Expression of pyrethroid metabolizing P450 enzymes characterizes highly resistant Anopheles vector species targeted by successful deployment of PBO-treated bednets in Tanzania.

Long lasting insecticidal nets (LLINs) are a proven tool to reduce malaria transmission, but in Africa efficacy is being reduced by pyrethroid resistance in the major vectors. A previous study that was conducted in Muleba district, Tanzania indicated possible involvement of cytochrome P450 monooxygenases in a pyrethroid resistance in An. gambiae population where pre-exposure to piperonyl butoxide (PBO) followed by permethrin exposure in CDC bottle bioassays led to partial restoration of susceptibility. PBO is a synergist that can block pyrethroid-metabolizing enzymes in a mosquito. Insecticide resistance profiles and underlying mechanisms were investigated in Anopheles gambiae and An. funestus from Muleba during a cluster randomized trial. Diagnostic dose bioassays using permethrin, together with intensity assays, suggest pyrethroid resistance that is both strong and very common, but not extreme. Transcriptomic analysis found multiple P450 genes over expressed including CYP6M2, CYP6Z3, CYP6P3, CYP6P4, CYP6AA1 and CYP9K1 in An. gambiae and CYP6N1, CYP6M7, CYP6M1 and CYP6Z1 in An. funestus. Indeed, very similar suites of P450 enzymes commonly associated with resistant populations elsewhere in Africa were detected as over expressed suggesting a convergence of mechanisms across Sub-Saharan African malaria vectors. The findings give insight into factors that may correlate with pyrethroid PBO LLIN success, broadly supporting model predictions, but revision to guidelines previously issued by the World Health Organization is warranted.

Culex erythrothorax (Diptera: Culicidae): Activity periods, insecticide susceptibility and control in California (USA).

The mosquito Culex erythrothorax Dyar is a West Nile virus (WNV) vector that breeds in wetlands with emergent vegetation. Urbanization and recreational activities near wetlands place humans, birds and mosquitoes in close proximity, increasing the risk of WNV transmission. Adult Cx. erythrothorax abundance peaked in a wetland bordering the San Francisco Bay of California (USA) during the first 3 hours after sunset (5527 ± 4070 mosquitoes / trap night) while peak adult Culex tarsalis Coquillett abundance occurred during the subsequent 3 h period (83 ± 30 Cx. tarsalis). When insecticide resistance was assessed using bottle bioassay, Cx. erythrothorax was highly sensitive to permethrin, naled, and etofenprox insecticides compared to a strain of Culex pipiens that is susceptible to insecticides (LC50 = 0.35, 0.71, and 4.1 µg/bottle, respectively). The Cx. erythrothorax were 2.8-fold more resistant to resmethrin, however, the LC50 value was low (0.68 µg/bottle). Piperonyl butoxide increased the toxicity of permethrin (0.5 µg/bottle) and reduced knock down time, but a higher permethrin concentration (2.0 µg/bottle) did not have similar effects. Bulk mixed-function oxidase, alpha-esterase, or beta-esterase activities in mosquito homogenates were higher in Cx. erythrothorax relative to the Cx. pipiens susceptible strain. There was no difference in the activity of glutathione S-transferase between the two mosquito species and insensitive acetylcholine esterase was not detected. Larvicides that were applied to the site had limited impact on reducing mosquito abundance. Subsequent removal of emergent vegetation in concert with larvicide applications and reduced daily environmental temperature substantially reduced mosquito abundance. To control Cx. erythrothorax in wetlands, land managers should consider vegetation removal so that larvicide can efficiently enter the water. Vector control agencies may more successfully control adult viremic Cx. erythrothorax that enter nearby neighborhoods by applying adulticides during the 3 h that follow sunset.

Discovery of novel piperonyl derivatives as diapophytoene desaturase inhibitors for the treatment of methicillin-, vancomycin- and linezolid-resistant Staphylococcus aureus infections.

Inhibition of S. aureus diapophytoene desaturase (CrtN) could serve as an alternative approach for addressing the tricky antibiotic resistance by blocking the biosynthesis of carotenoid pigment which shields the bacterium from host oxidant killing. In this study, we designed and synthesized 44 derivatives with piperonyl scaffold targeting CrtN and the structure-activity relationships (SARs) were examined extensively to bring out the discovery of 21b with potent efficacy and better hERG safety profile compared to the first class CrtN inhibitor benzocycloalkane derivative 2. Except the excellent pigment inhibitory activity against wild-type S. aureus, 21b also showed excellent pigment inhibition against four pigmented MRSA strains. In addition, H2O2 killing and human whole blood killing assays proved 21b could sensitize S. aureus to be killed under oxidative stress conditions. Notably, the murine study in vivo validated the efficacy of 21b against pigmented S. aureus Newman, vancomycin-intermediate S. aureus Mu50 and linezolid-resistant S. aureus NRS271.

Biorational substitution of piperonyl butoxide in organic production: effectiveness of vegetable oils as synergists for pyrethrums.

Piperonyl butoxide is a semi-synthetic synergist for natural pyrethrum and synthetic pyrethroid insecticides in phytochemicals and biocides. As such it is used in large quantities for crop treatments, stored grain protection, disinfestation of grain storage facilities and indoor uses. Piperonyl butoxide is consequently a regular contaminant in stored grains, and subsequently in corresponding cereal food products and meat via feed uses. Therefore it is regularly monitored and its MRL is ongoing a reassessment. It is also considered as a possible human carcinogen and a suspected endocrine disruptor. For all these reasons and considerations most of the countries have already banned its use in Organic Farming as France in 2017. Thus, ecological substitution of with biorational and sustainable solutions is required. Vegetable oils have been described as exhibiting similar potency and synergistic effects. We have reviewed the literature and have proceeded to ecotoxicological efficacy tests in order to determine the best and most durable substitution candidates. Sesame and rape seed oil were determined to be the most efficient.

The interactions of piperonyl butoxide and analogues with the metabolic enzymes FE4 and CYP6CY3 of the green peach aphid Myzus persicae (Hemiptera: Aphididae).

BACKGROUND: Piperonyl butoxide (PBO) is a well-known insecticide synergist capable of interacting with phase 1 metabolic enzymes, specifically esterases and cytochrome P450s. In this study, structure-activity relationship analyses were used to characterise the interaction of around 30 analogues of PBO with the esterase FE4 and the P450 CYP6CY3 from insecticide-resistant Myzus persicae (Sulzer), in order to predict the synthesis of more potent inhibitors. RESULTS: Enzyme inhibition studies were performed against esterase and oxidase activities and, together with in silico modelling, key activity determinants of the analogues were identified and optimised. Novel analogues were then designed and synthesised, some of which showed greater inhibition against both enzymatic systems: specifically, dihydrobenzofuran moieties containing an alkynyl side chain and a butyl side chain against FE4, and benzodioxole derivatives with a propyl/butyl side chain and an alkynyl ether moiety for CYP6CY3. CONCLUSIONS: In vitro assays identified potential candidate synergists with high inhibitory potency. The in vivo confirmation of such results will allow consideration for a possible use in agriculture. © 2016 Society of Chemical Industry.

Synergistic effect of piperonyl butoxide on acute toxicity of pyrethrins to Hyalella azteca.

A series of acute toxicity tests with the amphipod Hyalella azteca was performed to quantify the synergistic effect of piperonyl butoxide (PBO) on pyrethrin toxicity. Concentrations of PBO <4 µg/L caused no toxicity enhancement, whereas toxicity increased with PBO concentrations between 4 µg/L and 15 µg/L. Additive toxicity calculations showed that true synergism accounted for an increase in pyrethrin toxicity (decrease in median lethal concentration) of 1.4-fold to 1.6-fold and varied only slightly between 4 µg/L and 15 µg/L PBO, whereas direct toxicity of PBO accounted for an additional increase in mixture toxicity (up to 3.2-fold) that was proportional to PBO concentration. The results can be used to assess the risk of measured or predicted co-occurring concentrations of PBO and pyrethrins in surface waters. Environ Toxicol Chem 2016;35:2111-2116. © 2016 SETAC.

Retention and efficacy of ultra-low volume pesticide applications on Culex quinquefasciatus (Diptera: Culicidae).

To combat mosquitoes and the public health hazards they present, spraying chemical adulticides is an efficient and timely control method for immediate reduction of adult populations. With the growing consciousness of environmental and public health concerns, effective mosquito control means not only maximizing the effectiveness (in terms of mosquito mortality rates) of the pesticide application, but also minimizing the unintended effects (health hazard and environmental pollution). A series of experiments was carried out to assess the efficacy and deposition of ultra-low volume (ULV) sprays on adult mosquitoes which included the influence of chemical type, spray volume, spray concentration, droplet size, and deposit location (where the droplets land on the mosquito). A modified Potter Tower was used to apply an extremely fine spray (volume median diameter ∼20 µm) on caged adult mosquitoes (Culex quinquefasciatus). Reslin (50 g/L bioresmethrin) was diluted in either water or D-C-Tron plus spray oil (782 g/L paraffinic petroleum oil), Twilight (89 g/L phenothrin) was diluted in D-C-Tron, and the mosquito mortality was assessed 24 h after spraying. A fluorescent tracer was added to the spray mixture to determine the amount of spray on mosquitoes. A fluorescent microscope was also used to view the deposit of droplets on mosquitoes. It was found that droplet retention and mortality were reduced with the larger droplet sizes. Large water-based droplets tend to bounce off adult mosquitoes. There is a tendency for droplets approximately 20 µm in size to be retained on the fine hairs on the mosquito. The largest spray deposit was found on the adult mosquito wings and the lowest deposit on the head. Mortality was higher for formulations diluted with oil compared to those diluted with water. ULV applications with ultra-fine sprays (VMD 20 µm) and oil-based products resulted in maximum target efficacy under laboratory conditions, at minimum cost, and with the minimum amount of chemical adulticides.

PREPARATION OF B-CYCLODEXTRIN-THIABENDAZOLE-PIPERONYL BUTOXIDE SUPRAMOLECULAR COMPLEX AND ITS ACTIVITY AGAINST BLUE AND GREEN MOULD DECAY ON INOCULATED SATSUMA FRUIT.

The supramolecular complex of ß-cyclodextrin-thiabendazole-piperony butoxide (ßCD-TBZ/PBO) was prepared and its structure was characterized by 1H NMR. Additionally, the antifungal activity of ßCD-TBZ/PBO was investigated in comparison with the commercially available thiabendazole (TBZ) fungicide by in vitro tests and on artificially inoculated 'Okitsu' satsuma fruit dipped in water at 20 degrees C or at 50 degrees C to control postharvest blue (Penicillium italicum) and green mould (P. digitatum). ß-CD-TBZ/PBO is stable for several months when stored as powder in a dark bottle. At pH 7.0 the water solubility of the ßCD-TBZ/PBO complex was consistently higher than free TBZ. Water dip at 20 degrees C did not affect decay incidence caused by blue mould but favoured the development of green mould during 4-8 days of storage at 20 degrees C with respect to untreated (control) fruit. Water at 50 degrees C effectively reduced the incidence of blue mould and totally suppressed green mould during the first 4 days but lost its efficacy afterwards. By contrast, both TBZ and ßCD-TBZ/PBO had a lasting effect and were equally effective in controlling green and blue mould decay when applied at 20 degrees C and 60 mg L(-1) active ingredient (a.i.). When applied at 50 degrees C and 20 mg L(-1) a.i. the activity of the complex against blue mould was inferior than the corresponding treatment with TBZ. In vitro assays revealed a significant effectiveness of ßCD-TBZ/PBO complex at low concentration compared to commercial formulation of TBZ.

Fumigant toxicity of Citrus sinensis essential oil on Musca domestica L. adults in the absence and presence of a P450 inhibitor.

Essential oils (EOs) are potential tools for controlling Musca domestica L. In a fumigant assay, M. domestica adults treated with Citrus sinensis EO (LC50=3.9mg/dm(3)), with (4R)(+)-limonene (95.1%) being its main component, died within 15min or less. The terpenes absorbed by the flies and their metabolites, analyzed using SPME fiber, were (4R)(+)-limonene (LC50=6.2mg/dm(3)), α-pinene (LC50=11.5mg/dm(3)), ß-pinene (LC50=6.4mg/dm(3)), and two new components, carveol (LC50=1122mg/dm(3)) and carvone (LC50=19mg/dm(3)), in a proportion of 50, 6.2, 12.5, 6.3 and 25%, respectively. Carveol and carvone were formed by oxidation of (4R)(+)-limonene mediated by cytochrome P450, as was suggested by a fumigation assay on flies previously treated with piperonyl butoxide, a P450 inhibitor. In this experiment, an increase in the toxicity of the EO and (4R)(+)-limonene was observed, as well as a lower production of carveol and carvone.

Effects of cytochrome P450 inhibitors on peroxidase activity.

OBJECTIVES: Of several enzymes metabolizing xenobiotics, cytochrome P450 (CYP) and peroxidase enzymes seem to be most important. One of the major challenges in studies investigating metabolism of xenobiotics is to resolve which of these two groups of enzymes is predominant to metabolize individual xenobiotic compounds. Utilization of selective inhibitors of CYP and peroxidase enzymes might be a useful tool to identify the contribution of these enzymes to metabolism of xenobiotics in samples, where both types of enzymes are present. The aim of this study was to investigate specificities of several known CYP inhibitors to these enzymes; whether they inhibit only the CYP enzymes and do not inhibit peroxidases. METHODS: Since the oxidation of o-anisidine catalyzed by a model peroxidase used, horseradish peroxidase (HRP), is a two-substrate reaction, the inhibition potential of tested chemicals was studied with respect to both peroxidase substrates, o-anisidine and hydrogen peroxide. Initial velocities of o-anisidine oxidation by HRP under various conditions were determined spectrophotometrically. RESULTS: The CYP inhibitors metyrapone, troleandomycine, disulfiram, sulfaphenazole, quinidine and 1-aminobenzotriazole do not inhibit o-anisidine oxidation catalyzed by HRP. In contrast, ketoconazole, diethyldithiocarbamate, ellipticine, α-naphtoflavone, proadifen SKF525A, piperonylbutoxide, were found to inhibit not only the CYPs, but also the HRP-mediated oxidation of o-anisidine. Interestingly, α-naphtoflavone inhibits oxidation of o-anisidine by HRP with respect to H2O2, but not with respect to o-anisidine. Diethyldithiocarbamate is the most potent peroxidase inhibitor of o-anisidine oxidation with Ki with respect to o-anisidine of 10 µM and Ki with respect to H2O2 of 60 µM, being even the better peroxidase inhibitor than the classical "peroxidase inhibitor" - propyl gallate (Ki with respect to o-anisidine of 60 µM and Ki with respect to H2O2 of 750 µM). CONCLUSIONS: The results of the present study demonstrate that 1-aminobenzotriazole, a potent inhibitor of various CYP enzymes, seems to be the best candidate suitable for utilization in studies evaluating participation of CYP enzymes in metabolism of xenobiotics in various complex biological materials containing both CYP and peroxidase enzymes. Moreover, precaution to prevent misinterpretation of results is necessary in cases when proadifen SKF525A, piperonylbutoxide, diethyldithiocarbamate, ketoconazole, α-naphtoflavone and ellipticine are used in similar studies (as CYP inhibitors in various complex biological materials containing both CYP and peroxidase enzymes), since these chemicals can except of CYP enzymes inhibit also peroxidase-mediated reactions.

Efficacy of Duet dual-action adulticide against caged Aedes albopictus with the use of an ultra-low volume cold aerosol sprayer.

Duet was field evaluated against caged Aedes albopictus, with the use of a truck-mounted ultra-low volume (ULV) cold aerosol sprayer at the rate of 90.6 ml/ha. Cages were placed in 3 rows stationed 30.5, 61.0, and 91.5 m downwind of the spray vehicle. Initial knockdown was >99% with mortality ranging between 95.8% and 98.0% across the distances. Volume median diameter (VMD) and droplet density were slightly reduced (16.4% and 18.6%, respectively) by distance. Reduction in VMD and droplet density, however, did not reduce mortality. The ULV application of Duet is an effective adulticide against Ae. albopictus and may be a useful tool for use in mosquito abatement programs.

Evaluation of Pioneer eco-backpack sprayer and Twister XL backpack sprayer using Aqualuer against caged adult Aedes albopictus and Culex quinquefasciatus.

A Pioneer Eco-Backpack electric cold ultra-low volume (ULV) sprayer and a gas-powered Twister XL 3950 series 2 motorized knapsack ULV sprayer with Aqualuer (20.6% permethrin AI) were evaluated against caged adult Aedes albopictus and Culex quinquefasciatus in St. Augustine, FL. The Pioneer Eco-Backpack sprayer provided 100% knockdown of both species of mosquitoes at 15 min; the Twister XL backpack sprayer resulted in 17-23% knockdown at 15 min. Both backpack sprayers with Aqualuer resulted in 100% mortality of both species at 24 h. The new Pioneer Eco-Backpack sprayer powered by electricity could be a potential tool for mosquito control.

Percutaneous absorption of an insect repellent p-menthane-3,8-DIOL: a model for human dermal absorption.

p-Menthane-3,8-diol(38DIOL) was recently introduced as a natural topical insect repellent in the commercial product "OFF! Botanicals" lotion. The objective of this study was to provide an estimate of the potential for 38DIOL systemic absorption in humans. Carbon-14-labeled 38DIOL formulated in the lotion and in an ethanol solution was applied to excised pig skin in an in vitro flow-through test system predictive of skin absorption in humans. Twenty-four hours after application, radiolabel recovered from the dermis and receptor fluid was summed to determine percent absorption. At a dose of approximately 80 microg/cm(2) of 38DIOL in the lotion, a value of 3.5 +/- 0.8% of applied dose was obtained with pig skin. The corresponding value for 38DIOL in ethanol (90 microg/cm(2)) was not significantly different (3.0 +/- 1.2%). Most of the applied dose of 38DIOL was found to evaporate from pig skin (77 +/- 8% for the lotion and 87 +/- 1% for ethanol solution), thus limiting percutaneous absorption values. For reference purposes, the pig skin absorptions of piperonyl butoxide (PBO) at 100 microg/cm(2) in isopropanol, N,N-diethyl-m-toluamide (DEET) at 500 microg/cm(2) in ethanol, and neat isododecane at 650 microg/cm(2) (in order of increasing volatility) were 15 +/- 6%, 23 +/- 3%, and 0.09 +/- 0.05% of applied dose respectively. Isododecane was lost almost exclusively from the skin surface by evaporation. For additional reference, absorptions of PBO, DEET, and 38DIOL were found to be higher with excised rat skin.

Evaluation of the fate of the active ingredients of insecticide sprays used indoors.

The fate of the active ingredients of insecticide sprays after use in indoor environments was investigated. Indoor air sampling was performed through two types of adsorbents, namely, TENAX TA and XAD-2 (10 L). After sampling, both adsorbents were ultrasonically extracted and analyzed by Gas Chromatography coupled to Mass Spectroscopy. The separation and analysis of the selected compounds were satisfactory and fast (duration of the chromatographic run: 40 min). The method was linear for all examined chemicals over the tested range (2 to 50 ng of absolute compound); limits of detection ranged from 0.42 to 1.32 ng of absolute compound. The method was then applied in the determination of the active ingredients of three commercially available insecticide sprays that were separately used in a full-scale environmental chamber (30 m(3)). After spraying, the fate of the active ingredients [propoxur, piperonyl butoxide (PBO) and pyrethrin insecticides] was monitored over 40 minutes, with and without ventilation. Both adsorbent materials were proven to be efficient and the differences in the concentrations deriving from sampling with both materials were in almost all cases less than 10%. All chemicals were removed in rates that exceeded 80%, after the 40 minutes of monitoring, exhibiting different decay rates. The removal of insecticides was not significantly affected by the ventilation of the chamber. The correlation analysis of propoxur, PBO and pyrethrins with the aerosols of various sizes (15 fractions, from 0.3 to > 20 microm) showed that propoxur and PBO mainly associated with the medium size aerosols (3-7.5 microm) while pyrethrins seem to link more with heavier particles (> 10 microm).

Release of piperonyl butoxide and permethrin from synergized ear tags on cattle and effects on horn fly mortality.

A study was conducted to determine the release rates of piperonyl butoxide (PBO) and permethrin from synergized insecticidal cattle ear tags and their effects on mortality of the horn fly, Hematobia irritans irritans (L.) (Diptera: Muscidae). PBO was released from the ear tags at a higher rate than permethrin in both winter and summer trials. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the winter trial was 50.4 and 30.3%, respectively. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the summer trial was 66.7 and 44.7%, respectively. There was a significant correlation between the cumulative daily high ambient temperature (degrees C) and the cumulative release of both PBO and permethrin. Compared with the susceptible horn fly strain, the permethrin-resistant strain demonstrated 7.9- and 12.8-fold resistance to permethrin at the levels of LC50 and LC90, respectively. When exposed to filter paper wipes taken from the shoulders of cattle treated with the PBO-synergized permethrin tags from the summer trial, the resistant strain demonstrated reduced mortality compared with the susceptible strain. The mortality of the resistant strain at 2- and 3-h exposure exhibited a pattern of declining fly mortalities as a result of the decreased release of PBO and permethrin, as well as the decline in the ratio of PBO:permethrin released from the tags after 8 wk. A similar decline in horn fly mortalities was observed in the susceptible strain at 30-min exposure time that coincided with the pattern of reduced release of PBO and permethrin from the ear tags over the course of summer trial.

Profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary GC-MS.

Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a pyrethroid insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an insecticide vaporizer.

Environmental concentrations, fate, and risk assessment of pyrethrins and piperonyl butoxide after aerial ultralow-volume applications for adult mosquito management.

One of the most effective ways of managing adult mosquitoes that vector human and animals diseases is the use of ultralow-volume insecticides. Because of concerns about the safety of the insecticides used for the management of adult mosquitoes, we conducted an environmental fate and efficacy study in Princeton and Colusa (both CA, USA) after aerial applications of pyrethrins and piperonyl butoxide (PBO). One hour before application, PBO concentrations in water were 0.008 and 0.2175 microg/L for Princeton and Colusa, respectively. One hour after the spray event in Princeton, the average PBO concentrations were 0.0125 microg/cm2 on ground-deposition pads and 0.1723 microg/L in water samples, with concentrations decreasing significantly over time. One hour after the spray event in Colusa, the average PBO concentrations were 0.0199 microg/cm2 on deposition pads and 1.274 microg/L in water samples, with concentrations decreasing significantly over time. A significant time and location effect for both deposition pads and water samples in Princeton and Colusa was observed (p<0.001 and p=0.014, respectively). Pyrethrins were not detected in nearly all ground and water samples. One hour after application, mortality of Culex tarsalis and Culex pipiens in sentinel cages was significantly higher than at the control site for both locations (p<0.001). Risk quotients for aquatic surrogate species in Princeton and Colusa were 0.002 or less at 1 h after application, which did not exceed the U.S. Environmental Protection Agency risk quotient level of concern for endangered aquatic organisms of 0.05. Our results suggest that the amounts of pyrethrins and PBO deposited on the ground and in water after aerial ULV insecticide applications are lower than those estimated by previous exposure and risk assessments.

Deposition of pyrethrins and piperonyl butoxide following aerial ultra-low volume applications in the Coachella Valley, California.

Data on adulticide deposition were collected during studies optimizing aerial ultra-low volume applications and droplet size in the desert environment of the Coachella Valley, Riverside County, California. Pyrenone 25-5 and BVA Spray 13 oil were applied by a single-engine, fixed wing aircraft equipped with 2 Micronair AU5000 atomizers. Data recorded by a portable weather station documented that weather conditions were suitable for application. Adulticide residue was collected using 24-cm-diameter filter papers positioned along 2-3 transects, with 3 positive controls held outside of the treated zone. The trace amounts of 2 major insecticidal components (pyrethrin I and II) and the synergist piperonyl butoxide (PBO) were detected from samples near the center of the spray zone by high-performance liquid chromatography (HPLC); pyrethrin deposition was highest at the center, 156 microg/m2, and it was not detectable 60 m beyond the center of the transect, whereas PBO deposition was 5,000 microg/m2 at the center but was not detectable beyond 150 m. Droplet diameters on spinning Teflon slides were larger than expected for the rated output of the atomizers. For these single swath trials, the lack of swath overlap due to drift resulted in low mortality in sentinel mosquitoes. Detection of residues was limited to the centroid of droplet densities on spinning glass slides and with mortality among sentinel mosquitoes, indicating HPLC may be useful in detecting postspray residues.

Comparison of two partial least squares infrared spectrometric methods for the quality control of pediculosis lotions.

Two vibrational spectroscopy procedures have been developed and compared for the direct and simultaneous determination of piperonyl butoxide and tetramethrin, the active ingredients of alcoholic capillary lotions, for hair pediculosis diseases. Nine lotions, purchased from the Spanish market, were analyzed using both, attenuated total reflectance (ATR) and transmission FT-IR measurements, and based on the use of partial least squares (PLS) multivariate calibration. A reduced set of 15 matched standards (11 for calibration and 4 for validation) was employed using both measurement modes. The spectral wave number ranges between 1757 and 1712 cm(-1) was selected to determine tetramethrin by both, transmittance and reflectance measurements. For the analysis of piperonyl butoxide the 1513-1479 cm(-1) and 1576-1479 cm(-1) regions were selected for ATR and transmission measurements, respectively. Results found for commercial samples compared well with those obtained by a liquid chromatography reference method that evidenced the applicability of the proposed strategy for the analysis of commercial formulations.