Pharmacopoeial Impurities Research Articles

Sustainable multi-analyte HPTLC estimation of meloxicam, diclofenac and diacerein along with its major degradation product and official impurity; rhein: Comprehensive greenness and whiteness evaluation

A sustainable HPTLC method has been developed for the simultaneous determination of Meloxicam (MLX), Diclofenac (DCF) with Diacerein (DCN), and its pharmacopoeial impurity and main degradation product, Rhein (RIN). Reviewing the literature revealed that no HPTLC method has been reported for the simultaneous determination of the three cited drugs along with RIN. Merck TLC plates precoated with 60F 254 silica gel on aluminium sheet were used as stationary phase and were developed with a green mobile phase composed of ethyl acetate: ethanol: water (9.5: 1: 0.5 v/v/v respectively). Densitometric scanning was performed at 259 nm for DCN and RIN, while MLX and DCF were detected at 360 nm and 281 nm, respectively. The proposed method was validated according to the ICH guidelines regarding linearity, range, accuracy, precision, specificity, and robustness. Additionally, the environmental impact of the developed method was assessed using the analytical eco-scale (AES), the green analytical procedure index (GAPI) and the Analytical GREEnness calculator (AGREE). Moreover, the method’s sustainability was evaluated and compared with previously published methods using the novel RGB 12 model in terms of the 12 white analytical chemistry (WAC) perspectives. Finally, successful application of the proposed method was carried out for the estimation of the cited compounds in their combined formulations as well as for the detection and quantification of DCN impurity; RIN, at concentrations below its pharmacopoeial limit. The present study represents the first sustainable and economic HPTLC separation and determination of the four cited compounds simultaneously as well as a sensitive method for testing the purity of DCN in bulk form and combined formulations.

Advanced Spectrophotometric Resolution Techniques for a Spectrally Overlapping Spasmolytic Binary Mixture along with Dichloroaniline as a Toxic Impurity: Application to Content Uniformity Testing.

Irritable bowel syndrome (IBS) is a common disorder leading to undesirable pain. Phloroglucinol (PHG) and trimethylphloroglucinol (TMG) are co-formulated as spasmolytic medication that is considered to be effective in reducing smooth muscle spasm. 3,5-Dichloroaniline (DCL) is a specified PHG pharmacopoeial impurity which needs to be monitored to avoid its toxic effects. Different smart approaches are presented to provide simple, reliable, and economic spectrophotometric methods able to resolve the severe overlap in the spectra of PHG and TMG in their pure and pharmaceutical forms, in addition to their estimation in the presence of DCL as a toxic impurity of PHG without any need for initial separation. The presented work includes univariate methods, derivative ratio (DR), ratio difference (RD), mean centering (MCR) and deconvulated Fourier method (DF), which were able to determine PHG and TMG simultaneously in their binary mixture. Firstly, DCL was estimated in the zero order, where the two drugs have zero absorption at 247.0 nm, and then its contribution was eliminated by applying ratio subtraction method. Multivariate chemometric partial least squares (PLS) and principal component regression (PCR) models were also applied to determine PHG and TMG simultaneously in the presence of the impurity, DCL. Univariate methods were applied in the range 5.0-30.0, 2.5-25.0, and 1.0-12.0 µg/mL for PHG, TMG, and DCL, respectively. The proposed chemometric models were used in the range 6.0-14.0, 5.0-25.0 and 2.0-10.0 µg/mL for PHG, TMG, and DCL, respectively. These analytical approaches succeeded in estimating the cited drugs in their pharmaceutical formulation and assessing content uniformity of dosage units. The methods were statistically compared with a reported HPLC method, and the results revealed no significance statistical difference. This work provides for the first time successful univariate and multivariate PLS and PCR methods to assess PHG and TMG in the presence of DCL as a toxic impurity along with content uniformity testing of dosage units. Comparative univariate and multivariate spectrophotometric analytical approaches are presented, for the first time, for estimation of spasmolytic formulation of PHG and TMG in the presence of DCL as a PHG toxic impurity. Successful application to content uniformity testing of Stopspasm® dosage form is demonstrated. A statistical study, including t-tests and one-way analysis of variance (ANOVA), was conducted.

Synthesis, characterization and control of eight process-related and two genotoxic fingolimod impurities by a validated RP-UPLC method.

An HPLC method has been described in the European Pharmacopoeia and United States Pharmacopeia for the determination of nine organic impurities (imp A-I) in fingolimod hydrochloride, a synthetic sphingosine-1-phosphate receptor modulator. The manufacturing process of fingolimod hydrochloride consists of multistep chemical synthesis wherein controls of precursors, intermediates and process steps should be performed to assure the final quality of the drug substance. We synthesized and isolated eight process-related impurities (FINI imp A-H) of fingolimod, which were different from the pharmacopoeial impurities. One unknown process-related impurity was found as a key intermediate (FINI) and was identified by LC-MS. Characterization of all of the impurities were done using spectroscopic techniques (1 H and 13 C NMR, FTIR, MS), and the mechanistic pathways to the formation of these impurities were also discussed. Two of these impurities were evaluated as potential genotoxic impurities owing to their alerting structures and alkylating properties (alkyl sulfonates and alkyl halides, class 3, ICH M7). We also developed and validated an RP-UPLC method in line with ICH Q2 guidelines for control these impurities (FINI imp A-H) and to assure the pharmacopoeial quality drug substance.

Green chromatographic methods for simultaneous micro-determination of empagliflozin, linagliptin with metformin and its pharmacopoeial impurities in pure form and triple combination tablets: A comparative study

Green analytical chemistry (GAC) is gaining great interest with the respect of global environmental pollution control (EPC). Consequently, we have developed two green chromatographic methods for the simultaneous precise and selective estimation of empagliflozin (EMP), linagliptin (LNA) with Metformin (MET) and its pharmacopoeial impurities cyanoguanidine (CGN) and melamine (MLN). The scientific database lacks any analytical reports tackling such concurrent estimation of the five cited analytes. The first developed method is a reversed phase HPLC-DAD employing Agilent C18 column (4.6 × 250 mm, 5 μm p.s.) and a mobile phase composed of methanol and 0.01 M sodium dihydrogen orthophosphate buffer of pH 2.55 (adjusted with orthophosphoric acid) eluted in a gradient mode with detection at 218 and 224 nm.The second method is HPTLC using Merk TLC plates precoated with 60 F 254 silica gel on aluminium sheet as the stationary phase developed with ethanol: ethylacetate: water (3.5: 3:1, v/v/v, respectively) as mobile phase and scanned at 216 and 224 nm. The proposed methods offered neat separation and quantitation of the five analytes in their pure form and in the triple combination tablets. Both methods were validated as per the ICH guidelines in terms of linearity, range, accuracy, precision, specificity and robustness. Moreover, Greenness assessment of the developed methods was carried out using the Analytical Eco-Scale. Further evaluation of the methods’ ecofriendliness and comparison with previously reported methods was performed using NEMI, GAPI and the novel AGREE tool.

Simultaneous analysis of several antihypertensive drugs in different combinations: Application for determination of drug degradation products and process impurities

Hydrochlorothiazide is a widely used thiazide diuretic. Its combinations with either olmesartan medoxomil or fosinopril sodium are well known antihypertensive combinations that compare positively than other related combined therapies. A first RP-HPLC method was introduced for simultaneous estimation of two antihypertensive combinations containing hydrochlorothiazide with either olmesartan medoxomil or fosinopril sodium. The work was extended to quantify the drugs along with their degradation products; salamide as hydrochlorothiazide degradate and olmesartan as olmesartan medoxomil degradate. Also, it succeeded to determine the pharmacopoeial impurity of hydrochlorothiazide (chlorothiazide). The established RP-HPLC was performed on RP-C18 column utilizing gradient mixture of 0.05 M KH2PO4 (pH 3 with aqueous O-phosphoric acid), acetonitrile, and methanol. Temperature was adjusted to 35 °C and UV detection was done at 205 nm for fosinopril sodium and at 225 nm for the rest of the cited components.ICH guidelines were used to validate the method and all the results affirmed efficiency of the method. In addition, it was effectively used for measuring hydrochlorothiazide in binary mixtures with either olmesartan medoxomil or fosinopril sodium in their available pharmaceutical formulation. Also, the statistical comparison with published methods was executed and no noteworthy difference concerning accuracy and precision was detected.

AQbD-Oriented UHPLC/MS/MS Method Development for Glycopeptides Assessment in Pharmaceutical Forms.

Vancomycin and teicoplanin are glycopeptide antibacterials that inhibit the bacteria cell wall synthesis showing activity against gram-positive bacteria. Development of the sensitive method is of great importance for quality control of these drugs that are fermentation products. Modification of the fermentation conditions could cause the differences in the relative amount of the total substance or component, as it is the case with teicoplanin. The main objective of this study was development of the sensitive and effective ultra high performance liquid chromatography - tandem mass sprectrometry (UHPLC-MS/MS) method for simultaneous quantification of vancomycin, all six subcomponents of teicoplanin, and its pharmacopoeial impurity A in pharmaceutical forms. The scientific-based Quality by Design approach was implemented in the MS and UHPLC method development. Detection and quantification of analytes were carried out in positive electrospray ion mode by multiple reaction monitoring. Capillary voltage, cone voltage and collision energy were optimized by implementing experimental design methodology and optimal values for each fragment ion were obtained by performing experiments according to 'Rechtschaffen' design matrix. An ACQUITY CSH Phenyl-hexyl (2.1 × 50mm, particle size 1.7μm) column was chosen for the separation under the gradient elution mode with the mobile phase consisted of 0.1% formic acid in water (mobile phase A) and acetonitrile (mobile phase B). Optimal gradient elution parameters were achieved by applying 'Rechtschaffen' design too. Method operable design regions were constructed for investigated MS and chromatographic parameters. The method was fully validated, and its applicability was confirmed throughout the ability to follow the behavior of vancomycin and teicoplanin under stress conditions.

Synthesis, Analytical Characterization and Spectroscopic Investigation of Chloramphenicol Impurity A for the Quality Control of Chloramphenicol and its Formulation as Per International Compendium.

The main aim of the present work is to synthesize chloramphenicol impurity A (CLRMIMP- A) in the purest form and its subsequent characterization by using a panel of sophisticated analytical techniques (LC-MS, DSC, TGA, NMR, FTIR, HPLC, and CHNS) to provide as a reference standard mentioned in most of the international compendiums, including IP, BP, USP, and EP. The present synthetic procedure has not been disclosed anywhere in the prior art. A simple, cheaper, and new synthesis method was described for the preparation of CLRM-IMP-A. It was synthesized and characterized by FTIR, DSC, TGA, NMR (1H and 13C), LC-MS, CHNS, and HPLC. CLRM-IMP-A present in drugs and dosage form can alter the therapeutic effects and adverse reaction of a drug considerably, it is mandatory to have a precise method for the estimation of impurities to safeguard the public health. Under these circumstances, the presence of CLRM-IMP-A in chloramphenicol (CLRM) requires strict quality control to satisfy the specified regulatory limit. The synthetic impurity obtained was in the pure form to provide a certified reference standard or working standard to stakeholders with defined potency. The present research describes a novel technique for the synthesis of pharmacopoeial impurity, which can help in checking/controlling the quality of the CLRM in the international markets.

A VALIDATED STABILITY INDICATING RP-HPLC METHOD FOR ESTIMATION OF TOLFENAMIC ACID IN PRESENCE OF ITS PHARMACOPOEIAL IMPURITIES

Objective: The proposed research work was conducted to develop a single reverse-phase high-performance chromatography (RP-HPLC) method capable of separating two Pharmacopoeial related impurities as well as degradation product of Tolfenamic acid (TA). The drug was subjected to various stress conditions recommended under ICH Q1A (R2) guidelines.
 Methods: The desired separation of two Pharmacopoeial impurities and one degradant generated under oxidative stress was carried out using Sunfire ODS C-18 (250 x 4.6 mm, 5 µm) column maintained at 40 °C. Isocratic elution was carried out using acetonitrile and ammonium dihydrogen orthophosphate buffer (10 mmol, pH 2.5) in the ratio of 80:20 v/v. The detection was carried out at 205 nm using flow rate of 1 ml/min. The developed method was validated as per ICH Q2 (R1) guidelines for specificity, linearity, accuracy, precision, Limit of detection (LOD), Limit of Quantification (LOQ) and robustness.
 Results: Linearity response of TA was found at a concentration range of 10-100µg/ml, with a correlation coefficient of 0.9987. The Pharmacopoeial impurity A and impurity B showed linearity results at concentration of 0.1-1µg/ml, with correlation coefficient of 0.9984 for Impurity A and 0.9989 for Impurity B. The % recovery during accuracy studies for TA and the two impurities were within the acceptance range of 95-105%. LOD and LOQ for TA were found to be 4.561µg/ml and 133.771µg/ml respectively. For impurity A, LOD and LOQ were found to be 0.035 µg/ml and 0.106 µg/ml and for Impurity B, LOD and LOQ were 0.042 µg/ml and 0.128 µg/ml. With slight variation of organic phase in mobile phase and flow rate the method exhibited good robustness. Under forced degradation studies the drug was found stable under hydrolytic, photolytic and thermal stress conditions, but was found susceptible for degradation under oxidative stress with appearance of a degradant peak. From on the RRT values of Pharmacopoeial impurities and the formed degradant it was inferred that the developed method is selective for the drug in the presence of impurities or degradants.
 Conclusion: The developed stability-indicating method is found to be simple, rapid, accurate, precise and robust as compared to other proposed methods while determining TA in presence of its Pharmacopoeial impurities and degradation products. Hence the developed method can be used for analysis of stability samples of TA in presence of its related impurities.

Baclofen impurities: Facile synthesis and novel environmentally benign chromatographic method for their simultaneous determination in baclofen.

An efficient, economic and high yielding method was described for the synthesis of baclofen (BAC) pharmacopoeial impurities (impurity A and impurity B) which can be used for gram-scale synthesis. Furthermore, a novel ecofriendly thin-layer chromatographic TLC-densitometric method was established and validated for the determination of BAC and its synthesized impurities. The developed TLC-densitometric method is based on the chromatographic separation using TLC plates (60 F254 ) using a green mobile phase of ethyl acetate-methanol-ammonia solution, 33% (8:2:0.1, by volume) with UV scanning at 220 nm. The proposed method was validated with respect to International Conference on Harmonization guidelines. The validated method was successfully applied for determination of BAC in pure form and in its commercial dosage form. Additionally, the greenness profile of the developed method was evaluated and compared with those of the reported chromatographic methods. The developed method was found to be superior to the published methods, being environmentally benign.

Validated potentiometric method for the determination of sulfacetamide sodium; application to its pharmaceutical formulations and spiked rabbit aqueous humor

Specific, accurate and precise electrochemical method was developed and validated for the determination of sulfacetamide sodium in presence of its co-formulated drug (prednisolone acetate) and its pharmacopoeial impurities. The method was based on fabrication of membrane sensor. The characteristics of electrochemical response were estimated, and the proposed sensor displayed excellent characteristics for the determination of sulfacetamide sodium in bulk powder, laboratory prepared mixtures, dosage forms and in spiked biological fluid (Rabbit aqueous humor). The sensor was constructed through the use of tetradodecylammonium bromide (TDB) as an anion exchanger and 2-nitrophenyl octyl ether (NPOE) as a plasticizer in polyvinyl chloride (PVC) matrix. The performance characteristics, sensitivity and selectivity were evaluated according to IUPAC guidelines. Linearity was achieved over the concentration range of 1 × 10−4.5–1 × 10−2 M with Nernstian slope of 51.086 mV/decade over the pH range of 5–7. The sensor showed a rapid response (10–15 s) and good stability (up to 4 weeks). The obtained results were statistically compared with the official methods and no significant difference was found regarding accuracy and precision.

Identification of four new degradation products of epirubicin through forced degradation, LC-UV, MSn and LC-MS-TOF studies.

Epirubicin (EPI) was subjected to International Conference on Harmonization recommended forced degradation under the conditions of hydrolysis, oxidation, dry heat and photolysis to characterize its possible impurities and/or degradation products. The drug was found highly unstable to alkaline hydrolysis even at room temperature, unstable to acid hydrolysis at 80°C and to oxidation at room temperature. The hydrolytic and oxidative degradation products were resolved on an Agilent RP8 (150 mm × 4.6 mm; 5 µm) column with isocratic elution using mobile phase composed of ammonium formate (10 mM, pH 3.0), acetonitrile and methanol. The drug degraded to four oxidative products (O-I, O-II, O-III and O-IV) and to one acid hydrolyzed product (A-I). Purity of each peak in liquid chromatography-ultraviolet (LC-UV) chromatogram was ascertained through photodiode array (LC-PDA) analysis. The products were characterized through electrospray ionization-mass spectrometry (+ESI-MS(n)) studies on EPI and liquid chromatography-time of flight mass spectrometry (LC-MS-TOF) studies on degraded drug solutions. The products, O-I-O-IV, were characterized as 2-hydroxy-8-desacetylepirubicin-8-hydroperoxide, 4-hydroxy-8-desacetylepirubicin-8-hydroperoxide, 8-desacetylepirubicin-8-hydroperoxide and 8-desacetylepirubicin, respectively, and product A-I was characterized as deglucosaminylepirubicin. While A-I was found to be a pharmacopoeial impurity, all oxidative products were found to be new degradation impurities. The mechanisms and pathways of degradation of EPI were discussed and outlined.

Four new degradation products of doxorubicin: An application of forced degradation study and hyphenated chromatographic techniques

Forced degradation study on doxorubicin (DOX) was carried out under hydrolytic condition in acidic, alkaline and neutral media at varied temperatures, as well as under peroxide, thermal and photolytic conditions in accordance with International Conference on Harmonization (ICH) guidelines Q1(R2). It was found extremely unstable to alkaline hydrolysis even at room temperature, unstable to acid hydrolysis at 80°C, and to oxidation at room temperature. It degraded to four products (O-I–O-IV) in oxidative condition, and to single product (A-I) in acid hydrolytic condition. These products were resolved on a C8 (150mm×4.6mm, 5µm) column with isocratic elution using mobile phase consisting of HCOONH4 (10mM, pH 2.5), acetonitrile and methanol (65:15:20, v/v/v). Liquid chromatography–photodiode array (LC–PDA) technique was used to ascertain the purity of the products noted in LC–UV chromatogram. For their characterization, a six stage mass fragmentation (MS6) pattern of DOX was outlined through mass spectral studies in positive mode of electrospray ionization (+ESI) as well as through accurate mass spectral data of DOX and the products generated through liquid chromatography–time of flight mass spectrometry (LC–MS–TOF) on degraded drug solutions. Based on it, O-I–O-IV were characterized as 3-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 1-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 9-desacetyldoxorubicin-9-hydroperoxide and 9-desacetyldoxorubicin, respectively, whereas A-I was characterized as deglucosaminyl doxorubicin. While A-I was found to be a pharmacopoeial impurity, all oxidative products were found to be new degradation impurities. The mechanisms and pathways of degradation of doxorubicin were outlined and discussed.

Isolation and characterization of a degradation product in leflunomide and a validated selective stability-indicating HPLC–UV method for their quantification

Leflunomide (LLM) is subjected to forced degradation under conditions of hydrolysis, oxidation, dry heat, and photolysis as recommended by International Conference on Harmonization guideline Q1A(R2). In total, four degradation products (I–IV) were formed under different conditions. Products I, II and IV were formed in alkaline hydrolytic, acidic hydrolytic and alkaline photolytic conditions. LLM and all degradation products were optimally resolved by gradient elution over a C18 column. The major degradation product (IV) formed in hydrolytic alkaline conditions was isolated through column chromatography. Based on its 1H NMR, IR and mass spectral data, it was characterized as a British Pharmacopoeial impurity B. The HPLC method was found to be linear, accurate, precise, sensitive, specific, rugged and robust for quantification of LLM as well as product IV. Finally, the method was applied to stability testing of the commercially available LLM tablets.

Synthesis of European pharmacopoeial impurities A, B, C, and D of cabergoline

For the use of analytics, European pharmacopoeial impurities A, B, C, and D of cabergoline were synthesized. Ergocryptine was chosen as a starting material and synthesis was accomplished via two approaches, different in length and stereochemical outcome. A longer, indirect approach was realized through otherwise problematic oxidations of the 9,10-dihidrolysergol derivative, to the corresponding aldehyde and carboxylic acid. This was achieved by the use of activated DMSO and a Pinnick oxidation sequence. All four synthesized impurities are used as analytical standards in cabergoline manufacturing processes.

A rapid stability indicating LC-method for determination of praziquantel in presence of its pharmacopoeial impurities

This study reports for the first time about a stability indicating RP-HPLC method for quantitative determination of Praziquantel (PZQ) in bulk powder and dosage form and in presence of its pharmacopoeial impurities. The chromatographic separation was carried out on (Caltrex AI®) calixarene column, a relatively new packing material. Chromatography was done using an isocratic binary mobile phase consisting of ACN and 25mM ammonium acetate (NH4Ac) in the ratio of 40:60 at flow rate of 1mLmin−1, 30°C and 210nm wavelength for detection. The elution time of PZQ was found to be 6.15±0.03min. The method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. The robustness study was done for small changes in temperature, flow rate, wavelength of detection and % of ACN in mobile phase. Stability tests were done through exposure of the analyte solution to five different stress conditions: Reflux with 1N HCl, reflux with 1N NaOH, reflux with 30% H2O2, thermal degradation of powder and exposure to UV radiation. Limits of detection and quantification were found to be 0.56 and 1.70μgmL−1, respectively. The recovery value of this method was 100.30%±1.10 and the reproducibility was within 1.31.

RP-ZrO2 Stationary Phase as an Alternative to Separate of Doxazosin Impurities

Degradation products and related compounds occurring in drugs as impurities have often very similar properties as the parent substance. Therefore new analytical separation methods which show appropriate selectivity are required. Apart from improvements on silica-based reversed phases the attention has also been focused on other materials such as modified inorganic supports. In this study a polystyrene-coated zirconia was examined as an alternative in analysis of parent drug (doxazosin) and its impurities. Doxazosin and its five pharmacopoeial impurities were separated within 16 min. The suitability of the developed method was verified and confirmed by means of linearity, precision, inter-day precision, robustness and determination of LOD as well as LOQ. The results proved the potential of zirconia-based stationary phases to be useful alternatives in the field of drug analysis.

An innovative approach to the analysis of 3-[4-(2-methylpropyl)phenyl]propanoic acid as an impurity of ibuprofen on a carbon-coated zirconia stationary phase

3-[4-(2-Methylpropyl)phenyl]propanoic acid has been introduced as impurity F to the European Pharmacopoeia in its Supplement 4.2. In contrast to other impurities, which are evaluated by HPLC, the content of impurity F is determined by gas chromatography after previous derivatization. Thus a novel reversed-phase HPLC method was developed to simplify the evaluation of pharmacopoeial impurity F of ibuprofen. Favourable properties of zirconia stationary phases were employed for this purpose. The HPLC separation was achieved on a Zr-CARB column (150mm×4.6mm i.d., 5μm) using the mobile phase acetonitrile–phosphate buffer (pH 3.5, 25mM) (38:62, v/v), temperature 80°C and the flow rate 1.2mlmin−1. The fluorescence detection was employed to enhance the sensitivity of the method. Optimal detection parameters were chosen on the basis of fluorescence spectra of the analytes. The excitation and emission wavelengths were 220nm and 285nm, respectively. The analysis was completed within 25min. The subsequent validation of the method confirmed the applicability of method for the analytical assay of impurity F.

Titania-based stationary phase in separation of ondansetron and its related compounds

Improvements in stationary phase stability have been and remain a great task for research of new stationary phases. Metal oxide-based stationary phases appear as one of perspective alternatives to classical silica based stationary phases regarding to their similar effectiveness, different selectivity, different retention mechanism and mainly better chemical and thermal stability. In this study, the retention behaviour of ondansetron and its five pharmacopoeial impurities on TiO 2-based reversed phase was investigated. The influence of buffer type, pH and concentration on retention was studied. Different types and amount of organic solvent in mobile phase were tested. The effect of temperature and flow rate on separation was investigated. The separation conditions were optimized and developed method validated. The retention parameters – retention time ( t R), retention factor ( k′), theoretical plate number ( N), resolution between peaks due to nearby peaks ( R s) and symmetry factor ( A s) have been compared to parameters achieved on polybutadiene-coated zirconia column. The thermodynamic parameters of retention of analysed compounds – enthalpy, entropy and Gibbs free energy – were calculated and compared to those achieved on polybutadiene-coated zirconia column. This work proves similarity of retention behaviour of ondansetron and its five related compounds on zirconia-based and titania-based stationary phases and potential utilisation of polyethylene covered TiO 2-based reversed stationary phase as an alternative to polybutadiene-coated ZrO 2 stationary phase in pharmaceutical analysis of ondansetron.

Potential employment of non-silica-based stationary phases in pharmaceutical analysis

The absolute majority of the HPLC applications use silica-based columns for the separation of active substance and its impurities. However, stationary phases based on metal oxides appear as an interesting alternative. The aim of our study was to investigate the potential utilization of metal oxide-based stationary phases in analytical evaluation of ondansetron and its five pharmacopoeial impurities. In our study commercially available ZrO 2-based columns (e.g. Zr-PBD, Zr-PS, Zr-C18) and TiO 2-based column were used. The effect of an organic modifier (type and ratio), a buffer (type, pH and concentration) and the influence of temperature was investigated. The separation of ondansetron and its five pharmacopoeial impurities was successfully accomplished on a Zirchrom ®-PBD column using a mobile phase consisting of acetonitrile-ammonium phosphate (25 mM, pH 7.0) (18:82, v/v). Detection was performed at 216 nm and the analysis was completed within 7.5 min. The paper proves metal oxide-based stationary phases as an alternative to classical silica-based stationary phases in pharmaceutical analysis.

A validated high performance liquid chromatographic method for analysis of isosorbide mononitrate in bulk material and extended release formulations

A reversed phase HPLC method using C 18 column was developed for the quantitative determination of isosorbide mononitrate (IMN) in the bulk material and extended release dosage forms. The method was specific to IMN and able to resolve the drug peak from the pharmacopoeial impurities and formulation excipients. The method was accurate, precise, and linear within the desired range. In addition to analysis of assay and dissolution samples, the method was successfully used for analysis of drug–excipient compatibility samples of IMN used for development of extended release formulations in our laboratory and their subsequent stability studies. The method was also used for analysis of IMN in commercially available raw material.