Benzoyl peroxide assay using high-pressure liquid chromatography

A highly specific assay for benzoyl peroxide was developed using high-pressure liquid chromatography. A concentration curve was recorded from 0.1 to 3.0 microgram with a correlation coefficient of 0.9969. The standard deviation for 10 individual analyses of a benzoyl peroxide preparation was +/- 0.547 (1.80% RSD).     

Assessment of antioxidant activity of some antileprotic drugs

DPPH (alpha,alpha-diphenyl-beta-picryl hydrazyl) (CAS 217-591-8), a stable free radical can be used to determine the antioxidant activity (AOA) of some drugs. In the present study the DPPH method was used for the first time to test AOA of dapsone (CAS 80-08-0), clofazimine (CAS 2030-63-9) and rifampicin (CAS 13282-42-1) in vitro and deproteinated blood method. Ascorbic acid (CAS 50-81-7) was used as a control in the study, which showed concentration-dependent antioxidant activity. Rifampicin showed a per se effect but it showed concentration dependent decrease in the DPPH absorbance. Ascorbic acid, dapsone and rifampicin showed DPPH scavenging activity both in vitro and deproteinated blood method. Clofazimine did not have any influence on DPPH. This method may be extended to different drugs for testing their AOA in biological fluids.     

Reversed-phase ion-pair liquid chromatography of some quaternary ammonium drugs

The resolving power of a reversed-phase liquid chromatographic method that makes use of a mobile phase system with two counter-ions of opposite charge (N,N-dimethyloctylamine and sodium octanesulphonate) for the separation of quaternary ammonium drugs, is compared with that obtained using more traditional ion-pairing systems. Efficient, selective and well-resolved separations could only be obtained by the combined effects of the eluent modifiers.     

Determination of procainamide and N-acetylprocainamide in biological fluids by high-pressure liquid chromatography

A modification of a high-pressure liquid chromatographic method for the simultaneous determination of procainamide and N-acetylprocainamide in plasma is described. The deficieicies in the specificity of the existing method were overcome by replacing the cation-exchange column and the mobile phase. The recovery and reproducibility of both procainamide and N-acetylprocainamide from human, dog, and rat plasma and urine spiked with either compound were excellent in the concentration range of 0.05--10 microgram/ml for plasma and 0.5--20 microgram/ml for urine. The comparison of this method with a specific extraction method for sets of plasma samples from human subjects and rats receiving N-acetylprocainamide and procainamide, respectively, showed no statistically significant difference.     

Determination of polythiazide in pharmaceutical dosage forms by high-pressure liquid chromatography.

A method is presented for the quantitative analysis of polythiazide tablets by high-pressure liquid chromatography. The powdered tablets are extracted with methanol, containing quinoline as the internal standard, and assayed by comparison of peak heights after liquid chromatography. The chromatographic conditions employed may be adapted for the determination of many other thiazide and nonthiazide diuretics.     

Determination of polyvinylpyrrolidone using high-performance liquid chromatography

Polyvinylpyrrolidone (PVP) is a versatile polymer with innate surface activity. It is very difficult to accurately assay due to its wide molecular weight range and amphiphilic nature. This study evaluated a reversed-phase HPLC method to separate and quantify PVP K15. The assay used a Hicrome C18 150 mm x 3 microm HPLC column in combination with an 80/20 propanol-1-ol: deionised water, 0.01% TFA mobile phase, which resolved the polymer as a single peak, tR = 10.69+/-0.17 min (n=120) at 243 nm. The column's performance was constant throughout the study, N (theoretical plates) = 1729+/-22 and the peak symmetry remained good (As ranged from 0.74 to 0.92, n=10 over the calibration range). The developed assay proved to be accurate, sensitive and capable of recovering PVP K15 from pharmaceutical formulations. The limits of quantification and detection were calculated statistically as 2.40 and 0.72 mg ml(-1), respectively. Assay reproducibility assessed at five concentrations gave an average coefficient of variance <3.5% and the accuracy of the analytical method was 102.62+/-2.04%. The recovery of PVP K15 from directly compressed tablets and Refresh eye drops was 98.02+/-2.73 and 108.35+/-6.52%, respectively.     

高压液相层析法测定分配系数——Ⅰ.反相层析法测定肉桂酸及有关化合物的分配系数

本文报道了用反相层析法测定分配系数(P)的方法,并测定了具有辐射防护作用的肉桂酸及有关化合物的分配系数。实验测得的log P值同Hansch π加和法所得到的计算值相符,偏差低于10%。高压液相层析法测定分配系数具有快速、重现性好和操作简便等优点。     

Laboratory automation of high-pressure liquid chromatography.

An automated system for high-pressure liquid chromatography was developed. The system is built around commercial modules wherever possible, modified to varying degrees. An automatic sampler, a sample pump, a high-pressure sampling valve, a recorder with an integrator, and a high-pressure liquid chromatograph comprise the commercial instruments. Relays, solenoid valves, and timers control chromatographic events, i.e., duration of sampling and rinse, mobile phase pump refill, sample injection, and chromatographic time. The automated system is dependable over long periods of unattended operation. With the 40-sample capacity of the sample tray and the last sample stop capability, the automated system produces, for example, 40 20-min chromatograms in approximately 13 hr of unattended operation. Data demonstrate the reliability and utility of the system.     

去甲斑蝥素片的高效液相色谱质量检测

目的 研究去甲斑蝥素片的质量控制方法。方法采用HPLC法,色谱柱Polarls C_(18)柱(5 μ,4.6mm×250mm),检测波长为211 um,流动相为:水:乙醇(85:15),以磷酸调节pH至3.1。结果 去甲斑蝥素在25～1000mg·L~(-1)范围内呈线性系统,r=0.9 999,最低检出限为0.2mg·L~(-1),平均回收率为100.84％,平均RSD为1.335％。结论 该方法快速、准确,重现性好,适用于该制剂的含量测定。     

Determination of ethimizol and two of its metabolites in serum by high-pressure liquid chromatography

A liquid chromatographic assay has been developed for the determination of ethimizol and two of its metabolites in serum. The analysed compounds are preseparated from serum by a micro-column packed with an octadecylsilanized silica gel. Components of the micro-column eluate are analysed on a silica-gel-packed column by means of a high-performance liquid chromatograph fitted with a photometric detector. At 262 nm the detection limit of the injected amount of ethimizol is about 5 ng. The mass spectra of two ethimizol metabolites isolated from rat serum are presented. The suitability of the developed assay for pharmacokinetic studies of ethimizol is demonstrated.     

Determination of gemcitabine and its metabolite in human plasma using high-pressure liquid chromatography coupled with a diode array detector

AIM:Toestablishahighpressureliquidchromatography(HPLC)methodfordeterminationoftheconcentrationofgemcitabine(dFdC)anditsmetabolite(dFdU)inhumanplasma.METHODS:Plasma1.0mLspikedwithfloxuridineasaninternalstandardwasextractedwith3.0mLofmethanol-acetonitrile(v/v,1:9).Thesupernatantwasevapo-ratedat60oCandtheresiduewasreconstitutedwith0.5mLofthesolutionusedasthemobilephase.Aftercentrifugation,50μLofthesupernatantwasinjectedintotheHPLCsystem.SeparationwasachievedonaC18(4.6mm×250mm,5μm)c…     

Determination of enantiomeric drugs in physiological fluids using on-line solid phase derivatizations and reversed-phase liquid chromatography

A new analytical approach has been developed for the determination of d,l-amphetamine in urine using on-line solid phase derivatizations in HPLC-UV/FL. Several other enantiomeric drugs were also investigated using the same method. The method was validated by several experiments, including: (1) kinetic studies for the reaction of each enantiomeric drug with the solid phase chiral reagent; (2) "single blind spiking" experiments; and (3) polarimetry for confirmation of the enantiomeric composition determined by the solid phase diastereomer formation-HPLC-UV/FL method. The resulting diastereomers were well resolved (Rs = 1.05-1.40) under typical reversed-phase HPLC conditions. Enantiomeric contamination at the 1.1% level could be detected. The lowest amount of d,l-amphetamine that could be simultaneously derivatized and detected was about 50 ng ml-1. The linearity of the overall measurement was 3-4 orders of magnitude. d,l-Amphetamine spiked into urine at different concentration levels and different d,l-ratios, only followed by filtration, were directly injected into the on-line solid phase derivatization-HPLC-UV/FL system for quantitation with relative standard deviations 1.8-6.4% and relative errors 0.6-9.8%.     

Determination of major boswellic acids in plasma by high-pressure liquid chromatography/mass spectrometry

Until now, dexamethasone is the medication of choice to reduce peritumoral edema associated with primary and secondary brain tumors. Because of the severe side effects accompanying such a treatment the interest in alternative agents that may be co-administered with glucocorticoids and help to reduce the required dose is constantly increasing. Boswellia serrata gum resin extracts (BSE), which have been designated an orphan drug status by the European Medicines Agency (EMA) in 2002 for the treatment of peritumoral edema, may represent a promising supplemental herbal remedy. However, clinical studies on the effect of BSE on brain edema as well as analyzes of serum levels are very scarce. Based on that background a prospective, placebo controlled, and double blind clinical pilot trial was conducted on 14 patients applying for the first time a high dose of 4200 mg BSE per day and 13 patients receiving placebo. For monitoring the serum levels of all major boswellic acids (BAs) a highly sensitive HPLC-MS method has been developed that allows the determination of KBA and AKBA from 5.0 ng/ml to 3000 ng/ml and of αBA, βBA, AαBA and AβBA from 0.5 ng/ml to 12,000 ng/ml. It is the first validated method that covers such a wide concentration range, which makes it suitable to be used as standard method in clinical trials as it compensates for the great pharmacokinetic variability in the plasma levels of BAs observed in clinical practice. Average steady concentrations (ng/ml) in the range of 6.4-247.5 for KBA, 0-15.5 for AKBA, 36.7-4830.1 for αBA, 87.0-11948.5 for βBA, 73.4-2985.8 for AαBA and 131.4-6131.3 for AβBA were determined in the verum group. The here quantified steady state levels suggest βBA to be a possible candidate for the anti-inflammatory and anti-edemateous effects of BSE. In general, the serum level analysis underlines the promising clinical results of BSE on cerebral edema.     

Separation of penicillin G potassium and its degradation products using high-pressure liquid chromatography

A high-pressure liquid chromatographic technique was developed for the separation of penicillin G potassium and several of its decomposition products. The method utilized a buffered acetonitrile-phosphate mobile phase on a reversed-phase C18 column. Separation of penicillin G potassium and six degradation products was attained within 25 min.     

Liquid-lipquid partition coefficients by high-pressure liquid chromatography.

Lipid-water partition values can be rapidly and reliably measured by high-pressure liquid chromatography (HPLC) on bonded octadecylsialne supports. This method has been developed and applied to a family of hypotensive triaminopyrimidine 3-oxides. The measured column retention values for this class of compounds correlate well with the values calculated by the Hansch method. We believe that this technique is an important addition to the methodology of Hansch analysis.     

Ceftazidime determination in serum by high-pressure liquid chromatography

A rapid and sensitive high-pressure liquid chromatographic method with simple sample preparation was developed for the quantitative analysis of the beta-lactam antibiotic ceftazidime (CAS 78439-06-2, Fortum). A good linear relationship was established between the peak area and the amount of ceftazidime injected over a concentration range of 1 to 200 microg/ml. The detection limit of the method was calculated to be 0.9 microg/ml. Stability was shown at 4 degrees C and at -196 degrees C for time periods of 2 h and 84 days, respectively.     

Protein binding of some nonsteroidal anti-inflammatory drugs studied by high-performance liquid affinity chromatography

The protein binding of indomethacin, sulindak and diclofenac sodium is studied in the presence of some competitors: phenylbutazon and diazepam. A high-performance liquid affinity chromatography based on chiral stationary phases with immobilized human serum albumin is used. The competition of the markers and the drugs for two major high- and low-affinity binding sites is investigated. Using a mathematical procedure proposed by the same authors in a previous work the affinity constants of the binding drugs and markers for both types of site are calculated. An analogous behaviour is established for the three drugs-they have nearly the same affinity for the primary binding sites marked by phenylbutazon and diazepam and only one type of low-affinity site (diazepam-binding sites) is involved in binding. That can be explained assuming an overlapping sites.