements and purge and trap gas chromatography with flame photometric detection (GC-FPD) and demonstrate that the delivery of seawater from the underway pump did not significantly affect endogenous DMS concentrations. Combining the continuous flow DMS analysis with high-frequency hydrographic, optical, biological and meteorological measurements will greatly improve the spatial–temporal resolution of seagoing measurements and improve our understanding of DMS cycling.

Spatio-temporal variation of organotin compounds in seawater and sediments from Cape Town harbour, South Africa using gas chromatography with flame photometric detector (GC-FPD)

The spatio-temporal variation of two organotin compounds (OTCs) of tributyltin and triphenyltin in the seawater and sediment of Cape Town harbour was investigated. The organotin compounds were determined by GC-FPD following prior extraction with 0.02% tropolone. The concentration of OTCs varies for locations in Cape Town harbour. The concentration of OTCs in seawater ranges from 0.067±0.01 to 111.290±32.20×10−3μg/l for TBT while that of TPT ranges between between ND±SD and 23008.0±0.03×10−3μg/l respectively between locations. Relatively higher concentrations were measured for TBT and TPT during summer than in winter and spring seasons (p⩽0.05). Apparently, the observed high or low values recorded for TBT in Cape Town harbour could be the result of an increase or decrease in the traffic of ships and boats. TBT was detected in all the sediment samples analysed except for location 9 (entrance to harbour), the two control sites (which are located far away from the inner harbour where boating activities are taking place), and location 12 (Robinson dry dock 2) where the samples were not at all found. For the control sites, antifouling compounds TBT and TPT were not detected throughout except for TBT that was found in control A during summer. The seasonal variation of OTC abundance in sediment was also investigated. The results indicated that TBT is present throughout the seasons but is predominantly present in this order summer>winter>spring.

Dissipation rate of different commercial formulations of malathion applied to tomatoes

Dissipation of malathion following one application of different commercial formulations of Malathion 57% EC, Malathiom-kemanova 57% EC, Malatox 57% EC and Actathion 57% EC were estimated by employing optimized QuEChERS technique and gas chromatography with flame photometric detector (GC-FPD). The average recoveries of malathion on tomato for fortification levels of 0.01 and 1.0 mg kg−1 were observed to be 91.7 and 96.9%, respectively. The LOQ for tomato was found to be 0.1 μg kg−1. Malathion residue was dissipated below its maximum residue limit (MRL) of 0.5 after 14 days. Half-life and preharvest interval (PHI) were calculated to be 2.88 (13), 3.59 (14), 3.58 (11), 3.21 (11) days for Actathion, Malatox, Malathiom-kemanova and Malathion, respectively. These data could provide guidance for the proper and safe use of malathion on tomato. Key words: Dissipation, malathion, formulation, tomatoes, QuEChERS

Oxidative Degradation and Detoxification of Chlorpyrifos by Ultrasonic and Ozone Treatments

Chlorpyrifos is an organophosphate pesticide, widely used on fruit and vegetable crops. Here, we report on the oxidative degradation of standard chlorpyrifos by individual and combined effects of ultrasonic irradiation (US) and ozone (O3). A standard chlorpyrifos solution (1 mg L-1) was treated with 1 MHz US, O3 and its combination (US/O3) for 0, 10, 20, 30, 40, 50 and 60 min. Reduction of residual chlorpyrifos was determined by gas chromatography with flame photometric detection (GC-FPD) while ion chromatography (IC) was used to determine the concentration of anions as major degradation products. US/O3 combined treatment had a synergistic effect in reducing chlorpyrifos concentrations, with the highest rate of degradation occurring within the first 10 min. Moreover, chloride, nitrate and sulphate anion concentrations obtained from chlorpyrifos treated with US/O3 combination, were significantly higher, compared to those treated with ultrasonic irradiation or ozone alone. A sharp decrease in pH from 7.46 to 4.49 was also observed for the combined treatment. The degradation pathway of chlopyrifos, after treatment, was confirmed by gas chromatography mass spectrometry (GC-MS). All treatments resulted in similar main fragment ions at m/z 351, 314, 286, 258, 197 and 97. The lethal concentration (LC50), over a series (0-100) mg L-1 of standard chlorpyrifos solutions, was estimated and compared to the treated chlorpyrifos. All the treatments directly detoxified chlorpyrifos with LC50 values against brine shrimps (Artemia salina L.) of 10.21, 103.54 and 234.09 mg L-1 for US, O3 and US/O3 treated chlorpyrifos solutions, respectively. The brine shrimp test showed highest toxicity in standard chlorpyrifos with an LC50 value of 7.22 mg L-1.

One-step extraction for gas chromatography with flame photometric detection of 18 organophosphorus pesticides in Chinese medicine health wines

An easy, rapid and selective gas chromatography with flame photometric detection (GC-FPD) method was established for simultaneously determining 18 organophosphorus pesticides (OPPs) in 80 Chinese medicine (CM) health wines. This method was based on a simple one-step extraction procedure using a little solvent without any further cleanup steps. The optimized extraction solvent for the pesticides is acetone:dichloromethane (1:1, V/V) with extraction recovery of 79.0–109.1% and relative standard deviation (RSD) of 0.36–12.68%, respectively. The limits of detection (LODs) of the established GC-FPD method for all investigated pesticides ranged from 1 to 15ngmL−1 and limits of quantification (LOQs) from 4 to 50ngmL−1. Out of all 80 CM health wines, 18 OPPs were found in 8 samples at low concentrations of 8.2–37.9ngmL−1. These pesticides were successfully confirmed by GC–MS. This is the first report of determining OPPs in CM health wines, providing references for monitoring the quality of CM health wine in routine analysis.

Optimisation of a fast DMS sensor (FDS) for real time quantification of dimethyl sulfide production by algae

Production of dimethyl sulfide (DMS) from marine samples is often quantified using gas chromatography techniques. Typically, these are labour intensive and have a slow sample turnover rate. Here we demonstrate the use of a portable fast DMS sensor (FDS) that utilises the chemiluminescent reaction of DMS and ozone to measure DMS production in aqueous samples, with a maximum frequency of 10 Hz. We have developed a protocol for quantifying DMS production that removes potential signal interference from other biogenic trace gases such as isoprene (2-methyl-1,3-butadiene) and hydrogen sulfide. The detection limit was 0.89 pM (0.02 ppbv) when using a DMS standard gas mixture. The lowest DMS production rates quantified with the FDS and verified using conventional gas chromatography with flame photometric detection (GC-FPD) were around 0.01 nmol min−1. There was a strong correlation in DMS production when comparing the FDS and GC-FPD techniques with a range of marine samples (e.g., r2 = 0.94 for Emiliania huxleyi). However, the combined dataset showed the FDS measured 22% higher DMS production than the GC-FPD, with the differences in rates likely due to interfering gases, for example hydrogen sulfide and isoprene. This possible overestimation of DMS production is smaller than the two-fold difference in DMS production between day and night samples from a culture of E. huxleyi. The response time of the instrument to changes in DMS production is method dependent (e.g., geometry of incubation vessel, bubble size) and was approximately 4 min under our conditions when using a culture of E.huxleyi (800 ml) with aeration at 100 ml min−1. We suggest the FDS can reduce sample handling, is suitable for short- and long-term measurements of DMS production in algal cultures, and will widen the range of DMS research in marine environments.

Specific accumulation of organotin compounds in tissues of the rock shell, Thais clavigera

Concentrations of organotin compounds (butyltins and phenyltins) were determined in gonad, accessory sex organs, penis, digestive gland, kidney, radula with sac, oesophagus with crop, stomach, hypobranchial gland, rectum, mantle, osphradium, ctenidium, heart, salivary gland, head ganglia and muscle of imposex-exhibiting female and male rock shells (Thais clavigera), by gas chromatography with flame photometric detection (GC-FPD). Different tissue distributions were observed between butyltin and phenyltin compounds. More than 1000 ng TBT/g wet wt. were observed in ovary, digestive gland, kidney, heart, ctenidium, osphradium, stomach, head ganglia and penis, of both imposex-exhibiting females and males. More than 1000 ng TPT/g wet wt. were found in almost all tissues of both sexes. Approximately one-third or more of total TBT was accumulated in the digestive glands of both females and males, respectively. Meanwhile, approximately 40–50% and one-half of total TPT accumulated in the digestive glands of females and males, respectively.

Effects of the processing steps on parathion levels during honey production and parathion removal by macroporous adsorption resins

The effects of different steps in honey production on parathion levels and parathion removal from honey using macroporous adsorption resins (MARs) were investigated in this study. Parathion residues were quantified by gas chromatography with flame photometric detection (GC-FPD) after each processing step including preheating, filtration, vacuum concentration and pasteurization. The four processing steps could reduce the initial parathion level of 2.77 to 2.73, 2.53, 2.30 and 2.23 mg/kg, respectively, and the total loss of parathion was only 19%. Meanwhile, different types of MARs were used in parathion adsorption, and the results from removal experiments showed that LS-803 resin was more efficient in removing parathion from honey than other resins LS-903, LSA-21 and LSA-900B, with the adsorption rate of above 90%.

Cloud point extraction coupled with ultrasonic-assisted back-extraction for the determination of organophosphorus pesticides in concentrated fruit juice by gas chromatography with flame photometric detection

A new method for the determination of nine organophosphorus pesticides (OPPs): Dichlorvos, methamidophos, acephate, diazinon, dimethoate, chlorpyrifos, parathion-methyl, malathion and parathion-ethyl in concentrated fruit juice was developed using the cloud point extraction coupled with ultrasonic-assisted back-extraction prior to gas chromatography with flame photometric detection (GC-FPD) analysis. The parameters and variables that affect the extraction were investigated. Under optimum conditions: a solution containing 6% (W/V) polyethylene glycol 6000 (PEG 6000) and 20% (W/V) Na2SO4 for the extraction of the OPPs. The coacervation phase obtained was back extracted with ethyl acetate. The upper ethyl acetate solution was centrifugated simply for further cleanup for the sake of automatic injection. A preconcentration factor of 50 was obtained for these nine pesticides. Using this method, the limits of detection (LOD) and limits of quantification (LOQ) were in the range of 0.5–3.0 and 1.5–9.0μgkg−1 in concentrated fruit juice, respectively; the relative standard deviations (RSD) were <9%.

Effects of the processing steps on chlorpyrifos levels during honey production

The effects of different steps in honey production on chlorpyrifos levels were investigated. Chlorpyrifos residues were quantified by gas chromatography with flame photometric detection (GC-FPD) after each stage including preheating, filtration, vacuum concentration and pasteurization. The total loss of chlorpyrifos in honey was about 70% during the processing. Among these four stages, filtration and vacuum concentration had the significant effects on chlorpyrifos level, and the mean losses were 21.3 and 60.9, respectively.

Degradation behaviour of methamidophos and chlorpyrifos in apple juice treated with pulsed electric fields

Apple juice (13 °Brix) spiked with methamidophos and chlorpyrifos (2–3 mg/l of each compound) was treated by pulsed electric fields (PEF), and pesticide residues were quantified by gas chromatography with flame photometric detection (GC-FPD). Results showed that electric field strength (8–20 kV/cm) and pulse number (6–26 pulses) have significant effects on the degradation of methamidophos and chlorpyrifos. PEF treatment is effective for the degradation of methamidophos and chlorpyrifos residues in apple juice, and chlorpyrifos is much more labile to PEF than methamidophos. An increase in either pulse number or electric field strength could speed the degradation of methamidophos and chlorpyrifos, and the kinetics equations and related parameters quantitatively characterized the degradation behavior of the pesticides. The exponential model better fits the experimental data for all treatments than the linear model.

Determination of Organophosphorus Pesticides in Soybean Oil, Peanut Oil and Sesame Oil by Low-Temperature Extraction and GC-FPD

A low-temperature clean-up method for residue determination was developed and validated for 14 organophosphorus pesticides in soybean oil, peanut oil and sesame oil by gas chromatography with flame photometric detector (GC-FPD). A different matrix influenced the response and retention time of pesticides. Hence matrix-matched calibration standards were used to counteract the matrix effect. The pesticide responses in blank samples of soybean oil, peanut oil and sesame oil were within the linear range of 0.02–1 mg kg−1 and the correlation coefficients were higher than 0.9989. Average recoveries obtained from different oil samples at three fortified levels were higher than 50% with relative standard deviations (RSDs) of less than 15%. The limit of detections (LODs) of studied pesticides ranged from 2 to 5 μg kg−1. Thirty-nine commercial samples were analyzed, and the results were confirmed by gas chromatography–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode.

Application of Solvent Sublation for the Determination of Organophosphorous Pesticides in Vegetables by Gas Chromatography with a Flame Photometric Detector

An effective method for separating and enriching organophosphorous pesticides (OPPs) from vegetables by solvent sublation and the OPPs determination by gas chromatography with flame photometric detector (GC-FPD) has been developed. The effects of organic solvent, nitrogen flow rate, pH of the solution, sublation time etc. on the sublation efficiency of OPPs were investigated in detail, and the optimal conditions of solvent sublation were selected. The floated product of vegetables in the optimal conditions was determined by GC-FPD. The limits of detection (LODs) ranged from 1.2 microg kg-1 (for dimethoate) to 3.5 microg kg-1 (for chlorpyrifos). The recoveries of spiked vegetable samples were from 81.3 to 98.9%, and RSD values were from 0.46 to 4.83%. The results show that this method is simple, sensitive and rapid.

Optimisation of pressurised liquid extraction for elimination of sulphur interferences during determination of organotin compounds in sulphur-rich sediments by gas chromatography with flame photometric detection

A simple method for species-selective analysis of organotin compounds (OTCs) (butyl and phenyl) in sediments was developed. The sample preparation procedure was specifically optimised for sulphur-rich sediments to eliminate interferences from elemental sulphur and organosulphur compounds. Tin species were extracted from sediment samples using pressurised liquid extraction technique (PLE), ethylated - with simultaneous extraction to isooctane - in aqueous phase with sodium tetraethylborate (NaBEt(4)) and separated/detected by gas chromatography with flame photometric detection (GC-FPD). PLE operational variables (extraction temperature and pressure, solvent composition and number of static extraction steps) and extract handling routine were fine-tuned to minimise the amount of extracted interferents while keeping OTCs recovery at an acceptable level. Best results were obtained after extraction of sediment samples with methanol/water (75% v/v methanol) solution of acetic acid/sodium acetate with tropolone addition (0.6 g l(-1)). Derivatisation of low temperature, high-pressure (50 degrees C, 13.8 MPa) extracts gives isooctane extracts which are clean enough to be directly analysed by GC-FPD without any further cleanup. Interferences from elemental sulphur were completely eliminated while concentrations of other interferents were reduced to the level not impairing quantitation of OTCs under the study. No negative effects in terms of chromatographic column deterioration were observed after repeated injections of such extracts. Two certified reference materials, BCR646 and PACS-2, were analysed to assess performance of the method. Recoveries of all OTCs under the study, except MBT, were in the range of 91-114%. MBT extraction efficiency was low (34-47%) therefore the method is unsuitable for precise determinations of this compound.