A rapid LC coupled with electrospray ionization (ESI) MS/MS method was developed and validated for the quantification of paroxetine in heparinized human plasma. The plasma samples were prepared by the solid-phase extraction method without drying or reconstitution. Elution was done with 0.5 mL 0.2%(v/v) formic acid in methanol-acetonitrile (65 + 35, v/v). The analyte and the internal standard (IS; imipramine hydrochloride) were chromatographed on a BDS Hypersil C18 column. The analyte was analyzed by LC/MS/MS with only 1.7 min run time. An ESI interface was chosen for ionization of the analyte from the sample matrix. Selected reaction monitoring mode for detection of paroxetine and the IS were achieved by using m/z 330.17/192.10 and 281.13/86.14, respectively. The LC retention times for paroxetine and imipramine were 0.94 and 1.05 min, respectively. The method was linear in the concentration range of 0.5-80.0 ng/mL with r > or = 0.9995. Recovery of paroxetine and imipramine ranged from 90 to 95%. The assay has been successfully applied to bioequivalence study samples for estimation of paroxetine in healthy human subjects.

SK3530.2HCl,(2-(5-(4-(2-hydroxyethyl)piperazin-1-ylsulfonyl)-2-n-propoxyphenyl)-5-ethyl-7-n-propyl-3,5-dihydro-4H-pyrrolo[3,2-d]pyrimidin-4-one dihydrochloride), is a novel a new phosphodiesterase type V (PDE V) inhibiting agents. The pharmaceutical development of SK3530 necessitated the availability of an assay for the quantification and purity determination of SK3530 active pharmaceutical ingredient (API) and its pharmaceutical dosage form. A reversed-phase high performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection was developed, consisting of separation on a C18 column with a CapcellPack MG (4.6 mm x 150 mm, 5 microm) column with ammonium acetate buffer (pH 4.0, 20 mM)-acetonitrile (60:40, v/v) as the isocratic mobile phase and UV detection at 250 nm. The method has been shown good chromatographic separation for SK3530 and the other related substances. The method was found to be linear 200-300 microg/ml, precise and accurate. Stress testing showed degradation products, which were well separated from the parent compound, confirming its stability-indication capacity. Moreover, the use of LC-MS and on-line diode array detection enabled us to propose structures for degradation products.

A simple, accurate, and sensitive spectrophotometric method for analysis of selective serotonin reuptake inhibitors (SSRIs) has been developed and validated. The analysis was based on the formation of colored charge-transfer complexes between the intact molecule of SSRI drug as an n-electron donor and each of tetracyanoquinodimethane (TCNQ) or p-chloranilic acid (pCA) as electron acceptors. The formed complexes were measured spectrophotometrically at 842 and 520 nm for TCNQ and pCA, respectively. Different variables and parameters affecting the reactions were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9975-0.9996) were found between the absorbances and the concentrations of the investigated drugs in the concentration ranges of 4-50 and 20-400 microg/mL with TCNQ and pCA, respectively. With all the investigated drugs, TCNQ gave more sensitive assays than pCA; the limits of assay detection were 2.5-4.8 and 20-40 microg/mL with TCNQ and pCA, respectively. The intra- and interassay precisions were satisfactory; the relative standard deviations did not exceed 2%. The proposed procedures were successfully applied to the analysis of the studied drugs in pure form and pharmaceutical formulations with good accuracy; the recovery values were 98.4-102.8 +/- 1.24-1.81%. The results obtained from the proposed method were statistically comparable with those obtained from the previously reported methods.

A selective and sensitive reversed-phase HPLC method was developed for the determination of the antidepressant paroxetine in plasma. The method is based on the purple chromogen formed by a displacement reaction of paroxetine with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile at 80 degrees C for 20 minutes. For the assay, the drug was extracted from 1 mL of plasma with chloroform and, after sample alkalinization, derivatized with TCNQ; then the reaction mixture was directly injected into a C18 column. Desipramine was used as internal standard. The mobile phase was acetonitrile-water (70:30) at a flow-rate of 1.0 mL/min, and the derivatives were eluted at 13.1 and 15.5 minutes for paroxetine and desipramine, respectively, and detected at 567 nm. Calibration curve was found linear over the range of 20-400 ng/mL, and the detection limit was 2 ng/mL at a signal-to-noise ratio of 3/1. Recoveries determined for 3 concentrations range between 81.3% and 88.1%. Intraday and interday relative standard deviation values were found to be within 3.8%-13.5% and 8.2%-14.6%, respectively. With this developed method, a pharmacokinetic study was performed for paroxetine.

Simple, sensitive, and accurate visible spectrophotometric methods are described for the determination of paroxetine hydrochloride (PA) in tablets. Among them, the first 3 methods are based on the ion-pair complexes of PA formed with bromothymol blue (BTB), bromophenol blue (BPB), and bromocresol green (BCG) in aqueous acidic buffers. The complex species extracted into chloroform were quantitatively measured at 414 nm with BTB and BCG and at 412 nm with BPB. Beer's law was obeyed over the concentration ranges of 2-20, 2-16, and 2-16 microg/mL, respectively. The fourth method described is based on a coupling reaction between PA and 7-chloro-4-nitrobenzofurazon (NBD-Cl) in borate buffer, pH 8.5, in which a yellow reaction product that was measured at 478 nm was formed. The Beer's law range for this method was 2-10 microg/mL. The last method developed describes the interaction of PA base, as an n-electron donor, with 7,7,8,8-tetracyanoquinodimethane (TCNQ), as a pi-acceptor, in acetonitrile to give blue-colored TCNQ- radical anion with absorption maxima at 750 and 845 nm. Measured at 845 nm, the absorbance-concentration plot was rectilinear over the range of 1.5-15 microg/mL. The new methods developed were successfully applied to the determination of PA in tablets without any interference from common tablet excipients. The results of the methods were in good agreement with those obtained with an official liquid chromatographic method. This report describes first colorimetric methods for the determination of PA.

Three simple and sensitive spectrophotometric methods were developed and validated for determination of the hydrochloride salts of fluoxetine, sertraline, and paroxetine in their pharmaceutical dosage forms. These methods were based on the reaction of the N-alkylvinylamine formed from the interaction of the free secondary amino group in the investigated drugs and acetaldehyde with each of 3 haloquinones, i.e., chloranil, bromanil, and 2,3-dichloronaphthoquinone, to give colored vinylamino-substituted quinones. The colored products obtained with chloranil, bromanil, and 2,3-dichloronaphthoquinone exhibit absorption maxima at 665, 655, and 580 nm, respectively. The factors affecting the reactions were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9986-0.9999) were found between the absorbances and the concentrations of the investigated drugs in the range of 4-120 microg/mL. The limits of detection for the assays ranged from 1.19 to 2.98 microg/mL. The precision values of the methods were satisfactory; the relative standard deviations were 0.56-1.24%. The proposed methods were successfully applied to the determination of the 3 drugs in pure and pharmaceutical dosage forms with good accuracy; the recoveries ranged from 99.1 to 101.3% with standard deviations of 1.15-1.92%. The results compared favorably with those of reported methods.

The hydrolysis and photolysis of paroxetine HCI, a selective serotonin reuptake inhibitor, in aqueous buffer solutions (pH 5, 7, and 9), in synthetic humic water, and in lake water were investigated at 25 degrees C in the dark and in a growth chamber outfitted with fluorescent lamps simulating the ultraviolet (UV) output of sunlight. Paroxetine was degraded completely within 4 d by simulated sunlight in all aqueous media. Photolysis of paroxetine HCI was accelerated by increasing pH. The t1/2 values at pH 5, 7, and 9 were 15.79, 13.11, and 11.35 h, respectively. The half-lives of paroxetine in synthetic humic water and two lake waters were slightly longer than in pH 7 buffer. Two photoproducts were detected and their structures were identified by liquid chromatography-mass spectrometry in positive mode. Photoproduct I was found to be photolytically unstable, being gradually degraded after 12 to 18 h of irradiation. However, photoproduct II was photolytically very stable throughout the experiment period, indicating that it was persistent to further photodegradation. In the dark, paroxetine in all aqueous solutions was found to be stable over a 30-d period. In conclusion, paroxetine is a relatively photolabile drug that has a possibility of photodegradation by sunlight in surface water.

The antidepressant agent paroxetine hydrochloride (POT) was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and osteryoung square wave voltammetry (OSWV). A sensitive method is described for the determination of POT in its pure form and in human plasma. The linear relationship between concentration and peak current permits the quantification of POT by CV, DPV and OSWV in the concentration range of 2 x 10(-5)- 8 x 10(-4) M. Applicability to tablets and human plasma analysis has been illustrated. Furthermore, a HPLC method with diode array detection was developed. Linearity was established between 2 x 10(-7)- 6 x 10(-5) M for POT. The described methods were successfully employed with high degrees of precision and accuracy for the estimation of total drug content in human plasma and pharmaceutical dosage forms of POT.

A rapid and specific liquid chromatographic mass spectrometric (LC-MS-MS) method has been developed for the determination of paroxetine in human plasma. The procedure involves a liquid-liquid extraction of paroxetine and fluoxetine (internal standard) with cyclohexane-ethyl acetate. The standard curve was linear over a working range of 0.2-50 ng/ml. The lower limit of quantitation was 0.2 ng/ml. No endogenous compounds were found to interfere with the analysis. The absolute recovery was 70.8% for paroxetine and 84.1% for the internal standard. The accuracy of inter-assay and intra-assay accuracy was in the ranges -4.8 to -0.5% and -3.4 to 4.8%, respectively. This method proved to be suitable for bioequivalence studies by being simple, selective and reproducible.

This write-up provides a review on the development of validated stability-indicating assay methods (SIAMs) for drug substances and products. The shortcomings of reported methods with respect to regulatory requirements are highlighted. A systematic approach for the development of stability-indicating methods is discussed. Critical issues related to development of SIAMs, such as separation of all degradation products, establishment of mass balance, stress testing of formulations, development of SIAMs for combination products, etc. are also addressed. The applicability of pharmacopoeial methods for the analysis of stability samples is discussed. The requirements of SIAMs for stability study of biotechnological substances and products are also touched upon.

A high performance liquid chromatography (HPLC) method for the assay of fentanyl citrate, alfentanil hydrochloride, and sufentanil citrate swab samples was developed and validated in order to control a cleaning procedure. The swabbing procedure involved Super POLX 1200 wipers moistened with water. The assay employed extraction of swabs with water and analysis by isocratic, reversed-phase, HPLC with varying ultraviolet (UV) detection for desired sensitivity, depending on the analyte. The method was shown to be selective and linear from the limits of quantitation (0.10, 0.20, and 0.15 microg/swab for fentanyl citrate, alfentanil, and sufentanil, respectively) to over three times these concentrations. The assay limits (detection levels) per swab area were set at least at 0.2% of the concentrations of the actives in the drug products (0.02, 0.10, and 0.10 microg/swab or approximately 0.03, 0.02, and 0.2% for fentanyl citrate, alfentanil, and sufentanil, respectively). It should be noted that all active concentrations listed in this work were calculated based on the salt form concentration for fentanyl (citrate salt) and the free base forms for alfentanil and sufentanil. No reference standard was available for alfentanil hydrochloride and sufentanil citrate. Drug product was used instead throughout this study.

The stability indicating properties of the USP method for the assay of fentanyl in fentanyl citrate injection were evaluated [1] by analyzing fentanyl drug substance and product after acid, hydrogen peroxide, heat, and light treatment. N-phenyl-N-(4-piperidinyl)propionamide (PPA), which is a known degradation product/process impurity of fentanyl, was not adequately resolved from the fentanyl peak, and mobile phase adjustments did not improve the resolution (Fig. 1). Therefore, the USP method did not meet the requirements for a stability-indicating assay. In addition, the wavelength in the USP method was too high (230 nm) to provide adequate levels for the quantitation of the related substances of fentanyl and, in addition, the acetate ions in the mobile phase could interfere with a lower wavelength detection. An isocratic, reversed phase, stability indicating, high performance liquid chromatographic (HPLC) method for the assay of fentanyl and related substances in fentanyl citrate injection, USP has been developed and validated. The chromatographic conditions employed an Inertsil C8, 5 column (25 cm x 4.6 mm), a mobile phase of aqueous perchloric acid [0.23%, w/v]-acetonitrile [65:35, v/v], and ultraviolet (UV) detection at 206 nm. Under the chromatographic conditions of the method, PPA and seven other known process impurities were separated from the active. Degradation studies showed that the active eluted as a spectrally pure peak resolved from its degradation products.

This paper describes the development and validation of an isocratic, reversed-phase, high performance liquid chromatographic (HPLC) method for the assay of 200-mg troglitazone tablets. The chromatographic conditions of the method employ a YMC ODS-A, 120 A (4.6 x 150 mm, 5 microm) column, isocratic elution with (50 mM aqueous NaH2PO4, pH 4.0):acetonitrile:methanol,(35:50:15, v/v/v) as the mobile phase at a flow rate of 1.0 ml/min, a 10 microl injection volume, and ulltraviolet (UV) detection at 225 nm. The active was analyzed at ambient column temperature, using peak area responses.

A regio and stereospecific synthesis of 2-methyl-(Z)-4-(phenylimino)naphth[2,3-d]oxazol-9-one (1) was achieved by using titanium tetrachloride in methylene chloride in the preparation of the imine. The regiochemistry was assigned by single-crystal X-ray analysis. In vitro tests showed that this diastereomer is selectively active for some solid cancer tumors.

The utility of reverse-phase high-performance liquid chromatography (HPLC), desorption chemical-ionization mass spectrometry (DCI-MS) and tandem mass spectrometry (MS/MS) for the characterization of triacylglycerols in complex mixtures has been further explored. Triacylglycerols of anhydrous bovine milk fat were separated by using two reverse-phase C18 HPLC columns, and eluents were monitored with an evaporative light-scattering detector. Fifty-eight fractions were resolved and analyzed by positive ion isobutane DCI-MS. The formation of protonated molecules and of major fragments corresponding to the random loss of any one of the constituent fatty acids readily identified acyl carbon numbers and the number of double bonds within each fatty acid. MS/MS was only required when the original mass spectra indicated the presence of more than one triacylglycerol or of impurities in a fraction. Protonated molecules produced by DCI were fragmented using high energy collisional activation, and the resulting ions were detected by MS/MS. Odd-chain triacylglycerols were also readily distinguished using this methodology. The positive ion DCI and MS/MS techniques described here demonstrate the usefulness of this approach for the characterization of triacylglycerols in complex mixtures.

Reported is the case of a 24-year-old white man with inoperable giant cell carcinoma of the thyroid who achieved tumor regression following therapy with bleomycin, Adriamycin and cisplatinum. After 2 courses of chemotherapy, the tumor was deemed operable, and the patient underwent total thyroidectomy followed by radiation to the neck and upper mediastinum without maintenance chemotherapy. Two-and-one-half years after the initial diagnosis, he developed pulmonary metastases which again responded to Adriamycin and cisplatinum therapy. The above approach suggests that inoperable thyroid carcinoma can be made operable by preoperative combination chemotherapy. This treatment program deserves further exploration for a greater number of patients.

A sub-minute enantioselective normal phase high performance liquid chromatographic (HPLC) method for the analysis of a chiral precursor molecule employed frequently in folic acid syntheses was developed, optimized and successfully validated according to ICH-guidelines. It could be shown that ultra-high performance chromatography (UHPLC) can give significant advantages compared to traditional HPLC not only in reversed phase HPLC, but also for enantioselective separations in normal phase mode. Novel 3μm-particle sizes allow developing analytical chromatographic methods completely resolving two enantiomers in the shortest time possible while preserving high efficiency and low detection limits. By offering increased resolution, sensitivity and speed, enantioselective UHPLC (eUHPLC) improves sample throughput, productivity and provides considerably faster access to information on enantiomeric purity also under non-aqueous conditions.

A simple, rapid, precise and accurate isocratic reversed phase stability indicating HPLC method was developed and validated for the simultaneous determination of atenolol and lercanidipine hydrochloride in commercial tablets. The chromatographic separation was achieved on phenomenex Gemini C18 (250×4.6 mm, 5 μm) column using a mobile phase consisting of acetonitrile and buffer (20 mM potassium dihydrogen phosphate pH 3.5) in the ratio of (55:45, v/v) at a flow rate of 1.0 ml/min and UV detection at 235 nm. The linearity of the proposed method was investigated in the range of 40-160 μg/ml (r(2)=0.9995) for atenolol and 8-32 μg/ml (r(2)=0.9993) for lercanidipine. Degradation products produced as a result of stress studies did not interfere with the detection of atenolol and lercanidipine and the assay can thus be considered stability-indicating.

A rapid, isocratic stability indicating high performance liquid chromatographic method was developed and validated for the estimation of lornoxicam in its powder for injection. The analysis was performed on a Shimadzu VP-ODS (4. 6 mm x 15 cm, 5 µm) column. The mobile phase consisted of sodium acetate (pH 5.8; 0.05 M) and methanol (45:55) flowed at 1.0 ml/min. Detection was carried out at 290 nm. The developed method had the good ability to separate lornoxicam well from the degradation products. The regression data showed good linear relationship at the concentration range of 4.04-20.20 μ/mL with r(2)=0.9999. Specificity, linearity, accuracy, precision and robustness of the method were evaluated to validate the proposed method. Stressed degradation studies were conducted to provide an indication of its stability indicating property. The limits of detection and quantitation were 9.70 and 33.94 ng /ml, respectively. Lornoxicam was found to be stable in the mobile phase in 24 h. The co-existed excipients had no interference with the analytical procedure. Additional peaks appeared in the chromatograms of five kinds of forced degraded samples (light, heat, acid, base and oxidation degradation). Mean recovery assessed at three levels was from 99. 7 to 100.3%, indicating the good accuracy of the method. Repeatability and inter-day RSD of the method was determined to be 0.38% and 0.81%, respectively. The HPLC method was demonstrated to be robust for intentional minor changes of ratio, pH change, salt concentration and column temperature. The method should be utilized as the routine analysis and quality control of lornoxicam in injectable formulation.

A simple and rapid HPLC method for determination of chlorogenic acid (5-O-caffeoylquinic acid) in mate tea extracts was developed and validated. The chromatography used isocratic elution with a mobile phase of aqueous 1.5% acetic acid-methanol (85:15, v/v). The flow rate was 0.8 mL/min and detection by UV at 325 nm. The method showed good selectivity, accuracy, repeatability and robustness, with detection limit of 0.26 mg/L and recovery of 97.76%. The developed method was applied for the determination of chlorogenic acid in mate tea extracts obtained by ethanol extraction and liquid carbon dioxide extraction with ethanol as co-solvent. Different ethanol concentrations were used (40, 50 and 60%, v/v) and liquid CO₂ extraction was performed at different pressures (50 and 100 bar) and constant temperature (27 ± 1 °C). Significant influence of extraction methods, conditions and solvent polarity on chlorogenic acid content, antioxidant activity and total phenolic and flavonoid content of mate tea extracts was established. The most efficient extraction solvent was liquid CO₂ with aqueous ethanol (40%) as co-solvent using an extraction pressure of 100 bar.

OBJECTIVE Telmisartan is a potent, long-lasting, nonpeptide antagonist of the angiotensin II type-1 (AT(1)) receptor that is indicated for the treatment of essential hypertension. Hydrochlorothiazide is a widely prescribed diuretic and it is indicated for the treatment of edema, control of essential hypertension and management of diabetes insipidus. In the current article a new, accurate, sensitive, precise, rapid, reversed phase high performance liquid chromatography (RP-HPLC) method was developed for determination of related substances of Telmisartan and Hydrochlorthiazide in tablet dosage form. MATERIALS AND METHODS Simultaneous determination of related substances was performed on Kromasil C(18) analytical column (250 × 4.6 mm; 5μm pertical size) column at 40°C employing a gradient elution. Mobile phase consisting of solvent A (solution containing 2.0 g of potassium dihydrogen phosphate anhydrous and 1.04 g of Sodium 1- Hexane sulphonic acid monohydrate per liter of water, adjusted to pH 3.0 with orthophosphoric acid) and solvent B (mixture of Acetonitrile: Methanol in the ratio 80:20 v/v) was used at a flow rate of 1.0 ml min(-1). UV detection was performed at 270 nm. RESULTS During method validation parameter such as precision, linearity, accuracy, specificity, limit of detection and quantification were evaluated, which remained within acceptable limits. CONCLUSIONS HPLC analytical method is linear, accurate, precise, robust and specific, being able to separate the main drug from its degradation products. It may find application for the routine analysis of the related substances of both Telmisartan and Hydrochlorthiazide in this combination tablets.

A novel gradient reversed-phase ultra performance liquid chromatographic method has been developed for quantitative determination of Esomeprazole magnesium and its seven impurities in pharmaceutical dosage forms. Chromatographic separation has been achieved on an Acquity BEH C18, 50mm×2.1mm, 1.7μm with buffered mobile phase consisting solvent A (0.04molar (M) glycine (pH 9.0) buffer) and solvent B (mixture of acetonitrile and Milli-Q water in the ratio 90: 10 (v/v); respectively) delivered at flow rate of 0.21mL min(-1) and the detection wavelength 305nm. Resolution of Esomeprazole magnesium and all the seven potential impurities has been achieved greater than 2.0 for all pairs of compounds. The drug was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Esomeprazole magnesium was found to degrade significantly in oxidative and acid hydrolysis stress conditions and stable in base, hydrolytic and photolytic degradation conditions. The degradation products were well resolved from main peak and its impurities, thus proved the stability indicating power of the method. The stress samples were assayed against a reference standard and the mass balance was found to be close to 99.1%. So this method was also suitable for Assay determination of Esomeprazole magnesium in pharmaceutical dosage forms. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.

Ferrous sulfate tablets are a supplementary iron source for people who suffer from iron deficiency anemia. A simple, fast, and QC-friendly HPLC method was developed and validated to determine elemental iron in ferrous sulfate drug products. A TSK-GEL Super octadecylsilyl column (50 x 4.6 mm id, 2 microm particle size) with a mobile phase consisting of 0.06 M methanesulfonic acid in water-acetonitrile (40 + 60, v/v) and UV detection at 282 nm were used for this method. Separation of the elemental iron peak from the matrix was achieved within 5 min. This method was successfully validated according to International Conference on Harmonization guidelines, and shown to be stability-indicating for the shelf-life samples of ferrous sulfate tablets, as well as selective for the analyte of interest.

Simultaneous determination of aniracetam and its related impurities (2-pyrrolidinone, p-anisic acid, 4-p-anisamidobutyric acid and (p-anisoyl)-4-methyl-2-pyrrolidinone) was accomplished in the bulk drug and in a tablet formulation using a high performance liquid chromatographic method with UV detection. Separation was achieved on a Hypersil BDS-CN column (150 mm × 4.0 mm, 5 μm) using a gradient elution program with solvent A composed of phosphate buffer (pH 4.0; 0.010 M) and solvent B of acetonitrile-phosphate buffer (pH 4.0; 0.010 M)(90:10, v/v). The flow rate of the mobile phase was 1.0 mL min(-1) and the total elution time, including the column re-equilibration, was approximately 20 min. The UV detection wavelength was varied appropriately among 210, 250 and 280 nm. Injection volume was 20 μL and experiments were conducted at ambient temperature. The developed method was validated in terms of system suitability, selectivity, linearity, range, precision, accuracy, limits of detection and quantification for the impurities, short term and long term stability of the analytes in the prepared solutions and robustness, following the ICH guidelines. Therefore, the proposed method was suitable for the simultaneous determination of aniracetam and its studied related impurities.

A sensitive and selective reversed-phase liquid chromatographic (RP-LC) method was developed and validated to determine octopamine, tyramine and Tyrosine (Tyr) in complex matrices as formulations and phytoextracts (Citrus aurantium), after pre-column derivatization with o-phthaldialdehyde (OPA) reagent. The chromatographic separations were performed at room temperature on a Phenomenex Luna C18 column using methanol and sodium acetate buffer (pH 5.5) by varying composition gradient elution as mobile phase and detected flurometrically at λ(em)=455 nm with λ(ex)=340 nm. The results obtained by the proposed method were compared with those achieved by a validated direct RP-LC method with fluorescence detection at λ(em)=310 nm with λ(ex)=275 nm, as reference method, using a Phenomenex Gemini C18 column under isocratic elution conditions with acetonitrile and sodium 1-heptanesulphonate (pH 3), as mobile phase. The higher sensitivity of the derivatization method (detection limit about 0.06 pmol) allowed the sure determination of octopamine present in traces in the examined samples. The repeatability of method (RSD) was ≤1.90% and there was no significant difference between repeatability and intermediate precision data. Recovery studies showed good results 99.5-101.3% with RSD ranging from 0.8 to 1.2%. All analyses were performed by mild conditions in absence of preliminary difficult extraction methodologies or laborious step of sample pre-treatment.

A validated stability-indicating HPLC method was developed for the analysis of azithromycin (AZ) and its related compounds in raw materials, capsule, and suspension using an Xterra RP C18 column at 50 degrees C with UV detection at 215 nm. Isocratic elution was employed using the mobile phase 14 mM disodium hydrogen phosphate (pH 10.5, adjusted by 1 M NaOH)-methanol-acetonitrile-tetrahydrofuran (40.0 + 30.0 + 30.0 + 0.1, v/v/v/v). AZ and 14 of its related compounds were separated and quantified. The described method was linear over the range of 2-1800 microg/mL AZ with (r = 0.9999). The stability of AZ was studied under accelerated acidic, alkaline, and oxidative conditions. The proposed method was used to investigate the kinetics of acidic and alkaline hydrolysis process of AZ at different temperatures, and the apparent pseudo first-order rate constant, half-life, and activation energy were calculated. The major peak detected from the degradation of AZ in alkaline and acidic conditions was decladinosylazithromycine, while azithromycin N-oxide was detected from the oxidative degradation. Long-term stability studies for capsule and oral suspension were carried out. The proposed stability-indicating method was completely validated according to the U.S. Food and Drug Administration requirements.