Pathogen-microbiome interactions and the virulence of an entomopathogenic fungus.

Bacteria shape interactions between hosts and fungal pathogens. In some cases, bacteria associated with fungi are essential for pathogen virulence. In other systems, host-associated microbiomes confer resistance against fungal pathogens. We studied an aphid-specific entomopathogenic fungus called Pandora neoaphidis in the context of both host and pathogen microbiomes. Aphids host several species of heritable bacteria, some of which confer resistance against Pandora. We first found that spores that emerged from aphids that harbored protective bacteria were less virulent against subsequent hosts and did not grow on plate media. We then used 16S amplicon sequencing to study the bacterial microbiome of fungal mycelia and spores during plate culturing and host infection. We found that the bacterial community is remarkably stable in culture despite dramatic changes in pathogen virulence. Last, we used an experimentally transformed symbiont of aphids to show that Pandora can acquire host-associated bacteria during infection. Our results uncover new roles for bacteria in the dynamics of aphid-pathogen interactions and illustrate the importance of the broader microbiological context in studies of fungal pathogenesis. IMPORTANCE: Entomopathogenic fungi play important roles in the population dynamics of many insect species. Understanding the factors shaping entomopathogen virulence is critical for agricultural management and for the use of fungi in pest biocontrol. We show that heritable bacteria in aphids, which confer protection to their hosts against fungal entomopathogens, influence virulence against subsequent hosts. Aphids reproduce asexually and are typically surrounded by genetically identical offspring, and thus these effects likely shape the dynamics of fungal disease in aphid populations. Furthermore, fungal entomopathogens are known to rapidly lose virulence in lab culture, complicating their laboratory use. We show that this phenomenon is not driven by changes in the associated bacterial microbiome. These results contribute to our broader understanding of the aphid model system and shed light on the biology of the Entomophthorales-an important but understudied group of fungi.

Accuracy and completeness of autobiographical memory: evidence from a wearable camera study.

A small wearable camera, SenseCam, passively captured pictures from everyday experience that were later used to evaluate the accuracy and completeness of autobiographical memory. Nine undergraduates wore SenseCams that took pictures every 10 s for two days. After one week and one month, participants first recalled their experiences from specific time periods (timeslices), then reviewed the corresponding pictures to make corrections and report information omitted from initial recall. Results demonstrated the utility of wearable cameras as research tools, and illustrated several characteristics of everyday memory. Recall contents reflected the structure of undergraduate lives. Three different types of omissions were reported: neglected, reminded, and forgotten. Pictures stimulated memory, even for non-visual information (e.g., feelings, thoughts), increasing recall by 23%. The mean completeness of initial recall was 79% (upper bound), with at least 21% forgetting. Accuracy was self-scored by participants (M = 89%), and the mean error rate (11%) provided evidence against strong reconstructive and copy theories of memory. The characteristics of errors shed light on the cognitive processes underlying them. Ratings of recall (confidence, reliving, knowledge, and frequency) supported the episodic/semantic distinction, the dual-process theory of repetition, and reconstructive imagery. Metamemory measures showed a positive correlation between confidence and accuracy.

Untangling an insect's virome from its endogenous viral elements.

BACKGROUND: Insects are an important reservoir of viral biodiversity, but the vast majority of viruses associated with insects have not been discovered. Recent studies have employed high-throughput RNA sequencing, which has led to rapid advances in our understanding of insect viral diversity. However, insect genomes frequently contain transcribed endogenous viral elements (EVEs) with significant homology to exogenous viruses, complicating the use of RNAseq for viral discovery. METHODS: In this study, we used a multi-pronged sequencing approach to study the virome of an important agricultural pest and prolific vector of plant pathogens, the potato aphid Macrosiphum euphorbiae. We first used rRNA-depleted RNAseq to characterize the microbes found in individual insects. We then used PCR screening to measure the frequency of two heritable viruses in a local aphid population. Lastly, we generated a quality draft genome assembly for M. euphorbiae using Illumina-corrected Nanopore sequencing to identify transcriptionally active EVEs in the host genome. RESULTS: We found reads from two insect-specific viruses (a Flavivirus and an Ambidensovirus) in our RNAseq data, as well as a parasitoid virus (Bracovirus), a plant pathogenic virus (Tombusvirus), and two phages (Acinetobacter and APSE). However, our genome assembly showed that part of the 'virome' of this insect can be attributed to EVEs in the host genome. CONCLUSION: Our work shows that EVEs have led to the misidentification of aphid viruses from RNAseq data, and we argue that this is a widespread challenge for the study of viral diversity in insects.

Induction of Daptomycin Tolerance in Enterococcus faecalis by Fatty Acid Combinations.

Enterococcus faecalis is a Gram-positive bacterium that normally exists as an intestinal commensal in humans but is also a leading cause of nosocomial infections. Previous work noted that growth supplementation with serum induced tolerance to membrane-damaging agents, including the antibiotic daptomycin. Specific fatty acids found within serum could independently provide tolerance to daptomycin (protective fatty acids), yet some fatty acids found in serum did not and had negative effects on enterococcal physiology (nonprotective fatty acids). Here, we measured a wide array of physiological responses after supplementation with combinations of protective and nonprotective fatty acids to better understand how serum induces daptomycin tolerance. When cells were supplemented with either nonprotective fatty acid, palmitic acid, or stearic acid, there were marked defects in growth and morphology, but these defects were rescued upon supplementation with either protective fatty acid, oleic acid, or linoleic acid. Membrane fluidity decreased with growth in either palmitic or stearic acid alone but returned to basal levels when a protective fatty acid was supplied. Daptomycin tolerance could be induced if a protective fatty acid was provided with a nonprotective fatty acid, and some specific combinations protected as well as serum supplementation. While cell envelope charge has been associated with tolerance to daptomycin in other Gram-positive bacteria, we concluded that it does not correlate with the fatty acid-induced protection we observed. Based on these observations, we conclude that daptomycin tolerance by serum is driven by specific, protective fatty acids found within the fluid.IMPORTANCE With an increasing prevalence of antibiotic resistance in the clinic, we strive to understand more about microbial defensive mechanisms. A nongenetic tolerance to the antibiotic daptomycin was discovered in Enterococcus faecalis that results in the increased survival of bacterial populations after treatment with the drug. This tolerance mechanism likely synergizes with antibiotic resistance in the clinic. Given that this tolerance phenotype is induced by incorporation of fatty acids present in the host, it can be assumed that infections by this organism require a higher dose of antibiotic for successful eradication. The mixture of fatty acids in human fluids is quite diverse, with little understanding between the interplay of fatty acid combinations and the tolerance phenotype we observe. It is crucial to understand the effects of fatty acid combinations on E. faecalis physiology if we are to suppress the tolerance physiology in the clinic.

Second Harmonic Generation Spectroscopy of Membrane Probe Dynamics in Gram-Positive Bacteria.

Bacterial membranes are complex mixtures with dispersity that is dynamic over scales of both space and time. To capture adsorption onto and transport within these mixtures, we conduct simultaneous second harmonic generation (SHG) and two-photon fluorescence measurements on two different gram-positive bacterial species as the cells uptake membrane-specific probe molecules. Our results show that SHG not only can monitor the movement of small molecules across membrane leaflets but also is sensitive to higher-level ordering of the molecules within the membrane. Further, we show that the membranes of Staphylococcus aureus remain more dynamic after longer times at room temperature in comparison to Enterococcus faecalis. Our findings provide insight into the variability of activities seen between structurally similar molecules in gram-positive bacteria while also demonstrating the power of SHG to examine these dynamics.

Utilizing Facebook and Automated Telephone Calls to Increase Adoption of a Local Smoke Alarm Installation Program.

CONTEXT: Innovative strategies are needed to improve the prevalence of working smoke alarms in homes. To our knowledge, this is the first study to report on the effectiveness of Facebook advertising and automated telephone calls as population-level strategies to encourage an injury prevention behavior. OBJECTIVE: We examine the effectiveness of Facebook advertising and automated telephone calls as strategies to enroll individuals in Baltimore City's Fire Department's free smoke alarm installation program. PARTICIPANTS: We directed our advertising efforts toward Facebook users eligible for the Baltimore City Fire Department's free smoke alarm installation program and all homes with a residential phone line included in Baltimore City's automated call system. DESIGN: The Facebook campaign targeted Baltimore City residents 18 years of age and older. In total, an estimated 300 000 Facebook users met the eligibility criteria. Facebook advertisements were delivered to users' desktop and mobile device newsfeeds. A prerecorded message was sent to all residential landlines listed in the city's automated call system. RESULTS: By the end of the campaign, the 3 advertisements generated 456 666 impressions reaching 130 264 Facebook users. Of the users reached, 4367 individuals (1.3%) clicked the advertisement. The automated call system included approximately 90 000 residential phone numbers. Participants attributed 25 smoke alarm installation requests to Facebook and 458 to the automated call. CONCLUSION: Facebook advertisements are a novel approach to promoting smoke alarms and appear to be effective in exposing individuals to injury prevention messages. However, converting Facebook message recipients to users of a smoke alarm installation program occurred infrequently in this study. Residents who participated in the smoke alarm installation program were more likely to cite the automated call as the impetus for their participation. Additional research is needed to understand the circumstances and strategies to effectively use the social networking site as a tool to convert passive users into active participants.

Lateral Ge Diffusion During Oxidation of Si/SiGe Fins.

This Letter reports on the unusual diffusion behavior of Ge during oxidation of a multilayer Si/SiGe fin. It is observed that oxidation surprisingly results in the formation of vertically stacked Si nanowires encapsulated in defect free epitaxial strained SixGe1-x. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) shows that extremely enhanced diffusion of Ge occurs along the vertical Si/SiO2 oxidizing interface and is responsible for the encapsulation process. Further oxidation fully encapsulates the Si layers in defect free single crystal SixGe1-x (x up to 0.53), which results in Si nanowires with up to -2% strain. Atom probe tomography reconstructions demonstrate that the resultant nanowires run the length of the fin. We found that the oxidation temperature plays a significant role in the formation of the Si nanowires. In the process range of 800-900 °C, pure strained and rounded Si nanowires down to 2 nm in diameter can be fabricated. At lower temperatures, the Ge diffusion along the oxidizing Si/SiO2 interface is slow, and rounding of the nanowire does not occur, while at higher temperatures, the diffusivity of Ge into Si is sufficient to result in dilution of the pure Si nanowire with Ge. The use of highly selective etchants to remove the SiGe could provide a new pathway for the creation of highly controlled vertically stacked nanowires for gate all around transistors.

The effects of end-of-day picture review and a sensor-based picture capture procedure on autobiographical memory using SenseCam.

Emerging "life-logging" technologies have tremendous potential to augment human autobiographical memory by recording and processing vast amounts of information from an individual's experiences. In this experiment undergraduate participants wore a SenseCam, a small, sensor-equipped digital camera, as they went about their normal daily activities for five consecutive days. Pictures were captured either at fixed intervals or as triggered by SenseCam's sensors. On two of five nights, participants watched an end-of-day review of a random subset of pictures captured that day. Participants were tested with a variety of memory measures at intervals of 1, 3, and 8 weeks. The most fruitful of six measures were recognition rating (on a 1-7 scale) and picture-cued recall length. On these tests, end-of-day review enhanced performance relative to no review, while pictures triggered by SenseCam's sensors showed little difference in performance compared to those taken at fixed time intervals. We discuss the promise of SenseCam as a tool for research and for improving autobiographical memory.

Enterococcus faecalis Readily Adapts Membrane Phospholipid Composition to Environmental and Genetic Perturbation.

The bacterial lipid membrane, consisting both of fatty acid (acyl) tails and polar head groups, responds to changing conditions through alteration of either the acyl tails and/or head groups. This plasticity is critical for cell survival as it allows maintenance of both the protective nature of the membrane as well as functioning membrane protein complexes. Bacteria that live in fatty-acid rich environments, such as those found in the human host, can exploit host fatty acids to synthesize their own membranes, in turn, altering their physiology. Enterococcus faecalis is such an organism: it is a commensal of the mammalian intestine where it is exposed to fatty-acid rich bile, as well as a major cause of hospital infections during which it is exposed to fatty acid containing-serum. Within, we employed an untargeted approach to detect the most common phospholipid species of E. faecalis OG1RF via ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS). We examined not only how the composition responds upon exposure to host fatty acids but also how deletion of genes predicted to synthesize major polar head groups impact lipid composition. Regardless of genetic background and differing basal lipid composition, all strains were able to alter their lipid composition upon exposure to individual host fatty acids. Specific gene deletion strains, however, had altered survival to membrane damaging agents. Combined, the enterococcal lipidome is highly resilient in response to both genetic and environmental perturbation, likely contributing to stress survival.

Scanning tropospheric ozone and aerosol lidar with double-gated photomultipliers.

The Ozone Profiling Atmospheric Lidar is a scanning four-wavelength ultraviolet differential absorption lidar that measures tropospheric ozone and aerosols. Derived profiles from the lidar data include ozone concentration, aerosol extinction, and calibrated aerosol backscatter. Aerosol calibrations assume a clear air region aloft. Other products include cloud base heights, aerosol layer heights, and scans of particulate plumes from aircraft. The aerosol data range from 280 m to 12 km with 5 m range resolution, while the ozone data ranges from 280 m to about 1.2 km with 100 m resolution. In horizontally homogeneous atmospheres, data from multiple-elevation angles is combined to reduce the minimum altitude of the aerosol and ozone profiles to about 20 m. The lidar design, the characterization of the photomultiplier tubes, ozone and aerosol analysis techniques, and sample data are described. Also discussed is a double-gating technique to shorten the gated turn-on time of the photomultiplier tubes, and thereby reduce the detection of background light and the outgoing laser pulse.

Comprehensive analysis of drugs of abuse in urine using disposable pipette extraction.

The extraction of basic, acidic, and neutral drugs of abuse from a low volume of urine (0.2 mL) using disposable pipette extraction (DPX) is described. DPX is a solid-phase extraction device that uses loosely contained sorbent inside a pipette tip fitted with a screen. This device provides faster extraction times because conditioning steps are not required. In this study, the DPX used a modified divinyl benzene sorbent containing both cation-exchange and reversed-phase mechanisms that facilitates the retention of basic and acidic/neutral drugs, respectively. With this device, a comprehensive method of analysis was developed for a diverse group of drugs and drug classes in urine including amphetamines, opiates, cocaine and its metabolites, tetrahydrocannabinol metabolite, tricyclic antidepressants, meperidine, methadone, and phencyclidine. Recoveries of the majority of drugs analyzed were 90% or greater with relative standard deviations of less than 10%. Additional validation involved the analysis of urine specimens previously analyzed by a local forensic toxicology laboratory.

Overproduction of Phospholipids by the Kennedy Pathway Leads to Hypervirulence in Candida albicans.

Candida albicans is an opportunistic human fungal pathogen that causes life-threatening systemic infections, as well as oral mucosal infections. Phospholipids are crucial for pathogenesis in C. albicans, as disruption of phosphatidylserine (PS) and phosphatidylethanolamine (PE) biosynthesis within the cytidine diphosphate diacylglycerol (CDP-DAG) pathway causes avirulence in a mouse model of systemic infection. The synthesis of PE by this pathway plays a crucial role in virulence, but it was unknown if downstream conversion of PE to phosphatidylcholine (PC) is required for pathogenicity. Therefore, the enzymes responsible for methylating PE to PC, Pem1 and Pem2, were disrupted. The resulting pem1Δ/Δ pem2Δ/Δ mutant was not less virulent in mice, but rather hypervirulent. Since the pem1Δ/Δ pem2Δ/Δ mutant accumulated PE, this led to the hypothesis that increased PE synthesis increases virulence. To test this, the alternative Kennedy pathway for PE/PC synthesis was exploited. This pathway makes PE and PC from exogenous ethanolamine and choline, respectively, using three enzymatic steps. In contrast to Saccharomyces cerevisiae, C. albicans was found to use one enzyme, Ept1, for the final enzymatic step (ethanolamine/cholinephosphotransferase) that generates both PE and PC. EPT1 was overexpressed, which resulted in increases in both PE and PC synthesis. Moreover, the EPT1 overexpression strain is hypervirulent in mice and causes them to succumb to system infection more rapidly than wild-type. In contrast, disruption of EPT1 causes loss of PE and PC synthesis by the Kennedy pathway, and decreased kidney fungal burden during the mouse systemic infection model, indicating a mild loss of virulence. In addition, the ept1Δ/Δ mutant exhibits decreased cytotoxicity against oral epithelial cells in vitro, whereas the EPT1 overexpression strain exhibits increased cytotoxicity. Taken altogether, our data indicate that mutations that result in increased PE synthesis cause greater virulence and mutations that decrease PE synthesis attenuate virulence.

The analysis of delta9-tetrahydrocannabinol and metabolite in whole blood and 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in urine using disposable pipette extraction with confirmation and quantification by gas chromatography-mass spectrometry.

Essential to forensic laboratories is the desire to find a more sensitive, rapid method of analyzing Delta9-tetrahydrocannabinol (THC) and metabolite in biological specimens. Disposable pipette extraction (DPX) is a valuable method in extracting THC and 11-nor-Delta9-tetrahydrocannabinol-9-carboxylic acid (THCc) in blood and THCc in urine. Less waste and solvent usage; smaller specimen volume; clean chromatograms; and utilization of lowcost equipment and consumables were achieved using this method. Differing from traditional solid-phase extraction devices, DPX uses loosely packed sorbent allowing thorough mixing with the specimen without requiring vacuum for elution. Prior to extraction, urine specimens were hydrolyzed and proteins precipitated from blood. Specimen volume requirements were 1 mL of blood and 0.2 mL of urine. The limits of quantitation for THC and THCc in blood were 1 and 2 ng/mL, respectively, and 3 ng/mL for THCc in urine. With R2 values > or = 0.99, blood calibration curves were linear from 1 to 200 ng/mL and 2 to 500 ng/mL for THC and THCc, respectively, with urine THCc linear from 3 to 2000 ng/mL.

Analysis of 10 ß-agonists in pork meat using automated dispersive pipette extraction and LC-MS/MS.

An analytical procedure for the analysis of 10 ß-adrenergic agonists (cimaterol, terbutaline, salbutamol, isoxsuprine, ractopamine, cimbuterol, clenbuterol, brombuterol, mabuterol and mapenterol) in pork meat was developed and validated using LC-MS/MS. An automated dispersive pipette extraction (DPX) was employed on a Hamilton Microlab® NIMBUS96® platform to extract the analytes of interest prior to LC-MS/MS analysis. The extraction time was <20 min with a total LC-MS/MS run time of 9.6 min. The method was fully validated in accordance with the international guidelines (European Commission Decision 2002/657/EC and National Standards of People's Republic of China, GB/T 22286-2008) for limit of detection, limit of quantitation, carryover, extraction efficiency, matrix effects, linearity, and within and between-run precision. The proposed method can be successfully used in the routine determination of 10 ß-adrenergic agonists in pork and as a potential solution for compliance monitoring in regulatory laboratories.

Clinical evaluation of BR96 sFv-PE40 immunotoxin therapy in canine models of spontaneously occurring invasive carcinoma.

PURPOSE: The immunotoxin BR96 sFv-PE40 is an effective antitumor agent against human breast and lung carcinoma xenografts in rodents. This study was designed to (a) determine the frequency with which canine carcinoma cells express Lewis(y) (Le(y)) antigen, thereby identifying canine carcinoma types suitable for the clinical evaluation of BR96 sFv-PE40, and (b) determine the safety and efficacy of BR96 sFv-PE40 in a canine model of spontaneously occurring cancers for investigation of targeted therapy. EXPERIMENTAL DESIGN: Carcinoma tissue samples were obtained from client-owned dogs presented for medical care. The tissues were assessed for Le(y) antigen expression using immunohistochemical methods. Dogs with tumors expressing Le(y) antigen were offered enrollment in a clinical trial to receive twice-weekly infusions of 4 to 12 mg/m(2) BR96 sFv-PE40. Clinical toxicity and response data were assessed at each treatment. RESULTS: Twenty-two of 61 carcinomas evaluated were positive for Le(y) expression, including mammary, prostate, lung, and rectal carcinomas, and 12 dogs were enrolled in the clinical trial. The primary side effect was transient emesis. Partial responses or disease stabilization were noted in dogs with inflammatory mammary, bronchogenic, rectal, and tonsillar carcinoma. At least nine of the dogs developed antibodies to the immunotoxin after two to five infusions. CONCLUSIONS: Although development of anti-BR96 sFv-PE40 antibodies limited the long-term effectiveness of this immunotoxin in dogs, rapid clinical responses in several aggressive canine carcinomas suggest the immunotoxin has utility for treatment of certain naturally occurring tumors and that its clinical evaluation for treatment of similar human carcinomas is warranted.

Variations in enzymatic hydrolysis efficiencies for amitriptyline and cyclobenzaprine in urine.

A collaborative study was conducted to investigate discrepancies in recoveries of two commonly prescribed compounds, amitriptyline and cyclobenzaprine, in patient urine samples when hydrolyzed with different enzymes from different sources. A 2- to 10-fold increase in analyte recoveries was seen for patient samples hydrolyzed using a recombinant ß-glucuronidase (IMCSzyme™) over samples hydrolyzed with ß-glucuronidase from Haliotis rufescens We report outcomes from four commercially available ß-glucuronidase enzymes (IMCSzyme™, Patella vulgata, Helix pomatia and H. rufescens) on patient samples that tested positive for amitriptyline and cyclobenzaprine. Our results confirm reduced hydrolysis of glucuronides by ß-glucuronidases isolated from mollusks, but near complete conversion when using the recombinant enzyme. Our premise is that systematic differences in hydrolysis efficiencies due to varying substrate affinity among enzyme subtypes potentially impacts accuracy and reliability of measurements.

Canine digital tumors: a veterinary cooperative oncology group retrospective study of 64 dogs.

We compared clinical characteristics and outcomes for dogs with various digital tumors. Medical records and histology specimens of affected dogs from 9 veterinary institutions were reviewed. Risk factors examined included age, weight, sex, tumor site (hindlimb or forelimb), local tumor (T) stage, metastases, tumor type, and treatment modality. The Kaplan-Meier product limit method was used to determine the effect of postulated risk factors on local disease-free interval (LDFI), metastasis-free interval (MFI), and survival time (ST). Outcomes were thought to differ significantly between groups when P < or = .003. Sixty-four dogs were included. Squamous cell carcinoma (SCC) accounted for 33 (51.6%) of the tumors. Three dogs presented with or developed multiple digital SCC. Other diagnoses included malignant melanoma (MM) (n = 10; 15.6%), osteosarcoma (OSA) (n = 4; 6.3%), hemangiopericytoma (n = 3; 4.7%), benign soft tissue tumors (n = 5; 7.8%), and malignant soft tissue tumors (n = 9; 14%). Fourteen dogs with malignancies had black hair coats, including 5 of the 10 dogs with MM. Surgery was the most common treatment and, regardless of the procedure, had a positive impact on survival. None of the patient variables assessed, including age, sex, tumor type, site, and stage, had a significant impact on ST. Both LDFI and MFI were negatively affected by higher T stage, but not by type of malignancy. Although metastasis at diagnosis correlated with a shorter LDFI, it did not have a significant impact on ST. On the basis of these findings, early surgical intervention is advised for the treatment of dogs with digital tumors, regardless of tumor type or the presence of metastatic disease.

Automated QuEChERS tips for analysis of pesticide residues in fruits and vegetables by GC-MS.

This paper reports the development of an automated method of QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) using pipet tips fitted with filtration screens and containing primary-secondary amine, magnesium sulfate, and graphitized carbon black. These tips are referred to as "QuEChERS Tips". Using loosely contained sorbent, dispersive solid phase extraction (dSPE) cleanup was performed with the QuEChERS Tips and automation. The main advantage of the QuEChERS Tips is that they are readily automated because this dSPE method does not require centrifugation. High recoveries (70-117%) and good reproducibilities (<12%) are shown for over 200 pesticides using automated QuEChERS Tips and GC-MS in various sample matrices.

Disposable pipette extraction for the analysis of pesticides in fruit and vegetables using gas chromatography/mass spectrometry.

Organochlorine, organophosphate pesticides and fungicides in fruits and vegetables were analyzed using disposable pipette extraction (DPX) followed by gas chromatography-mass spectrometry-selective ion monitoring (GC/MS-SIM). The intrinsic rapid mixing capabilities of DPX result in fast and efficient extractions, and eluates are concentrated by using minimal elution solvent volumes rather than solvent evaporation methods. Matrix-matched calibrations were performed with reversed phase mechanisms (DPX-RP), and the limits of detection (LOD) were determined to be lower than 0.1 microg/mL for all targeted pesticides in carrot and orange sample matrices. Coefficients of determination (r(2)) were greater than 0.995 for most studied pesticides. DPX-RP exhibited recoveries between 72 and 116% for nonpolar and slightly polar pesticides (logP>2) with most of the recoveries over 88%. Only very polar pesticides (e.g., acephate, mathamidophos) were not extracted well using DPX-RP.

Multiresidue analysis of pesticides in fruits and vegetables using disposable pipette extraction (DPX) and micro-luke method.

Simple and rapid methods for the analysis of pesticides in produce samples have been developed. The current study involves analysis of nonpolar and polar pesticides using GC-ECD and GC-NPD, respectively. The nonpolar pesticides were extracted using disposable pipette extraction (DPX) following a preliminary acetone extraction based on the Luke method. Recoveries of the fortified pesticides ranged between 70.5 and 110.0%, with relative standard deviations (% RSD) below 10% for most target analytes. From calibration plots, the limits of detection (LOD) were determined to be <0.05 ppm for most studied pesticides with coefficients of determination (r(2)) >0.99. A micro-Luke method was adapted and used for the analysis of polar pesticides, which greatly reduces the volumes of solvent and time for sample preparation. This new method of analysis, combining DPX and micro-Luke, was compared directly with the modified Luke method for analysis of pesticides in produce samples over a 9 week period. This study validates the suitability for routine analysis of pesticides in acetone extract of fruits and vegetables using the proposed DPX and micro-Luke method.