Chromatography as an analytical tool for selected antibiotic classes: a reappraisal addressed to pharmacokinetic applications

Quantitative determination of gatifloxacin, levofloxacin, lomefloxacin and pefloxacin fluoroquinolonic antibiotics in pharmaceutical preparations by high-performance liquid chromatography

The objective of this research was to develop and validate analytical methods for quantitative determination of fluoroquinolones of third generation. Simple and rapid chromatographic method was developed and validated for quantitative determination of four quinolone antibiotics in tablets and injection preparations. The fluoroquinolones studied were gatifloxacin (GAT), levofloxacin (LEV), lomefloxacin (LOM) and pefloxacin (PEF). The quinolones were analyzed by using a LiChrospher 100 RP-18 column (5 microm, 125 mm x 4 mm) and a mobile phase constituted of water:acetonitrile (80:20, v/v) with 0.3% of triethylamine and pH adjusted to 3.3 with phosphoric acid. The flow rate was 1.0 mL/min and the analyses were performed using UV detector with wavelengths varying from 279 to 295 nm. The analyses were performed at room temperature (24 +/- 2 degrees C). All fluoroquinolones were separated within 5 min. The calibration curves were linear (r>or=0.9999) over a concentration range from 4.0 to 24.0 microg/mL. The relative standard deviation (R.S.D.) was < 1.0% and average recovery was above 99.54%.

Analysis of macrolide antibiotics by liquid chromatography

A compilation of the most representative single and multianalyte HPLC methods for the analysis of macrolide antibiotics published during the last two decades is presented in this paper. Its scope is the coverage of two main areas which require the determination of macrolide antibiotics at a low concentration level, i.e. pharmacokinetic studies and residue analysis. Both of these areas involve the treatment of biological and foodstuff matrices, respectively. A detailed explanation of the different sample preparation procedures as well as the experimental conditions and the main analytical features are provided for each referred method in order to allow the reader to select the most suitable conditions for their particular purpose.

Voltammetric investigation of macrolides by an HPLC-coulometric assay

Voltammograms of macrolides, including anhydroerythromycin A, azithromycin, erythromycin A, erythromycin A enol ether, pseudoerythromycin A enol ether, oleandomycin and tylosin have been investigated using a dual electrode cell in combination with a high-throughput LC method. The half-wave potentials (E(1/2)) of the seven macrolides investigated ranged from 0.734 to 0.866 V, and the current responses reached the maxima at over 1.0 V. The current response of the downstream electrode displayed a non-linear behavior at high potentials over +0.75 V, probably because of polarization of solvent components, e.g., water. The HPLC-coulometric assay was optimized with the potentials of the upstream and downstream electrodes at +0.65 and +0.85 V, respectively. This method is suitable for detection of 14- and 15-membered macrolides (sensitivity<0.05 microg ml(-1)), but not for a 16-membered macrolide, tylosin (sensitivity>0.1 microg ml(-1)). The assay shows interferences from biomatrices in rat's blood plasma and serum, and human urine, but they were effectively removed by a cold acetonitrile extraction method.

Inhibition of microbial metabolism in anaerobic lagoons by selected sulfonamides, tetracyclines, lincomycin, and tylosin tartrate

Antibiotics are used to maintain healthy livestock and to promote weight gain in concentrated animal feed operations. Antibiotics rarely are metabolized completely by livestock and, thus, are often present in livestock waste and in waste-treatment lagoons. The introduction of antibiotics into anaerobic lagoons commonly used for swine waste treatment has the potential for negative impacts on lagoon performance, which relies on a consortium of microbes ranging from fermentative microorganisms to methanogens. To address this concern, the effects of eight common veterinary antibiotics on anaerobic activity were studied. Anaerobic microcosms, prepared from freshly collected lagoon slurries, were amended with individual antibiotics at 10 mg/L for the initial screening study and at 1, 5, and 25 mg/L for the dose-response study. Monitored metabolic indicators included hydrogen, methane, and volatile fatty acid concentrations as well as chemical oxygen demand. The selected antibiotics significantly inhibited methane production relative to unamended controls, thus indicating that antibiotics at concentrations commonly found in swine lagoons can negatively impact anaerobic metabolism. Additionally, historical antibiotic usage seems to be a potential factor in affecting methane production. Specifically, less inhibition of methane production was noted in samples taken from the lagoon with a history of multiple-antibiotic use.

Stability indicating reversed-phase ion-pairing liquid chromatographic determination of vertilmicin sulfate as bulk drug and in injections

A simple reversed-phase high performance liquid chromatographic method was developed for the analysis of vertilmicin sulfate, a novel aminoglycoside (AG). UV detection was used to determine vertilmicin sulfate and its related compounds in drug substance and products without sample derivatization. The method was used to determine the content of vertilmicin and its related compounds and test the stability of vertilmicin sulfate as drug substance and in injections, which was required for registration of new drug.

HPLC method for simultaneous determination of cefprozil diastereomers in human plasma

A high-performance liquid chromatography method was developed for the determination of cefprozil diastereomers in human plasma. Cefprozil exists as cis and trans isomer at the ratio of 90:10. Plasma samples were prepared by protein precipitation using acetonitrile, trichloroacetic acid and methylene chloride. After the mixtures were vortexed and centrifuged, the aqueous supernatant was injected into a reversed-phase C8 column. The mobile phase consisted of acetonitrile, glacial acetic acid and distilled water at the volume ratio of 5.5:1.75:92.75 (pH 2.7). The signals were monitored with UV detection at 280 nm. The calibration curves of cis and trans isomer were linear in concentration ranges of 0.1-25 and 0.02-2.5 microg/mL with the correlation coefficient of 0.9999 and 0.9989, respectively. After oral administration of cefprozil in humans, Cmax and Tmax of total cefprozil were 18.80 +/- 2.14 microg/mL and 2.06 +/- 0.62 h. This method was sensitive with excellent selectivity and reproducibility, and successfully applied to a bioavailability study of cefprozil in healthy subjects.

Determination of the purity of ampicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica column

A micellar electrokinetic chromatographic (MEKC) method and a fast reversed-phase liquid chromatographic one have been developed for determining the purity of ampicillin. MEKC separation of ampicillin and its related substances was performed with the use of an untreated fused-silica capillary and 40 mM phosphate-borate buffer, pH 7.5 containing 75 mM SDS. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 5.2 and ACN, the flow rate being 4.0 mL/min. Both methods were successfully validated. Linearity, relative response factors, limits of quantitation, intermediate precision, and accuracy were evaluated. The methods proved to be fast, reliable, and sufficiently sensitive and, accordingly, well-suited for control of purity of ampicillin substance, injections, and capsules. A combination of both methods can be very useful in the confirmation of impurity profiles.

A kinetic study on the degradation of erythromycin A in aqueous solution

The pH is a critical factor determining the rate of the degradation of erythromycin A in aqueous solutions. However, the kinetics of the acid- and base-catalyzed degradation is still uncertain. This study used a sensitive coulometric detection method to determine concentrations of erythromycin A and its degradation products. To determine the buffer-independent rate constants, sodium acetate (0.05-0.2 M) and Tris-HCl (0.1-0.5 M) were used in a pH range of 3.5-5.5 and 7.0-9.0, respectively. In acidic conditions, anhydroerythromycin A appeared to be produced directly through an internal dehydration of erythromycin A-6,9-hemiketal which simultaneously established an equilibrium with erythromycin A enol ether on the other hand. In weakly alkaline conditions, hydroxide ion appeared to catalyze the hydrolysis of the lactonyl ester bond of erythromycin A-6,9-hemiketal by the pseudo-first-order kinetics, and the C13 --> C11 translactonization and internal dehydration reactions subsequently occurred to form pseudoerythromycin A enol ether. We suggest here a predictive model for reasonable interpretation of the kinetics of erythromycin A degradation in aqueous solutions, in which the observed rate constant was expressed by the sum of the partial reaction rate constants for the acid- and base-catalyzed degradation of erythromycin A-6,9-hemiketal as a function of pH in a range of 3.0-10.0.

Determination of the fluoroquinolone enrofloxacin in edible chicken muscle by supercritical fluid extraction and liquid chromatography with fluorescence detection

A supercritical fluid extraction (SFE) method for the extraction of enrofloxacin from a chicken breast muscle was examined. A liquid chromatograph, equipped with a fluorescence detector, was used for the detection of enrofloxacin. Optimal extraction parameters, such as extraction time, supercritical fluid volume, modifier concentration, pressure, and temperature, were determined by examining SFE recoveries from control muscle samples spiked with enrofloxacin at different levels. In all of the experiments, high recovery values were observed, ranging from 101 to 104%. The extraction of enrofloxacin from real muscle samples was examined in chickens that were treated orally with enrofloxacin. Extraction was carried out by the SFE method after each oral treatment and under optimal extraction conditions at set intervals over time. The SFE, combined with liquid chromatographic analysis, showed that the concentration of enrofloxacin in the chicken muscles decreased continuously with time, giving a negligible concentration 72 h after the treatment. These results suggest that SFE is a useful approach for the extraction of enrofloxacin from chicken breast muscles.

LC determination of impurities in azithromycin tablets

A LC method with UV detection for determining azithromycin impurities in tablets as pharmaceutical form has been developed. It is to be employed in routine and stability tests. A linear gradient elution was employed starting with 47% A and 53% B to reach 28% A and 72% B at 48 min. Mobile phase A was KH2PO4 10 mM (H2O) at pH 7.00. B was a mixture methanol:acetonitrile 1:1 (v/v). UV detection was performed at 210 nm. The chromatographic column was Phenomenex Synergi MAX-RP 4 microm 250 x 460 mm kept at 50 degrees C. Six impurities were separated and identified and it was possible to quantify five out of the six with reasonable accuracy and precision.

Molecularly imprinted polymers for on-line clean up and preconcentration of chloramphenicol prior to its voltammetric determination

The performance of a molecularly imprinted polymer (MIP) as a selective solid-phase extraction sorbent for the clean-up and preconcentration of the antibiotic chloramphenicol is described. The MIP was prepared using chloramphenicol as the template, (diethylamino)ethyl methacrylate as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking monomer, and using tetrahydrofuran as the solvent. Detection of chloramphenicol was carried out by square-wave voltammetry at electrochemically activated carbon fiber microelectrodes. Chloramphenicol was eluted from the MIP microcolumn with methanol. Different experimental variables (sample pH, eluent volume, analyte and eluent flow rates and sample volume) associated with the rebinding/elution process were optimized. For a 250 mL sample, a nominal enrichment factor of 500 was attained, and for a chloramphenicol concentration of 3.0x10(-8) mol L(-1) (9.7 microg L(-1)) a recovery of 96+/-4% was obtained. A range of linearity for chloramphenicol between 3.0x10(-8) and 1.0x10(-5) mol L(-1) was obtained by loading 17 mL of analyte solutions of different concentration, eluting with 0.5 mL methanol, evaporating under a stream of nitrogen and dissolving the residue in phosphate buffer of pH 7.8. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of chloramphenicol. The applicability of the MIP for both clean up and preconcentration was demonstrated by determining chloramphenicol in ophthalmic solutions and spiked milk at different concentration levels.

CE versus LC for simultaneous determination of amoxicillin/clavulanic acid and ampicillin/sulbactam in pharmaceutical formulations for injections

A rapid, capillary electrophoresis method was evaluated for determination of amoxicillin and clavulanic acid in Augmentin as well as ampicillin and sulbactam in Unasyn preparations for injections. Phosphate-borate buffer at pH 8.66 containing 14.4% sodium dodecyl sulfate was used as a mobile phase. The method was validated. Reproducibility, precision, accuracy and assay linearity in concentration of amoxicillin 0.05-3.03 mg/ml and ampicillin 0.05-3.08 mg/ml, as well as clavulanic acid 0.02-2.02 mg/ml and sulbactam 0.05-2.08 mg/ml were established. This new method is fast, inexpensive and limits consumption of organic solvents when compared with alternative high performance liquid chromatography (HPLC) method, used for drug analysis. Statistical analysis by Student's t-test showed no significant differences between the results obtained by the two methods t(calculated) 0.32 and 1.69 for amoxicillin and clavulanic acid and 0.67 and 1.93 for ampicillin and sulbactam were smaller than t(tabulated).

HPLC separation of antibiotics present in formulated and unformulated samples

Analysis of antibiotics in formulated and unformulated samples demand a highly specific and rapid method as many antibiotics (e.g. beta-lactams) have serious stability problems. HPLC techniques can provide a valuable tool for generating highly pure preparations for characterizing the antimicrobial activities. In the present review article, column and mobile phase conditions for the various classes of antibiotics viz. penicillins, cephalosporins, macrolides, tetracyclines, aminoglycosides, quinolones, rifamycins etc. have been presented from April 1998 to November 2000. A brief discussion on chemical structure, spectrum of activity and action mechanism of each class has also been given.

Multiresidue determination of (fluoro)quinolone antibiotics in swine kidney using liquid chromatography-tandem mass spectrometry

New antibiotics were recently developed, among which are the (fluoro)quinolones. This paper presents an analytical method which allows the determination of 11 (fluoro)quinolones in swine kidneys: norfloxacin, ofloxacin, cinoxacin, oxolinic acid, nalidixic acid, flumequine, enrofloxacin, enoxacin, ciprofloxacin, danofloxacin and marbofloxacin. The procedure involves a rapid and efficient pre-treatment by solid-phase extraction (recoveries 83-98%), followed by the sensitive and selective determination of all compounds in a single run using LC-ESI-MS-MS. Multiple reaction monitoring (MRM) was used for selective detection of each (fluoro)quinolone. Quinine was selected as internal standard. The accuracy of the method, expressed as recovery, was between 89 and 109%; the repeatability had a maximum RSD lower than 15%. The limits of detection (LOD) were much lower than the respective Maximum Residue Limits (MRL)/4.

Analysis of quinolone residues in edible animal products

A comprehensive review on the analysis of quinolone antibacterials is presented. The review covers most of the methods described for the determination of quinolone residues in edible animal products. Sample handling, chromatographic conditions and detection methods have been discussed. A summary of the most relevant information about the analytical procedures has been included.

Non-derivatization approach to high-performance liquid chromatography-fluorescence detection for aminoglycoside antibiotics based on a ligand displacement reaction

An indirect fluorescence detection method has been developed for detecting the aminoglycoside antibiotics following chromatographic separation. This approach to detection is based on a displacement reaction between the aminoglycosides and a copper(II)-L-tryptophan (L-Trp) complex, Cu(L-Trp)2. The aminoglycosides, which contain multiple amino groups, have strong affinities for the Cu(II) ion and displace L-Trp from the Cu(L-Trp)2 complex. The resulting increase in L-Trp fluorescence, which is quenched when coordinated to Cu(II), is indicative of the presence of the aminoglycoside. Fluorescence titration data indicate that there is a stoichiometric ratio of 1:1 between the reaction of the aminoglycosides with Cu(L-Trp)2. This HPLC detection scheme is implemented postcolumn by mixing a buffered Cu(L-Trp)2 solution with the column eluent prior to detection. The aminoglycosides were separated with the use of a column packed with a polymeric strong cation-exchanger. Separation and detection variables were optimized and are discussed. The detection limits for the aminoglycosides tested ranged from 4.2 to 14.5 ng injected (S/N=3). A linear working curve was achieved for amikacin in the range of 29-586 ng for a six point linearity test. The developed separation and detection scheme was further tested by analyzing commercial pharmaceutical formulations of these antibiotics.

Analysis of trace levels of sulfonamide and tetracycline antimicrobials in groundwater and surface water using solid-phase extraction and liquid chromatography/mass spectrometry

A method has been developed for the trace analysis of two classes of antimicrobials consisting of six sulfonamides (SAs) and five tetracyclines (TCs), which commonly are used for veterinary purposes and agricultural feed additives and are suspected to leach into ground and surface water. The method used solid-phase extraction and liquid chromatography/mass spectrometry (LC/MS) with positive ion electrospray. The unique combination of a metal chelation agent (Na2EDTA) with a macroporous copolymer resulted in quantitative recoveries by solid-phase extraction (mean recovery, 98 +/- 12%) at submicrogramper-liter concentrations. An ammonium formate/formic acid buffer with a methanol/water gradient was used to separate the antimicrobials and to optimize the signal intensity. Mass spectral fragmentation and ionization characteristics were determined for each class of compounds for unequivocal identification. For all SAs, a characteristic m/z 156 ion representing the sulfanilyl fragment was identified. TCs exhibited neutral losses of 17 amu resulting from the loss of ammonia and 35 amu from the subsequent loss of water. Unusual matrix effects were seen only for TCs in this first survey of groundwater and surface water samples from sites around the United States, requiring that TCs be quantitated using the method of standard additions.

Determination of residues of enrofloxacin and its metabolite ciprofloxacin in biological materials by capillary electrophoresis

A method for the analysis of enrofloxacin and ciprofloxacin in chicken muscle using marbofloxacin as internal standard is proposed. Clean-up and pre-concentration of the samples are effected by solid-phase extraction and determination is carried out by capillary electrophoresis using a photodiode array detector. The calibration graphs are linear for enrofloxacin and ciprofloxacin from 10 to 300 microg/kg. The method recoveries for enrofloxacin and ciprofloxacin are 74 and 54%, respectively. The limit of detection for the two compounds is lower than 25 microg/kg, which allows the detection of positive muscle samples at the required maximum residue limits.

Prediction of electrophoretic behaviour of a series of quinolones in aqueous methanol

Quinolones are a family of antibacterial agents used in human and veterinary clinics. The examination of protonation equilibria is essential because their antibacterial activity is pH-dependent. In this work, dissociation constants of quinolones in MeOH-water mixtures were obtained using capillary electrophoresis. The method is based on a model that relates electrophoretic mobility of the solute with pH. The effect of pH, pKa and activity coefficient on electrophoretic behaviour was considered. Standard pH values for buffer solutions were previously determined in MeOH-water mixtures, and the pH can thus be measured in these media as in water. This model is also used to obtain the optimum conditions for the separation of a series of substances because it allows one to predict the resolution between adjacent peaks from a few experimental data.

Validation of an analytical procedure for the determination of the fluoroquinolone ofloxacin in chicken tissues

A novel analytical procedure was developed for the determination of the fluoroquinolone ofloxacin in chicken kidney, liver, muscle and fat plus skin tissues. The procedure involved a preliminary extraction with 0.15 M HCl followed by solid-phase extraction clean-up. The purification step was performed using a polymeric sorbent coated cartridge. Ofloxacin was analyzed by reversed-phase HPLC using UV detection at 295 nm. The mobile phase used was water-acetonitrile-triethylamine (83:14:0.45, v/v, pH 2.30). The use of triethylamine and the acidic pH modulated the retention of ofloxacin and avoided chemical tailing. The amine modifier and acetonitrile content of the mobile phase were optimized to provide the best selectivity. A flow-rate of 1 ml/min was used and ofloxacin eluted at approximately 5.1 min. HPLC analysis of the tissue samples was performed in 12 min. The procedure was validated according to the International Conference on Harmonisation guidelines across the concentration ranges (100 microg/kg-1.7 mg/kg for kidney and liver tissues and 50 microg/kg-1.0 mg/kg for muscle and fat plus skin tissues). The linearity, the intra- and inter-day accuracies and precisions were determined. The limits of quantification were 50 microg/kg for muscle and fat plus skin tissues and 100 microg/kg for liver and kidney tissues. The procedure was specific and the accuracy values were lower than 20% at the limit of quantitation of spiked samples. The recovery values ranged from 80 to 100%. The limits of detection were established at 60 microg/kg for liver and kidney tissues and at 25 microg/kg for muscle and fat plus skin tissues. Finally, ofloxacin was found to be stable in acidic conditions. The developed procedure is simple, sensitive, accurate and adapted to routine sample analyses such as those carried out for residue depletion studies.

Rapid and sensitive quantitation of antibiotics in fermentations by electrospray mass spectrometry

Electrospray ionisation mass spectrometry (ESI-MS) has been used for the determination and quantitation of a broad range of 24 antibiotics, from groups including aminoglycosides, beta-lactams, tetracyclines, antifungals and glycopeptides. Spectra have been acquired for all 24 antibiotics derived from pure samples dissolved in acetonitrile/water, along with samples extracted from complex fermentation liquor. Quantitation was carried out by the detection of the protonated molecules, using time-scheduled single-ion monitoring (SIM). ESI-MS was used to detect and quantify to 5-microM levels. A one-step extraction of antibiotics with an organic solvent (methanol) was used for this rapid and simple procedure. Specificity is not matched by other methods and antibiotic analogues (e.g. the five forms of erythromycin) can be determined within minutes.

Current methodologies for the analysis of aminoglycosides

The aminoglycosides are a large and diverse class of antibiotics that characteristically contain two or more aminosugars linked by glycosidic bonds to an aminocyclitol component. Structures are presented for over 30 of the most important members of this family of compounds. The use of aminoglycosides in clinical and veterinary medicine and in agriculture is described. Qualitative methods for aminoglycoside analysis include X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The major part of this article comprises a comprehensive review of quantitative methods for the determination of aminoglycosides. These are microbiological assay, radiochemical assay, radioimmunoassay, enzyme immunoassay, fluoroimmunoassay and other immunoassays, spectrophotometric and other non-separative methods, gas chromatography (GC), thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), and capillary electrophoresis (CE). Simple spectrophotometric methods may be adequate for the assay of bulk pharmaceuticals and their formulations. Microbiological assays make useful semi-quantitative screening tests for the analysis of veterinary drug residues in food, but rapid enzyme immunoassays are more suitable for accurate measurements of aminoglycosides in complex matrices. Automated immunoassays are the most appropriate methods for serum aminoglycoside determinations during therapeutic drug monitoring. HPLC techniques provide the specificity and sensitivity required for pharmacokinetic and other research studies, while HPLC-MS is employed for the confirmation of veterinary drug residues. The potential for further development of chromatographic and CE methods for the analysis of biological samples is outlined.

Pharmacokinetics of traditional Chinese syndrome and recipe: a hypothesis and its verification (I)

AIM:To propose a hypothesis defining the absorption, distribution, metabolism and elimination of traditional Chinese recipe (TCR)component in blood of healthy subjects and patients, and estimate its correctness.METHODS:The pharmacokinetics (PK) of same dose of drug was studied in the animal model of traditional Chinese syndrome (S)and healthy animals. The classification, termi-nology, concept and significance of the hypothesis were set forth with evidence provided in the present study. The hypotheses consisted of traditional Chinese syndrome PK (S-PK) and traditional Chinese recipe PK (R-PK). Firstly, the observed tetramethylpyrazine (TMP) PK in healthy, chronically reserpinized rats (rat model of spleen deficiency syndrome, RMSDS) and RMSDS treated with Sijunzi decoction (SJZD) for confirmation were used to verify S-PK; secondly, the ferulic acid (FA) PK in healthy and high molecular weight dextran (HMWD)-induced rabbit model with blood stasis syndrome (RDBSS) was also used to verify S-PK; and lastly, TMP PK parameters in serum of healthy rats after orally taken Ligusticum wallichii (LW), LW and Salvia miltiorrhiza (LW&SM) decoctions were compared to verify R-PK.RESULTS:The apparent first-order absorption Ka,(13.61 plus minus 2.56)h(-1) ,area under the blood drug concentration-time curve AUC, (24.88 plus minus 9.76)&mgr;gcenter doth(-1)mL(-1) , maximum drug concentration C(max), (4.82 plus minus 1.23)&mgr;gcenter dotmL(-1) of serum TMP in RMSDS were increased markedly(P< 0.05) compared with those Ka = (5.41 plus minus1.91)h(-1), AUC = (5.20 plus minus 2.57)&mgr;gcenter doth(-1)center dotmL(-1), C(max) = (2.33 plus minus 1.77)&mgr;gcenter dotmL(-1) of healthy rats (HR). The apparent first-order rate constant for alpha and beta distribution phase alpha = (0.38 plus minus 0.09)h(-1), beta = (0.06 plus minus 0.03)h(-1) , the apparent first-order intercompartmental transfer rate constants K10 = (0.24 plus minus 0.07)h(-1), K(12) = (0.11 plus minus 0.02)h(-1), K(21) = (0.11 plus minus 0.02)h(-1) of serum TMP in RMSDS were decreased significantly (P <0.01) compared with those K(10) = (0.88 plus minus 0.20)h(-1), K(12) = (1.45 plus minus 0.47)h(-1), K(21) = (0.72 plus minus 0.22)h(-1) of HR. However, no apparent differences occurred between HR and RMSDS treated with SJZD. The serum FA concentration and its AUC (5.6690 plus minus 2.3541)&mgr;gcenter doth(-1)center dotmL(-1) in RMBSS were also higher than those AUC =(2.7566 plus minus0.8232)&mgr;gcenter doth(-1)center dotmL(-1) of healthy rabbits (P <0.05). The Ka (11.51 plus minus 2.82)h(-1), AUC (0.84 plus minus0.17)&mgr;gcenter doth(-1)center dotmL(-1) of LW & SM-derived TMP in serum were much lower (P <0.05) than those Ka = (19.58 plus minus 4.14)h(-1),AUC = (1.27 plus minus 0.26)&mgr;gcenter doth(-1)center dotmL(-1) of LW-derived TMP in serum after oral decoctions.CONCLUSION:The SDS and blood stasis syndrome state could affect significantly the pharmacokinetic parameters of drugs and the abnormal SDS pharmacokinetic parameters could be normalized by SJZD. The combination of Chinese medicine in TCR could reciprocally affect the pharmacokinetic parameters of other components absorbed into the systemic circulation. These results support the S and R-PK hypothesis.

Electrospray multistep ion trap mass spectrometry for the structural characterisation of poly

Electrospray 'soft' ionisation (ESI) and multistep mass spectrometry (MS(n)) techniques enable characterisation of a bioactive polymer, poly[(R,S)-3-hydroxybutanoic acid] (a-PHB), containing covalently bonded benzylpenicillin. The chemical structures of individual mass-selected bioactive macromolecules have been determined, and their fragmentation mechanisms have been compared with those of pure penicillin G. Copyright 2000 John Wiley & Sons, Ltd.