Deet Formulations Research Articles

Poly(oxyethylene)/Poly(oxypropylene) butyl ether prolongs the repellent effect of N,N-diethyl-3-toluamide on the skin.

N,N-diethyl-meta-toluamide (DEET) is a widely used insect repellent, with minimal skin permeation and sustained repellent activity in the superficial layers of the skin. In this study, we prepared a 10% DEET formulation consisting of 40% ethanol with or without 2% poly(oxyethylene)/poly(oxypropylene) butyl ether (POE-POP), an amphiphilic random copolymer. Further, we demonstrated the effects of POE-POP on tensile stress (stickiness), hydrophobicity, skin retention, permeation, and repellent activity of DEET. Stickiness was measured in male ICR mice (7-week old), and skin retention and permeation were evaluated in male Wistar rats (7-week old). In addition, female Aedes albopictus were used to measure the repellent action of DEET. The addition of POE-POP did not affect stickiness, volatility, and degradability but decreased logP and increased viscosity of DEET. Next, we demonstrated the behavior of DEET formulations in the rat skin. POE-POP prolonged the retention of DEET in the superficial layers of the rat skin (skin surface and stratum corneum) and decreased the penetration of DEET into rat skin tissues (epithelium and dermis). The repellent effect of DEET was also enhanced by the addition of POE-POP. However, severe skin damage was not observed after repetitive treatment with DEET formulations containing POE-POP for one month (twice a day). In conclusion, we demonstrated that a 10% DEET formulation consisting of 40% ethanol and 2% POE-POP attenuated the skin penetration and prolonged the repellent action of DEET without causing stickiness and skin damage. We conclude that the combination of ethanol and POE-POP is useful as a safe and effective delivery system for the development of insect repellent formulations containing DEET.

N,N-Diethyl-3-toluamide Formulation Based on Ethanol Containing 0.1% 2-Hydroxypropyl-β-cyclodextrin Attenuates the Drug's Skin Penetration and Prolongs the Repellent Effect without Stickiness.

N,N-diethyl-3-toluamide (DEET) is one of the most widely used insect repellents in the world. It was reported that a solution containing 6–30% cyclodextrin (CD) as a solvent instead of ethanol (EtOH) provided an enhancement of the repellent action time duration of the DEET formulation, although the high-dose CD caused stickiness. In order to overcome this shortcoming, we attempted to prepare a 10% DEET formulation using EtOH containing low-dose CDs (β-CD, 2-hydroxypropyl-β-CD (HPβCD), methyl-β-CD, and sulfobutylether-β-CD) as solvents (DEET/EtOH/CD formulations). We determined the CD concentration to be 0.1% in the DEET/EtOH/CD formulations, since the stickiness of 0.1% CDs was not felt (approximately 8 × 10−3 N). The DEET residue on the skin superficial layers was prolonged, and the drug penetration into the skin tissue was decreased by the addition of 0.1% CD. In particular, the retention time and attenuated penetration of DEET on the rat skin treated with the DEET/EtOH/HPβCD formulation was significantly higher in comparison with that of the DEET/EtOH formulation without CD. Moreover, the repellent effect of DEET was more sustained by the addition of 0.1% HPβCD in the study using Aedes albopictus. In conclusion, we found that the DEET/EtOH/HPβCD formulations reduced the skin penetration of DEET and prolonged the repellent action without stickiness.

Evaluation of a Novel User-Friendly Arthropod Repellent Gel, Verdegen.

Hand sanitizers are developed as alcohol-based liquid gel formulations, generally used to decrease the amount of infectious agents on human hands. Verdegen, LLC proposed to prepare an arthropod repellent gel for public use when the recent outbreaks of Zika infection vectored through Aedes mosquitoes in the American continents prompted multi-faceted emergency measures. Four different gel formulations were developed, comprising two of the most efficacious commercial arthropod repellent active ingredients, N,N-diethyl-3-methyl benzamide (deet) and 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester (picaridin), each at different concentrations (20 and 33% deet, or 20 and 33% picaridin). Compliance with the use of topical arthropod repellents remains an issue among military personnel. One of the most common complaints by Soldiers is that they do not like how the repellents applied on their skin leave behind an oily or greasy residue. These new gel formulations offer a user-friendly alternative for commonly used arthropod repellents formulations for the military and civilian personnel. We tested the efficacy and protection time of these new gel formulations in comparison with the commercially available cream formulations of deet and picaridin at similar concentrations. Our data show that gel formulations have better topical attributes, and offer equal or better biting protection for up to 48 h against host-seeking Aedes aegypti (L.) (Diptera: Culicidae) female mosquitoes.

Polymer-coated cationic silica nanoparticles for slow-release Pickering emulsions

Silica nanoparticles were functionalized with amine and quaternary ammonium groups using a two-step chemical surface modification, to allow coating with anionic polymers for emulsion stabilization. This strategy proved to render high colloidal stability in aqueous dispersions and strong electrostatic interactions with polyacrylic acid and poly(sodium 4-styrene sulfonate), over a wide pH range. These hybrid nanoparticles stabilized Pickering emulsions at very low concentrations (0.01 wt%), without added surfactants. Most stable emulsions were obtained with nanoparticles coated with polyacrylic acid, due to synergy of strong interfacial adsorption of nanoparticles enhanced by the long polymeric chains and the weak polyelectrolyte character of the polymer. These nanoparticles were able to prevent diffusion of N,N′-diethyl-m-toluamide (DEET), a common insect repellent, from oil-in-water emulsions into a model media. The release profile followed typical zero-order kinetics, demonstrating the potential of using the polymer-coated nanoparticles developed in this work in DEET formulations to achieve extended repellent action.

Topical and spatial repellent bioassays against the Australian paralysis tick, Ixodes holocyclus (Acari: Ixodidae)

AbstractThe Australian paralysis tick, Ixodes holocyclus, is the cause of significant human morbidity. Bites from the tick may result in paralysis, allergic reactions that can include anaphylaxis and death, mammalian meat allergies and the transmission of infectious agents. In recent years, there have been a number of papers published on the microbiome of the species, but to date, there is no published research on I. holocyclus management or personal protection options to prevent the bite from the species. The study herein focused on the latter; the use of repellents for the prevention of bites from I. holocyclus. Five personal repellents were tested along with coconut oil, and a citronella patch and wristband. These were all tested for repellency in a laboratory assay over the time intervals of 15 min, 1, 2, 3 and 4 h post application. The personal repellents included the active ingredients of picaridin (9.3%), DEET (11.5%), lemon eucalyptus (36.0%), a combined formulation of citronella and tea tree oil (28.4%) and an extract of Andrographis paniculata (30% w/v). The coconut oil was 30% v/v. The citronella patch contained 120 mg/patch, whereas the citronella wristband contained 750 mg/band. Two spatial repellents were also tested in the laboratory for repellency and toxicity against I. holocyclus and tested for toxicity in the field. These included OFF!® Clip‐On™ (metofluthrin 312 g/kg) and Thermacell® (allethrin 219.7 g/kg). For the personal repellents at 4 h, there was no statistical difference in repellency between the formulations of picaridin, DEET and lemon eucalyptus, with over 84% repellency recorded for all. Thus, these would be the personal repellents recommended for preventing tick bites. The citronella patch produced 100% repellency over 4 h; however, as this type of product is known to only provide protection close to the patch, it is not recommended for routine use. For the spatial repellents, both produced significant repellency and toxicity in the laboratory, but failed to produce any tick mortality in the field, and their use cannot be recommended. This is the first published study investigating personal and spatial repellents for the prevention of tick bite from I. holocyclus.

Assessment of Angelica sinensis (Oliv.) Diels as a repellent for personal protection against mosquitoes under laboratory and field conditions in northern Thailand.

BackgroundAngelica sinensis (Oliv.) hexane extract (AHE) has been reported as a proven and impressive repellent against laboratory-reared female Aedes aegypti mosquitoes. With the aim of promoting products of plant origin as a viable alternative to conventional synthetic substances, this study was designed to transform AHE-based repellents for exploitable commercial production by enhancing their efficacy and assessing their physical and biological stability as well as repellency against mosquitoes under laboratory and field conditions.MethodsThe chemical profile of AHE was analyzed by qualitative gas chromatography-mass spectrometry (GC-MS) technique. AHE was supplemented with vanillin, as a fixative, and then investigated for repellency and comparison to the standard synthetic repellent, DEET, under both laboratory and field conditions. Determination of physical and biological stability as a repellent was carried out after keeping AHE samples under varying temperatures and for different storage times.ResultsGC-MS analysis revealed that AHE contained at least 21 phytochemical compounds, constituting 95.74 % of the total content, with the major constituent of 3-N-butylphthalide (66.67 %). Ethanolic formulations of AHE and DEET showed improvement of repellency in a dose-dependent manner when vanillin was added in laboratory assessment. While 5–25 % AHE alone provided median complete-protection times of 2.0–6.5 h against Ae. aegypti, these times were increased to 4.0–8.5 h with a combination of AHE and 5 % vanillin (AHEv). Protection times against Ae. aegypti were extended from 2.25 to 7.25 h to 4.25–8.25 h when 5–25 % DEET was combined with 5 % vanillin (DEETv). In determining stability, all stored AHE samples exhibited similar characteristics such as liquid phases with aromatic odor comparable to those of fresh preparations. Furthermore, repellent activity of stored AHE samples lasted for at least six months, with varied efficacy (4.5–10.0 h) against Ae. aegypti. Field trials revealed strong repellency from both 25 % AHEv and 25 % DEETv, with complete protection (100 %) against a wide range of local mosquito populations. A total of 5,718 adult female mosquitoes, with the most predominant being Culex quinquefasciatus (41.47 %), Armigeres subalbatus (41.13 %), and Culex vishnui (10.53 %), was collected during field applications. No local skin reaction or other allergic responses was observed during both laboratory and field study periods.ConclusionsAngelica sinensis proved to have not only impressive repellency against both laboratory Ae. aegypti and a wide range of natural mosquito populations, but also relative stability in physical and biological performance.

Sustained efficacy of the novel topical repellent TT-4302 against mosquitoes and ticks.

Mosquitoes and ticks are blood-feeding pests of humans and animals that can vector many important aetiological agents of disease. Previous research demonstrated that TT-4302 (Guardian(®) Wilderness) containing 5% geraniol applied to human subjects gave 5-6 h of repellency against mosquitoes (depending on species) and was repellent to ticks in vitro. This study was conducted to obtain an independent third-party evaluation of TT-4302 against Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) mosquitoes and to test the efficacy of the product in the field against ticks. TT-4302 provided an average of 6.5 h of repellency of ≥ 95% [Weibull mean protection time: 7.4 h, 95% confidence interval (CI) 5.8-11.3 h] for St. aegypti, whereas a 15% DEET formulation provided 4.7 h of repellency (Weibull mean protection time: 5.2 h, 95% CI 3.7-6.9 h). In tick field trials, the efficacy of TT-4302 did not differ significantly from that of a 25% DEET formulation against Amblyomma americanum (Ixodida: Ixodidae). TT-4302 was 81.3% repellent at 2.5 h after application, whereas DEET was 77.2% repellent at the same time-point. Results at 3.5 h after application were 71.4% for TT-4302 and 72.9% for DEET.

Comparative Laboratory and Field Evaluation of Repellent Formulations Containing Deet and Lemon Eucalyptus Oil Against Mosquitoes in Queensland, Australia1

A field trial comparing a formulation containing 40% deet (N,N-diethyl-3-methyl benzamide) in ethanol (Bushman) and 32% lemon eucalyptus oil (LEO; Mosi-guard) as protection against mosquitoes at Redcliffe, Queensland, Australia, was conducted in February 2012 and February 2013. The 40% deet formulation provided 100% protection against mosquitoes for 7 h, while the 32% LEO provided >95% protection for 3 h.

Field Evaluation and User Acceptability of Repellent Formulations Containing Deet Against Mosquitoes in Australia1

Field efficacy trials comparing 2 formulations of deet against mosquitoes in Redcliffe, Queensland, Australia were conducted in February 2009. A formulation containing 35% deet in a gel (Australian Defence Force deet) provided > 95% protection for 3 h, while a formulation containing 40% deet in ethanol (Bushman) in a spray applicator provided > 95% for 6 h. A user acceptability study showed that 82% of soldiers using the Bushman formulation during contingency operations for 14-28 days in Timor-Leste would recommend this formulation to others and believed that the formulation provided protection against mosquitoes.

A novel encapsulation of N,N-diethyl-3-methylbenzamide (DEET) favorably modifies skin absorption while maintaining effective evaporation rates

N,N-diethyl-3-methylbenzamide (DEET) is popular insect repellent which is considered safe and effective, yet is subject to considerable skin absorption. Skin absorption decreases effective repellency since less DEET is available for evaporation. We have investigated the extent to which DEET skin absorption can be reduced and evaporation sustained through encapsulation. DEET permeation through human skin in vitro was measured for an ethanolic solution standard and for two novel topical controlled-release formulations in which the DEET active material was temporarily sequestered within a permeable, charged-film microcapsule. Evaporation measurements were gathered using Tenax TA cartridges and a sampling pump drawing air over the skin. Three formulations were studied: a previously reported microcapsule formulation (Formulation A); a newly-developed microcapsule formulation (Formulation B); and a non-encapsulated ethanol control solution. Formulation B led to a 30% reduction in DEET permeation versus control. The two microcapsule DEET formulations exhibited 36–40% higher cumulative evaporation from the skin than did the control. The vapor trapping measurements in vitro show that Formulation B provided more than 48h of effective evaporation rate for repellency, while Formulation A provided less than 35h and the ethanol control less than 15h. This establishes a technical advantage for the controlled-release approach.

Field Evaluation of Deet Against <I>Anopheles farauti</I> at Ndendo (Santa Cruz) Island, Solomon Islands

Field efficacy studies comparing two formulations of deet (N,N-diethyl-3-methylbenzamide) against mosquitoes were conducted on Ndendo Island, Solomon Islands. The repellent study was conducted at Pala village in November 2008, and the only mosquito species collected was Anopheles farauti Laveran. A formulation containing 35% deet in a gel provided >95% protection for 2 h, whereas a formulation containing 40% deet in ethanol in a spray applicator provided >95% for only 1 h. This field study demonstrated again that repellents containing deet provide a relatively short period of complete protection against Anopheles spp.

Field Evaluation of Deet AgainstAnopheles farautiat Ndendo (Santa Cruz) Island, Solomon Islands

Field efficacy studies comparing two formulations of deet (N,N-diethyl-3-methylbenzamide) against mosquitoes were conducted on Ndendo Island, Solomon Islands. The repellent study was conducted at Pala village in November 2008, and the only mosquito species collected was Anopheles farauti Laveran. A formulation containing 35% deet in a gel provided >95% protection for 2 h, whereas a formulation containing 40% deet in ethanol in a spray applicator provided >95% for only 1 h. This field study demonstrated again that repellents containing deet provide a relatively short period of complete protection against Anopheles spp.

Formulations of Deet, Picaridin, and IR3535 Applied to Skin Repel Nymphs of the Lone Star Tick (Acari: Ixodidae) for 12 Hours

The efficacies of a 20% 1-methyl-propyl-2- (hydroxyethyl)-1-piperidinecarboxylate (picaridin) spray, 20% 3-(N-acetyl-N-butyl)aminopropionic acid ethyl ester (IR3535) spray, 20% picaridin lotion, 10% IR3535 lotion, and 33% N,N-diethyl-3-methylbenzamide (deet) cream in repelling nymphal lone star ticks, Amblyomma americanum (L.), were determined at 2-h intervals over 12 h using human subjects. A repellent formulation was applied in a 5-cm-wide band encircling a volunteer's lower leg. For each challenge, 70 host-seeking nymphs were released on each volunteer's ankle, and tick locations were recorded 10 min after the ticks were released. Ticks that crawled entirely across the repellent band were considered not repelled. For all formulations and time points, significantly fewer (all P < 0.0001) A. americanum nymphs crossed the treatment bands on the volunteers' ankles than crossed the corresponding area on the untreated control legs. Formulations containing > or = 20% active ingredient were highly effective, with <10% of the ticks crossing through the treatment bands for any challenge during the 12 h. At least 40% of ticks exposed to any formulation for any challenge fell or crawled off the volunteers. There was no difference in effectiveness between the 20% spray and 20% lotion formulations of picaridin. The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent. In the formulations tested, deet, picaridin, and IR3535 provided lasting protection against A. americanum.

Formulations of Deet, Picaridin, and IR3535 Applied to Skin Repel Nymphs of the Lone Star Tick (Acari: Ixodidae) for 12 Hours

The efficacies of a 20% 1-methyl-propyl-2-(hydroxyethyl)-1-piperidinecarboxylate (picaridin) spray, 20% 3-(N-acetyl-N-butyl)aminopropionic acid ethyl ester (IR3535) spray, 20% picaridin lotion, 10% IR3535 lotion, and 33% N,N-diethyl-3-methylbenzamide (deet) cream in repelling nymphal lone star ticks, Amblyomma americanum (L.), were determined at 2-h intervals over 12 h using human subjects. A repellent formulation was applied in a 5-cm-wide band encircling a volunteer’s lower leg. For each challenge, 70 host-seeking nymphs were released on each volunteer’s ankle, and tick locations were recorded 10 min after the ticks were released. Ticks that crawled entirely across the repellent band were considered not repelled. For all formulations and time points, significantly fewer (all P < 0.0001) A. americanum nymphs crossed the treatment bands on the volunteers’ ankles than crossed the corresponding area on the untreated control legs. Formulations containing ≥20% active ingredient were highly effective, with <10% of the ticks crossing through the treatment bands for any challenge during the 12 h. At least 40% of ticks exposed to any formulation for any challenge fell or crawled off the volunteers. There was no difference in effectiveness between the 20% spray and 20% lotion formulations of picaridin. The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent. In the formulations tested, deet, picaridin, and IR3535 provided lasting protection against A. americanum.

Insect repellents and sunscreen: implications for personal protection strategies against mosquito‐borne disease

To determine the protection times provided by insect repellent and sunscreen in combined formulations against biting mosquitoes. To determine if concurrent use of repellent and sunscreen influenced protection times. Insect repellent containing comparable concentrations of N, N-diethyl-3-methylbenzamide (DEET) with and without sunscreen were tested on human skin to determine the mean protection time (MPT) against Aedes aegypti (L.) in the laboratory. Further trials were undertaken to determine the effect on MPT of sunscreen reapplication over repellent every two hours. There was no significant difference in the MPT provided by 80% DEET with (MPT+/-SE=770+/-54.8 minutes) and without (MPT+/-SE=830+/-20.2 minutes) sunscreen or 7.14% DEET with (MPT+/-SE =240+/-15.5 minutes) and 6.98% DEET without (MPT+/-SE =230+/-18.4 minutes) sunscreen. Reapplication of sunscreen resulted in a significantly lower MPT of a 17.0% DEET formulation when sunscreen was reapplied concurrently (MPT+/-SE=330+/-25.2 minutes), compared with DEET alone (MPT+/-SE =400+/-12.7 minutes). When combined in a single formulation with sunscreen, the MPT provided by both high and low concentrations of DEET is not reduced. However, if sunscreen is reapplied over insect repellent, protection times can be reduced significantly. In areas of endemic mosquito-borne disease, the reapplication of a low concentration repellent and sunscreen formulation may provide the most effective protection from biting mosquitoes while minimising the risk of overexposure to DEET.

Microencapsulation decreases the skin absorption of N,N-diethyl-m-toluamide (DEET)

The insect repellent N,N-diethyl-3-methylbenzamide (DEET) is widely used and is generally regarded as safe when used according to label instructions. Yet many studies have shown it to be absorbed through the skin. The objective of this study was to determine whether the skin absorption rate of DEET could be decreased while maintaining an evaporation rate consistent with effective repellency. To this end, an aqueous suspension containing 14C-DEET (15%w/w) entrapped in walled polysaccharide microcapsules was prepared and tested for skin absorption in vitro using modified Franz cells maintained in a fume hood. The control formulation was 15%w/w DEET in ethanol. Two doses (3 microL and 5 microL per 0.79 cm2 cell) of each formulation were applied to split-thickness human cadaver skin (n=8/dose), and permeation was monitored for 24h. The microencapsulated DEET formulation lead to a 25-35% reduction of radiolabel permeation compared to the ethanolic DEET formulation. Skin levels of radioactivity at 24h were comparable, indicating that DEET evaporation from the microencapsulated formulation was comparable to or greater than that from ethanol. Hence microencapsulation increased the ratio of DEET evaporation rate to skin penetration rate relative to unencapsulated control in this in vitro study.

Field Evaluation Against Mosquitoes of Regular and Polymer-Based Deet Formulations in Manitoba, Canada, with Comment on Methodological Issues

Studies were carried out in Manitoba, Canada, to evaluate the efficacy of three repellent products for protection of human subjects against mosquito bites. All test substances contained the active ingredient N,N-diethyl-3-methylbenzamide (deet); two were polymer-based creams (3M Ultrathon Insect Repellent and Morflex DEET Insect Repellent 30) and the third (Muskol Insect Repellent) was an alcohol-based pump spray formulation. Application of repellent was to the forearm and lower legs of subjects at 0.75 or 0.83 mg deet/cm2. Exposure to mosquito attack was continuous, and efficacy was determined by measuring complete protection time (CPT). Regardless of whether delivered as a polymer cream or in alcohol, mean CPT was similar for the tested repellents at 623 +/- 107 to 644 +/- 163 min. By contrast, mean CPT for the different test subjects showed significant variation, ranging from 531 +/- 42 to 756 +/- 54 min. Mosquito collections from untreated human test subjects, Centers for Disease Control and Prevention (CDC) light traps and sweep-netting consisted primarily of Ochlerotatus sticticus (Meigen) and Aedes vexans (Meigen). Relative catch of these two species was similar for different sampling methods through much of the day, but not in the evening, when CDC light traps oversampled Ae. vexans relative to untreated human subjects. Results are used to highlight the need to account for intersubject variation when designing repellent studies, and also are used as a basis to discuss limitations associated with using relatively few subjects when testing repellents.

Field Evaluation Against Mosquitoes of Regular and Polymer-Based Deet Formulations in Manitoba, Canada, with Comment on Methodological Issues

Studies were carried out in Manitoba, Canada, to evaluate the efficacy of three repellent products for protection of human subjects against mosquito bites. All test substances contained the active ingredient N,N-diethyl-3-methylbenzamide (deet); two were polymer-based creams (3M Ultrathon Insect Repellent and Morflex DEET Insect Repellent 30) and the third (Muskol Insect Repellent) was an alcohol-based pump spray formulation. Application of repellent was to the forearm and lower legs of subjects at 0.75 or 0.83 mg deet/cm2. Exposure to mosquito attack was continuous, and efficacy was determined by measuring complete protection time (CPT). Regardless of whether delivered as a polymer cream or in alcohol, mean CPT was similar for the tested repellents at 623 ± 107 to 644 ± 163 min. By contrast, mean CPT for the different test subjects showed significant variation, ranging from 531 ± 42 to 756 ± 54 min. Mosquito collections from untreated human test subjects, Centers for Disease Control and Prevention (CDC) light traps and sweep-netting consisted primarily of Ochlerotatus sticticus (Meigen) and Aedes vexans (Meigen). Relative catch of these two species was similar for different sampling methods through much of the day, but not in the evening, when CDC light traps oversampled Ae. vexans relative to untreated human subjects. Results are used to highlight the need to account for intersubject variation when designing repellent studies, and also are used as a basis to discuss limitations associated with using relatively few subjects when testing repellents.

Evaluation of the Performance of Flow-through Anodic Fenton Treatment in Amide Compound Degradation

A flow-through anodic Fenton treatment (FAFT) system based on the batch AFT technology was previously developed to degrade pesticides in aqueous solution. As one of a series of benchtop and pilot-scale studies in process optimization, the goal of the reported work is to evaluate the performance of the FAFT system under various operating conditions, which is critical to bringing this technology into practical general use in the field. For this purpose, the removal efficiency of the parent pesticide and the concentration of the hydroxyl radical in FAFT were calculated on the basis of a previously developed FAFT kinetic model and used for the evaluation. N,N-Diethyl-3-methylbenzamide (DEET), an insect repellent, was used as a chemical probe. Experimental data showed that the key to a high treatment efficiency is to operate the FAFT system to achieve a maximum *OH production with a minimum input of energy and chemicals. For the anodic half-cell, the system should be operated under flow-through conditions with a self-developed optimum pH of 3.0, a relatively high flow rate, and the initial effluent recycled within 6-10 min to the FAFT system for further treatment; for the cathodic half-cell, it should have a fixed volume and be entirely replaced by another batch of cathodic solution only when the pH reaches a very high value. The delivery rate of the ferrous iron should be maintained at an electrolytic current between 0.01 and 0.02 A; the ratio of H2O2/Fe2+ should be between 5:1 and 10:1. NaCl was found to be the best electrolyte, with concentrations of 0.01-0.02 and 0.08 M in the anodic and cathodic half-cells, respectively. The FAFT system was successfully applied to degrade various model amide compounds and DEET formulations, which suggests the likelihood of extending this approach to other pesticide-containing wastewaters.

&lt;I&gt;N&lt;/I&gt;,&lt;I&gt;N&lt;/I&gt;-Diethyl Phenylacetamide (DEPA): A Safe and Effective Repellent for Personal Protection Against Hematophagous Arthropods

Repellents play an important role in protecting humans from the bites of insect pests. An effective and safe repellent will be useful in reducing human-vector contact and thereby help in the interruption of vector borne disease transmission. Because of the unavailability of m-toluic acid in India for the manufacture of N,N-diethyl m-toluamide (DEET), there is a need to develop an alternate effective and safe insect repellent. In total, 120 substituted amides were synthesized and tested for repellency at 1.0 mg/cm2 under laboratory conditions. Among these amides, N,N-diethyl phenylacetamide (DEPA), applied at 1.0 mg/cm2 in different oil bases, was found to exhibit promising repellency (6-8 h) in the laboratory when tested against Aedes aegypti (L.) The repellent DEPA was evaluated on army personnel in comparison with dimethylphthalate (DMP) and DEET against mosquitoes, black flies, and land leeches under field condition in the North-East Frontier area of India. Both DEPA and DEET displayed broad-spectrum repellency. DEPA was more effective than DMP against all test organisms. However, no significant difference was noticed between DEPA and DEET for repellency at 0.25 and 0.5 mg/cm2 against black flies and mosquitoes. DMP was the least effective among the three compounds in the field studies. The relative potency of DEPA in comparison with DEET and DMP for repellency against Phlebotomine sand flies also was determined. At 0.1 mg/cm2, both DEPA and DEET were found to be equally effective with a protection time from 4.37 +/- 0.08 to 4.45 +/- 0.15 h. Both compounds were significantly more effective than DMP. At 0.2 mg/cm2, DEPA and DEET provided protection times of 6.52 +/- 0.08 and 7.15 +/- 0.15 h, respectively. DEPA was formulated into a vanishing cream, a pharmacologically safe polymer-based liquid, and a liposphere lotion. The vanishing cream and the two-polymer liquid formulations enhanced protection times from 4.4 to 6.5 and 7.13 h, respectively, compared with an alcohol solution applied at 0.5 mg/cm2 on the forearm of human volunteers. Formulations of DEPA and DEET applied at 0.5 mg/cm2 on rabbits exposed to Ae. aegypti enhanced protection times compared with an alcohol solution and the liposphere lotion from 4.0 to 6.0 h and 4.0 to 5.0 h, respectively. Comparison of mean protection times of DEET and DEPA applied at a rate of 0.3 mg/cm2 to human volunteers exposed to Cx. quinque-fasciatus under field conditions indicated that the lotion formulations of DEET and DEPA provided significantly (Duncan's multiple-range test, P < 0.05) higher protection times than did alcohol solutions. Toxicological studies revealed that DEPA is safe.