Determination of Trichlorfon Pesticide Residues in Milk via Gas Chromatography with µ-Electron Capture Detection and GC-MS.

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with µ-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.1 µg/l, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to 250 µg/l. The intra- and inter-day accuracy (n = 6) ranged from 89.2%to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples.

Electroantennography in the study of two stingless bee species (Hymenoptera: meliponini)

Relatam-se aqui os resultados preliminares de estudos eletroantenográficos realizados com duas espécies de Frieseomellita brasileira. Os experimentos com F. silvestrii e F. varia mostraram que as antenas respondem aos extratos obtidos com hexano das cabeças e dos abdômens das duas espécies e da tíbia posterior de F. silvestrii (que transporta resinas coletadas de plantas). Respondem também aos compostos puros, 2-heptanol e 2-nonanol, e aos terpenos, a-cubebeno, humuleno e b-cariofileno, encontrados nas tíbias e no cerume de seus próprios ninhos.

Chemical basis for inter-colonial aggression in the stingless bee Scaptotrigona bipunctata (Hymenoptera: Apidae).

Inter-colonial aggression was tested using three colonies of Scaptotrigona bipunctata in a natural setting when their nests were moved and by artificial contact between individuals. Examination of the cuticular lipids of individuals from two colonies kept under identical conditions showed clear differences in their cuticular hydrocarbon profiles. The cuticular lipids were a mixture of hydrocarbons (saturated and unsaturated alkanes and alkenes) within the range of C23-C29. The use of multivariate analysis (PCA and discriminant analysis) showed that seven of the identified surface compounds are enough to separate workers from colonies A and B from each other.

Electroantennography in the study of two stingless bee species (Hymenoptera: Meliponini).

The first recorded electroantennographic preliminary studies on stingless bees have been performed using two species of Frieseomelitta from Brazil. Experiments with F. silvestrii and F. varia showed that antennae respond to hexane extracts of heads and abdomens of both species and posterior tibia of F. silvestrii (which carry plant resin), as well as to the pure compounds 2-heptanol and 2-nonanol, which occur in the mandibular glands of both species, and to the terpenes alpha-cubebene, humulene, and beta-caryophyllene found on their tibia and in the cerumen of their nests.

Comparative study of the cuticular hydrocarbon composition of Melipona bicolor Lepeletier, 1836 (Hymenoptera, Meliponini) workers and queens

In social insects, cuticular hydrocarbons are involved in species, kin, caste and nestmate recognition. Gas chromatography and mass spectrometry were used to compare the cuticular hydrocarbon composition of workers, males and queens of Melipona bicolor. The cuticular hydrocarbon composition of this species was found to consist mainly of C23, C25:1, C25, C27:1, C27, C29:1 and C29, which are already present in imagoes that have not yet abandoned the brood cell. This composition varied quantitatively and qualitatively between and within the castes and sexes. The newly emerged workers and young queens (virgins) had similar cuticular hydrocarbon profiles, which were different from those of the males. When the females start executing their tasks in the colony, the cuticular hydrocarbon profile differences appear. The workers have less variety, while the queens conserve or increase the number of cuticular hydrocarbon compounds. The queens have more abdominal tegumentary glands than the workers, which apparently are the source of the new cuticular compounds

Secretions of stingless bees: cephalic secretions of two Frieseomelitta species.

Gas chromatographic and mass spectrometric analysis of the volatile compounds in the mandibular glands of Frieseomelitta varia and the heads of Frieseomelitta silvestrii have revealed relatively simple or more complex mixtures of volatile oxygenated compounds. 2-Alkanols were found to be important components for both species. In F. varia the composition was essentially the same in samples from two widely separated areas and there were small differences between callows and mature, foraging bees. The first electroantennographic studies on stingless bees, using hexane extracts of heads of both species, have demonstrated a response in the workers' antennae to these, as well as to the pure compounds 2-heptanol and 2-nonanol.

A new type of exocrine gland and its function in mass recruitment in the ant Cylindromyrmex whymperi (Formicidae, Cerapachyinae).

Workers of the ant Cylindromyrmex whymperi display mass trail recruitment. Bioassays show that the trail pheromone originates from a unique gland between abdominal sternites 6 and 7. The gland has a hitherto unknown structural organization. Upon leaving the secretory cell, the duct cell widens to form a sclerotized pear-shaped reservoir chamber, lined with multiple duct cells. Each duct thus forms a miniature reservoir for the secretions of each single secretory cells, a novel structural arrangement in exocrine glands of social Hymenoptera.

(Z)-3-hexenyl (R)-3-hydroxybutanoate: a male specific compound in three North American decorator wasps Eucerceris rubripes, E. conata and E. tricolor.

The males of the decorator wasps Eucerceris have been observed to display abdomen-dragging behavior on plants surrounding their nest. It is thought that this applies a territorial-marking sex pheromone that serves to alert females to the males' territory for courtship and mating. The extracts of three species E. rubripes, E. conata, and E. tricolor have been analyzed by GC-MS. The gas chromatograms revealed the presence, in large quantities, of one common volatile compound in the male head extracts. By analogy with the closely related bee wolves Philanthus, we believe the pheromone is produced in the mandibular glands. Utilizing mass spectrometry, microreactions, FT-IR, and 1H and 13C NMR spectroscopy the structure of the pheromone was proposed to be (Z)-3-hexenyl 3-hydroxybutanoate, which was confirmed by synthesis. The absolute configuration of the chiral center was determined to be R for the three species by preparing the Mosher esters of the insect samples and comparing their GC retention times with a synthetic sample of known absolute configuration. In addition 2- and 3-hexenoic acid and some aromatic compounds were also found in varying quantities in both males and females along with hydrocarbons and fatty acids, although no species-specific profiles emerged.

Defensive role of secretion of ectal mandibular glands of the wasp Polistes dominulus.

Ectal mandibular glands of insects are exocrine glands localized in the anterior-lateral region of the head, close to the base of the mandibles. In social wasps, the gland is composed of secretory cells and a reservoir into which the secretion accumulates. At the time of emission the secretion flows onto a specialized cuticular area on the outside of the base of the mandibles. Secretion of Polistes dominulus is emitted only when wasps are greatly disturbed or in the presence of predators, and its function seems to be mainly defensive. Morphometric studies did not reveal any size differences between the glands of the queens and those of the workers. GC-MS analyses of the glands identified 32 compounds, mainly acids and aldehydes in the range C2-C18. The overall odor, caused by the mixture of aldehydes, is distinct. Workers do not respond strongly to the odor. The secretion probably serves as a warning signal to vertebrate predators.

Secretions of stingless bees: the Dufour gland of Nannotrigona testaceicornis.

The Dufour gland of Nannotrigona testaceicornis is a large, wide, pear-shaped sac. The gland secretion consists chiefly of the diterpene ester all-trans-geranylgeranyl acetate (64% of the total), together with a complex mixture of small amounts of cyclic ketals; mono-, sesqui-, and diterpene compounds; acetates; and other oxygenated compounds. Samples of N. testaceicornis collected at two sites in Brazil and one in México shared the same composition of their glands, suggesting that the species is uniform over this wide geographical area.

A nonspecific fatty acid within the bumblebee mating plug prevents females from remating.

The best mating strategy for males differs from that of females, because females gain from mating with several males (polyandry), but males gain from monopolizing the females. As a consequence, males have evolved a variety of methods, such as the transfer of inhibitory substances from their accessory glands, to ensure exclusive paternity of the female's offspring, generally with detrimental effects on female fitness. Inhibitory substances have been identified as peptides or other specific molecules. Unfortunately, in social insects male-mating traits are investigated only poorly, although male social insects might have the same fundamental influence on female-mating behavior as found in other species. A recently developed technique for the artificial insemination of bumblebee queens allowed us to investigate which chemical compound in the mating plug of male bumblebees, Bombus terrestris L., prevents females (queens) from further mating. Surprisingly, we found that the active substance is linoleic acid, a ubiquitous and rather unspecific fatty acid. Contrary to mating plugs in other insect species, the bumblebee mating plug is highly efficient and allows the males to determine queen-mating frequencies.

Recruitment pheromone in the harvester ant genus Pogonomyrmex.

Workers of the harvester ant genus Pogonomyrmex employ recruitment trail pheromones discharged from the poison gland. In P. barbatus, P. maricopa, P. occidentalis and P. rugosus we identified three pyrazines [2,5-dimethylpyrazine, trimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine (EDMP)] as major compounds of the volatile part of the poison-gland secretions. Laboratory and field tests revealed EDMP to be the main recruitment pheromone.

Chemical ecology of triatomine bugs: vectors of Chagas disease.

Knowledge of chemical ecology of haematophagous triatomine bugs (Hemiptera: Heteroptera: Reduviidae) could be of practical value because this polyphyletic subfamily includes species of medical importance, such as vectors of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), the aetiological agent of Chagas disease. For particular species of Dipetalogaster, Panstrongylus, Rhodnius and Triatoma, therefore, we review information on exocrine glands and products, interpreting their apparent roles as semiochemicals in the aggregation, alarm, defence, host-finding and sexual behaviour of these Triatominae.

Behavioral and chemical analysis of venom gland secretion of queens of the ant Solenopsis geminata.

Bioassays in a Y-tube olfactometer showed that workers of Solenopsis geminata (Hymenoptera: Formicidae) were attracted to venom gland extracts of queens. Gas chromatography coupled mass spectrometry analysis of individual glands of queens of S. geminata showed that the secretion is composed mainly of a large amount of 2-alkyl-6-methylpiperidine alkaloids and a tiny amount of a delta-lactone and a a-pyrone, which have been earlier identified as components of the queen attractant pheromone of Solenopsis invicta Buren. However, additional small amounts of a mixture of sesquiterpenes and pentadecene were found. The possible function of the sesquiterpenoid compounds is discussed.

Ambulatory management of burns.

Burns often happen unexpectedly and have the potential to cause death, lifelong disfigurement and dysfunction. A critical part of burn management is assessing the depth and extent of injury. Burns are now commonly classified as superficial, superficial partial thickness, deep partial thickness and full thickness. A systematic approach to burn care focuses on the six "Cs": clothing, cooling, cleaning, chemoprophylaxis, covering and comforting (i.e., pain relief). The American Burn Association has established criteria for determining which patients can be managed as outpatients and which require hospital admission or referral to a burn center. Follow-up care is important to assess patients for infection, healing and ability to provide proper wound care. Complications of burns include slow healing, scar formation and contracture. Early surgical referral can often help prevent or lessen scarring and contractures. Family physicians should be alert for psychologic problems related to long-term disability or disfigurement from burn injuries.

Chemistry, ontogeny, and role of pygidial gland secretions of the vinegaroon Mastigoproctus giganteus (Arachnida: Uropygi).

Pygidial gland secretions of the vinegaroon, Mastigoproctus giganteus, consist of 26% water and 74% short-chained fatty acids, with acetic acid and octanoic acids the dominant acids. The organic composition of the secretion consists of 83% acetic acid, 15% octanoic acid, 1% (Z)-5-octenoic acid, 0.0002% of the corresponding (E)-isomer, 0.11% heptanoic acid, 0.02% hexanoic acid, 0.007% decanoic acid, and in some individuals a trace of 2-nonanone. Formic acid is absent from the secretion. Glandular composition, especially in the concentrations of the minor components, varies dramatically among individuals and shows no age pattern differences among the four free-living subadult instars, or sex differences between adult males and females. Each individual exhibits its own specific blend of components which is identical in the two separate and different sized glands. The secretions act solely as allomones against potential predators, and do not act as pheromones, or elicit a communicative or behavioral response. Behavioral tests using live animals or a synthetic blend of vinegaroon secretion revealed that the secretion is maximally effective on sensitive respiratory, visual, or sensory systems of potential predators and is ineffective, or nearly so, when contact is restricted to inside the predator's mouth. Thus, the effectiveness of the secretion apparently results from its delivery as a spray of fine droplets, rather than as an exudate or vapor.

Chemical analysis of the swarming trail pheromone of the social wasp Polybia sericea (Hymenoptera: Vespidae).

The behaviour of those polistine wasps which found their nests by swarming, suggests that these species use trail pheromones for leading the swarm to the location chosen for the new nest. Apart from a recent report regarding the ropalidine Polybioides tabidus, where the pheromone is thought to originate from the Dufour gland, nothing is known about the chemistry of such pheromones. Polybia sericea is the only species for which the source of the trail pheromone, the Richards' gland, is known with certainty. The chemistry of the Richards' gland secretion of this species has been investigated in the present work and shown to be a complex mixture where the major compounds are alkyl and aromatic aldehydes, fatty acids, 3-phenylpropanoic acid, ketones, a macrolactone, a pyranone compound and nerolidol.

Effects of the neem tree compounds azadirachtin, salannin, nimbin, and 6-desacetylnimbin on ecdysone 20-monooxygenase activity.

The effects of azadirachtin, salannin, nimbin, and 6-desacetylnimbin on ecdysone 20-monooxygenase (E-20-M) activity were examined in three insect species. Homogenates of wandering stage third instar larvae of Drosophila melanogaster, or abdomens from adult female Aedes aegypti, or fat body or midgut from fifth instar larvae of Manduca sexta were incubated with radiolabeled ecdysone and increasing concentrations (from 1 x 10(-8) to 1 x 10(-3) M) of the four compounds isolated from seed kernels of the neem tree, Azadirachta indica. All four neem tree compounds were found to inhibit, in a dose-dependent fashion, the E-20-M activity in three insect species. The concentration of these compounds required to elicit a 50% inhibition of this steroid hydroxylase activity in the three insect species examined ranged from approximately 2 x 10(-5) to 1 x 10(-3).

Effect of carbon loading on the extraction properties of C-18 bonded silica used for solid-phase extraction of acidic and basic analytes.

A range of C-18 bonded phases for solid-phase extraction (SPE), with different carbon loadings and degrees of end capping, have been evaluated for the extraction of model acidic and basic analytes (anisic acid and propranolol, respectively). High carbon loadings (18 and 22%) were associated with poor extraction properties with losses on application and wash steps. Recovery of extracted analytes from such materials was also inefficient, suggesting poor mass transfer properties. A low-carbon-loaded phase (5%), though capable of efficient extraction of the analytes, was seen to be poorly retentive. The best SPE phases for either analyte were those of intermediate carbon loading (∼15%). Significant effects of end capping were only observed for the basic analyte propranolol, where retention was probably mediated by silanophilic interactions.

An investigation of the properties of a "shielded" phase for the solid phase extraction of acidic and basic compounds.

The extraction properties of Hisep, a novel bonded phase for solid phase extraction, have been investigated using a number of acidic and basic analytes and compared with those of a conventional ODS bonded material. Marked differences in extraction properties for the test analytes propranolol, anisic acid and ICI 128436 from aqueous buffer were noted between the two materials. Thus, extraction onto the ODS material was by both ionic and reversed-phase mechanisms whilst retention on the Hisep phase appeared to be mediated predominantly by reversed-phase hydrophobic interactions. The presence of dog plasma had no effect on the extraction of propranolol but did reduce the extraction efficiencies observed for anisic acid and ICI 128436 in a pH dependent manner.