Erythromycin is a macrolide antibiotic used mainly in the treatment of infections caused by gram-positive organisms. Erythromycin base is rap idly degraded in acidic media necessitating the use of structurally modified erythromycin derivatives or acid resistant dosage forms in order to decrease gastric inactivation of the drug. The majority of pharmacokinetic studies to-date have utilized relatively non-specific microbiological assay procedures which are unable to differentiate between concentrations of active erythromycin base and the inactive pro-drug derivatives. A high-performance liquid chromatographic (HPLC) technique is described for the simultaneous determination of erythromycin base and propionate (inactive pro-drug form) in human serum and urine following the oral administration of erythromycin estolate, an acid stable derivative of erythromycin. The method involves a solid-phase extraction step prior to chromatography on a C18 reversed-phase column with coulometric electrochemical detection. Sample handling and storage techniques are presented which minimize hydrolysis of the inactive ester moiety between sample collection and analysis, thereby more accurately reflecting the in vivo situation than in previously published studies. Results from single dose pharmacokinetic studies indicate that only 10-15% of the total erythromycin concentration in vivo is present as the active base component following oral administration of erythromycin estolate. This percentage increases to approximately 25% during multiple dose administration. Novel urinary excretion data are presented which reveal that approximately 40% and 55% of the total erythromycin excreted in urine is excreted as erythromycin base following single and multiple dosages respectively. Computer fitting of mean serum concentration-time data revealed that an open one compartment model with linear first order absorption and elimination best described the absorption and disposition of erythromycin, although poor computer fits for individual data sets were observed. Some evidence of non-linear elimination is presented utilizing both compartmental and non-compartmental pharmacokinetic techniques. Large intra-and inter-personal variability in erythromycin absorption and disposition was experienced which was evaluated in five subjects who each received one 500 mg erythromycin estolate tablet from the same batch, on three separate occasions. In addition. an HPLC method is described for the analysis of "total erythromycin" concentrations following erythromycin estolate administration which involves hydrolysis of the ester component prior to chromatography. as well as an HPLC method utilizing amperometric electrochemical detection capable of monitoring the stability of erythromycin base in stored biological fluids. These methods were uti I ized in various stability studies involving erythromycin base and propionate as well as for the analysis of erythromycin estolate dosage forms.

No description available.

by Tsoi Yeung-pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 105-106). / Chapter I. --- Acknowledgements --- p.i / Chapter II. --- Abstract --- p.ii / Chapter III. --- Table of contents --- p.iv / Chapter IV. --- List of Tables and Figures --- p.v / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Modes of chromatography / Chapter 1.2 --- Objective of the present study / References / Chapter Chapter 2. --- Instrumentation and theory --- p.8 / Chapter 2.1 --- Instrumentation of HPLC / Chapter 2.2 --- Theory of liquid chromatography / References / Chapter Chapter 3. --- Determination of citrate in pharmaceutical preparations by HPLC using indirect photometric detection --- p.21 / Chapter 3.1 --- Introduction / Chapter 3.2 --- Review of the analytical methods / Chapter 3.3 --- Theory of detection / Chapter 3.4 --- Experimental / Chapter 3.5 --- Results and discussion / Chapter 3.6 --- Conclusion / References / Chapter Chapter 4. --- Determination of camphor and menthol by HPLC using indirect conductometric detection --- p.74 / Chapter 4.1 --- Introduction / Chapter 4.2 --- Review of the analytical methods / Chapter 4.3 --- Theory of detection / Chapter 4.4 --- Experimental / Chapter 4.5 --- Results and discussion / Chapter 4.6 --- Conclusion / References

Siu Yuen Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 122-139). / Abstracts in English and Chinese. / Abstract (English) --- p.i / Abstract (Chinese) --- p.iii / Acknowledgments --- p.v / Table of Contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xvi / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter CHAPTER 2 --- LITERATURE REVIEW --- p.7 / Chapter 2.1 --- Traditional methods for studying zooplankton feeding selectivity --- p.7 / Chapter 2.1.1 --- Cell counting after laboratory feeding experiments --- p.7 / Chapter 2.1.2 --- Direct examination of gut contents --- p.8 / Chapter 2.1.3 --- Use of radioactive tracers --- p.9 / Chapter 2.1.4 --- Gut fluorescence method --- p.9 / Chapter 2.2 --- High Performance Liquid Chromatography analysis of phytoplankton pigments --- p.11 / Chapter 2.2.1 --- Principle --- p.11 / Chapter 2.2.2 --- Pigments as signature markers of phytoplankton --- p.11 / Chapter 2.2.3 --- Development of HPLC analysis of phytoplankton pigments --- p.16 / Chapter 2.2.4 --- Advantages of HPLC analysis of phytoplankton pigments --- p.17 / Chapter 2.2.5 --- Limitation of HPLC analysis of phytoplankton pigments --- p.18 / Chapter 2.3 --- Zooplankton feeding selectivity --- p.19 / Chapter 2.3.1 --- Ecological importance of zooplankton feeding selectivity --- p.19 / Chapter 2.3.2 --- Factors affecting zooplankton feeding selectivity --- p.19 / Chapter 2.3.3 --- Feeding selectivity of zooplankton studied in this study --- p.21 / Chapter 2.3.3.1 --- p. avirostirs --- p.21 / Chapter 2.3.3.2 --- Paracalanus spp --- p.22 / Chapter 2.3.3.3 --- Pseudevadne tergestina --- p.23 / Chapter 2.4 --- Pigment degradation in guts of zooplankton --- p.24 / Chapter 2.4.1 --- Experimental design --- p.24 / Chapter 2.4.2 --- Pigment degradation --- p.24 / Chapter 2.5 --- "Tolo Harbour, Hong Kong" --- p.26 / Chapter 2.5.1 --- Site description --- p.26 / Chapter 2.5.2 --- Phytoplankton and zooplankton in Tolo Harbour --- p.27 / Chapter CHAPTER 3 --- MATERIALS AND METHODS --- p.28 / Chapter 3.1 --- Field sampling --- p.28 / Chapter 3.1.1 --- Study of seasonal patterns in zooplankton feeding selectivity --- p.28 / Chapter 3.1.1.1 --- Collection of phytoplankton and zooplankton for pigment analysis --- p.28 / Chapter 3.1.1.2 --- Collection of phytoplankton and zooplankton for plankton enumeration --- p.30 / Chapter 3.1.2 --- Collection of phytoplankton and zooplankton for laboratory feeding experiments --- p.32 / Chapter 3.2 --- Laboratory experiments and data analysis --- p.33 / Chapter 3.2.1 --- Study of seasonal patterns in zooplankton feeding selectivity --- p.33 / Chapter 3.2.1.1 --- HPLC of phytoplankton pigments --- p.33 / Chapter 3.2.1.2 --- Fluorometric measurement of chlorophyll-α --- p.35 / Chapter 3.2.1.3 --- Plankton identification and enumeration --- p.36 / Chapter 3.2.2 --- Laboratory feeding experiments for investigation of pigment degradation in zooplankton gut --- p.37 / Chapter CHAPTER 4 --- RESULTS --- p.41 / Chapter 4.1 --- Information on Tolo Harbour --- p.41 / Chapter 4.1.1 --- Temperature and salinity in Tolo Harbour --- p.41 / Chapter 4.1.2 --- Plankton composition and community in Tolo Harbour --- p.43 / Chapter 4.1.2.1 --- Phytoplankton --- p.43 / Chapter 4.1.2.2 --- Zooplankton --- p.50 / Chapter 4.2 --- Seasonal zooplankton feeding selectivity investigated by HPLC phytoplankton pigment analysis --- p.53 / Chapter 4.2.1 --- Verification of HPLC pigment analysis by fluorometric analysis --- p.53 / Chapter 4.2.2 --- Correlations between phytoplankton cell densities and pigment concentrations in water samples --- p.55 / Chapter 4.2.3 --- Feeding selectivity of zooplankton on different phytoplankton groups --- p.73 / Chapter 4.2.4 --- Feeding selectivity of zooplankton on dinoflagellates --- p.87 / Chapter 4.2.5 --- Feeding selectivity of zooplankton on diatoms --- p.87 / Chapter 4.3 --- Feeding selectivity on phytoplankton by other cladoceran - Pseudevadne tergestina --- p.89 / Chapter 4.4 --- Pigment degradation in zooplankton guts after ingestion of phytoplankton --- p.90 / Chapter 4.5 --- Clearance rates of P. avirostris and Paracalanus spp. in feeding experiments --- p.101 / Chapter CHAPTER 5 --- DISCUSSIONS --- p.105 / Chapter 5.1 --- Experiment design --- p.105 / Chapter 5.2 --- Seasonal zooplankton feeding selectivity investigated by HPLC phytoplankton pigment analysis --- p.108 / Chapter 5.2.1 --- Correlations between phytoplankton cell densities and pigment concentrations in water samples --- p.108 / Chapter 5.2.2 --- Feeding selectivity of zooplankton on different phytoplankton groups --- p.108 / Chapter 5.2.3 --- Feeding selectivity of Pseudevadne tergestina --- p.111 / Chapter 5.3 --- Feeding experiments for investigating pigment degradation in guts of zooplankton --- p.112 / Chapter 5.3.1 --- Principle --- p.112 / Chapter 5.3.2 --- Degradation for different pigments in guts of P. avirostris and Paracalanus spp. --- p.112 / Chapter 5.4 --- Clearance rates of P. avirostris and Paracalanus spp. --- p.114 / Chapter 5.4.1 --- p. avirostris --- p.114 / Chapter 5.4.2 --- Paracalanus spp. --- p.115 / Chapter 5.5 --- Limitations of HPLC analysis of phytoplankton pigments --- p.116 / Chapter 5.6 --- Environmental events related to feeding selectivity of zooplankton in Tolo Harbour --- p.118 / Chapter 5.6.1 --- Energy transfer in trophic level --- p.118 / Chapter 5.6.2 --- Abilities of p. avirostris and Paracalanus spp. to control red tides in Tolo Harbour --- p.118 / Chapter CHAPTER 6 --- CONCLUSION --- p.120 / REFERENCES --- p.122 / APPENDIX

Selenonium cations are electron deficient species in which the central selenium atom is bonded to three carbon chains (aryl or alkyl). Trimethylselenonium iodide was synthesized by reaction of methyllithium with metallic selenium to produce methylselenolithium which was, in turn, reacted with the appropriate alkylbromide. The selenide thus formed was further methylated at the selenium atom with methyl iodide in methanol in the presence of sodium tetraphenylborate. After several recrystallizations the selenonium analytes were characterized by AAS, FT-IR, $ sp1$H-NMR, $ sp{13}$C-NMR, FAB-MS and LAMMA spectroscopic techniques and used as standards for analytical methods development. / The analysis was performed by high performance liquid chromatography with atomic absorption detection. The chromatography on a cynopropyl silica bonded phase was optimized for mobile phase composition by response surface analysis. The resulting surface response plots permitted a differentiation between the mechanisms of action of two mobile phase modifiers: triethylamine and trimethylsulfonium iodide. The improvement in chromatographic efficiency resulted in two to three fold decrease in the limit of detection. An extraction procedure with liquefied phenol was evaluated for the determination, by HPLC-AAS, of traces of selenonium cations in biological samples. The advantages and shortcomings of the HPLC-THG-AAS approach are discussed.

Amadori rearrangement product (ARP) of tryptophan with glucose was synthesized according to a published procedure, and its decomposition was studied at two different concentrations and at two temperatures, 110$ sp circ$C and 140$ sp circ$C over a period of 6 hrs. A RP-HPLC system was developed to separate and quantitate the decomposition products of the ARP. The results indicated that, the ARP can decompose to form the following products, hydroxymethylfurfural (HMF), maltol, indole, $ beta$-carbolines (norharman and harman) and tryptophan. Further, using the same analytical method, the following systems were also analyzed for the presence of the above mentioned products (a) D-glucose and D-mannose with tryptophan; (b) D-glucose; and (c) tryptophan. In addition, rate constants and activation energies for the decomposition and formation reaction were calculated. Plausible mechanisms for the formation of the decomposition products are suggested.

In cellular studies of patients with lipid related disorders such as mammary cancers, leukemia, and artheroscierosis, separation of molecular species of oxidized phosphatidylcholine (PC) can be an important assistance in research or diagnosis. Goals of this project were to optimize separation of oxidized and unoxidized PC molecular species in a single HPLC chromatogram followed by in line identification of hydroperoxides. Oxidized egg PC's were produced using UV light exposure in air. Separations were performed on an Ultrasphere ODS column and an Asahipak ODPVA column using a Waters 2695 system with photodiode array. The ODPVA column routinely gave 10 times larger plate numbers. Various mobile phase mixtures (methanol, acetonitrile, water) and gradients were tested. The optimum gradient on our system is (1) 5 minutes, 47 % methanol/40 % acetonitrile/13 water in a linear gradient to (2) 17 minutes, 49 % methanol/40 % acetonitrile/11 % water to (3) 18 minutes, 29 % methanol/60 % acetonitrile/11 % water linearly to (4) 50 minutes, 31 % methanol/60 % acetonitrile/9 % water continued isocratically to 110 minutes. Oxidized hydroperoxides were detected by fluorescence using a post column reaction with diphenyl-1 pyrenylphosphine (DPPP). Both iron (III) and pyridine were tested as catalysts for this reaction. / Department of Chemistry

Thesis (M.S.)--Youngstown State University, 1995. / Includes bibliographical references (leaves 69-71).

Thesis (M.S.)--Youngstown State University, 1995. / Includes bibliographical references (leaves 44-48).

Thesis (M.S.)--Central Connecticut State University, 1999. / Thesis advisor: James V. Arena, Ph. D. " ... in partial fulfillment of the requirements for the degree of Master of Science in Chemistry." Includes bibliographical references (leaf 48).