Wax esters are substantial constituents of natural waxes, which can be found in many living organisms. Properties of lipids, including wax esters, may be significantly influenced by the position of double bond. In this diploma thesis the location of double bonds was determined by dimethyl disulfide (DMDS) derivatization followed by detection using tandem mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). We managed to measure the APCI and ESI MS/MS spectra of 8 different wax esters with different position of double bond. Diagnostic ions determining double bond position were identified. This method could be used in HPLC/MS analysis of wax esters, which cannot be analyzed by GC/MS. It was shown that the DMDS derivatization reaction and mass detection with APCI ionization is also suitable for locating double bonds in alkenes.

No description available.

O dengue e o dengue hemorrágico são considerados como as arboviroses mais importantes do ponto de vista da saúde pública além de serem também as mais disseminadas. O greening ou huanglongbing (HLB), por sua vez, é uma doença de difícil controle e rápida disseminação que afeta seriamente a produção de citros no mundo todo. É considerada a pior doença de citros da atualidade pois não tem cura e leva ao declínio e morte das árvores em alguns anos. O DMDS é um composto sulfúrico volátil derivado de plantas e que tem despertado um crescente interesse devido a sua comprovada atividade repelente e inseticida além de ação nematicida e disinfectante do solo. Visando oferecer uma alternativa para o controle de ambas as doenças, este trabalho teve como objetivo desenvolver um método de microencapsulação por spray drying e spray congealing para o dimetil dissulfeto (DMDS), visando a redução da sua volatilidade através de uma liberação controlada para o ambiente. Dessa forma, tornar-se-ia viável sua utilização como repelente, larvicida e inseticida no combate ao vetor do dengue além da sua utilização como repelente no controle do greening nas lavouras de citrus. Tentou-se a microencapsulação através de spray congealing utilizando enxofre como microencapsulante mas não se obteve sucesso devido as características térmicas do enxofre. Foram obtidas micropartículas de DMDS microencapsulado em goma arábica através da técnica de spray drying. As micropartículas e o processo de secagem foram caracterizados com relação ao rendimento de secagem, rendimento de microencapsulação, morfologia, teor de água residual, atividade de água, densidades aparente e compactada e propriedades de fluxo. Confirmou-se a possibilidade de microencapsulação de DMDS por spray drying e eficiência da goma arábica na retenção do mesmo. As partículas obtidas apresentaram boas propriedades de atividade de água, teor de água residual e densidade mas propriedades de fluxo que requerem melhoria. Foi feito também um estudo simplificado da viabilidade técnico-econômica da implantação de uma unidade de produção de DMDS microencapsulado. Esse estudo foi baseado no processo de microencapsulação estudado. Foram analisados diversos parâmetros econômicos e através destas análises verificou-se que a produção de DMDS microencapsulado pelo método utilizado seria economicamente viável. / Dengue fever and dengue hemorrhagic fever are not only considered the most important arboviruses from public health standpoint but also the most disseminated ones. Greening or huanglongbing (HLB) is a citrus disease of difficult control and fast dissemination that affects citrus production all over the world. It is considered the worst citrus disease nowadays since it does not have a cure and it causes the decline and death of the trees in a few years. Dimethyl disulfide is a volatile sulphur compound derived from plants and that has aroused growing interest due to its proved repellence and insecticidal activity, soil disinfection and nematocidal properties. Therefore, this work aimed at developing a DMDS microencapsulation method via spray drying and spray congealing in order to decrease DMDS\' volatility through a controlled release to the environment and offer a control alternative to both diseases. This would make DMDS use as a repellent, larvicide and insecticide of dengue fever\'s vector and also its use in greening control as a repellent viable. We tried to microencapsulate the DMDS through spray congealing using sulfur as a microenpsulating agent but it was unsuccessful due to the thermal characteristics of sulfur. DMDS was microencapsulated in Arabic gum through spray drying. Drying yield, microencapsulation yield, morphology of the particles, residual water percentage, water activity, bulk and tapped density and flow properties were used to characterize the microparticles and the drying process. Feasibility of DMDS microencapsulation and Arabic gum efficiency in DMDS retention were confirmed. The microparticles presented good bulk and tapped density, residual water percentage and water activity properties though its flow properties requiring further improvement. A simplified technical-economical evaluation of a DMDS microencapsulation factory was also done. This evaluation was based on the studied microencapsulation process. Many economical parameters were analysed and those analyses showed that DMDS microparticles production using the studied method would be economically viable.

O dengue e o dengue hemorrágico são considerados como as arboviroses mais importantes do ponto de vista da saúde pública além de serem também as mais disseminadas. O greening ou huanglongbing (HLB), por sua vez, é uma doença de difícil controle e rápida disseminação que afeta seriamente a produção de citros no mundo todo. É considerada a pior doença de citros da atualidade pois não tem cura e leva ao declínio e morte das árvores em alguns anos. O DMDS é um composto sulfúrico volátil derivado de plantas e que tem despertado um crescente interesse devido a sua comprovada atividade repelente e inseticida além de ação nematicida e disinfectante do solo. Visando oferecer uma alternativa para o controle de ambas as doenças, este trabalho teve como objetivo desenvolver um método de microencapsulação por spray drying e spray congealing para o dimetil dissulfeto (DMDS), visando a redução da sua volatilidade através de uma liberação controlada para o ambiente. Dessa forma, tornar-se-ia viável sua utilização como repelente, larvicida e inseticida no combate ao vetor do dengue além da sua utilização como repelente no controle do greening nas lavouras de citrus. Tentou-se a microencapsulação através de spray congealing utilizando enxofre como microencapsulante mas não se obteve sucesso devido as características térmicas do enxofre. Foram obtidas micropartículas de DMDS microencapsulado em goma arábica através da técnica de spray drying. As micropartículas e o processo de secagem foram caracterizados com relação ao rendimento de secagem, rendimento de microencapsulação, morfologia, teor de água residual, atividade de água, densidades aparente e compactada e propriedades de fluxo. Confirmou-se a possibilidade de microencapsulação de DMDS por spray drying e eficiência da goma arábica na retenção do mesmo. As partículas obtidas apresentaram boas propriedades de atividade de água, teor de água residual e densidade mas propriedades de fluxo que requerem melhoria. Foi feito também um estudo simplificado da viabilidade técnico-econômica da implantação de uma unidade de produção de DMDS microencapsulado. Esse estudo foi baseado no processo de microencapsulação estudado. Foram analisados diversos parâmetros econômicos e através destas análises verificou-se que a produção de DMDS microencapsulado pelo método utilizado seria economicamente viável. / Dengue fever and dengue hemorrhagic fever are not only considered the most important arboviruses from public health standpoint but also the most disseminated ones. Greening or huanglongbing (HLB) is a citrus disease of difficult control and fast dissemination that affects citrus production all over the world. It is considered the worst citrus disease nowadays since it does not have a cure and it causes the decline and death of the trees in a few years. Dimethyl disulfide is a volatile sulphur compound derived from plants and that has aroused growing interest due to its proved repellence and insecticidal activity, soil disinfection and nematocidal properties. Therefore, this work aimed at developing a DMDS microencapsulation method via spray drying and spray congealing in order to decrease DMDS\' volatility through a controlled release to the environment and offer a control alternative to both diseases. This would make DMDS use as a repellent, larvicide and insecticide of dengue fever\'s vector and also its use in greening control as a repellent viable. We tried to microencapsulate the DMDS through spray congealing using sulfur as a microenpsulating agent but it was unsuccessful due to the thermal characteristics of sulfur. DMDS was microencapsulated in Arabic gum through spray drying. Drying yield, microencapsulation yield, morphology of the particles, residual water percentage, water activity, bulk and tapped density and flow properties were used to characterize the microparticles and the drying process. Feasibility of DMDS microencapsulation and Arabic gum efficiency in DMDS retention were confirmed. The microparticles presented good bulk and tapped density, residual water percentage and water activity properties though its flow properties requiring further improvement. A simplified technical-economical evaluation of a DMDS microencapsulation factory was also done. This evaluation was based on the studied microencapsulation process. Many economical parameters were analysed and those analyses showed that DMDS microparticles production using the studied method would be economically viable.

No description available.

Methyl bromide (MBr) was widely used as a soil fumigant to manage soilborne pests in plasticulture vegetable production; however, it has been banned by the United Nations Environment Programme. Alternatives to MBr must be implemented to sustain fresh market tomato productivity. Possible MBr alternatives include new fumigant compounds, improved plastic mulch, and grafting. Methyl iodide (MeI) and dimethyl disulfide (DMDS) were tested as fumigant alternatives to MBr for the control of yellow nutsedge and soilborne pathogens of tomato. Virtually impermeable film (VIF) and totally impermeable film (TIF) were tested for fumigant retention and yellow nutsedge control in tomato. Grafting onto resistant rootstocks was tested for bacterial wilt and nematode management in tomato. In the absence of a soil fumigant, TIF suppressed yellow nutsedge better than VIF. TIF increased fumigant retention compared to VIF at similar application rates. Reduced fumigant application rates could be used in combination with TIF while maintaining fumigant concentrations, weed control, and crop yields comparable to greater use rates with VIF. Shank applied DMDS rates could be lowered to 281 L/ha under TIF from 468 L/ha under VIF; shank applied MeI application rates could be reduced to 56 L/ha under TIF compared to 93 L/ha under VIF and drip applied DMDS could be reduced from 561 L/ha under VIF film to 374 L/ha under TIF. Grafting susceptible commercial tomato cultivars onto resistant tomato hybrid rootstocks increased yields and plant survival in bacterial wilt infested fields. "Cheong Gang", "BHN 998", and "BHN 1054" were the best performing rootstocks for bacterial wilt resistance and tomato fruit yield in severely infested fields. Grafting increased tomato yield and decreased root galling from root-knot nematodes in an infested field. Hybrid rootstock "RST 106" resulted in the lowest root-knot nematode galling. In conclusion, TIF with reduced rates of DMDS or MeI is a viable MBr alternative for fresh market tomato production to retain effective doses of fumigant, manage yellow nutsedge and maintain yields. Grafting is an effective MBr alternative to manage bacterial wilt and root-knot nematode and maintain tomato yields. / Ph. D.