Validated HPLC-MS/MS method for determination of quetiapine in human plasma.

A validated, highly sensitive and selective high-pressure liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantitative determination of quetiapine (QUE) in human Na2EDTA plasma with mass spectrometry (MS) detection. Clozapine (CLO) was employed as an internal standard. Samples were extracted using solid phase extraction (SPE). Oasis HLB cartridges and the concentration of quetiapine was determined by isocratic HPLC-MS/MS. The SRM mode was used for MS/MS detection. The method was validated over a concentration range of 1.0-382.2 ng/mL. Inter- and intra-day precision and accuracy of the proposed method were characterized by relative standard deviation (R.S.D.) and the percentage of deviation, respectively; both were lower than 8%. The developed method was employed in the pharmacokinetic study of quetiapine.

Validated HPLC-MS-MS method for simultaneous determination of atorvastatin and 2-hydroxyatorvastatin in human plasma-pharmacokinetic study.

Cholesterol-reducing statin drugs are the most frequently prescribed agents for reducing morbidity and mortality related to coronary heart disease. In this publication a validated, highly sensitive, and selective isocratic HPLC method is reported for quantitative determination of the major statin drug atorvastatin (ATV) and its metabolite 2-hydroxyatorvastatin (HATV). Detection was performed with an electrospray ionization triple-quadrupole mass spectrometer equipped with an ESI interface operating in positive-ionization mode. Multiple reaction monitoring (MRM) was used for MS-MS detection. The calibration plot was linear in the concentration range 0.10-40.00 ng mL(-1) for both ATV and HATV. Inter-day and intra-day precision and accuracy of the proposed method were characterized by measurement of relative standard deviation (RSD) and percentage deviation, respectively; both were less than 8% for both analytes. The limit of quantitation was 0.02 ng mL(-1) for ATV and 0.07 ng mL(-1) for HATV. The method was used for pharmacokinetic study of ATV and HATV. Pharmacokinetic data for all analytes are also reported.

Validated HPLC-MS/MS method for simultaneous determination of simvastatin and simvastatin hydroxy acid in human plasma.

Cholesterol lowering statin drugs are the most frequently prescribed agents for reducing morbidity and mortality related to coronary heart disease. This publication presents a validated, highly sensitive and selective isocratic HPLC method for the quantitative determination of the major statin drug simvastatin (SIM) and its metabolite simvastatin hydroxy acid (SIMA). Detection was performed on an electrospray ionization triple quadrupole mass spectrometer equipped with an ESI interface operated in positive and negative ionization mode. The multiple reaction-monitoring mode (MRM) was used to provide MS/MS detection. The linearity for the calibration curve in the concentration range of 0.10-16.00 ng/mL for SIM and 0.10-16.00 ng/mL for SIMA is presented. Inter- and intra-day precision and accuracy of the proposed method were characterized by relative standard deviation (R.S.D.) and percentage deviation, respectively; with both lower than 7% for all analytes. The limit of quantitation was 0.03 ng/mL for SIM and 0.02 ng/mL for SIMA. The devised method was employed in the pharmacokinetic study of SIM and the pharmacokinetic parameters of all analytes are also presented.

Validated HPLC-MS-MS method for determination of azithromycin in human plasma.

A validated, highly sensitive, and selective HPLC method with MS-MS detection has been developed for quantitative determination of azithromycin (AZI) in human Na2EDTA plasma. Roxithromycin (ROX) was used as internal standard. Human plasma containing AZI and internal standard was ultrafiltered through Centrifree Micropartition devices and the concentration of AZI was determined by isocratic HPLC-MS-MS. Multiple reaction monitoring mode (MRM) was used for MS-MS detection. The calibration plot was linear in the concentration range 2.55-551.43 ng mL(-1). Inter-day and Intra-day precision and accuracy of the proposed method were characterized by R.S.D and percentage deviation, respectively; both were less than 8%. Limit of quantification was 2.55 ng mL(-1). The proposed method was used to determine the pharmacokinetic profile of AZI (250-mg tablets).

The interactions between human dendritic cells and microbes; possible clinical applications of dendritic cells.

The dendritic cells comprise several subsets that induce and regulate the immune responses against foreign and self-antigens, and that can therefore function as initiators of protective immunity and inducers of central or peripheral tolerance. The different subpopulations of dendritic cells interact with and also influence other cell populations of the immune system, such as T and B lymphocytes and natural killer cells. The factors that determine the given dendritic cell functions depend on the state of maturation and the local microenvironment. The interactions between dendritic cells and microorganisms are rather complex, but progress in the past few years has shed light on several aspects of these interactions. This review lays emphasis on the interactions between human dendritic cells, important components of the intima of arterial specimens at areas predisposed to atherosclerotic lesions, and Chlamydia pneumoniae and cytomegalovirus, the human pathogens most strongly implicated in the development of atherosclerosis. In addition, several examples of the potential clinical applications of dendritic cells are described.

Determination of cyclodextrins and their derivatives by capillary electrophoresis with indirect UV and conductivity detection.

A fast and simple capillary electrophoretic method suitable for the determination of native alpha-, beta-, gamma-cyclodextrins, their randomly substituted tert-butyl derivatives (average degree of substitution 3.8-4.4), heptakis (2,6-di-O-methyl)- and heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin was developed. Naphthyl-2-sulfonic acid (2-NSA), 3-iodobenzoic acid (3-IBA) and (1S)-1-phenylethylamine (PHEA) were tested as selective complex forming and UV absorbing background electrolyte additives. The composition of optimized background electrolyte for the separation of uncharged cyclodextrins and their derivatives was: 15 mM 3-iodobenzoic acid titrated with tris[hydroxymethyl]aminomethane to pH 8.0, 5% (v/v) of acetonitrile. A complete resolution of mono-2-O-, mono-3-O- and mono-6-O-carboxymethyl-beta-cyclodextrin regioisomers was achieved in the optimized background electrolyte system: 40 mM PHEA titrated with 2-[N-morpholino]ethanesulfonic acid to pH 5.6. In addition to indirect UV detection a contactless conductometric detector was successfully utilized.

Optimization of background electrolytes for capillary electrophoresis I. Mathematical and computational model.

A mathematical and computational model is introduced for optimization of background electrolyte systems for capillary zone electrophoresis of anions. The model takes into account mono- or di- or trivalent ions and allows also for modeling of highly acidic or alkaline electrolytes, where a presence of hydrogen and hydroxide ions is significant. At maximum, the electrolyte can contain two co-anions and two counter-cations. The mathematical relations of the model are formulated to enable an easy algorithmization and programming in a computer language. The model assesses the composition of the background electrolyte in the analyte zone, which enables prediction of the parameters of the system that are experimentally available, like the transfer ratio, which is a measure of the sensitivity in the indirect photometric detection or the molar conductivity detection response, which expresses the sensitivity of the conductivity detection. Furthermore, the model also enables the evaluation of a tendency of the analyte to undergo electromigration dispersion and allows the optimization of the composition of the background electrolyte to reach a good sensitivity of detection while still having the dispersion properties in the acceptable range. Although the model presented is aimed towards the separation of anions, it can be straightforwardly rearranged to serve for simulation of electromigration of cationic analytes. The suitability of the model is checked by inspecting the behavior of a phosphate buffer for analysis of anions. It is shown that parameters of the phosphate buffer when used at neutral and alkaline pH values possess singularities that indicate a possible occurrence of system peaks. Moreover, if the mobility of any analyte of the sample is close to the mobilities of the system peaks, the indirect detector signals following the background electrolyte properties will be heavily amplified and distorted. When a specific detector sensitive on presence of the analyte were used, the signal would be almost lost due to the excessive dispersion of the peak.

Determination of cyclodextrin content using periodate oxidation by capillary electrophoresis.

A simple and general method suitable for the determination of cyclodextrin content in various matrices is described. The proposed method involves selective cleavage of C-C bonds with vicinal hydroxyl groups by means of periodate (Malaprade's reaction). The amount of produced iodate is monitored by capillary electrophoresis. Optimized electrophoretic conditions (20 mM disodium tetraborate with 1 mM tetradecyltrimethylammonium bromide, direct UV detection lambda = 200 nm) ensure complete separation of periodate and iodate ions and sufficient sensitivity towards iodate. Under optimized reaction conditions (2-fold excess of periodate, temperature 70 degrees C) reproducible quantitative results were obtained for alpha-, beta- and gamma-cyclodextrins as model samples. The proposed method was tested on a real sample of acrylamide--2'-O-allyl-beta-CD copolymer. The values of beta-cyclodextrin content were compared with those obtained by reference NMR measurement and were found to be identical.

Split-flow injector for capillary zone electrophoresis.

A simple construction of a split-flow injector eliminating some common problems connected with the use of such devices is described. It consists of a low-pressure pump, an injection valve and a delivery tube in which the separating capillary inlet is fixed. The sample is injected without moving the separating capillary inlet and without interrupting the applied voltage. The grounded electrophoretic electrode is close to the injection valve so that all metal parts of the injector are kept at a sufficiently low potential. Minimum length and small internal diameter of delivery tube minimizes additional sample zone broadening. The effects of some experimental parameters, such as the position of the separation capillary inlet with respect to the background solution flow direction and background solution flow-rate are experimentally studied. The injector was tested primarily for the electrokinetic injection.

Determination of thiodiglycolic acid in urine by capillary electrophoresis.

A sensitive capillary electrophoretic method was developed for the determination of thiodiglycolic acid (TDA) in urine which avoids the pretreatment of the urine sample. Several carrier electrolytes were examined. The most suitable carrier electrolyte system consisted of potassium hydrogen phthalate (5 mM), 2-(N-morpholino)ethanesulfonic acid (50 mM) and tetradecyltrimethylammonium bromide (0.5 mM), pH 5.2. Ten times diluted fresh midstream void urine was used for the determination. In this way, the concentrations of TDA between 5 and 50 mg/l in undiluted urine samples can be determined.

Putative chemical signals from white-tailed deer (Odocoileus virginianus). Urinary and vaginal mucus volatiles excreted by females during breeding season.

Urine and vaginal mucus samples from female white-tailed deer in estrus and mid-cycle were analyzed by combined gas chromatography-mass spectrometry (GC-MS). Forty-four volatiles were found in mucus and 63 in urine. The volatiles common to both vaginal mucus and urine included alcohols, aldehydes, furans, ketones, alkanes, and alkenes. Aromatic hydrocarbons were present only in the vaginal mucus, whereas pyrans, amines, esters, and phenols were found only in urine. Both estrous mucus and estrous urine could be identified by the presence of specific compounds not present in mid-cycle samples. Numerous compounds exhibited dependency on ovarian hormones.

Effects of salts on the stability of the cationic radical of phenothiazine derivatives.

Effects of cations and anions of various salts on the stability of the diethazine cation radical were studied in various mineral acids. It was found that stability is enhanced in the presence of salts that contain the same anion as that contained in the cation radical salt. Other anions decrease the stability. The influence of salt cations is negligible.

Selected applications of cyclodextrin selectors in capillary electrophoresis.

Through the use of alpha-, beta-, gamma- and heptakis(2,6-di-O-methyl)-beta-cyclodextrin as stereospecific selectors or electrolyte modifiers, both in capillary zone electrophoresis and isotachophoresis, selected model isomeric compounds (including optical isomers) were resolved. Soluble alkylhydroxyalkylcellulose derivatives were further added to the cyclodextrin-modified background electrolytes under study. Their presence was found to be essential, as demonstrated by improvements in both enantioselectivity and separation efficiency. The results obtained in both electrophoretic modes, under optimized conditions, are compared and discussed.

[Determination of sulbactam in human serum using capillary isotachophoresis]. / Stanovení sulbaktamu v lidském séru kapilární izotachoforézou.

A method of determination of sulbaktam in human serum by capillary isotachophoresis with the use of a conductivity detector was worked out. Prior to the proper analysis, a pretreatment of the sample of serum was carried out by extracting sulbaktam to butyl acetate. The total yield of the proposed analytical procedure with an extraction first stage approaches 94%. The smallest determinable amount of the sample corresponds to 1 micrograms of sulbaktam in 1 ml of serum. The reported method was employed to evaluate the samples of sera of volunteers after intravenous administration of the dosage form sulbaktam-ampicillin (VUFB) and the foreign pharmaceutical preparation Unasyn (Pfizer). Statistically insignificant differences in pharmacokinetic parameters have confirmed that the preparations are highly bio-equivalent.

Use of cyclodextrins in isotachophoresis. VII. Resolution of structurally related and chiral phenothiazines.

Commercially available phenothiazine derivatives were used for the study of cyclodextrin complex formation by cationic isotachophoresis with alpha-, beta- and gamma-cyclodextrin and methylated analogues of beta-cyclodextrin as leading electrolyte additives. The relationships between the type of solute substituent in the 10- and/or 2-position and the stability of the created cyclodextrin complex were studied and the results were utilized for the optimization of isotachophoretic conditions suitable for the resolution of the studied phenothiazine derivatives. Successful resolution of three racemic solutes was achieved.

Use of cyclodextrins in isotachophoresis. VI. Cyclodextrins as leading electrolyte additives for the separation of bile acids.

Cyclodextrins (CDs) and some of their methyl derivatives have been used for the optimization of the isotachophoretic separation of bile acids in aqueous electrolyte systems. The addition of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin to the leading electrolyte proved useful for both the solubilization and the structural differentiation of the solutes studied and led to the successful separation of their mixtures. Other CDs tested, even if they gave a satisfactory solubilization effect, did not support the resolution of bile acid mixtures.