Gas Chromatography-flame Photometric Detection Research Articles

The elimination and extraction of organosulfur compounds from real water and soil samples using metal organic framework/graphene oxide as a novel and efficient nanocomposite

In the present work, an efficient metal organic framework/graphene oxide (MOF-801/GO) sorbent was fabricated and employed for the detection of organosulfur pesticides (OSPs) in real samples using gas chromatography-flame photometric detection (GC-FPD). The optimal extraction parameters for the suggested solid-phase extraction (SPE) include sorbent amount (60 mg), extraction solvent (acetonitrile) and extraction time (5 min). The linear dynamic ranges and detection limits for organosulfur pesticides (OSPs) samples under above extraction conditions were ranged from 0.5 to 300 μg L−1 and 0.1–1.1 μg L−1, respectively. Moreover, the proposed SPE/GC-FDP method was applied for the analysis of pesticides in different real environmental water and soil samples. The obtained recoveries of the analytes in were between 92.0 and 106.8% and relative standard deviation (RSD) values were lower than 9.2%. The application of the MOF-801/GO as a sorbent in dSPE of OSPs analytes showed to be reliable, fast and sensible methodology for pesticides monitoring in different environmental samples.

Development of a new and facile method for determination of chlorpyrifos residues in green tea by dispersive liquid–liquid microextraction

In this work a simple, rapid, and environmentally friendly method has been established for the determination of chlorpyrifos residue in green tea by dispersive liquid–liquid microextraction and gas chromatography-flame photometric detection. Some experimental parameters that influence extraction efficiency, such as the kind and volume of disperser solvents and extraction solvents, extraction time, addition of salt and pH, were investigated. And the optimal experimental conditions were obtained, quantitative analysis was carried out using external standard method. The correlation coefficient of the calibration curves was 0.999 with in 0.05 mg/kg to 5 mg/kg. The results showed that under the optimum conditions, the enrichment factors of the chlorpyrifos was about 554.51, the recoveries for standard addition fell in the range from 91.94 to 104.70% and the relative standard deviations was 4.61%. The limit of quantification of chlorpyrifos in green tea was 0.02 μg/mL at the signal/noise ratio of 3.

The Assessment of Organophosphate Pesticide Exposure among School Children in Four Regions of Thailand: Analysis of Dialkyl Phosphate Metabolites in Students' Urine and Organophosphate Pesticide Residues in Vegetables for School Lunch.

In Thailand, pesticides containing organophosphates (OP) are frequently applied to crops to suppress insects. School children can be exposed to OPs on a daily basis, from food consumption to breathing and touching pesticides drifted near classrooms. Living in an agricultural area can also be one of the causes. As a result, it is important to monitor OPs residues in the food chain and biomarkers of exposure. The Gas Chromatography–Flame Photometric Detector method was employed to examine the relationship between OPs residue and DAPs (Diakly phosphate) in four targeted locations in Thailand, as well as to examine the residues of OPs in vegetable samples and DAPs in 395 school children’s urine samples. Vegetables were found to contain at least one OP, with chlorpyrifos being the most prevalent. The OPs detected frequencies for Sakon Nakhon, Chiang Mai, Phang Nga, and Pathum Thani are 96.1%, 94%, 91.7%, and 83.3%, respectively. The overall centration level of OPs showed 0.3261 mg/kg, 0.0636 mg/kg, 0.0023 mg/kg, 0.0150 mg/kg, 0.2003 mg/kg, 0.0295 mg/kg, and 0.0034 mg/kg for diazinon, dimethoate, pirimiphos-methyl, chlorpyrifos, profenofos, ethion, and triazophos, respectively. Nearly 98% of school children were detected with at least one DAP. The overall level of dimethyl phosphate metabolites (5.258 µmole/mole creatinine) in urine samples is higher than diethyl phosphate metabolites (2.884 µmole/mole creatinine), especially in the case of Pathum Thani. Our findings show a consistent relationship between OPs in vegetables from wet markets and DAPs in urine samples of school children in various parts of Thailand.

Cysteine residues are responsible for the sulfurous off-flavor formed in heated whey protein solutions

Odor-active volatile sulfur compounds are formed in heated food protein systems. In the present study, hydrogen sulfide (H2S) was found to be the most abundant sulfur volatile in whey protein solutions (whey protein isolate [WPI], a whey model system and single whey proteins) by gas chromatography-flame photometric detector (GC-FPD) analysis after heat treatments (60–90 °C for 10 min, 90 °C for 120 min and UHT-like treatment). H2S was detected in WPI after heating at 90 °C for 10 min, and was significantly increased at higher heat load (90 °C for 120 min and the UHT-like treatment). Site-specific LC-MS/MS-based proteomic analysis was conducted, monitoring desulfurization reactions in these protein systems to investigate the mechanism of H2S formation in heated WPI. Cysteine residues from beta-lactoglobulin were found to be responsible for the formation of H2S in heated WPI, presumably via beta-elimination.

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.

Evaluation of the Interaction Between Esters and Sulfur Compounds in Pineapple Using Feller’s Additive Model, OAV, and Odor Activity Coefficient

The volatile compounds in three cultivar pineapples (“Jinzuan, JZ,” “Niunai, NN,” and “iangshui, XS”) were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and gas chromatography-flame photometric detection (GC-FPD). The results showed that 47, 51, and 52 aroma compounds were identified in JZ, NN, and XS pineapple samples, respectively. Among these aroma compounds, the odor activity values (OAVs) of 15, 19, and 15 compounds were greater than 1. Methyl 2-methylbutanoate and ethyl 2-methylbutanoate presented the highest OAVs than others. Additionally, four, five, and four sulfur compounds were identified respectively, of which 1-propanethiol (PT) and 3-mercapto-1-hexanol were found for the first time in pineapple. The Feller additive model, OAV, and odor activity coefficient (γ) were used to investigate the interaction between esters (methyl butyrate (MB) and methyl 2-methylbutanoate (M2MB)) and sulfur compounds (methyl 3-methylthiopropionate (M3MP), ethyl 3-methylthiopropionate (E3MP), and PT). Among all mixtures, three groups of mixtures were shown to have a masking effect, two exhibited an additive effect, and one exerted a synergistic effect.

Identification of key odorants in traditional Shaoxing-jiu and evaluation of their impacts on sensory descriptors by using sensory-directed flavor analysis approaches

To determine the key odorants of a popular Chinses rice wine, Shaoxing-jiu, volatile compounds were analyzed by using sensory-directed flavor approaches, including gas chromatography-mass spectrometry (GC-MS), gas chromatography-flame photometric detector (FPD), gas chromatography olfactometry (GC-O), aroma recombination and omission experiments, and odorant addition experiments. Fifty-five volatile compounds were detected in traditional Shaoxing-jiu via GC-MS, more than those in mechanical Shaoxing-jiu. Thirty-four aroma-active compounds in traditional Shaoxing-jiu were determined via GC-O. According to aroma recombination and omission experiments, the aroma profile of the recombination model constructed by these aroma-active compounds at their detected concentrations was similar to that of traditional Shaoxing-jiu, and 15 of them were affirmed as key odorants. Among the key odorants, phenylethyl alcohol, furfural, γ-nonalactone and dimethyl trisulfide presented very highly significant aroma contributions, indicating that their omission would cause great aroma differences. Then odorant addition experiments highlighted the aroma impacts of these four paramount key odorants on sensory descriptors in traditional Shaoxing-jiu.

Determination of Organophosphate Pesticide Residues in Rice by Multiresidue Analysis

An analytical method was developed for determination of 47 organophosphate pesticides in rice by using solid-phase extraction for clean up. Pesticides in rice samples were extracted with acetone. The extract was cleaned up with 1 g C18 solid-phase extraction (SPE) cartridges and the pesticides were determined using a gas chromatography-flame photometric detector (GC-FPD).The recoveries of 47 pesticides ranged from 74%-126% and the detection limits were 0.005 - 0.04 μg/g. Several pre-treatment methods are compared for the simultaneous analysis of organophosphorus pesticides in rice. Cleanup with SPE showed results comparable to or better than those obtained by liquid-liquid extraction. The SPE method enhances the effect and reduces analytical cost and time.

Monitoring of the Organophosphate Pesticide Chlorpyrifos in Vegetable Samples from Local Markets in Northern Thailand by Developed Immunoassay.

Chlorpyrifos is an organophosphate pesticide that is wildly used among farmers for crop protection. However, there are concerns regarding its contamination in the environment and food chain. In the present study, an in-house indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) specific for detecting chlorpyrifos is developed and validated against gas chromatography–flame photometric detection (GC-FPD) as the conventional method. The developed ic-ELISA was used for detecting chlorpyrifos residue in vegetable samples. The developed ic-ELISA showed good sensitivity to chlorpyrifos at an IC50 of 0.80 µg/kg, with low cross-reactivity to other organophosphate pesticides. The 160 samples were collected from local markets located in the Chiang Rai, Chiang Mai, and Nan provinces in northern Thailand. The positive rate of chlorpyrifos residues in the vegetable samples was 33.8%, with the highest levels found in cucumbers, coriander, and morning glory, at 275, 145, and 35.3 µg/kg, respectively. The highest median levels of chlorpyrifos found in the detected samples were Chinese cabbage (332 μg/kg), cucumber (146.3 μg/kg) and Chinese Kale (26.95 μg/kg). The developed ic-ELISA is suitable for the rapid quantitation of chlorpyrifos residues.

Preparation and application of graphene oxide-based surface molecularly imprinted polymer for monolithic fiber array solid phase microextraction of organophosphate flame retardants in environmental water

Selectivity and high throughput are important for determination of trace level of various organophosphate flame retardants (OPFRs) in environmental matrices. In this work, three selective monolithic fibers for solid phase microextraction (SPME) were prepared and evaluated. They are graphene oxide (GO)-based surface trimethyl phosphate (TMP) imprinted polymeric fiber (GO/TMP-IPF), GO-based surface tri (2-chloroethyl) phosphate (TCEP) imprinted polymeric fiber (GO/TCEP-IPF) and GO-based surface triphenyl phosphate (TPhP) imprinted polymeric fiber (GO/TPhP-IPF). The imprinting factors of GO/TMP-IPF for TMP, GO/TECP-IPF for TCEP and GO/TPhP-IPF for TPhP were tested as high as 4.3, 4.5, 10.3, respectively. The three fibers were bound to a stainless steel wire to assemble a GO-based surface molecularly imprinted polymeric fiber array (GO/MIP-FA). GO/MIP-FA-SPME device was coupled to gas chromatography-flame photometric detector and carried out simultaneous determination of TMP, TCEP and TPhP in environmental water. Under the optimal conditions, ultralow limits of quantification (1.7 ng L−1-5.0 ng L−1); linearity (>0.99); intra- and inter-day precision expressed as relative standard deviations for an array in the range of 4.9-8.6% and 5.8-8.2%, respectively, and array-to-array reproducibility in the range of 7.2-9.1% were obtained. The GO/MIP-FA-SPME technique was successfully applied for the determination of OPFRs in various environmental water samples, and the relative recoveries were found to be in the range from 72.4 to 112.0%.

Determination of Organophosphorus Pesticide Residues in Winter Bamboo Shoots by Homogenate Extraction Coupled with Gas Chromatography-Flame Photometric Detector

Excessive use of organophosphorus pesticides (OPPs) in fruits and vegetables may affect human health. In this paper, a simple, rapid and effective method for the determination of five OPPs in winter bamboo shoots by gas chromatography-flame photometric detector (GC-FPD) was developed. Three extractants and three extraction methods were examined respectively. The results showed that the recovery rate was higher when the samples were extracted by acetonitrile and treated with homogenate extraction method. Under the optimized conditions, recoveries ranged from 82.12% to 91.48% with the relative standard deviation (RSD) of 1.51-4.20% and the limit of detection (LOD) of 0.005-0.02 μg/mL. Results showed that using acetonitrile as extractants and homogenate extraction in sample preparation is an effective method in determination of pesticide residues in winter bamboo shoots.

Rapid and accurate determination of trace volatile sulfur compounds in human halitosis by an adaptable active sampling system coupling with gas chromatography.

Halitosis with the main components of trace volatile sulfur compounds widely affects the quality of life. In this study, an adaptable active sampling system with two sample-collection modes of direct injection and solid-phase microextraction was developed for the rapid and precise determination of trace volatile sulfur compounds in human halitosis coupled with gas chromatography-flame photometric detection. The active sampling system was well designed and produced for efficiently sampling and precisely determining trace volatile targets in halitosis under the optimized sampling and detection conditions. The analytical method established was successfully applied for the determination of trace targets in halitosis. The limits of detection of H2 S, CH3 SH, and CH3 SCH3 by direct injection were 0.0140-23.0μg/L with good recoveries ranging from 82.2 to 118% and satisfactory relative standard deviations of 0.4-9.5% (n=3), respectively. The limit of detections of CH3 SH and CH3 SCH3 by solid-phase microextraction were 2.03 and 0.186 × 10-3 μg/L with good recoveries ranging from 98.3 to 108% and relative standard deviations of 5.9-9.0% (n=3). Trace volatile targets in positive real samples could be actually found and quantified by combination of direct injection and solid-phase microextraction. This method was reliable and efficient for the determination of trace volatile sulfur compounds in halitosis.

EFFECT OF OZONE MICROBUBBLES WITH VARIOUS TEMPERATURES ON THE CHLORPYRIFOS INSECTICIDE REMOVAL IN TANGERINE CV. SAI NAM PHUENG

Chlorpyrifos, a type of organophosphate insecticide, is widely used to destroy pests in the tangerine orchard to reduce the loss and maintain the quality of fruit. Consequently, the application of insecticides during production leads to the insecticide residues problem in tangerine that can be dangerous to human health. This study investigated the effect of ozone microbubbles (OMBs) on the removal of chlorpyrifos residues in the fruit. Tangerines were sprayed with chlorpyrifos solution at a concentration of 10 minutes. Then, they were treated with OMBs at different temperatures (15, 20 and 25 oC) for various exposing times (0, 10, 20, 30, 40, 50 and 60 minutes). Removal percentage of chlorpyrifos residues in tangerines was determined by gas chromatography-flame photometric detector (GC-FPD). The results showed that chlorpyrifos residues in tangerines were decreased at lower water temperature, especially at 15 oC resulting in the removal up to 81% after treating with OMBs for 30 minutes when compared to control (distilled water). After that, the fruits were stored at 25 oC for 7 days to determine quality changes. The percentage of weight loss, total soluble solids (TSS), titratable acidity (TA), disease incidence and ascorbic acid content in all treatments were not affected by OMBs. These results demonstrate that OMBs treatment at 15 oC is the most effective treatment for removing chlorpyrifos residues in tangerine and have no effects on the fruit quality.

The degradation behaviour, residue distribution, and dietary risk assessment of malathion on vegetables and fruits in China by GC-FPD

The gas chromatography-flame photometric detector (GC-FPD) was used to detect malathion residues content in vegetables (cherry tomatoes and broccoli) and fruits (mulberries, cranberries, and figs). The recoveries of samples were 76.2 ± 3.5%–103.9 ± 3.6% at a spike level of 0.01–10 mg/kg, the relative standard deviation (RSDs) were 2.1%–7.3%, and the limit of quantification (LOQs) were 0.01–0.02 mg/kg. On the basis of the normative field trials, the degradation half-life of malathion were 1.10–2.15 days, which indicated that malathion degrades quickly. The final distribution of malathion residues in various vegetables and fruits varied from <0.01 to 0.58 mg/kg. The long-term dietary risk assessment results showed that the national estimated daily intake (NEDI) of malathion in various populations of China ranged from 0.000021 to 0.000549 mg/kg bw, and the risk quotient (RQ) ranged from 0.007% to 0.183% and were less than 100%, which indicated that malathion has a low risk for long-term dietary intake these crops. The maximum residual limits (MRLs) of malathion can be set as 1 mg/kg for cherry tomatoes, broccoli, mulberries, cranberries, and 0.2 mg/kg for figs, respectively. These results would be considered as important references for monitoring and assessing the quality safety of agricultural products and protecting consumer health.

Micro-Flame Photometric Detection in Miniature Gas Chromatography on a Titanium Tile

A novel miniaturized gas chromatography–flame photometric detection device built within a titanium platform (Ti µGC–FPD) is presented. The 7.5 cm × 15 cm monolithic Ti device contains both an OV-101 coated separation column (5 m × 100 µm i.d.) and a shielded cavity to house the hydrogen-rich detector flame. The FPD employs a micro counter-current flame (about 250 µm in diameter) that is stabilized by opposing relatively low flows of oxygen and hydrogen (7–10 mL/min O2 and 40 mL/min H2). Under optimal conditions, the minimum detectable limits are about 70 pg S/s for sulfur and 8 pg P/s for phosphorous. The natural (i.e., unfiltered) selectivity for these responses over carbon is near 104.3 for S/C and 105 for P/C. Even greater selectivity over hydrocarbons can further still be obtained by employing conventional interference filters. Overall, good separations with stable and sensitive detector performance are obtained with the device, and its sturdy Ti structure supports robust operation. Results indicate that this Ti µGC–FPD device may be a useful alternative approach for incorporating selective FPD sensing in µGC analyses.

Representative commodity for six leafy vegetables based on the determination of six pesticide residues by gas chromatography

A residue analytical method was developed for the determination of trichlorfon, chlorpyrifos, dimethoate, β cypermethrin, deltamethrin, and chlorothalonilin in six leafy vegetables by gas chromatography–electron capture detector (GC–ECD) and gas chromatography–flame photometric detector (GC–FPD). The method had a good linearity (R2 ≥ 0.9924) and precision (RSD ≤ 14.0%). The limits of quantification (LOQ) of six pesticides were all 0.01 mg/kg. Average recoveries of six pesticides ranged from 81% to 119%. The developed method was successfully applied to study the initial deposits, degrade characteristics, and terminal residues for six pesticides applied to six leafy vegetables under the same dose of formulation. The half-life of six pesticides was in the range of 0.8–8.8 days. The highest initial deposits, maximal residues, and terminal residues were found on leaf mustard and sweet potato leaves as the same pesticides were applied in different crops. Therefore, leaf mustard can be selected as representative commodity in the same subgroup to realize the residual extrapolation. This conclusion should be considered as a complement on crop classification of China.

A method for determining glyphosate and its metabolite aminomethyl phosphonic acid by gas chromatography-flame photometric detection

As a globally popular herbicide, glyphosate (GLY) and its metabolite aminomethylphosphonic acid (AMPA) pose potential hazards to the ecological environment. In this study, a sensitive and reliable method for detecting GLY and AMPA was utilized to facilitate exposure risk assessment of the analytes in environmental systems such as water and soil. GLY and AMPA were extracted from the sample using a solid-phase extraction (SPE) procedure, derivatized by heptafluorobutyric anhydride and heptafluorobutanol, and detected by gas chromatography-flame photometric detection (GC-FPD). The linearities of GLY and AMPA in the range of 10–1000 ng/mL were good (r=0.9998, r=0.9991), and the limits of quantitation (LOQ) for GLY and AMPA were 0.37 and 0.81 ng/mL, respectively. The method has been successfully applied for detecting GLY and AMPA in water, soil and monitoring the degradation of GLY under different environmental conditions. Simulated migration characteristics of GLY and AMPA in soil were investigated for evaluating the potential hazards of GLY and AMPA to the ecological environment.

Metal organic frameworks-derived magnetic nanoporous carbon for preconcentration of organophosphorus pesticides from fruit samples followed by gas chromatography-flame photometric detection

In this work, magnetic nanoporous carbons (MNPCs) based on Zn/Co-MOFs was synthesized via a facial one-step carbonization method. The prepared MNPCs exhibited high specific surface areas, good chemical stability and high extraction efficiency for interest organophosphorus pesticides (OPPs). The good extraction performance of the MNPCs for interest OPPs can be primarily attributed to π-π interaction and hydrophobic interaction between MNPCs and OPPs. Based on it, MNPCs-based MSPE-GC-FPD method was established for the quantification of five OPPs in fruit samples. The main experimental conditions for MSPE of five target OPPs were investigated systematically and optimized, such as the desorption solvent and volume, extracted volume, ionic strength, extraction time and desorption time. Under the optimal conditions, the limits of detection (LODs, S/N = 3) were found to be in the range of 0.018 (ethion) -0.045 (malathion) μg/L. The linearity was 0.05-100 μg/L for phorate, diazinon, ethion and 0.1-100 μg/L for malathion, fenthion respectively. The reproducibility of the method was in the range of 3.5-9.7%. The recovery experiments were carried out by spiking target OPPs at three concentration levels to validate the accuracy of the proposed method, and the recoveries for target OPPs were 84-116%. The results show that the proposed method in this work can be successfully used to analyze OPPs residue in fruit sample.

A Rapid Analytical Method for the Selective Quenching-Free Determination of Thiols by GC-FPD

A rapid method is introduced, which facilitates the selective gas chromatography–flame photometric detection (GC–FPD) analysis of thiols. The method uses lead oxide particles or plumbite solution to complex thiols into a solid lead thiolate moiety that can be physically separated from complex sample matrices and then reconstituted as the original thiol in a simple replacement solvent for analysis. While both red or yellow forms of lead oxide are found to remove thiols from sample solutions, the latter does so about 10 times faster than the former. Comparatively, though, plumbite solution is most rapid in this regard and is still 10 fold faster than solid yellow lead oxide. For example, 98 ± 1% (n = 3) of a 1-butanethiol standard in hexane (600 ng µL− 1) was extracted after only 2 min of contact with a 0.06 M plumbite solution. The method allows thiols to be selectively isolated from co-eluting peaks and other sulfur species, which can simplify their determination. It also allows thiols to be removed from complex hydrocarbon matrices for analysis, which can greatly reduce interference from signal quenching when using a conventional FPD. For instance, analysis of a thiol standard in a commercial gasoline by this method showed that the FPD sulfur signal increased from 16 to 97% of its expected value by removing the quenching hydrocarbon interference. Accordingly, results indicate that this method could be a useful alternative approach for the selective analysis of such thiol-containing samples.

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.