Modular assembly of layer-by-layer capsules with tailored degradation profiles

Herein we report the preparation of layer-by-layer (LbL) assembled, biodegradable, covalently stabilized capsules with tunable degradation properties. Poly(L-glutamic acid) modified with alkyne moieties (PGA(Alk)) was alternately assembled with poly(N-vinyl pyrrolidone) (PVPON) on silica particles via hydrogen-bonding. The films were cross-linked with a bis-azide linker, followed by removal of the sacrificial template and PVPON at physiological pH through hydrogen bond disruption, yielding one-component PGA(Alk) capsules. To control the kinetics and location of capsule degradation, a number of approaches were investigated. First, a degradable bis-azide cross-linker was incorporated into the inherently enzymatically degradable capsules. Second, we assembled low-fouling capsules composed of nondegradable poly(N-vinyl pyrrolidone-ran-propargyl acrylate) (PVPON(Alk)) via hydrogen bonding with poly(methacrylic acid) (PMA) and combined this with the aforementioned system (PGA(Alk)/PVPON) to produce stratified hybrid capsules. The degradation profiles of these stratified capsules can be closely controlled by the number as well as the position of nondegradable barrier layers in the systems. The facile tailoring of the degradation kinetics makes this stratified LbL approach promising for the design of tailored drug-delivery vehicles.     

Stability-indicating HPLC method for determination of naftazone in tablets. Application to degradation kinetics and content uniformity testing

A simple, sensitive, stability-indicating HPLC method was developed and validated for the quantitative determination of the vasoprotective drug, naftazone in presence of its degradation products. The analysis was carried out on a Nucleosil 100-5 phenyl column (250 mm × 4.6 mm, 5 μm) using a mobile phase consisting of methanol-0.02 M sodium dihydrogen phosphate mixture (60:40, v/v) of pH 6.0. The analyses were performed at ambient temperature with a flow rate of 1.0 mL/min and UV detection at 270 nm. The method showed good linearity over the concentration range of 0.1-10.0 μg/mL with a lower detection limit of 0.032 and quantification limit of 0.096 μg/mL. The suggested method was successfully applied for the analysis of naftazone in its commercial tablets. Moreover, it was utilized to investigate the kinetics of alkaline, acidic and oxidative degradation of the drug. The apparent first-order rate constants, half-life times, and activation energies of the degradation process were calculated. The pH-rate profile curve was derived. Furthermore, the proposed method was successfully applied to the content uniformity testing of naftazone tablets.     

高效液相色谱法测定盐酸甲氯芬酯胶囊的含量

建立了用高效液相色谱测定盐酸甲氯芬酯胶囊含量的方法.采用Hypersil C18柱(5 μm,4.6 mm i.d.×200 mm),流动相为V(乙腈)∶V(0.12% NH4HCO3-0.50%三乙胺)溶液＝33∶67 (甲基磺酸调pH至3.0),流速: 1.0 mL/min,检测波长为225 nm.盐酸甲氯芬酯的线性范围为1.632～163.2 μg/mL,平均回收率为99.67%,RSD=1.8% (n=9).     

Polarographic determination of ampicillin in capsules and tablets

A new polarographic method is used for quantitative analysis of ampicillin dosage forms. The electroactive product is formed by acidic hydrolysis of ampicillin. It gives a well-developed reduction wave with half-wave potential of -0.91 V vs. SCE. The proposed method has good precision. A major advantage is the selectivity, which makes the determination of ampicillin possible without prior separation of the excipient.     

Determination of chlorthalidone and clonidine hydrochloride in tablets by HPLC

A rapid, reversed-phase high performance liquid chromatographic method is described for the determination of chlorthalidone and clonidine hydrochloride combinations in tablets. Individual tablets or composite samples were sonicated in water, diluted with methanol, and filtered prior to chromatographing. Chlorthalidone, formulated at 15 mg/tablet, was chromatographed on octadecylsilyl-bonded, 5 to 6-micrometers, spherical silica with 50% methanol in water mobile phase. Clonidine hydrochloride, formulated at 0.1 or 0.2 mg/tablet, was chromatographed on trimethylsilyl-bonded, 5 to 6-micrometers, spherical silica with 65% methanol in pH 7.9 phosphate buffer mobile phase. Both were determined with a spectrophotometric detector at 254 nm. Mean recoveries of the drugs from six synthetic tablet samples were 100.3% for chlorthalidone and 99.7% for clonidine hydrochloride (at 0.1 mg/tablet level) with coefficients of variation of 0.79 and 1.55%, respectively.     

Stability-indicating HPLC method for the determination of nicardipine in capsules and spiked human plasma. Identification of degradation products using HPLC/MS

In this stability-indicating, reversed-phase high-performance liquid chromatographic method for nicardipine (NIC), forced degradation has been employed and the formed degradants were separated on a C18 (150 mm × 3.9 mm, 5 μm) analytical column using a mobile phase consisted of 70% methanol: acetic acid containing 0.01 M triethylamine with pH 4. The flow rate was 1.0 mL/min and the photodiode array detection wavelength was 353 nm. Forced degradation of the drug was carried out under acidic, basic, photolytic, and oxidative stress conditions. Chromatographic peak purity data indicated no co-eluting peaks with the main peaks. This method resulted in the detection of seven degradation products. Among these, two major degradation products from basic hydrolysis, one from oxidation by H₂O₂ and four from photolytic stress were identified by mass spectral data. A good linear response was achieved over the range of 0.5–40 μg/mL with a limit of detection (LOD) of 0.011 μg/mL and limit of quantification (LOQ) of 0.036 μg/mL. The suggested method was successfully applied for the analysis of NIC in its commercial capsules, with mean% recovery value of 100.11 ± 2.26%. The method was extended to the in vitro determination on NIC in spiked human plasma samples with mean% recovery of 99.04 ± 5.67%. The suggested method was utilized to investigate the kinetics of photolytic induced degradation.     

Forced degradation studies of clobetasol 17‐propionate in methanol,propylene glycol,as bulk drug and cream formulations by RP‐HPLC

A rapid, simple, stability‐indicating forced degradation study of clobetasol 17‐propionate was conducted using RP‐HPLC. The method was used to analyze clobetasol 17‐propionate in methanol, propylene glycol, and a cream formulation. Isocratic elution of clobetasol and its degradation products was achieved using a Nova‐Pak® 4 μm C₁₈ 150 mm × 3.9 mm id cartridge column and a mobile phase of methanol: water (68:32 v/v) at a flow rate of 0.9 mL min^?1. Quantitation was achieved with UV detection at 239 nm. Nondegraded clobetasol was eluted at a retention time of 6.0 min. Clobetasol 17‐propionate was subjected to different stress conditions viz., acidic, basic, heat, oxidation, light, and neutral hydrolysis. The greatest degradation occurred under strong base and oxidative conditions. Strong base‐degraded clobetasol produced additional peaks at retention times of 1.8, 4.0, 5.0, and 8.0 min and clobetasol oxidation degradation peaks eluted at 2.2 and 24 min. Complete validation was performed for linearity, accuracy, and precision over the concentration range 0.15–15 μg mL^?1. All data were analyzed statistically and this RP‐HPLC method proved to be accurate, precise, linear, and stability indicating for the quantitation of clobetasol 17‐propionate in methanol, propylene glycol, and cream formulations.     

Argentimetric assay of captopril in bulk drug and in tablets

Three simple, selective and cost-effective procedures for the determination of captopril in bulk drug and in tablets are described. All the procedures make use of silver nitrate as a reagent and involve titrimetry and spectrophotometry as measurement techniques. In titrimetry (Method A), the aqueous solution of the drug is titrated directly with the standard silver nitrate solution to a potassium chromate end-point. In one spectrophotometric method (Method B), the sample solution is treated with excess of silver nitrate and a known amount of methyl orange and the increase in absorbance at 520 nm, caused by a decrease in pH due to release of nitric acid, is measured and related to drug concentration. The other spectrophotometric method (Method C) involves the addition of a measured excess of silver nitrate to the sample solution followed by the determination of residual silver ion by an ion-associate complex formation reaction involving eosin and 1,10-phenanthroline. The decrease in absorbance at 550 nm, which corresponds to Ag⁺ reacted with the drug, is measured and is found to be linearly related to drug concentration. All experimental variables involved in the methods were investigated and optimized. Stoichiometry of the reaction that forms the basis for titrimetry is found. Method A is applicable in the range of 1.0–20.0 mg of drug while methods B and C can be conveniently used in the concentration ranges of 2.5–50.0 and 0.25–4.0 μg ml^?1, respectively. Several optical characteristics such as molar absorptivity, Sandell sensitivity, limits of detection and quantification, and correlation coefficient were calculated. The methods were applied to the analysis of tablets containing captopril. Statistical treatment of the results indicates that the procedures are precise and accurate. The excipients used as additives in tablets did not interfere in the proposed procedures as revealed by the recovery studies.     

Phototoxicity testing by online irradiation and HPLC

A high-performance liquid chromatography (HPLC) system was developed for the determination of drug photostability and phototoxicity based on an automated column-switching system with aqueous online UV-A irradiation and hyphenated organic separation of the drug and its photoproducts. The photoreactor is built with an poly(ethylene-co-tetrafluoroethylene) (ETFE) reaction coil knitted around a UV-A light source. The chromatographic separation was performed with two special C₁₈ columns, which are also suitable for using with pure water as eluent. Degradation of chlorpromazine (CPZ) by ultraviolet light was investigated at pH 7 and pH 3. Furthermore chlorpromazine was irradiated in the presence of guanosine-5-monophosphate (GMP) in pH 7 buffered solution, leading to a new photoproduct. In the pH 3 irradiation studies of CPZ and GMP, no reaction was detected between the molecules.     

Chemometric determination of naproxen sodium and pseudoephedrine hydrochloride in tablets by HPLC

A new chemometric determination by high-performance liquid chromatography (HPLC) with photodiode array (PDA) detection was implemented for the simultaneous determination of naproxen sodium and pseudoephedrine hydrochloride in tablets. Three chemometric calibration techniques, classical least squares (CLS), principle component regression (PCR) and partial least squares (PLS) were applied to the peak area at multiwavelength PDA detector responses. The combinations of HPLC with chemometric calibration techniques were called HPLC-CLS, HPLC-PCR and HPLC-PLS. For comparison purposes the HPLC method called the classic HPLC method was used to confirm the results obtained from combined HPLC-chemometric calibration techniques. A good chromatographic separation between two drugs with losartan potassium as an internal standard was achieved using a Waters Symmetry C18 Column 5 microm 4.6+/-250 mm and a mobile phase containing 0.2 M acetate buffer and acetonitrile (v/v, 40:60). The multiwavelength PDA detection was measured at five different wavelengths. The chromatograms were recorded as a training set in the mobile phase. Three HPLC-chemometric calibrations and the classic-HPLC method were used to test the synthetic mixtures of naproxen sodium and pseudoephedrine hydrochloride in the presence of the internal standard. The HPLC-chemometric approaches were applied to real samples containing drugs of interest. The experimental results obtained from HPLC-chemometric calibrations were compared with those obtained by a classic HPLC method.     

HPLC测定四水合硫胺焦磷酸酯原料药含量

1999年,FDA批准了注射用的12种复合维生素(CERNEVIT-12),该制剂不同于以往的单纯性水溶性维生素与单纯性的脂溶性维生素组合,它是一种同时具备水溶性与脂溶性维生素的复合维生素产品,能够为患者提供全面的维生素支持.     

High-pressure liquid chromatographic determination of propoxyphene hydrochloride in tablets and capsules.

The determination of propoxyphene hydrochloride by gas chromatography (GC) has been examined. Under a number of operating conditions significant on-column decomposition has occurred. The amounts of decomposition have been found to be dependent on sample size, flow-rate, column temperature, liquid phase loading, and solid support material. In view of this work a high-pressure liquid chromatographic procedure for quantitating propoxyphene hydrochloride has been developed. This method has been found to be specific for propoxyphene hydrochloride in the presence of its heat decomposition products formed with and without acetaminophen. This method does not suffer from problems associated with GC procedures.     

High-performance liquid chromatographic separation of noreximide and norendimide in bulk material, tablets and animal feed

Noreximide, a sedative, is generally contaminated to some extent with its endo-isomer, norendimide, which produces excitation. A high-performance liquid chromatographic assay was developed to separate and quantitate these compounds on a 5-microns Ultrasphere ODS column with methanol-water (20:30) as mobile phase and detection at 254 nm. Assay of mixtures of these compounds in bulk material and tablets utilized isoniazide as internal standard. Peak area ratios were linear (r = 0.9999) over 1.4-66.2 micrograms of injected noreximide and 0.2-8.4 micrograms of injected norendimide. Overall percent recovery from simulated tablets containing noreximide alone was 99.6 +/- 0.8% (S.D., n = 3). Overall percent recoveries (+/- S.D.) from tablets containing a mixture of these compounds were 98.9 +/- 0.5% and 102.3 +/- 1.1% for noreximide and norendimide, respectively (n = 3). Noreximide in animal feed for long-term pharmacological studies was isolated by ether extraction and after work up, subjected to the same procedure, except that theophylline was the internal standard. Peak area ratios were linear over 0.2-19.3 micrograms of injected noreximide (r = 0.9999). Overall percent recoveries (+/- S.D., n = 3) of noreximide from spiked animal feed were 97.4 +/- 1.4% and 99.0 +/- 0.5% at the 500- and 5000-ppm levels, respectively. Limits of detection at the 95% confidence level (0.01 a.u.f.s., 20-microliters sample volume injected) were 1.67 microgram/ml and 2.56 micrograms/ml of noreximide and norendimide, respectively, in the final test solution.     

Porphyrin profiles in blood, urine and faeces by HPLC/electrospray ionization tandem mass spectrometry

A high-resolution high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry method is described for the analysis of porphyrins in blood, urine and faeces. The gradient elution reversed-phase HPLC system using acetonitrile-methanol-1 m ammonium acetate/acetic acid buffer (pH 5.16) as gradient solvent mixtures was able to separate all porphyrin metabolites, including the type I and type III isomers of uroporphyrin, hepta-, hexa- and penta-carboxylic acid porphyrins and coproporphyrin. The porphyrins were positively identified by the protonated molecules [M+H](+) and further characterized by tandem mass spectrometric analysis with each porphyrin giving a characteristic collisioninduced dissociation product ion spectrum. The mass chromatograms obtained by HPLC/ESI MS are useful for the differential diagnosis of the porphyrias, since each type of porphyria has a typical porphyrin excretion pattern.     

Gamma radiolytic degradation of the endrin insecticide in methanol and monitoring of radiolytic degradation products by HPLC

The objective of this investigation was to verify the degradation of endrin by gamma irradiation. ⁶⁰Co was used as radiation source for irradiation of 50 mg L^?1 endrin with a varied dose of 1–6 kGy. High performance liquid chromatography (HPLC) coupled with diode array detector was used as an analytical technique to monitor the degradation rate along with numbers of degradation products formed. At dose rate of 6 kGy ≥99% of endrin was degraded. It is proposed that utilization of ionization radiations can be an effective and efficient tool for the removal of halogenated pesticides.     

Generation of characteristic profiles of steroid hormones by reversed-phase HPLC

A method for the determination of steroid hormones by reversed-phase HPLC has been applied to the analysis of biological fluids from healthy individuals and patients with endocrine systems diseases. The obtained chromatographic profiles were processed by the method of principal component analysis and method of soft independent modeling of class analogy. The principle possibility of using the results of chemometric processing of the chromatographic profiles as an additional diagnostic criterion for the treatment of some endocrine pathologies has been shown.     

Determination and validation of duloxetine hydrochloride in capsules by HPLC with pre-column derivatization and fluorescence detection

A high-performance liquid chromatographic (HPLC) method is described for the determination of duloxetine hydrochloride in capsules. The method was based on pre-column derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole using the fluorimetric detection technique. Duloxetine hydrochloride was analyzed by HPLC using an Inertsil C18 column (5 μm, 150 × 4.6 mm) and mobile phase consisted of methanol and water (65:35, v/v). The fluorescence detector was adjusted at excitation and emission wavelengths of 461 and 521 nm, respectively. The linearity of the method was in the range of 10-600 ng/mL. Limits of detection and quantification were 0.51 and 1.53 ng/mL, respectively. The proposed method was successfully applied for determination of duloxetine hydrochloride in its pharmaceutical preparation. The results were in good agreement with those obtained using a reference method.     

Simultaneous quantification of (E) and (Z) isomers of rilpivirine and four degradation products in bulk and tablets by reversed-phase ultra-high-performance liquid chromatography and confirmation of all by molecular weight

The (E)-isomer of rilpivirine is an approved antiretroviral drug used to treat human immunodeficiency virus. A simple, fast, accurate, and precise analytical method is required to confirm the quality, purity, efficacy, and safety of drug substances and drug products containing rilpivirine. This research article offers a comprehensive ultra-high performance liquid chromatography method for the simultaneous separation and quantification of (E) and (Z) isomers of rilpivirine, including two amide impurities, one nitrile impurity, and one dimer impurity, in both bulk and tablet forms. After complete validation, the proposed reversed-phase ultra-high-performance liquid chromatography method has proven to be simple, fast, linear, accurate, and precise, with a lower limit of quantification and detection of 0.05 and 0.03 μg/ml, respectively, for all six analytes. Separation was achieved on a Waters Acquity ethylene bridged hybrid Shield RP18 (150 × 2.1 mm, 1.7 μm) column maintained at 35.0°C using a gradient elution of acetonitrile and 0.05% formic acid in 10 mM ammonium formate at a flow rate of 0.30 ml/min. A systematic forced degradation study on the undissolved rilpivirine revealed the formation of acid-base hydrolyzed amide impurities (Impurity-A and Impurity-B), oxidative nitrile impurities (Impurity-C), and Z-isomer and dimer impurities of rilpivirine (Impurity-D and Impurity-E) due to alkaline hydrolysis and photodegradation. The proposed method is primarily appropriate for applications requiring the precise determination of desired and undesired isomers of rilpivirine and its degradation products, such as those involving the safety, efficacy, and quality roles of rilpivirine in bulk and tablet forms. Additionally, the proposed ultra-high-performance liquid chromatography method in combination with a mass spectrometer and photo-diode array detector is helpful for the confirmation and correct identification of all analytes.