A normal phase enantioselective high performance liquid chromatographic method was developed for enantiomeric resolution of Ezetimibe it reduces the overall delivery of cholesterol to the liver. The enantiomers of Eze...A normal phase enantioselective high performance liquid chromatographic method was developed for enantiomeric resolution of Ezetimibe it reduces the overall delivery of cholesterol to the liver. The enantiomers of Ezetimibe were resolved on a Chiral Pak AS-H (250 × 4.6 mm, 5 μm) column using a mobile phase system containing n-Hexane, etha-nol, 2-Propanol and Trifloroacetic acid (84:12:4:0.1 v/v). The resolution between enantiomers was found to be more than 2.0. The limit of detection and limit of quantification of (R)-enantiomer were found to be 0.2 μg/mL and 0.5 μg/mL, respectively, for 10 μL injection volume. The sample solution and mobile phase were found to be stable for at least 48 h. The final optimized method was successfully applied to separate (R)-enantiomer from Ezetimibe and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs.展开更多
5-Fluorocytosine (5-FC) is used for the treatment of several infections. It is extremely important to monitor blood level concentration for maximum activity to avoid its side effects. A simple, faster, and more accura...5-Fluorocytosine (5-FC) is used for the treatment of several infections. It is extremely important to monitor blood level concentration for maximum activity to avoid its side effects. A simple, faster, and more accurate analytical method is developed and validated using high-performance liquid chromatography with UV detection in a very low-volume serum sample. Exactly 50 μL of serum was precipitated with 5% trichloroacetic acid. After mixing and centrifugation, 20 μL of supernatant was injected into the HPLC column. Detection was performed at 280 nm. The method is very specific and free from interfering substances due to different drugs and their different circulating metabolites. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.50 μg/L and 1.0 μg/L, respectively. The method was linear in the range of 5 - 150 μg/L in the serum sample. In method comparison, the correlation coefficient r<sup>2</sup> was 0.999 and the percentage recovery was 90% - 105% on four levels of the quality control samples. Within run and between run precision was found to be less than 2.2% at four different concentrations (5, 25, 50, and 100 μg/L). A simple, faster, and more accurate HPLC-UV method is developed which is very useful for monitoring 5-FC concentration in low volume serum samples without evaporation step and ion exchange chromatography within minutes.展开更多
A simple, rapid and rugged RP-HPLC method was developed for evaluation and quantification of impurities present in Pirfenidone (PFD) drug substance. Impurities were separated and determined on a Zorbax RX-C18 column (...A simple, rapid and rugged RP-HPLC method was developed for evaluation and quantification of impurities present in Pirfenidone (PFD) drug substance. Impurities were separated and determined on a Zorbax RX-C18 column (250 mm length, 4.6 mm inner diameter and 5.0 μm particle size, octadecylsilane chemically bonded to porous silica) with 0.02 M KH2PO4 buffer and acetonitrile as mobile phase using a simple gradientelution program. The column flow rate of 1.0 mL per minute was used for the separation. The detection wave length was fixed at 220 nm. The method was substantiated with respect to specificity, precision, linearity, range, accuracy, ruggedness, limit of detection and quantitation. The impurities were identified as 2-hydroxy-5-methylpyridine and Iodobenzene. The linearity range obtained was 0.017 to 0.380 μg/mL for 2-hydroxy-5-methylpyridine, 0.047 to 0.382 μg/mL for Pirfenidone and 0.030 to 0.99 μg/mL for Iodobenzene with the retention times of 3.248 min, 10.608 min and 24.241 min for 2-hydroxy-5-methylpyridine, Pirfenidone and Iodobenzene, respectively. The percentage recoveries of 2-hydroxy-5-methylpyridine and Iodobenzene were in the range of 94.08% - 104.12%. The LOD and LOQ values were found 0.000005 mg/mL, 0.000017 mg/mL for 2-hydroxy-5-methylpyridine and 0.009 μg/mL, 0.030 μg/mL for Iodobenzene, respectively. The method is found to be suitable for the quantitation of impurities along with Pirfenidone drug substance. The method was validated as per the International Conference on Harmonization (ICH) guidelines.展开更多
The internal standard (IS) method is the best method for the analysis of samples, as it is independent of errors in injection volume, changes in sample volumes, and changes in sensitivity of the detector, etc. Use of ...The internal standard (IS) method is the best method for the analysis of samples, as it is independent of errors in injection volume, changes in sample volumes, and changes in sensitivity of the detector, etc. Use of an internal standard allows for the correction of losses due to sample clean-up of complex samples. An ideal IS is a compound that has properties very similar to, and that behaves as the compounds to be analysed. Ideally, only in the last step of analysis (HPLC), the IS should be well separated from the compounds of the mixture to be analysed. After testing several existing compounds with negative results, we decided to synthesise the 19-O-β-D-galactopyranosyl-13-O-β-D-glucopyranosyl-steviol as IS. This is the 19-galactosyl ester of steviolmonoside (13-O-β-D-glucopyranosyl-steviol). The IS was made according to published methods. Steviolmonoside (SM) was made from purified commercial rubusoside (Rub) by refluxing it in 10% KOH for 2 h. SM was precipitated and crystallized from MeOH. The hydroxyls of the glucose unit of SM were protected by acetylation. The acetylated SM was crystallized from acetone and dissolved in 1,2-dichloroethane. Then Ag2CO3 on Celite and tetra-acetylated galactopyranosyl bromide were added and the mixture was refluxed for 2 h. After cooling, BaO in MeOH was added to remove the acetyl groups. The 1,2-dichloroethane fraction was then extracted three times with equal volumes of water and the water fraction containing the IS was further purified on a C18 flash chromatography column. Traces of unreacted SM were removed by preparative HPLC on an Alltima C18 column (250 mm × 22 mm, particle size 10 μm) with AcCN:water (35:65, 20 ml/min). Detection was at 210 nm (KNAUER, “Smartline” UV detector 2500). The collected IS fraction from the HPLC was completely dried. Mixtures of steviol glycosides (SVglys) containing IS could be purified over SPE cartridges without change of the SVgly over IS ratio. The calibration curves for rebaudioside A (RebA) and stevioside (ST) were linear b展开更多
Acetazolamide(molecular mass(MM),222)belongs to the class of sulfonamides(R-SO2-NH2)and is one of the strongest pharmacological inhibitors of carbonic anhydrase activity.Acetazolamide is excreted unchanged in the urin...Acetazolamide(molecular mass(MM),222)belongs to the class of sulfonamides(R-SO2-NH2)and is one of the strongest pharmacological inhibitors of carbonic anhydrase activity.Acetazolamide is excreted unchanged in the urine.Here,we report on the development,validation and biomedical application of a stable-isotope dilution GC-MS method for the reliable quantitative determination of acetazolamide in human urine.The method is based on evaporation to dryness of 50 mL urine aliquots,base-catalyzed derivatization of acetazolamide(d0-AZM)and its internal standard[acetylo-2H3]acetazolamide(d3-AZM)in 30 vol%pentafluorobenzyl(PFB)bromide in acetonitrile(60 min,30C),reconstitution in toluene(200 mL)and injection of 1-mL aliquots.The negative-ion chemical ionization(NICI)mass spectra(methane)of the PFB derivatives contained several intense ions including[M]‒at m/z 581 for d0-AZM and m/z 584 for d3-AZM,suggesting derivatization of their sulfonamide groups to form N,N-dipentafluorobenzyl derivatives(R-SO2-N(PFB)2),i.e.,d0-AZM-(PFB)2 and d3-AZM-(PFB)2,respectively.Quantification was performed by selected-ion monitoring of m/z 581 and 83 for d0-AZM-(PFB)2 and m/z 584 and 86 for d3-AZM-(PFB)2.The limits of detection and quantitation of the method were determined to be 300 fmol(67 pg)and 1 mM of acetazolamide,respectively.Intra-and inter-assay precision and accuracy for acetazolamide in human urine samples in pharmacologically relevant concentration ranges were determined to be 0.3%e4.2%and 95.3%e109%,respectively.The method was applied to measure urinary acetazolamide excretion after ingestion of a 250 mg acetazolamide-containing tablet(Acemit®)by a healthy volunteer.Among other tested sulfonamide drugs,methazolamide(MM,236)was also found to form a N,N-dipentafluorobenzyl derivative,whereas dorzolamide(MM,324)was hardly detectable.No GC-MS peaks were obtained from the PFB bromide derivatization of hydrochlorothiazide(MM,298),xipamide(MM,355),indapamide and metholazone(MM,366 each)or brinzolamide(MM,384).We demonstrate for the firs展开更多
文摘A normal phase enantioselective high performance liquid chromatographic method was developed for enantiomeric resolution of Ezetimibe it reduces the overall delivery of cholesterol to the liver. The enantiomers of Ezetimibe were resolved on a Chiral Pak AS-H (250 × 4.6 mm, 5 μm) column using a mobile phase system containing n-Hexane, etha-nol, 2-Propanol and Trifloroacetic acid (84:12:4:0.1 v/v). The resolution between enantiomers was found to be more than 2.0. The limit of detection and limit of quantification of (R)-enantiomer were found to be 0.2 μg/mL and 0.5 μg/mL, respectively, for 10 μL injection volume. The sample solution and mobile phase were found to be stable for at least 48 h. The final optimized method was successfully applied to separate (R)-enantiomer from Ezetimibe and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs.
文摘5-Fluorocytosine (5-FC) is used for the treatment of several infections. It is extremely important to monitor blood level concentration for maximum activity to avoid its side effects. A simple, faster, and more accurate analytical method is developed and validated using high-performance liquid chromatography with UV detection in a very low-volume serum sample. Exactly 50 μL of serum was precipitated with 5% trichloroacetic acid. After mixing and centrifugation, 20 μL of supernatant was injected into the HPLC column. Detection was performed at 280 nm. The method is very specific and free from interfering substances due to different drugs and their different circulating metabolites. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.50 μg/L and 1.0 μg/L, respectively. The method was linear in the range of 5 - 150 μg/L in the serum sample. In method comparison, the correlation coefficient r<sup>2</sup> was 0.999 and the percentage recovery was 90% - 105% on four levels of the quality control samples. Within run and between run precision was found to be less than 2.2% at four different concentrations (5, 25, 50, and 100 μg/L). A simple, faster, and more accurate HPLC-UV method is developed which is very useful for monitoring 5-FC concentration in low volume serum samples without evaporation step and ion exchange chromatography within minutes.
文摘A simple, rapid and rugged RP-HPLC method was developed for evaluation and quantification of impurities present in Pirfenidone (PFD) drug substance. Impurities were separated and determined on a Zorbax RX-C18 column (250 mm length, 4.6 mm inner diameter and 5.0 μm particle size, octadecylsilane chemically bonded to porous silica) with 0.02 M KH2PO4 buffer and acetonitrile as mobile phase using a simple gradientelution program. The column flow rate of 1.0 mL per minute was used for the separation. The detection wave length was fixed at 220 nm. The method was substantiated with respect to specificity, precision, linearity, range, accuracy, ruggedness, limit of detection and quantitation. The impurities were identified as 2-hydroxy-5-methylpyridine and Iodobenzene. The linearity range obtained was 0.017 to 0.380 μg/mL for 2-hydroxy-5-methylpyridine, 0.047 to 0.382 μg/mL for Pirfenidone and 0.030 to 0.99 μg/mL for Iodobenzene with the retention times of 3.248 min, 10.608 min and 24.241 min for 2-hydroxy-5-methylpyridine, Pirfenidone and Iodobenzene, respectively. The percentage recoveries of 2-hydroxy-5-methylpyridine and Iodobenzene were in the range of 94.08% - 104.12%. The LOD and LOQ values were found 0.000005 mg/mL, 0.000017 mg/mL for 2-hydroxy-5-methylpyridine and 0.009 μg/mL, 0.030 μg/mL for Iodobenzene, respectively. The method is found to be suitable for the quantitation of impurities along with Pirfenidone drug substance. The method was validated as per the International Conference on Harmonization (ICH) guidelines.
文摘The internal standard (IS) method is the best method for the analysis of samples, as it is independent of errors in injection volume, changes in sample volumes, and changes in sensitivity of the detector, etc. Use of an internal standard allows for the correction of losses due to sample clean-up of complex samples. An ideal IS is a compound that has properties very similar to, and that behaves as the compounds to be analysed. Ideally, only in the last step of analysis (HPLC), the IS should be well separated from the compounds of the mixture to be analysed. After testing several existing compounds with negative results, we decided to synthesise the 19-O-β-D-galactopyranosyl-13-O-β-D-glucopyranosyl-steviol as IS. This is the 19-galactosyl ester of steviolmonoside (13-O-β-D-glucopyranosyl-steviol). The IS was made according to published methods. Steviolmonoside (SM) was made from purified commercial rubusoside (Rub) by refluxing it in 10% KOH for 2 h. SM was precipitated and crystallized from MeOH. The hydroxyls of the glucose unit of SM were protected by acetylation. The acetylated SM was crystallized from acetone and dissolved in 1,2-dichloroethane. Then Ag2CO3 on Celite and tetra-acetylated galactopyranosyl bromide were added and the mixture was refluxed for 2 h. After cooling, BaO in MeOH was added to remove the acetyl groups. The 1,2-dichloroethane fraction was then extracted three times with equal volumes of water and the water fraction containing the IS was further purified on a C18 flash chromatography column. Traces of unreacted SM were removed by preparative HPLC on an Alltima C18 column (250 mm × 22 mm, particle size 10 μm) with AcCN:water (35:65, 20 ml/min). Detection was at 210 nm (KNAUER, “Smartline” UV detector 2500). The collected IS fraction from the HPLC was completely dried. Mixtures of steviol glycosides (SVglys) containing IS could be purified over SPE cartridges without change of the SVgly over IS ratio. The calibration curves for rebaudioside A (RebA) and stevioside (ST) were linear b
文摘Acetazolamide(molecular mass(MM),222)belongs to the class of sulfonamides(R-SO2-NH2)and is one of the strongest pharmacological inhibitors of carbonic anhydrase activity.Acetazolamide is excreted unchanged in the urine.Here,we report on the development,validation and biomedical application of a stable-isotope dilution GC-MS method for the reliable quantitative determination of acetazolamide in human urine.The method is based on evaporation to dryness of 50 mL urine aliquots,base-catalyzed derivatization of acetazolamide(d0-AZM)and its internal standard[acetylo-2H3]acetazolamide(d3-AZM)in 30 vol%pentafluorobenzyl(PFB)bromide in acetonitrile(60 min,30C),reconstitution in toluene(200 mL)and injection of 1-mL aliquots.The negative-ion chemical ionization(NICI)mass spectra(methane)of the PFB derivatives contained several intense ions including[M]‒at m/z 581 for d0-AZM and m/z 584 for d3-AZM,suggesting derivatization of their sulfonamide groups to form N,N-dipentafluorobenzyl derivatives(R-SO2-N(PFB)2),i.e.,d0-AZM-(PFB)2 and d3-AZM-(PFB)2,respectively.Quantification was performed by selected-ion monitoring of m/z 581 and 83 for d0-AZM-(PFB)2 and m/z 584 and 86 for d3-AZM-(PFB)2.The limits of detection and quantitation of the method were determined to be 300 fmol(67 pg)and 1 mM of acetazolamide,respectively.Intra-and inter-assay precision and accuracy for acetazolamide in human urine samples in pharmacologically relevant concentration ranges were determined to be 0.3%e4.2%and 95.3%e109%,respectively.The method was applied to measure urinary acetazolamide excretion after ingestion of a 250 mg acetazolamide-containing tablet(Acemit®)by a healthy volunteer.Among other tested sulfonamide drugs,methazolamide(MM,236)was also found to form a N,N-dipentafluorobenzyl derivative,whereas dorzolamide(MM,324)was hardly detectable.No GC-MS peaks were obtained from the PFB bromide derivatization of hydrochlorothiazide(MM,298),xipamide(MM,355),indapamide and metholazone(MM,366 each)or brinzolamide(MM,384).We demonstrate for the firs
