Multiple green spectroscopic methods for erdosteine determination in bulk and dosage form with extensive greenness evaluation

Four simple, sensitive, economical, and eco-friendly spectrophotometric and spectrofluorimetric methods for the assay of erdosteine (ERD) in bulk and dosage form have been developed and validated as per the current ICH guidelines. Method I involved the addition of the powerful oxidizing agent, potassium permanganate to ERD and measuring the oxidation product at 600 nm. Another oxidizing agent; ceric ammonium sulfate was used in Method II where ERD is oxidized resulting in a decline in the absorbance intensity of cerium (IV) ions, measured at 320 nm. Similarly, Method III employed the use of ceric ammonium sulfate, However, the fluorescence intensity of the resulting cerium (III) ions was recorded at λex/λem 255/355 nm, respectively. Whereas in Method IV, ERD was added to acriflavine leading to a proportional decrease in its native fluorescence. Various reaction conditions affecting the intensity of measurement were attentively investigated, optimized, and validated. All the suggested methods did not require any tedious extraction procedures nor organic solvents. The implementation of the proposed methods in ERD assay resulted in linear relationships between the measured signals and the corresponding concentrations of ERD in the range of 1-6, 0.1-1.0, 0.01-0.1, and 10-100 μg/mL with LOD values 0.179, 0.024, 0.0027 and, 3.2 μg/mL for methods I, II, III and IV respectively. The suggested methods were successfully applied to ERD analysis in pure form and in commercial capsules. Furthermore, the eco-friendliness of the proposed methods was thoroughly checked using various greenness testing tools. Lastly, this work, not only presents highly sensitive, green, mix-and-read methods for ERD determination, but also, describes the determination of ERD spectrofluorimetrically for the first time in the literature.

White sustainable luminescent determination of nifuroxazide using nitrogen-sulphur co-doped carbon quantum dots nanosensor in bulk and various pharmaceutical matrices

Nifuroxazide (NFX) is an antimicrobial agent that is frequently used as an intestinal antiseptic and recently was proven to have anticancer properties. This work employs the use of nitrogen and sulphur co-doped carbon quantum dots (NSC-dots) luminescent nanoparticles to propose a highly sensitive, sustainable, white and green spectrofluorometric method for NFX detection in bulk and pharmaceutical dosage forms. l-Cysteine and citric acid were the precursors to synthesize water soluble NSC-dots by a quick and environmentally-friendly hydrothermal process. NSC-dots' native fluorescence was measured at λem = 416 nm following excitation at 345 nm. Addition of NFX resulted in quantitative quenching of NSC-dots' luminescence, which represents the principle over which this luminescent method was based. Additionally, the mechanism of fluorescence quenching was studied and discussed. The analytical procedure was validated according to the ICH-guidelines. Linear response for NFX was obtained in the dynamic range 0.04-15 μg mL-1. The estimated NFX detection and quantification limits were 0.005 and 0.015 μg mL-1, respectively. The proposed method was employed for NFX quantification into two commercial pharmaceutical dosage forms. The calculated percentage recoveries (R%), percentage relative standard deviations (RSD%), and percentage error (Er%) were satisfactory. Comparison with other reported methods showed that the proposed method is superior in several aspects. Evaluation of the whiteness of the proposed method using the RGB 12 algorithm combined with the most widely used greenness evaluation tools, the Analytical Eco-Scale and AGREE, demonstrated its superiority and sustainability over other previously published spectrofluorimetric methods for the assay of NFX in various dosage forms.

Development of a sustainable multianalyte MEKC method for quantitation of the antihyperlipidemic drugs ezetimibe together with three statins. Greenness and whiteness appraisal studies

Implementing powerful and sustainable research that complies with green analytical chemistry (GAC) and white analytical chemistry (WAC) fundamentals can downsize the environmental compliance costs and fruitfully affects practical and economic issues. Within this framework, rapid and white analytical micellar electrokinetic capillary chromatography (MEKC) methodology was developed for the synchronized estimation of the antihyperlipidemic drugs Ezetimibe (EZE), Atorvastatin (ATO), Rosuvastatin (ROS) and Simvastatin (SIM). The technique was established using fused silica capillary (50 cm, 50 µm id) and the background electrolyte was 0.025 M borate buffer pH 9.2 containing 0.025 M sodium dodecyl sulfate (SDS) and 10% v/v acetonitrile as the organic modifier. Diode array detector was adjusted at 243 nm for ATO and ROS and 237 nm for EZE and SIM. Separation was accomplished within 10 min with migration times of 4.12, 5.42, 8.23 and 8.74 min for ROS, ATO, EZE and SIM respectively. The 4 drugs were quantitated in the concentration range of 10-100 μg/mL and the correlation coefficients were not less than 0.9993. The high sensitivity was illustrated by values of the detection and quantitation limits. The limits of detection for ROS, ATO, EZE and SIM were 0.52, 0.75, 0.42 and 0.64 μg/mL, respectively, whereas, the limits of quantitation values were 1.73, 2.50, 1.40 and 2.13 μg/mL for the studied drugs, respectively. In addition to validation, as reported by the ICH guidelines, greenness and whiteness assessment using the novel AGREE calculator and the holistic functionality model RGB12 were performed. The results proved the efficiency and whiteness of the suggested technique to be routinely implemented in quality control laboratories for the assay of the four drugs and the binary mixtures of EZE with either ATO, ROS or SIM in fixed-dose combined tablets.

Green "turn-off" luminescent nanosensors for the sensitive determination of desperately fluorescent antibacterial antiviral agent and its metabolite in various matrices

Nitazoxanide (NTX) is an antimicrobial drug that was used for the treatment of various protozoa. However, during the coronavirus pandemic, NTX has been redirected for the treatment of such virus that primarily infect the respiratory tract system. NTX is now used as a broad-spectrum antiviral agent. In this study, a highly sensitive and green spectrofluorometric method was developed to detect NTX in various dosage forms and its metabolite, tizoxanide (TX), in human plasma samples using nitrogen and sulfur co-doped carbon quantum dots nanosensors (C-dots). A simple and eco-friendly hydrothermal method was used to synthetize water soluble C-dots from citric acid and l-cysteine. After excitation at 345 nm, the luminescence intensity was measured at 416 nm. Quenching of C-dots luminescence occurred upon the addition of NTX and was proportional to NTX concentration. Assessment of the quenching mechanism was performed to prove that inner filter effect is the underlying molecular mechanism of NTX quenching accomplished. After optimizing all experimental parameters, the analytical procedure was evaluated and validated using the ICH guidelines. The method linearity, detection and quantification limits of NTX were 15 × 10-3-15.00 µg/mL, 56.00 × 10-4 and 15 × 10-3 µg/mL, respectively. The proposed method was applied for the determination of NTX in its commercial pharmaceutical products; Nanazoxid® oral suspension and tablets. The obtained % recovery, relative standard deviation and % relative error were satisfactory. Comparison with other reported spectrofluorimetric methods revealed the superior sensitivity of the proposed method. Such high sensitivity permitted the selective determination of TX, the main metabolite of NTX, in human plasma samples making this study the first spectrofluorimetric method in literature that determine TX in human plasma samples. Moreover, the method greenness was assessed using both Eco-Scale and AGREE approaches to prove the superiority of the proposed method greenness over other previously published spectrofluorimetric methods for the analysis of NTX and its metabolite, TX, in various dosage forms and in human plasma samples.

Fast and Sensitive Bioanalytical Method for the Determination of Deucravacitinib in Human Plasma Using HPLC-MS/MS: Application and Greenness Evaluation

Plaque psoriasis is a common, long-lasting illness that affects the immune system and causes significant negative impacts on a patient's physical health, well-being, and ability to work effectively. Deucravacitinib (DEU) is the first oral medication used in the treatment of plaque psoriasis, a chronic skin condition that causes red, scaly patches on the skin. DEU is a type of medication called an oral Janus kinase (JAK) inhibitor, which works by blocking specific enzymes that play a role in the inflammation and immune response associated with psoriasis. Therefore, a quick, easy, novel, reliable, sensitive, and straightforward liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach was used to analyze DEU in plasma samples. The LC-MS/MS method for the determination of DEU in human plasma was based on using trimethoprim as an internal standard (IS). The separation of DEU and IS was carried out via liquid-liquid extraction (LLE). The extract was then subjected to the chromatographic system separation using the ACE-C18 column (4.6 × 100 mm, 5 µm). The mobile phase employed consisted of methanol and a solution of 2 mM ammonium formate (80:20 v/v, respectively). The flow rate used was set at 0.9 mL min^-1. The creative strategy was performed by running an ABSCIEX API 4000 mass spectrometer with an electron spray ionization source in multiple reaction monitoring (MRM) mode. The ion transitions m/z 426.3 → 358.2 were used for DEU quantitation, while the ion transitions m/z 291.1 → 261.1 were used for trimethoprim quantitation. The accuracy, precision, linearity, recovery, and selectivity of DEU were deemed acceptable when validated for a concentration range between 0.500 and 601.050 ng/mL, utilizing a weighting factor of 1/x².

Forced Degradation and Stability-Indicating Study for the Binary Mixture of Allopurinol and Thioctic Acid Using Validated HPLC-DAD Method

BACKGROUND

Careful review of the scientific databases revealed that no stability-indicating analytical method is available for the binary mixture of Allopurinol (ALO) and Thioctic Acid (THA).

OBJECTIVE

A comprehensive stability-indicating HPLC-DAD procedure has been executed for concurrent analysis of ALO and THA.

METHODS

Successful chromatographic separation of the cited drugs was reached using Durashell C18 column (4.6 × 250 mm, 5 µm particle size). The mobile phase was comprised of a mixture of acidified water (pH 4.0) using phosphoric acid and acetonitrile pumped in gradient elution mode. For quantification of ALO and THA, their respective peak areas were recorded at 249 nm and 210 nm. A systematic validation of analytical performance was investigated in terms of system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection and quantification limits.

RESULTS

ALO and THA peaks emerged at retention times 4.26 and 8.15 min, respectively. Linear ranges for ALO and THA were 5-100 µg/mL and 10-400 µg/mL, respectively with correlation coefficient values exceeding 0.9999. Both drugs were exposed to conditions of neutral, acidic and alkaline hydrolysis, oxidation and thermal decomposition. Stability-indicating features have been demonstrated by resolution of the drugs from their forced degradation peaks. For verification of peak identity and purity, the diode-array-detector (DAD) was utilized. In addition, degradation pathways for the cited drugs were postulated. Besides, separation of both analytes from about 13 medicinal compounds of different therapeutic classes disclosed optimum specificity of the proposed method.

CONCLUSION

Advantageous application of the validated HPLC method for the concurrent analysis of ALO/THA in their tablet dosage form was accomplished.

HIGHLIGHTS

So far, the described HPLC-DAD method is considered the first detailed stability-indicating analytical study for this pharmaceutical mixture.

HPLC-Fluorescence Detection Method for Concurrent Estimation of Domperidone and Naproxen. Validation and Eco-Friendliness Appraisal Studies

This work demonstrates a simple and reliable HPLC method with fluorimetric detection for simultaneous estimation of domperidone (DOM) and naproxen (NAP). Successful chromatographic separation was accomplished using Inertsil ODS C18 column (5 μm, 4.6 × 150 mm) with gradient elution of the mobile phase consisting of 0.01 M phosphate buffer (pH 5.5) solution and acetonitrile. The gradient elution started with 25% acetonitrile increased linearly to 65% in 5 min, then kept at this percentage till the end of the run. The mobile phase was pumped at a flow rate of 1.0 mL/min. The excitation wavelength at 284 nm was found suitable for both DOM and NAP since it corresponds to a maximum for the minor component DOM and measurable excitation for NAP, while using 316 and 355 nm as emission wavelengths for DOM and NAP, respectively. Peaks eluted with excellent resolution at retention times 4.4 and 6.3 min for DOM and NAP, respectively. Performance of the proposed method was tested according to ICH guidelines in regard to linearity, ranges, precision, accuracy, robustness, detection and quantitation limits. Calibration curves were linear in the ranges of 0.8–3.6 and 1.0–2.5 µg/mL for DOM and NAP respectively with correlation coefficients not less than 0.9996. The validated method was successfully applied to the analysis of DOM and NAP in their laboratory prepared tablets resembling the commercial dosage form, and assay results were favorably compared with a published reference HPLC method. The method’s greenness was assessed using the Analytical Eco-Scale and the novel Analytical Greenness metric (AGREE).

Simultaneous Quantitation of Paracetamol and Lornoxicam in the Presence of Five Related Substances and Toxic Impurities by a Selective HPLC-DAD Method

OBJECTIVE

This research describes the simultaneous quantitation of paracetamol (PRM) and lornoxicam (LRX) with five of their related substances and toxic impurities, including, 4-nitrophenol (NTP), 4-aminophenol (AMP), 4-chloroacetanilide (CAC), N-phenylacetamide (NPA), and 2-aminopyridine (APD) using a specific HPLC-diode array detector (DAD) method.

METHODS

The chromatographic separation involves the use of a XTerra C18 column as the stationary phase and a mobile phase consisting of acetonitrile and 0.025 M phosphate buffer (pH 6). The separation was performed using gradient elution mode at 1.0 mL/min flow rate and detection at 260 nm for the determination of PRM and LRX. For detecting PRM and LRX in the presence of their toxic impurities, 270 nm was used. Validation of the suggested HPLC method was accomplished with regard to linearity, ranges, detection and quantitation limits, robustness, accuracy, precision, and specificity.

RESULTS

Excellent resolution of the mixture components was accomplished at retention times 4.2, 4.8, 7.4, 11.1, 13.5, 14.7, and 15.3 min for APD, AMP, PRM, NPA, LRX, NTP, and CAC, respectively. Linearity was established for PRM and LRX within concentration ranges of 10-100 and 10-60 µg/mL, respectively. The correlation coefficients obtained were >0.9997. The suggested method was confirmed to be a specific stability-indicating through the selective separation of PRM and LRX from their related substances, degradants, and impurities.

CONCLUSION

The proposed method was successfully utilized for the sensitive and selective determination of PRM and LRX in their pharmaceutical formulation.

HIGHLIGHTS

To the best of our knowledge, this is the first impurity profiling assay method for this combination in the presence of five of their toxic related substances and impurities. Taking into consideration that at least two of the studied impurities (AMP and APD) are actually reported degradation products for the main drugs, the suggested method can be considered stability-indicating as well.

Multi-analyte HPLC–DAD Method for Concurrent Analysis of Six Antimicrobials and Three Proton Pump Inhibitors Frequently used in Management of Helicobacter pylori Infection: Application to Simulated Intestinal Fluid Samples

The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump inhibitors, namely amoxicillin (AMX), doxycycline (DOX), furazolidone (FRZ), lansoprazole (LNS), levofloxacin (LVF), metronidazole (MTZ), omeprazole (OMZ), pantoprazole (PNZ) and tinidazole (TNZ). The selected nine drugs are frequently included in various treatment regimens of Helicobacter pylori infection. Successful separation was accomplished using the analytical column Agilent Zorbax Eclipse plus-C18 (250 × 4.6 mm, 5 µm particle size) and a mobile phase prepared from phosphate buffer pH 5 and acetonitrile pumped at a flow rate 1 mL/min using a gradient elution program. The gradient elution started with buffer/acetonitrile ratio 90:10, then it was altered in 15 min to reach 40:60 by volume. Quantification of the analytes was based on measuring peak areas of AMX at 230 nm, LVF, LNS and PNZ at 290 nm, OMZ at 300 nm, MTZ and TNZ at 320 nm, and DOX and FRZ at 360 nm. The separated compounds eluted at retention times 5.68, 6.43, 7.82, 8.84, 9.42, 10.75, 12.82, 13.74 and 14.90 min for AMX, MTZ, LVF, TNZ, DOX, FRZ, OMZ, PNZ and LNS respectively. Validation of the proposed HPLC procedure was carefully studied according to the ICH items: ranges, precision, accuracy, linearity, robustness and limits of detection and quantitation. The linear dynamic ranges were 5–100, 5–50, 2–40, 10–100, 10–100, 5–50, 2.5–30, 3–30 and 2–30 µg/mL for AMX, MTZ, LVF, TNZ, DOX, FRZ, OMZ, PNZ and LNS, respectively with correlation coefficients > 0.9993. Application fields of the validated method included analysis of laboratory-prepared binary dosage forms along with analysis of several ternary mixtures in spiked simulated intestinal fluid.

Development and greenness assessment of a stability-indicating HPLC-DAD method for simultaneous determination of allopurinol and benzbromarone

The growing interest in Green Analytical Chemistry (GAC) principles through the replacement of polluting analytical procedures with greener ones, has encouraged us to develop an eco-friendly stability-indicating HPLC with diode array detection method (HPLC-DAD) for simultaneous determination of allopurinol (ALP) and benzbromarone (BNZ). Effective separation was accomplished using Durashell C18 column (4.6 × 250 mm, 5 µm particle size) with gradient elution of the mobile phase composed of 0.02 M ammonium acetate (pH 5.0) and methanol. Quantification of ALP and BNZ was based on measuring their peak areas at 251 nm. ALP and BNZ peaks eluted at retention times 4.85 and 10.30 min respectively. The proposed HPLC procedure was carefully validated in terms of system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. The linearity range for both ALP and BNZ was 5-100 µg/mL with correlation coefficients >0.9999. Forced degradation conditions of neutral, acidic, and alkaline hydrolysis, oxidation, and thermal degradation were applied on both drugs. Good resolution of the drugs from their forced degradation products proved that the proposed method is stability-indicating. In addition, the resolution of both drugs from about 10 pharmacologically or chemically related pharmaceutical compounds of different medicinal categories showed the high specificity of the proposed method. The validated HPLC method was successfully applied to the simultaneous determination of both drugs in their tablet dosage forms. Furthermore, greenness assessment and comparison with previously published methods were carried out using two different GAC metrics, namely, the national environmental method index (NEMI) and the analytical Eco-Scale.

Application of MEKC and UPLC with Fluorescence Detection for Simultaneous Determination of Amlodipine Besylate and Bisoprolol Fumarate

OBJECTIVE

Two chromatographic methods were described for simultaneous determination of the antihypertensive drugs amlodipine besylate (AML) and bisoprolol fumarate (BIS).

METHODS

Method I applies micellar electrokinetic capillary chromatography using a deactivated fused silica capillary (25 cm effective length × 50 μm internal diameter). The background electrolyte consisted of 0.01 M borate buffer (pH 9.2) containing 0.025 M sodium dodecyl sulphate and methanol in the ratio of 80:20 (v/v). Valsartan (VAL) was used as an internal standard. Diode array detector was set at 238, 224, and 210 nm for measuring AML, BIS, and VAL, respectively. Method II involves using ultra-performance liquid chromatography with fluorescence detection. Zorbax SB-C8 column (2.1 × 100 mm, 1.8 μm particle size) was used with isocratic elution of the mobile phase composed of 0.1% trifluoroacetic acid, acetonitrile, and methanol in the ratio of 55:35:10 (v/v) at a flow rate of 0.6 mL/min. Fluorescence detection was done using excitation wavelengths 230 and 370 nm and emission wavelengths 305 and 450 nm for BIS and AML, respectively. Validation parameters were carefully studied including linearity, ranges, precision, accuracy, robustness, detection, and quantification limits.

RESULTS

Method I showed good linearity over the range 10-100 μg/mL for both dugs. Method II's linear ranges were 0.001-0.1 and 0.02-1 µg/mL for BIS and AML, respectively.

CONCLUSION

The proposed methods were successfully validated and applied for assay of the studied drugs in their fixed-dose combination tablets.

HIGHLIGHTS

To the best of our knowledge, this study suggests the first electro-chromatographic and LC with fluorescence detection methods for simultaneous determination of amlodipine and bisoprolol.

Validated capillary zone electrophoretic method for simultaneous analysis of benazepril in combination with amlodipine besylate and hydrochlorothiazide

In this work, a novel, simple, and quick capillary zone electrophoresis (CZE) method was proposed for simultaneous analysis of benazepril (BEN) with other co-administrated antihypertensive drugs, amlodipine besylate (AML) and hydrochlorothiazide (HCT), using a diode array detector (DAD). A fused silica capillary (78.5 cm total length, 70 cm effective length, and 75 μm id) was used in separation using a 40 mM phosphate buffer pH 7.5 as a running background electrolyte (BGE) under a positive potential of 30 KV, at a stable temperature of 25 °C for capillary during separation. Hydrodynamic injections were performed for 12 s at 50 mbar, and detection was performed at 210 nm for AML and BEN, at 225 nm for HCT, and at 232 nm for xipamide (XIP) added as an internal standard (IS). Separation of the three analyzed drugs and the IS was performed in less than 8 min. Migration times were 4.06, 5.23, 6.69, and 7.3 min for AML, HCT, BEN, and XIP, respectively. The findings proved that the proposed method was linear in the range of 10–80 μg/mL for all drugs with correlation coefficients >0.9994. The limit of detection (LOD) values of AML, HCT, and BEN were 1.004, 1.224, and 0.896 μg/mL, respectively, whereas the limit of quantification (LOQ) values were 3.124, 3.727, and 2.749 μg/mL for the cited drugs, respectively. Peak identity and purity were confirmed by DAD. The developed CZE method was applied for the analysis of the three antihypertensive drugs successfully in their combined pharmaceutical tablets, and it can be used for the quality control of single-pill combination (SPC) samples of these drugs in short time.

Validated specific HPLC-DAD method for simultaneous estimation of paracetamol and chlorzoxazone in the presence of five of their degradation products and toxic impurities

This work demonstrates a specific and reliable HPLC with diode array detection (DAD) method for the simultaneous estimation of paracetamol (PAR) and chlorzoxazone (CZ) in the presence of five of their degradation products and toxic impurities; namely; 4-aminophenol (AP), 4-nitrophenol (NP), acetanilide (AT), 4-chloroacetanilide (CA) and 2-amino-4-chlorophenol (ACP). Successful chromatographic separation was accomplished using Waters Symmetry C8 column (3.9 × 150 mm, 5 μm) with gradient elution of the mobile phase consisting of 0.05 M phosphate buffer pH 7.5 and methanol. The gradient elution started with 5% (by volume) methanol ramped up linearly to 50% in 10 min, and then maintained at this percentage afterward till the end of the run. The mobile phase was pumped at a flow rate of 1.0 mL/min. The multiple wavelength detector was adjusted at 244 and 285 nm to quantify PAR and CZ, respectively. Additionally, the wavelength 270 nm was found suitable for monitoring the separation of the entire mixture of PAR, CZ, and their impurities. Seven peaks eluted with excellent resolution at retention times 3.4, 5.7, 8.0, 10.1, 10.8, 13.5, and 14.4 min for AP, PAR, NP, AT, ACP, CZ, and CA, respectively. Performance of the proposed method was validated with respect to linearity, range, precision, accuracy, specificity, robustness, detection, and quantitation limits. Calibration curves were linear in the ranges of 10-75 and 10-100 µg/mL for PAR and CZ, respectively with correlation coefficients not less than 0.9998. The proposed method proved to be specific and stability indicating by the resolution of both drugs from their degradation products and toxic impurities. Validated HPLC method was successfully applied to the analysis of PAR and CZ in their combined capsules dosage form, and assay results were favorably compared with a published reference HPLC method. DAD served as an efficient tool for peak identity and purity verification.

Validated spectrophotometric determination of maduramicin ammonium using three charge transfer complexation reactions

Direct spectrophotometric determination of Maduramicin ammonium (MAD) represents an analytical challenge since it is a weak UV-absorbing and lacking a strong chromophore. This work represents the first spectrophotometric determination of MAD as no direct spectrophotometric or colorimetric determination methods for MAD are available in the literature. The present study illustrates the development of three simple, rapid and inexpensive colorimetric methods for the routine quality control analysis of MAD based on the formation of colored charge transfer complexes with three electron acceptors namely p-chloranilic acid (p-CA), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and picric acid (PA). The color products of MAD with p-CA, DDQ and PA were measured at 519, 588 and 405nm respectively. The proposed methods were validated in terms of linearity, ranges, precision, accuracy, robustness and limits of detection and quantification. MAD was effectively determined over concentration ranges of 100-1000, 25-250 and 30-150μg/mL using p-CA, DDQ and PA, respectively with good linearity as shown by the values of correlation coefficients not less than 0.9991. The developed methods were successfully implemented in the assay of MAD powder pharmaceutical formulation for veterinary use.

Gradient HPLC-Diode Array Detector Stability-Indicating Determination of Lidocaine Hydrochloride and Cetylpyridinium Chloride in Two Combined Oral Gel Dosage Forms

A simple, rapid, and selective HPLC-diode array detector method was developed for the simultaneous determination of lidocaine hydrochloride (LD) and cetylpyridinium chloride (CPC) in two combined pharmaceutical formulations. Effective chromatographic separation was achieved on a Zorbax SB-C8 (4.6 250 mm, 5 m particle size) column with gradient elution using a mobile phase composed of 0.05 M phosphoric acid and acetonitrile. The gradient elution started with 25 (v/v) acetonitrile, ramped up linearly to 85 in 5 min, and then was constant until the end of the run. The mobile phase was pumped at a flow rate of 1.2 mL/min. The multiple wavelength detector was set at 214 and 258 nm, and quantification of the analytes was based on measuring their peak areas. The retention times for LD and CPC were about 3.4 and 7.3 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, range, precision, accuracy, selectivity, robustness, LOD, and LOQ. Calibration curves were linear in the range of 5200 and 10400 g/mL for LD and CPC, respectively, with correlation coefficients >0.999. The proposed method was proven to be stability-indicating by the resolution of the two analytes from the related substance and potential impurity (2,6-dimethylaniline) as well as from forced-degradation products. The validated HPLC method was extended to the analysis of LD and CPC in two combined oral gel preparations for which the two analytes were successfully resolved from the pharmaceutical adjuvants and quantified with recoveries not less than 97.9.

Validated HPLC Determination of the Two Fixed Dose Combinations (Chlordiazepoxide Hydrochloride and Mebeverine Hydrochloride; Carvedilol and Hydrochlorothiazide) in Their Tablets

Simple, rapid, and selective RP-HPLC methods with UV detection were developed for simultaneous determination of chlordiazepoxide hydrochloride and mebeverine hydrochloride (Mixture I) and carvedilol and hydrochlorothiazide (Mixture II). The chromatographic separation in both mixtures was achieved by using an RP-C8 (octylsilyl) analytical column. For Mixture I, a mobile phase composed of acetonitrile0.05 M disodium hydrogen phosphatetriethylamine (50 + 50 + 0.2, v/v/v), pH 2.5, was used; the detector wavelength was 247 nm. For Mixture II, the mobile phase consisted of acetonitrile0.05 M disodium hydrogen phosphate (50 + 50, v/v), pH 4.0, and the detector was set at 220 nm. Quantification of the analytes was based on measuring their peak areas. Both mixtures were resolved in less than 6 min. The reliability and analytical performance of the proposed HPLC procedures were statistically validated with respect to linearity, range, precision, accuracy, selectivity, robustness, LOD, and LOQ. The linear dynamic ranges were 2.5150 and 2.5500 g/mL for chlordiazepoxide HCl and mebeverine HCl, respectively, and 0.25200 and 0.25150 g/mL for carvedilol and hydrochlorothiazide, respectively. The validated HPLC methods were successfully applied to the analysis of their commercial tablet dosage forms, for which no interfering peaks were encountered from common pharmaceutical adjuvants.

Comprehensive stability-indicating high-performance liquid chromatography coupled with diode array detection method for simultaneous determination of amprolium hydrochloride and ethopabate in powder dosage form for veterinary use

This research deals with the development of a stability-indicating high-performance liquid chromatography method for simultaneous determination of amprolium hydrochloride and ethopabate. To the best of our knowledge, no comprehensive stability-indicating method has been reported for analysis of this mixture. Separation was achieved using Kromasil cyano column with gradient elution of the mobile phase composed of sodium hexane sulfonate solution and methanol. Quantification was based on measuring peak areas at 266 nm. Amprolium and ethopabate peaks eluted at retention times 10.42 and 18.53 min, respectively. The proposed procedure was validated with respect to system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. Linearity ranges for amprolium and ethopabate were 1.5-240 and 1-160 μg/mL, respectively. Analytes were subjected to stress conditions of hydrolysis, oxidation and thermal degradation. The proposed method enabled resolution of drugs from their forced-degradation products and amprolium related substance (2-picoline). Moreover, specificity was verified by resolution of the analytes from about 22 drugs used in antimicrobial veterinary products. The validated method was successfully applied to assay of the combined veterinary powder dosage form, additionally it was implemented in the accelerated stability study of the dosage form when stored for six months at 40°C and 75% relative humidity.

Quick Test for Determination of N-Bombs (Phenethylamine Derivatives, NBOMe) Using High-Performance Liquid Chromatography: A Comparison between Photodiode Array and Amperometric Detection

The emergence of a new class of novel psychoactive substances, N-benzyl-substituted phenethylamine derivatives so-called "NBOMes" or "Smiles", in the recreational drug market has forced the development of new sensitive analytical methodologies for their detection and quantitation. NBOMes' hallucinogenic effects mimic those of the illegal psychedelic drug lysergic acid diethylamide (LSD) and are typically sold as LSD on blotter papers, resulting in a remarkable number of fatalities worldwide. In this article, four halide derivatives of NBOMe, namely, 2-(4-fluoro-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, 2-(4-chloro-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, 2-(4-bromo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, and 2-(4-iodo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethan-1-amine, were detected and quantified simultaneously using a high-performance liquid chromatographic method, and two detection systems were compared: photodiode array detection (detection system I) and amperometric detection via a commercially available impinging jet flow-cell system incorporating embedded graphite screen-printed macroelectrodes (detection system II). Under optimized experimental conditions, linear calibration plots were obtained in the concentration range of 10-300 and 20-300 μg mL^-1, for detection systems I and II, respectively. Detection limit (limit of detection) values were between 4.6-6.7 and 9.7-18 μg mL^-1, for detection systems I and II, respectively. Both detectors were employed for the analysis of the four NBOMe derivatives in the bulk form, in the presence of LSD and adulterants commonly found in street samples (e.g. paracetamol, caffeine, and benzocaine). Furthermore, the method was applied for the analysis of simulated blotter papers, and the obtained percentage recoveries were satisfactory, emphasizing its advantageous applicability for the routine analysis of NBOMes in forensic laboratories.

Simple mix-and-read assays for the determination of baclofen in pharmaceutical formulation

This study demonstrates three simple and inexpensive spectrophotometric mix-and-read assays for the determination of the skeletal muscle relaxant, baclofen (BAC) in pharmaceutical formulations. The proposed methods are based on the reaction of the primary amine group of BAC with various derivatizing reagents to yield different colored products. Method I depends on the reaction of BAC with vanillin in borate buffer pH 11.5 to give a yellow colored product with maximum absorbance at 401 nm. While method II describes the reaction with eosin Y in citric-phosphate buffer pH 2.2 forming an orange-red product measured at 548 nm. Method III depends on Hantzsch condensation reaction that yields a yellow product measured at 339 nm. Different experimental variables influencing development and stability of the obtained colored product are optimized. Validation of the three methods regarding linearity, ranges, precision, accuracy and limits of detection and quantification was performed. Regression analysis showed good linearity over the concentration ranges of 10–35, 5–20 and 5–25 μg/mL for methods I, II and III, respectively with correlation coefficient values not less than 0.999. Additionally, detection limits of BAC are 1.58, 0.94 and 0.79 μg/mL for methods I, II and III, respectively. Finally, the suggested procedures are successfully used for assay of BAC in its tablets. The main advantages of the proposed mix-and-read assays are being inexpensive and rapid with no requirement for laborious extraction techniques with equivalent or superior sensitivity compared to other published spectrophotometric procedures. Such advantages promote the suggested methods for the high throughput assay of BAC dosage forms, a critical component in quality control studies for pharmaceutical industries.

Application of HPTLC, spectrofluorimetry and differential pulse voltammetry for determination of the antifungal drug posaconazole in suspension dosage form

This work presents the development, validation and application of three simple and direct analytical methods for determination of posaconazole (PSZ) in its pure form and in suspension dosage form. Method I is based on high performance thin layer chromatography (HPTLC) where effective separation of PSZ and the internal standard (itraconazole) was achieved using Merck HPTLC plates (20×10cm aluminium plates with 250μm layer thickness precoated with silicagel 60 F₂₅₄) and a mobile phase composed of acetone and chloroform (1:2, by volume), followed by densitometric measurement of the drugs' spots at 262nm. Method II involves measurement of the native fluorescence of PSZ in 0.1M H₂SO₄ at excitation and emission wavelengths of 260 and 365nm, respectively. Method III depends on the voltammetric analysis of PSZ. A well-defined cathodic wave was obtained for PSZ in Britton-Robinson buffer pH 6.5 using the differential-pulse mode at the hanging mercury drop electrode (HMDE). The developed methods were validated according to the International Conference on Harmonization (ICH) guidelines regarding linearity, ranges, accuracy, precision, robustness and limits of detection and quantification. The proposed methods showed good linearity over the concentration ranges 5-50, 0.05-0.3, 0.005-0.05μg/mL PSZ for methods I, II, and III respectively. Intra and inter-day precision were verified by the RSD% values which were less than 2%. The proposed methods were successfully applied for the quantification of PSZ in suspension dosage form with no observable interferences. Assay methods were favorably compared with those obtained by previously reported HPLC method.

Development and validation of a versatile HPLC-DAD method for simultaneous determination of the antiviral drugs daclatasvir, ledipasvir, sofosbuvir and ribavirin in presence of seven potential impurities. Application to assay of dosage forms and dissolution studies

This study describes a simple, sensitive, specific and generic HPLC-DAD method for simultaneous determination of four drugs prescribed for treatment of Hepatitis C Virus (HCV) infection. Investigated drugs include daclatasvir (DAC), ledipasvir (LED), sofosbuvir (SOF) and ribavirin (RIB). Successful separation was accomplished using Thermohypersil BDS-C8 column (4.6 × 250 mm, 5 µm) with gradient elution of the mobile phase consisted of mixed phosphate buffer pH 7.5 and methanol. Gradient elution started with 25% methanol, ramped up linearly to 80% in 15 min then kept constant till the end of the run. Flow rate was 1.5 mL/min. Peak areas were measured at 235, 260, 315, and 332 nm for RIB, SOF, DAC, and LED, respectively. Peaks of the analytes were perfectly resolved with retention times 2.0, 12.1, 14.7, and 17.2 min for RIB, SOF, DAC, and LED, respectively. The developed method was validated according to ICH guidelines with respect to system suitability, linearity, ranges, accuracy, precision, specificity, robustness, and limits of detection and quantification. The proposed method showed good linearity in the ranges 5-500, 2-300, 0.5-75, and 0.5-75 µg/mL for RIB, SOF, DAC, and LED respectively. Limits of detection were 0.10-0.66 μg/mL for the analyzed drugs. Specificity was established by separation of target drugs from 7 process-related impurities for SOF including its major metabolite (GS-331007). Applicability of the proposed method to real life situations was assessed through the analysis of four different pharmaceutical formulations and satisfactory results were obtained. Additionally, dissolution profiles of the 4 drugs were studied using the developed method.

Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Infrared (GC-IR) Analyses of the Chloro-1- n-pentyl-3-(1-naphthoyl)-Indoles: Regioisomeric Cannabinoids

The analytical differentiation of the indole ring regioisomeric chloro-1- n-pentyl-3-(1-naphthoyl)-indoles is described in this report. The regioisomeric chloroindole precursor compounds, N- n-pentyl chloroindole synthetic intermediates, and the target chloro-substituted naphthoylindoles showed the equivalent gas chromatographic elution order based on the position of chlorine substitution on the indole ring. The regioisomeric chloro-1- n-pentyl-3-(1-naphthoyl)-indoles yield electron ionization mass spectra having equivalent major fragments resulting from cleavage of the groups attached to the central indole nucleus. Fragment ions occur at m/z 127 and 155 for the naphthyl and naphthoyl cations common to all indoles having the naphthoyl group substituted at the indole-3 position. Fragments resulting from the loss of the naphthoyl and/or n-pentyl groups from the molecular radical cation yield the cations at m/z 318, 304, 248, and 178. The characteristic (M-17)⁺ fragment ion at m/z 358 resulting from the loss of OH radical is significant in the mass spectra of all these compounds with 1-naphthoyl groups substituted at the indole-3 position. The vapor phase infrared spectra provide a number of characteristic absorption bands to identify the individual isomers.

Click chemistry inspired copper sulphide nanoparticle-based fluorescence assay of kanamycin using DNA aptamer

A highly selective and sensitive fluorescence assay for kanamycin has been developed that depends on complementation of two splits of DNA aptamer. One DNA split was labeled with CuS nanoparticle and the other was decorated with biotin, which enabled coupling with streptavidin magnesphere paramagnetic particles (PMPs). Complementation of the two-aptamer splits happened only in the presence of kanamycin and the subsequent sandwich was separated via a magnet. The released Cu(II) was reduced to Cu(I) by sodium ascorbate and finally catalyzed the click reaction between fluorogenic 3-azido-7-hydroxycoumarin and propargyl alcohol to afford the corresponding fluorescent 1,4-disubstituted-1,2,3-triazole. The fluorescence signal produced (λ_ex. = 365 nm, λ_em. = 470 nm) was dependent on kanamycin concentration. Fluorescence signal amplification was found to be in good linear relationship with the logarithm of kanamycin concentration in the range of 0.04-20 nM. Furthermore, the proposed assay showed a good reproducibility, high selectivity and low detection limits for kanamycin determination. In addition, the capability of the proposed method to detect kanamycin in biological samples with satisfactory results was demonstrated.

GC-MS and GC-IR Analyses of the Methoxy-1-n-pentyl-3-(1-naphthoyl)-indoles: Regioisomeric Designer Cannabinoids

The indole ring regioisomeric methoxy-1-n-pentyl-3-(1-naphthoyl)-indoles represent indole ring-substituted analogs of the synthetic cannabinoid JWH-018. The electron ionization mass spectra show equivalent regioisomeric major fragments resulting from cleavage of the groups attached to the central indole nucleus. The characteristic (M-17)+ fragment ion at m/z 354 resulting from the loss of OH group is significant in the mass spectra of all four compounds. Fragmentation of the naphthoyl and/or pentyl groups yields the cations at m/z 314, 300, 244 and 216. The vapor-phase infrared spectra provide a number of characteristic absorption bands to identify the individual isomers. Gas chromatographic separations on a capillary column containing a film of trifluoropropylmethyl polysiloxane (Rtx-200) provided excellent resolution of these compounds, their precursor indoles and intermediate pentylindoles. The elution order appears related to the degree of crowding of indole ring substituents.

Validated spectrophotometric and chromatographic methods for analysis of the recently approved hepatitis C antiviral combination ledipasvir and sofosbuvir

This work describes five simple and reliable spectrophotometric and chromatographic methods for analysis of hepatitis C antiviral binary mixture of ledipasvir (LPV) and sofosbuvir (SBV). Method I is based on the use of A_max and derivative spectrophotometry with the zero-crossing technique where LPV was determined using its A_max and ¹D amplitudes at 324 and 338nm respectively, while SBV was determined by measuring the ¹D amplitudes at 276nm. Method II involves the application of the ratio spectra derivative spectrophotometry. For LPV, 12μg/mL SBV was used as divisor and the ¹DD amplitudes at 239.8nm were plotted against LPV concentrations; while by using 10μg/mL LPV, the amplitudes at 279.2nm were found proportional to SBV concentrations. Method III depends on ratio-difference measurement where the peak to trough amplitudes between 229.2 and 268.4nm were measured and correlated to LPV concentration. Similarly, the amplitudes between 268.6 and 229.2nm in the SBV ratio spectra were recorded. For method IV, the two compounds were separated using HPTLC sheets of silica gel and a mobile phase composed of chloroform-methanol (94:6) followed by densitometric measurement of LPV and SBV spots at 331 and 267nm respectively. Method V depends on HPLC-DAD. Effective chromatographic separation was achieved using Thermohypersil C8 column (4.6×250mm, 5μm) with a mobile phase consisting of 0.01M sodium dihydrogen phosphate (pH 2.5) and methanol (20:80) at a flow rate 1.2mL/min and detection at 332 and 262nm for LPV and SBV respectively. Analytical performance of the developed methods was validated according to the ICH guidelines with respect to linearity, ranges, precision, accuracy, detection and quantification limits. The validated methods were successfully applied to the simultaneous analysis of LPV and SBV in mixtures of different proportions and their combined tablet dosage form.

Validated Spectrophotometric and RP-HPLC-DAD Methods for the Determination of Ursodeoxycholic Acid Based on Derivatization with 2-Nitrophenylhydrazine

This work describes the development, validation, and application of two simple, accurate, and reliable methods for the determination of ursodeoxycholic acid (UDCA) in bulk powder and in pharmaceutical dosage forms. The carboxylic acid group in UDCA was exploited for the development of these novel methods. Method 1 is the colorimetric determination of the drug based on its reaction with 2-nitrophenylhydrazine hydrochloride in the presence of a water-soluble carbodiimide coupler [1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride] and pyridine to produce an acid hydrazide derivative, which ionizes to yield an intense violet color with maximum absorption at 553 nm. Method 2 uses reversed-phase HPLC with diode-array detection for the determination of UDCA after precolumn derivatization using the same reaction mentioned above. The acid hydrazide reaction product was separated using a Pinnacle DB C8 column (4.6 × 150 mm, 5 μm particle size) and a mobile phase consisting of 0.01 M acetate buffer (pH 3)-methanol-acetonitrile (30 + 30 + 40, v/v/v) isocratically pumped at a flow rate of 1 mL/min. Ibuprofen was used as the internal standard (IS). The peaks of the reaction product and IS were monitored at 400 nm. Different experimental parameters for both methods were carefully optimized. Analytical performance of the developed methods were statistically validated for linearity, range, precision, accuracy, specificity, robustness, LOD, and LOQ. Calibration curves showed good linear relationships for concentration ranges 32-192 and 60-600 μg/mL for methods 1 and 2, respectively. The proposed methods were successfully applied for the assay of UDCA in bulk form, capsules, and oral suspension with good accuracy and precision. Assay results were statistically compared with a reference pharmacopeial HPLC method, and no significant differences were observed between proposed and reference methods.

Validated stability-indicating HPLC-DAD method for determination of the recently approved hepatitis C antiviral agent daclatasvir

A comprehensive stability indicating HPLC with diode array detection method was developed for the determination of the recently approved antiviral drug daclatasvir dihydrochloride (DCV) which is used for the treatment of chronic Hepatitis C Virus (HCV) genotype 3 infection. Effective chromatographic separation was achieved using Waters C8 column (4.6×250mm, 5μm particle size) with isocratic elution of the mobile phase composed of mixed phosphate buffer pH 2.5 and acetonitrile in the ratio of 75:25 (by volume). The mobile phase was pumped at a flow rate of 1.2mL/min, and quantification of DCV was based on measuring its peak areas at 306nm. DCV eluted at retention time 5.4min. Analytical performance of the proposed HPLC procedure was thoroughly validated with respect to system suitability, linearity, range, precision, accuracy, specificity, robustness, detection and quantification limits. The linearity range was 0.6-60μg/mL with correlation coefficient>0.99999. The drug was subjected to forced degradation conditions of neutral, acidic and alkaline hydrolysis, oxidation and thermal degradation. The proposed method proved to be stability-indicating by resolution of the drug from its forced-degradation products. The validated HPLC method was successfully applied to analysis of the cited drug in its tablets.

The effect of increased lipoproteins levels on the disposition of vincristine in rat

Background

Vincristine (VCR), an antineoplastic agent, is a key component in the treatment of acute lymphoblastic leukemia, lymphomas, rhabdomyosarcoma, neuroblastoma, and Wilms’ tumor diseases. Recently, high incidence of hyperlipidemia was reported to be associated with allogenic hematopoietic stem cell transplantation and VCR/L-asparaginase therapy.

The aim of this study is to test the effects of incremental increase in lipoproteins levels on vincristine disposition in rat.

Method

To study VCR pharmacokinetics and protein binding, rats (n = 25) were assigned to three groups, normal lipidemic (NL), intermediate (IHL) and extreme hyperlipidemic (HL). Hyperlipidemia was induced by ip injection of (1 g/Kg) poloxamer 407 in rats. Serial blood samples were collected using the pre-inserted jugular vein cannula for 72 h post VCR (0.15 mg/Kg) i.v. dose. VCR unbound fractions in NL, IHL and HL plasma were determined using ultrafiltration kits.

Results

VCR demonstrated a rapid distribution phase (6–8 h) followed by a slower elimination phase with a mean elimination t½ of ~ 14 h. VCR exhibited moderate binding to plasma proteins ~ 83 %. It showed a relatively small Vc (~0.17 L/Kg) and a larger Vβ (1.53 L/Kg) indicating good tissue distribution. As the lipoproteins levels were increased, no significant changes were noted in VCR unbound fraction, plasma concentration, or volume of distribution indicating low affinity to lipoprotein binding. Induced HL also did not affect VCR elimination where similar VCR AUC_0-∞, Cl and elimination phase t½ were reported along the different lipemic groups.

Conclusion

Incremental increase in lipoprotein levels resulted in no significant effect on VCR disposition as such ALL malignant lymphoma and allogenic hematopoietic stem cell transplantation patients need not to worry about HL-VCR interaction. Whether, HL can potentiate another drug-drug or drug-disease interaction involving VCR warrants further studying and monitoring to ensure therapeutic safety and efficiency.

Validated spectrophotometric methods for determination of sodium valproate based on charge transfer complexation reactions

This work presents the development, validation and application of four simple and direct spectrophotometric methods for determination of sodium valproate (VP) through charge transfer complexation reactions. The first method is based on the reaction of the drug with p-chloranilic acid (p-CA) in acetone to give a purple colored product with maximum absorbance at 524nm. The second method depends on the reaction of VP with dichlone (DC) in dimethylformamide forming a reddish orange product measured at 490nm. The third method is based upon the interaction of VP and picric acid (PA) in chloroform resulting in the formation of a yellow complex measured at 415nm. The fourth method involves the formation of a yellow complex peaking at 361nm upon the reaction of the drug with iodine in chloroform. Experimental conditions affecting the color development were studied and optimized. Stoichiometry of the reactions was determined. The proposed spectrophotometric procedures were effectively validated with respect to linearity, ranges, precision, accuracy, specificity, robustness, detection and quantification limits. Calibration curves of the formed color products with p-CA, DC, PA and iodine showed good linear relationships over the concentration ranges 24-144, 40-200, 2-20 and 1-8μg/mL respectively. The proposed methods were successfully applied to the assay of sodium valproate in tablets and oral solution dosage forms with good accuracy and precision. Assay results were statistically compared to a reference pharmacopoeial HPLC method where no significant differences were observed between the proposed methods and reference method.

Selective determination of dimenhydrinate in presence of six of its related substances and potential impurities using a direct GC/MS method

A novel simple, direct and selective gas chromatography–mass spectrometry (GC/MS) procedure was developed for the determination of the antihistamine drug dimenhydrinate (DMH) in presence of six of its related substances and potential impurities, namely, diphenylmethane, diphenylmethanol, benzophenone, orphenadrine, caffeine and 8-chlorocaffeine. The method involved resolution of the underivatized compounds using a trifluoropropylmethyl polysiloxane (Rtx-200) capillary column and the mass spectrometric detection was carried out in the electron-impact (EI) mode. Excellent baseline separation of DMH and the cited related substances was achieved in less than 15 min. Quantification of the parent drug DMH was based on measuring its peak area. The reliability and analytical performance of the proposed method were validated with respect to linearity, range, precision, accuracy, specificity, robustness, detection and quantification limits. Calibration curve of DMH was linear over the range 50–500 μg/mL with determination coefficient (R²) = 0.9982. The proposed method was successfully applied for the assay of DMH in tablets dosage form with recoveries >96.80%.

Mass spectral studies on 1-n-pentyl-3-(1-naphthoyl)indole (JWH-018), three deuterium-labeled analogues and the inverse isomer 1-naphthoyl-3-n-pentylindole

RATIONALE

A number of synthetic cannabinoids such as the 1-alkyl-3-acylindoles are the target of significant designer drug activity. One of the first waves of these compounds identified in clandestine samples was 1-n-pentyl-3-(1-naphthoyl)indole, JWH-018. These totally synthetic molecules can be prepared in a number of regioisomeric forms.

METHODS

The electron ionization mass spectrometric (EI-MS) fragmentation of the 1-n-pentyl-3-(1-naphthoyl)indole is compared to its inverse isomer 1-naphthoyl-3-n-pentylindole. These two substances are directly available from indole using identical precursor reagents and similar reaction conditions. Stable isotope deuterium labeling of the three major regions of the JWH-018 molecule allows confirmation of the structures of the major fragment ions. The spectra for the 1-n-pentyl-3-(1-naphthoyl)-d(5) -indole, 1-n-pentyl-3-(1-d(7) -naphthoyl)indole and 1-d(11) -n-pentyl-3-(1-naphthoyl)indole provide significant assistance in elucidating the structures for the major fragment ions in JWH-018.

RESULTS

The EI mass spectra for these isomers show a number of unique ions which allow for the differentiation of the 1-alkyl-3-acylindole compounds from the inverse regioisomeric 1-acyl-3-alkylindoles. The fragment ion [M-17](+) at m/z 324 for JWH-018 was formed by the elimination of a hydroxyl radical and the spectra of the three deuterium-labeled derivatives indicated the loss of hydrogen from the naphthalene ring. Further structural analogues suggest the hydrogen to come from the 8-position of the naphthalene ring.

CONCLUSIONS

The three deuterium-labeled analogues provide significant assistance in confirming the structures for the major fragment ions in the mass spectrum of the traditional synthetic cannabinoid compound, 1-n-pentyl-3-(1-naphthoyl)indole, JWH-018. The 1-naphthoyl-3-n-pentylindole inverse regioisomer can be easily differentiated from the traditional synthetic cannabinoid compound.

GC-MS analysis of the regioisomeric methoxy- and methyl-benzoyl-1-pentylindoles: Isomeric synthetic cannabinoids

The regioisomeric 1-n-pentyl-3-(methoxybenzoyl)indoles and the 1-n-pentyl-3-(methylbenzoyl)indoles represent potential designer modifications in the synthetic cannabinoid drug category. These six compounds were prepared by a two-step synthetic method. The analytical properties and methods of regioisomeric differentiation were developed in this study. The molecular ion represents the base peak in the EI mass spectra for most of the compounds in this group. The meta- and para-isomers in each series display fragment ions at equivalent masses with some differences in relative abundance of these ions. The ortho-substituted isomers for both the methoxybenzoyl and methylbenzoyl series show a unique fragment ion occurring at M-17. Deuterium labeling for the methoxy group in the ortho-methoxybenzoyl isomer (ortho-OCD3) confirmed the ortho-substituent as the source of the hydrogen in OH (M-17) elimination. The two sets of regioisomers were well resolved by capillary gas chromatography and the elution order reflected increasing molecular linearity. In both sets of compounds the ortho-isomer eluted first and the para-isomer showed the highest retention time. The HPLC separation showed the ortho-isomer eluting first and the meta-isomer eluting last in both sets of regioisomers.

A Comparative Study of Newly Developed HPLC-DAD and UHPLC-UV Assays for the Determination of Posaconazole in Bulk Powder and Suspension Dosage Form

Objective. To develop and compare HPLC-DAD and UHPLC-UV assays for the quantitation of posaconazole in bulk powder and suspension dosage form. Methods. Posaconazole linearity range was 5-50 μg/mL for both assays. For HPLC-DAD assay, samples were injected through Zorbax SB-C18 (4.6 × 250 mm, 5 μm) column. The gradient elution composed of the mobile phase acetonitrile: 15 mM potassium dihydrogen orthophosphate (30 : 70 to 80 : 20, linear over 7 minutes) pumped at 1.5 mL/min. For UHPLC-UV assay, samples were injected through Kinetex-C18 (2.1 × 50 mm, 1.3 μm) column. The mobile phase composed of acetonitrile: 15 mM potassium dihydrogen orthophosphate (45 : 55) pumped isocratically at 0.4 mL/min. Detection wavelength was 262 nm in both methods. Results. The run time was 11 and 3 minutes for HPLC-DAD and UHPLC-UV assays, respectively. Both assays were linear (r (2) > 0.999) with CV% and % error of the mean <3%. Limits of detection and quantitation were 0.82 and 2.73 μg/mL for HPLC-DAD and 1.04 and 3.16 μg/mL for UHPLC-UV, respectively. The methods quantitated PSZ in suspension dosage form with no observable interferences. Conclusions. Both assays were proven sensitive and selective according to ICH guidelines. UHPLC-UV assay exhibited some economic and chromatographic separation superiority.

Validated Stability-Indicating HPLC-DAD Method for the Simultaneous Determination of Diclofenac Sodium and Diflunisal in Their Combined Dosage Form

A simple, rapid, and highly selective HPLC-DAD method was developed for the simultaneous determination of diclofenac sodium (DIC) and diflunisal (DIF) in pure form and in their combined formulation. Effective chromatographic separation was achieved using a Zorbax SB-C8 (4.6×250 mm, 5 μm particle size) column with a mobile phase composed of 0.05 M phosphoric acid, acetonitrile, and methanol in the ratio of 40:48:12 (by volume). The mobile phase was pumped isocratically at a flow rate of 1 mL/min, and quantification of the analytes was based on measuring their peak areas at 228 nm. The retention times for diflunisal and diclofenac were about 7.9 and 9.5 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. Calibration curves were linear in the ranges of 5–100 μg/mL for both drugs with correlation coefficients >0.9998. The proposed method proved to be selective and stability-indicating by the resolution of the two analytes from four of their related substances and potential impurities as well as from forced-degradation (hydrolysis, oxidation, photolysis, and dry heat) products. The validated HPLC method was successfully applied to the analysis of DIC and DIF in their combined dosage form (suppositories). The proposed method made use of the diode array detector (DAD) as a tool for peak identity and purity confirmation.