Flame Photometric Detector Research Articles

Characterization of the major aroma-active compounds in peach (Prunus persica L. Batsch) by gas chromatography–olfactometry, flame photometric detection and molecular sensory science approaches

Aroma profiles and aroma-active compounds of “Yulu” peach from Fenghua (the peach known for the best flavor and quality in China) were investigated by headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), gas chromatography–olfactometry (GC–O), gas chromatography–mass spectrometry (GC–MS), and flame photometric detection (FPD). The combination of these methods improved the analysis and identification of aroma substances compared to the combination of a single aroma extraction method and GC–MS. A total of 85 aroma-active compounds, including 10 sulfur compounds were detected. Methional, methyl 3-(methylthio)propionate, methionol, and benzothiazole were first detected in peaches. These aroma compounds cannot only supplement the database of aroma substances of peaches, but also provide data support for traceability of the origins of “Yulu” peaches. In addition, the odor activity value (OAV) was used to identify the contributions of the most important compounds. The results indicated that hexanal, 3-methylbutanal, (E)-2-hexen-1-ol, 3-mercaptohexyl acetate, (E,E)-2,4-decadienal, 2-methylpropanal, γ-decalactone, 2-methylbutanal, theaspirane, and δ-decalactone were the key aroma-active compounds. The key characteristic aroma components were further ascertained by aroma reconstitution and omission experiments, which showed that the fruity, floral, sulfur, and sour notes could be well simulated. Finally, the perceptual interactions between different sulfur compounds and fruity recombination (FR) were explored. 3-mercaptohexanol and 4-methyl-4-mercaptopentan-2-one could significantly decrease the threshold of FR. The possible reason was that these two sulfur compounds had synergistic effects with the aroma compounds in FR, with the U model confirming the results of these synergistic effects. The perceptual interactions provide a basis for the regulation of characteristic fruity aroma of peach products.

Exposure to Organophosphate and Neonicotinoid Insecticides and Its Association with Steroid Hormones among Male Reproductive-Age Farmworkers in Northern Thailand.

Several studies indicated organophosphate (OP) and neonicotinoid (NEO) insecticides are endocrine disruptors; however, data are scarce. This cross-sectional study recruited 143 male farmworkers aged 18–40 years in Fang district, Chiang Mai province, northern Thailand. OP exposure was assessed by measuring urinary dialkylphosphate (DAPs) using a gas-chromatography flame photometric detector. Urinary NEOs, their metabolites (NEO/m) and serum steroid hormones were measured using liquid chromatography–tandem mass spectrometry. Characteristics of participants were determined by face-to-face interviews. DAPs and five NEO/m were detected in more than 60% of samples. The concentration of diethylphosphate was highest among DAP metabolites (geometric mean concentration (GM: 23.9 ng/mL) and the concentration of imidacloprid (IMI) was highest among NEO/m (GM: 17.4 ng/mL). Linear regression models showed that the IMI level was positively associated with testosterone, dehydrocorticosterone (DHC) and dehydroepiandrosterone (DHEA) levels. Imidacloprid-olefin and DHEA levels were positively associated. Thiamethoxam (THX) were inversely associated with DHC and deoxycorticosterone levels. Clothianidin (CLO), THX and N-desmethyl-acetamiprid levels were positively associated with the androstenedione level. CLO and THX levels were inversely associated with the cortisone level. In conclusion, the association between NEO insecticides exposure and adrenal androgens, glucocorticoids and mineralocorticoids, suggest potential steroidogenesis activities. Our findings warrant further investigation.

Persistence and diffusion behaviour of chlorpyrifos in five different species of vegetables: A comparative analysis

Understanding of pesticide persistence and diffusion on the fresh vegetables are extremely important in food safety and decontamination process. In this study, we examine the persistence and diffusion behaviour of chlorpyrifos pesticide in five different species of vegetables. The chlorpyrifos pesticide was spiked on the vegetable surfaces and the extracted samples from peel and tissues were subjected to Gas Chromatography equipped with a Flame Photometric Detector (GC-FPD). Further, the chlorpyrifos diffusion behaviour was compared with the osmotic potential, shear strength, cuticular chemical profile and microstructure of peel surface of vegetables. The persistence analysis results revealed that chlorpyrifos level was decreased in peel surface and diffusion rate was increased in inner tissue with respect to durations. Within 72 h exposure, chlorpyrifos reached 0.7 cm depth into the inner tissue of vegetables. Significant level of chlorpyrifos diffusion with P ≤ 0.05 was observed in beetroot (2.47%), khon khol (1.46%) and brinjal (0.92%) compared to cucumber and potato. Remarkably, there was no direct linkage between the chlorpyrifos diffusion rate, osmotic potential and toughness of vegetables. In addition, the Gas Chromatography Mass Spectroscopy (GC-MS) and Scanning Electron Microscopy (SEM) analyses revealed that epicuticular surface microstructure and chemical profiles were not correlated with the chlorpyrifos diffusion in all the tested vegetables. The study results concludes that chlorpyrifos diffusion is vegetable species specific and it is highly variable between the species.

Monitoring and Statistical Analysis of Formation of Organochlorine and Organobromine Compounds in Drinking Water of Different Water Intakes.

The main drawback of drinking water chlorination involves the formation of quite hazardous disinfection by-products (DBPs), represented mainly by halogenated species. Based on the authors’ monitoring data since 2002, the prevalence of chlorine over bromine in the composition of volatile DBPs was shown for the drinking water in Ufa (Russia). However, the situation was completely reversed in the case of semi-volatile DBPs. The principal goal of the present study involved rationalization of the results of the long-term monitoring. Gas chromatography–mass spectrometry (GC-MS) was used for the qualitative and quantitative analysis of volatile DBPs. Identification of semi-volatile compounds was carried out with GC-MS, while gas chromatography with an atomic emission detector (GC-AED) was used for their quantification. A significant contribution of oxygen to the composition of semi-volatile compounds proves the decisive role of the dissolved organic matter oxidative destructive processes. Statistical analysis revealed notable linear correlations for trihalomethane and haloacetic acid formation vs. chlorine dose. On the contrary, halogenated semi-volatile products do not demonstrate any correlations with the water quality parameters or chlorine dose. Principal component analysis (PCA) placed them into separate groups. The results allow for proposing that formation of the organohalogenated species involved the fast penetration of bromine into the humic matter molecules and, further, their oxidative destruction by active chlorine.

The use of a digital micromirror array as a temporal gate and spatial-filtering device for laser-induced breakdown spectroscopy and laser ablation molecular isotopic spectrometry

A digital micromirror array (DMMA) is used in a simple and inexpensive approach for spatially resolved temporal gating of atomic emission detection in laser-induced breakdown spectroscopy (LIBS). Selected mirrors in the array are actuated at a time delayed from the primary laser pulse, permitting optical gating with a response time of 160 ns while using a conventional CCD detector. Detector gating is shown to decrease noise from short-lived spectroscopic background (both continuum and N II from air), improving signal-to-background ratios by 22-times for selected samples and emission lines. The utility of rapid temporal gating is also demonstrated for the optical detection of isotopes using the laser-ablation molecular isotope spectrometry (LAMIS) experiment. Optical temporal gating and spatial filtering are used to isolate regions of the laser-induced plasma, enhancing signal from molecular emission. The potential of the simple technique for use in field-portable LIBS and LAMIS experiments is explored.

Atomic emission detector with gas chromatographic separation and cryogenic pre-concentration (CryoTrap–GC–AED) for atmospheric trace gas measurements

Abstract. A gas detection system has been developed, characterized, and deployed for pressurized gas-phase sample analyses and near-real-time online measurements. It consists of a cryogenic pre-concentrator (CryoTrap), a gas chromatograph (GC), and a new high-resolution atomic emission detector (AED III HR). Here the CryoTrap–GC–AED instrumental setup is presented, and the performance for iodine (1635 ± 135 counts I atom−1 pptv−1), sulfur (409 ± 57 counts S atom−1 pptv−1), carbon (636 ± 69 counts C atom−1 pptv−1), bromine (9.1 ± 1.8 counts Br atom−1 pptv−1), and nitrogen (28 ± 2 counts N atom−1 pptv−1) emission lines is reported and discussed. The limits of detection (LODs) are in the low parts per trillion by volume range (0.5–9.7 pptv), and the signal is linear to at least 4 orders of magnitude, which makes it a suitable method for diverse volatile organic compound (VOC) measurements in the atmosphere, even in remote unpolluted regions. The new system was utilized in a field study in a boreal forest at Hyytiälä, Finland, in late summer 2016, which made monoterpene measurements possible among other VOCs. Furthermore, pressurized global whole-air samples, collected on board the Lufthansa Airbus A340-600 IAGOS–CARIBIC aircraft in the upper troposphere and lower stratosphere region, were measured with the new setup, providing data for many VOCs, including the long-lived organosulfur compound carbonyl sulfide.

Enhancement of Chemiluminescence Intensity of S2* in Non-premixed Hydrogen Microjet Flame in the Photometric Detector for Sulfur Detection.

A transparent quartz rod (q) placed vertically on top of a non-premixed hydrogen microjet flame in a flame photometric detector (qFPD) was developed and evaluated for sulfur detection. The microjet flame burned around the quartz rod because of Coanda effect, forming an extended downstream flame zone with a relatively low temperature between 550 and 650 °C, which is favorable to the formation of S2*. The emission intensity of S2* and the signal-to-noise ratio (SNR) of sulfur response were enhanced 2.6- and 2.1-fold, respectively. It was found that the quartz rod of diameter 4 mm with a tip shape of semicircle placed 6 mm above the nozzle yielded the highest SNR. The limits of detection (LOD) for seven kinds of tested sulfur-containing compounds of qFPD were 0.3-0.5 pg S s-1, which is 5-7 times better than that of commercially available FPD detectors (LOD: 1.6-2.8 pg S s-1). The selectivity of sulfur over carbon was 105 on qFPD when the SNR for the mass flow rate of S and C atoms was ∼3 times. It was the first time that a quartz rod was used vertically on top of a microjet hydrogen-rich flame in FPD to enhance the chemiluminescence of S2* and improve the LOD down to 0.3-0.5 pg S s-1.

Are chewing sticks effective in decreasing oral malodour? A bioanalytical evaluation

‘Bad breath’ or ‘Halitosis’ is of significant concern to majority of the population resulting in various physiological and psycho-social effects. Bad breath is caused by Volatile sulphur Compounds (VSCs) formed through microbial degradation of proteinaceous material in the oral cavity. The most common of these VSCs are hydrogen sulphide (H2S), methyl mercaptan (CH3SH) and dimethyl sulphide (CH3)2S. The use of herbal chewing sticks for oral hygiene has been in practice traditionally among Indian population. Fresh twigs of neem, miswak, babool, arjun etc. are used of which, neem and miswak are more popular. Current study evaluates the efficacy of the use of chewing sticks made from neem (Azadirachta indica) and miswak (Salvadora persica) in decreasing oral malodor and compares the efficacy with that of using marketed toothpaste. Decrease in VSCs level can be a good indicator to evaluate the suitability of using herbal chewing stick in the management of oral hygiene. Present study has been conducted on voluntarily consented, healthy human male subjects (n = 6) with VSCs > 300 ng/mL in a three-way crossover, randomized sequence, with two days of washout period as interval between treatments. VSCs from mouth air are measured by Gas Chromatography (GC) fitted with a Flame photometric detector (FPD). The variations in VSCs before and after use of two types of chewing sticks are statistically compared with those after the use of marketed toothpaste.

Ecological and Human Health Risk Assessment of Pesticide Residues in Fish and Sediments from Vea Irrigation Reservoir

The low yield of food production ascribed to harm caused by pests has led to the application of pesticides to food crops. Pesticide residues from the application on crops are mostly found in foods that can cause diseases for consumers of such products. A total of 37 pesticide residues consisting of 15 organochlorines (OC), 13 organophosphorus (OP) and 9 synthetic pyrethroids (SP) were determined. The QuEChERS method was exploited for extraction and clean-up. Gas Chromatograph was used for detection and quantification which was equipped with an electron capture detector and pulse flame photometric detector. The results showed that the mean concentrations of pesticides in fish ranged from 0.007 mg·kg-1 to 1.026 mg·kg-1 for OCs, 0.002 mg·kg-1 to 0.190 mg·kg-1 for OPs and 0.004 mg·kg-1 to 0.032 mg·kg-1 for SP. Sediments have mean concentrations ranged from 0.005 mg·kg-1 to 1.207 mg·kg-1 for OCs. OP ranges from 0.002 mg·kg-1 to 0.399 mg·kg-1 and 0.003 mg·kg-1 to 0.202 mg·kg-1 for synthetic pyrethroids. Maximum Residue Limits were exceeded in both fish and sediment samples except for malathion, fenitrothion, profenofos, gamma-chlordane, and deltamethrin. Exposure in children ranged from 4.60 × 10-6 mg·kg-1·d-1 to 2.36 × 10-3 mg·kg-1·d-1 and in adults it is from 1.97 × 10-6 mg·kg-1·d-1 to 1.01 × 10-3 mg·kg-1·d-1. Health risk estimation revealed a non-cancer risk potential of β-HCH in sediment and aldrin and p,p'-DDE in fish. Carcinogenic risk assessed for organochlorine pesticide residues indicates cancer benchmark concentrations greater than 10-4 to 10-6 threshold for acceptance.

Molecular Characteristics of Light Cycle Oil Hydrodesulfurization over Silica-Alumina-Supported NiMo Catalysts.

A detailed understanding of the catalytic upgrading of light cycle oil (LCO) is important to achieve effective deep hydrodesulfurization (HDS) when LCO is mixed with straight run gas oil in the diesel pool. Herein, HDS of polyaromatic-rich LCO was studied at the molecular level over three NiMo catalysts on silica–alumina supports, which were synthesized on the pilot scale using different silica/alumina mixing procedures. Gas chromatography with atomic emission detection and two-dimensional gas chromatography with time-of-flight mass spectrometry were used to evaluate the HDS performance through determining the feed and product compositions, respectively, at the molecular level. Furthermore, the textural properties of the catalysts were evaluated using Raman spectroscopy, transmission electron microscopy, and the temperature-programmed desorption of NH3. The performance of the best catalyst was attributed to its higher content of octahedrally coordinated Mo oxide species, a lower number of layered stacks, and the more acidic sites on the surface. In addition, the hydrotreating reactivity of various family groups in LCO over the catalyst was investigated.

N,N-Dichlorobenzyl amine: An effective decontaminant for highly toxic chemical warfare agents sulfur mustard and VX

The chemical decontamination of vesicant, bis(2-chloroethyl)sulfide (Sulfur Mustard, SM) and nerve agent O-ethyl S-2-(N,N-diisopropylaminoethyl) methylphosphonothiolate (VX) has been achieved by an operationally simple method by using a new positive chlorine bearing reagent N,N-dichlorobenzylamine. Deactivation of these highly toxic chemical warfare agents has been achieved in acetonitrile-water medium. Before attempting the reactions on these highly toxic real agents, the reagent has been successfully tested for its decontaminating efficiency on the non-toxic simulants (2-chloroethyl phenyl sulfide, a simulant of Sulfur Mustard and O,S-diethyl methylphosphonothioate, simulant of VX). Progress of the decontamination reactions have been monitored by gas chromatography coupled with a flame photometric detector working in sulfur detection mode (GC-FPD(S)), 1H and 31P{1H} NMR spectroscopy. The products obtained after decontamination of Sulfur Mustard (SM) and VX have been thereafter identified by GC-MS technique. This reagent has been found to be highly advantageous over earlier reported decontaminating reagents in terms of - ease of preparation, cost effectiveness, stability, good shelf life and instantaneous conversion of both SM and VX into nontoxic products at room temperature.

Characterization of the key aroma compounds in Laoshan green teas by application of odour activity value (OAV), gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-qMS)

To investigate the key aroma compounds in Laoshan green teas (Huangshan (S1), Changling (S2), and Fangling (S3)), gas chromatography-mass spectrometry-olfactometry (GC-MS-O), a flame photometric detector (FPD), odor activity value (OAV), and comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-qMS) were employed. A total of 50 aroma compounds were perceived and 24 compounds were identified as important compounds related to OAV, such as dimethyl sulfide (OAV: 126–146), skatole (OAV: 27–50), furaneol (OAV: 8–27), (Z)-jasmone (OAV: 16–23), 2-methylbutanal (OAV: 15–22), and 3-methylbutanal (OAV: 68–87). Furthermore, the S-curve method was used to research the effect of aroma compounds on the threshold of aroma recombination (AR). The AR thresholds decreased from 3.8 mL to 0.45, 0.66, 0.93, 0.95, 0.75, 1.09, 3.01, and 2.57 mL after addition of eight compounds (skatole, furaneol, (Z)-jasmone, α-damascenone, sclareololide, dihydroactinidiolide, vanillin, and δ-valerolactone), indicating that those compounds (OAV >1) were contributors to the overall aroma of Laoshan teas.

Method development for the determination of Synthetic Musks and Organophosphorus Pesticides in Human Adipose Tissue

Synthetic musks and organophosphorus pesticides represent a potential risk to the human health since exposure can lead to distinct types of carcinogenesis and endocrine disorders. These are lipophilic compounds as such, prone to deposit and persist in fat tissues, mainly in adipose tissue. Very few studies have reported on the occurrence and accumulation profile of these contaminants in human adipose tissue.Analytical methods for the detection and quantification of synthetic musks and organophosphorus pesticides in adipose tissue are lacking. In this study, the efficacy of different extraction with ultrasonic homogenizer and dispersive solid-phase extraction (d-SPE) clean-up methods were evaluated in human adipose tissue. The relative sample clean-up was assessed by measurement of total lipid content. The quantification of four synthetic musks and six organophosphorus pesticides were performed by gas chromatography (GC) mass spectrometry (MS) and flame photometric detection (FPD), respectively.The d-SPE clean-up with 50 mg PSA, 150 mg MgSO4, 100 mg C18EC and 50 mg Z-Sep provided the most effective clean-up, removing the greatest amount of interfering substances including lipids and simultaneously ensuring good chromatographic separation and recoveries. Method detection limits were between 4 to 9 ng/g for synthetic musk and 1 to 7 ng/g for organophosphorus pesticides in adipose tissue. The proposed method was applied to adipose tissue of obese patients and positive samples were confirmed with GC tandem mass spectrometry. Galaxolide was found in all the samples tested with concentrations ranging from 0.08 to 0.5 μg/g of adipose tissue. No other synthetic musk studied was detected. Organophosphorus pesticides were not found in the analysed samples.The developed analytical procedures were successful and can easily be applied to biomonitoring these compounds in human adipose tissue.

Characterization of aroma-active compounds and perceptual interaction between esters and sulfur compounds in Xi baijiu

The aroma-active compounds of three Xi baijiu samples (Xijiulan, Y1, Xijiuyinxiangguizhou, Y2 and Xijiuyinzhi, Y3) were analyzed by gas chromatography–olfactometry (GC–O), GC–flame photometric detection (FPD) and odor activity value (OAV). The results indicated that a total of 92 aroma compounds were determined, including 16 sulfur compounds. Furthermore, 2-methyl-3-furanthiol (OAV: 31–220), 3-mercapohexyl acetate (OAV: 1870), dimethyl trisulfide (OAV: 333–400), 3-mercaptohexanol (OAV: 34–36), β-damascenone (OAV: 1317–1342), 2-butylfuran (OAV: 629–672), ethyl 3-methylbutanoate (OAV: 655–899), ethyl hexanoate (OAV: 687–729), and ethyl octanoate (OAV: 1164–1362) exhibited much higher OAVs and aroma intensities (AIs) than other compounds. Finally, the perceptual interactions between five sulfur compounds and six esters were studied using Feller’s additive model in Y2. Among the 30 binary mixtures, 12 groups showed an additive effect, 4 groups exhibited a synergistic effect, and 14 groups exerted a masking effect. These data indicated that dimethyl disulfide and 2-methyl-3-furanthiol had masking and additive effects on the aroma of esters.

Molecularly imprinted polymers immobilized on graphene oxide film for monolithic fiber solid phase microextraction and ultrasensitive determination of triphenyl phosphate

Triphenyl phosphate (TPhP), a typical model of organophosphorus flame retardants (OPFRs), has been regarded as emerging environmental contaminants of health concern. In this study, TPhP molecularly imprinted polymers immobilized on graphene oxide (GO) film (TPhP-MIPs/GO) monolithic fiber for direct immersion solid phase microextraction (DI-SPME) was fabricated and evaluated. Compared with TPhP molecularly imprinted polymers (TPhP-MIPs) monolithic fiber, TPhP-MIPs/GO fiber had bigger extraction capacity, stronger hydrophilicity and faster mass transfer rate. Furthermore, TPhP-MIPs/GO fiber displayed excellent selectivity for TPhP among its structure analogues. It was thermally stable up to 320 °C so that it can withstand the high temperature of gas chromatography (GC) injection port for desorption and detection by flame photometric detector (FPD). Under optimal conditions, TPhP-MIPs/GO-SPME-GC/FPD method was developed by yielding satisfactory ultralow limit of quantification (0.4 ng L−1); linearity (≥0.99), good intra- and inter-day precision for a single fiber and fiber-to-fiber reproducibility. The method was applied for the determination of TPhP in environmental water and the relative recoveries were found to be in the range from 70 to 110%. TPhP was detected in three out of four environmental water samples at concentration levels from 0.04 to 0.12 ng mL−1, illustrating light pollution of TPhP in most environmental water.

Multiresidue determination of pesticide in fishery products by a tandem solid-phase extraction technique

In order to simplify the survey of pesticide (including carbamate, organochlorine, organophosphate and synthetic pyrethroid pesticides) residues in fishery products (including bivalve, crustacean, fish and cuttlefish), multiresidue determination methods were developed through a solid phase extraction (SPE) technique. In the present procedures, samples were extracted with acetonitrile except for bivalve and cuttlefish samples. Mixed solvent of water, acetone and acetonitrile was added to bivalve prior to homogenization, whereas water was needed in cuttlefish samples for blending. For both kinds of sample, an additional procedure of salting-out was needed during extraction. Tandem SPE cartridges of C18 and aminopropyl, using acetonitrile as the only solvent, were used to clean up extracts from either method. A total of 91 pesticides in four major pesticide groups were tested in this study. Gas chromatography (GC, equipped with electron capture detector and flame photometric detector) and high-performance liquid-chromatography (HPLC) equipped with fluorescence detector were used for analysis. The validation of the method was evaluated for each fishery product using samples spiked with all pesticide standards at three concentration levels. The results indicated percentage of recovery ranged from 60% - 120% and coefficients of variation < 20% for all but 10 of the pesticides analyzed (including 1-naphthol, 3-hydroxy carbofuran, aldicarb sulfoxide, heptachlor, trifuralin, acephate, dichlorvs, methamidophos, monocrotophos and omethoate). Residue extraction techniques described in this report are rapid and suitable for screening of pesticide residues in monitoring programs.

Analytical Methods for the Determination of Dialifos Residue in Agricultural Products

A method using gas chromatography (GC) was developed to determine insecticide dialifos in agricultural products. Dialifos were extracted with acetone, the filtrate was evaporated to 50 mL and mixed with 50 mL of petroleum ether; the mixture was then extracted with dichlormathane twice. The extracts were evaporated to dry, dissolved in acetone, and then determined by gas chromatography equipped with a flame photometric detector (FPD) and a DB-1 capillary column. Recovery studies were carried out by spiking the standard dialifos at the levels of 0.05∼0.15, 0.5∼1.5 and 0.5∼1.5 ppm to rice, citrus fruit and kiwi fruit, respectively. Average recoveries were 88.5∼93.4%, 94.4∼97.0% and 93.0∼99.7% and the detection limits were 0.01, 0.05 and 0.05 ppm, respectively. No residue of dialifos was detected in agricultural products which were sampled from traditional markets.

Multiresidue analysis of 176 pesticides and metabolites in pre-harvested fruits and vegetables for ensuring food safety by gas chromatography and high performance liquid chromatography

A broad-range, sensitive and reliable multiresidue analytical method is presented for identifying and inspecting 176 pesticide residues, including organophosphate, organochlorine, synthetic pyrethroid, organonitrogen and carbamate, in pre-harvested fruits and vegetables. Pesticide residues were extracted from samples with acetone, followed by liquid-liquid partition and solid-phase extraction. Seventy one and 83 pesticides were determined, respectively, by gas chromatography with a flame photometric detector and an electron capture detector. Nineteen carbamate pesticides and several metabolites were measured by high-performance liquid chromatography (HPLC) with a post-column derivation system and a fluorescence detector; and three additional pesticides, i.e., carbendazim, thiabendazole, and imidacloprid, were detected by HPLC using an ultraviolet detector at 280 nm. The proposed method was validated for 14 fruits and 8 vegetables using samples spiked with pesticide standards (0.1-5.0 μg/g) in triplicate. Good sensitivity and repeatability were obtained with detection limits of 0.001-0.03 μg/g, and all limits of detection were lower than one-fifth of their specific maximum residue levels. The recovery rates for most pesticides in various fruits and vegetables were 60-120% with relative standard deviations < 20%. With more than 4,300 samples collected from the field examined to assess the performance, it is proposed that this method be applied for routine monitoring, legislation implementation and farmer education programs.

The screening of organophosphorus, organochlorine and synthetic pyrethroid pesticides residues in beef fat by tandem solid-phase extraction technique

For regulatory monitoring of pesticides in environmental matrices, a multiresidue analysis through solid phase extraction (SPE) technique and using gas chromatographic determination of organochlorine(OC), organophosphorus(OP) and synthetic pyrethroid pesticides residues in beef fat was studied. The group of pesticides was added to dissolved beef fat (0.5 g) and blended with 8% de-activation florisil. The florisil/fat mixture was packed into disposable filtration columns. This column was tandem with an octadecyl SPE column and was eluted with acetonitrile. The pesticide residues were determined by gas chromatography with electron capture and flame photometric detectors. Three kinds (including OC, OP and synthetic pyrethroid) with a total of 71 pesticides (including their metabolites) were tested in this study. With the exception of isoxthion and flucythrinate with high recovery rates (122% ± 13% and 137% ± 31%, respectively), according to the correlation coefficients for the 71 extracted pesticide standard curves (ranging from 0.9915 ± 0.0176 to 0.9999 ± 0.0200, n = 5), average recovery rate (ranging from 68 ± 9% to 117 ± 11%, n = 25 for each insecticide), inter-assay variability (ranging from 3 ± 3% to 17 ± 12%, n = 25 for each insecticide), intra-assay variability(ranging from 3 to 19%, n = 5 for each insecticide) indicated that the methodology is acceptable for the extraction, determination, and screening of theses residues in beef fat. The detection limits for OCs, OPs and synthetic pyrethroid pesticides are 2-21 ng/g, 6-31 ng/g and 3-118 ng/g, respectively. Comparing with studies conducted by the National Analytical Reference Laboratory in Western Australia in the field of pesticide residue testing in beef fat, the results indicated that the present method could accurately measure commonly used pesticide chemicals.

A multiresidue method for determining 136 pesticides and metabolites in fruits and vegetables: Application of macroporous diatomaceous earth column

A fast and easy multiresidue method using the macroporous diatomaceous earth (MDE) column for determining 136 pesticide an metabolite residues in fruits and vegetables was developed. The MDE column was used instead of the separation funnel for liquid/liquid partition in sample preparation. Through MDF columns, the preparation of test solution became easier and faster than traditional funnel liquid/liquid partition. The emulsion problem can also be avoided. Fifty one pesticides including acephate were determined by gas chromatography (GC) with a pulsed flame photometric detector (GC/PFPD) and 63 pesticides including aldrin were detected by GC with electron capture detection (GC/ ECD). Twenty carbamate peticides and metabolites including aldicarb were determined by high performance liquid chromatography with a post-column derivaization system and a fluorescence detector (HPLC/FLD) and two benzimidazole pesticides including carbendazim and thiabendazole were detected by HPLC with an ultraviolet detector (HPLC/UV). Recovery studies were performed by spiking pesticides (0.05-2.0 ppm) in fruit and vegetable samples, and the triplicate results showed satisfactory recoveries and repeatability. The detection limits ranged from 0.003 to 0.2 ppm. The developed multireside method can be employed to other pesticides or matrices with an easier and less solvent consumption way to prepare sample solution. It is an environment-friendly and useful method for routine pesticide analysis.