Simultaneous determination of methocarbamol and aspirin by RP‐HPLC using fluorescence detection with time programming: its application to pharmaceutical dosage form

A new simple, rapid and sensitive reversed‐phase liquid chromatographic method was developed and validated for the simultaneous determination of methocarbamol (MET) and aspirin (ASP) in their combined dosage form. The separation of these compounds was achieved within 6.0 min on a CLC Shim‐pack C₈ column (250 × 4.6 mm, 5 µm particle size) using isocratic mobile phase consisting of acetonitrile and 0.02 M dihydrogenphosphate buffer (30:70, v/v) at pH = 5.0. The analysis was performed at a flow rate of 1.0 mL/min with fluorescence detection at 277/313 nm for MET and 298/410 nm for ASP using real‐time programming. The selectivity, linearity of calibration, accuracy, inter‐ and intra‐day precision and recovery were examined as parts of the method validation. The concentration–response relationship was linear over concentration ranges of 0.02‐0.20 and 0.02‐0.40 µg/mL for MET and ASP, respectively, with a limit of detection of 6 and 32 ng/mL for MET and ASP, respectively. The proposed method was successfully applied for the analysis of both MET and ASP in prepared tablets with average recoveries of 99.88 ± 0.65% for MET and 100.44 ± 0.78% for ASP. The results were favourably compared to those obtained by a reference method. Copyright © 2012 John Wiley & Sons, Ltd.     

A very simple high‐performance liquid chromatographic method with fluorescence detection for the determination of gemifloxacin in human breast milk

A high‐performance liquid chromatographic method with fluorescence detection was developed and validated for the determination of gemifloxacin in human breast milk. The proposed method allows the determination of gemifloxacin in breast milk samples without complex sample preparation. The samples were mixed with a mobile phase and filtered with a 0.45 µm polytetrafluoroethylene filter before analysis. Chromatographic separation was carried out on a C18 column (150 × 4.6 mm, 5 µm I.D.) using methanol:50 mM ortho‐phosphoric acid solution (40:60) as the mobile phase with a 1.0 mL/min flow rate. Quantitation was performed using fluorescence detection with an excitation wavelength at 272 nm and an emission wavelength at 395 nm. The linear range was found to be 0.1–2.5 µg/mL. The method was applied successfully for the determination of gemifloxacin in breast milk obtained from a breastfeeding mother after oral administration of a single tablet that included 320 mg gemifloxacin per gemifloxacin tablet. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous determination of metolazone and losartan potassium in their binary mixtures using high‐performance liquid chromatography with fluorimetric detection: application to combined tablets and spiked human plasma

A new, specific and sensitive reversed‐phase high‐performance liquid chromatography method was developed for the simultaneous determination of metolazone (MET) and losartan potassium (LOS). Good chromatographic separation was achieved within 6.0 min on a 150 × 4.6 mm i.d., 5 µm Waters, Ireland and ProDIGY 5 ODS 3 100 A column. A mobile phase containing a mixture of methanol and 0.02 M phosphate buffer (65:35, v/v) at pH 3.0 was used. The analysis was performed at a flow rate of 1 mL/min with fluorescence detection at 410 nm after excitation at 230 nm. Aspirin (ASP) was used as an internal standard. The proposed method was rectilinear over 2.0–40.0 (MET) and 40.0–800.0 ng/mL (LOS), with limits of detection of 0.22 and 4.52 ng/mL and limits of quantification of 0.68 and 13.70 ng/mL for MET and LOS, respectively. The method was successfully applied for the simultaneous analysis of the studied drugs in their laboratory‐prepared mixtures, single tablets and co‐formulated tablets. Moreover, the method was applied to an in vitro drug release (dissolution) test. The method was further extended to the determination of LOS in spiked human plasma. Statistical evaluation and comparison of data obtained using the proposed and comparison methods revealed no significant difference between the two methods in addition to good accuracy and precision for the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of some dihydroxybenzenesulphonic acid derivatives and their degradation product and main impurity (hydroquinone) by ion‐pair liquid chromatography

A simple and sensitive high‐performance liquid chromatography method was developed and validated for the determination of calcium dobesilate (DOB) or ethamsylate (ETM) in the presence of their degradation product, hydroquinone (HQ). The analyses were carried out on Promosil C₁₈ column (4.6 mm × 250 mm, 5 µm particle size) using an ion‐pair mobile phase consisting of methanol–1.5 mm tetra‐butyl ammonium bromide in 0.06 m phosphate buffer (25 : 75, v/v) at pH 6.0 with fluorescence detection at 286/333 nm. Pindolol was used as an internal standard. The proposed method was found to be rectilinear over the concentration ranges of 0.05–0.5 µg/mL for DOB, 0.1–0.8 µg/mL for ETM and 0.005–0.1 µg/mL for HQ. The method was applied for the determination of the studied drugs in different dosage forms and biological fluids. The results of the proposed method were statistically compared with those obtained by the comparison methods revealing no significance differences in the performance of the methods regarding accuracy and precision. Moreover, applying a time‐programmed fluorescence technique was valuable for the detection of trace amounts of HQ as an impurity and allowed purity testing of ETM or DOB within the BP pharmacopeial limit (0.1%). Copyright © 2013 John Wiley & Sons, Ltd.     

A validated HPLC method for the determination of dimethyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylene dioxybiphenyl‐2,2′‐dicarboxylate (DDB) with fluorescence detection in raw material and pill form: application to an in vitro dissolution test and a content uniformity test

A simple, sensitive and rapid HPLC method with fluorescence detection for the determination of dimethyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylene dioxybiphenyl‐2,2′‐dicarboxylate (DDB) in the raw material and pill form was developed. Liquid chromatography was performed on a C₁₈ column (250 × 4.6 mm i.d., 5 µm particle size), the mobile phase consisted of methanol and 0.05 M sodium dihydrogen phosphate buffer (80 : 20, v/v), and the apparent pH of the mobile phase was adjusted to 3. The fluorescence detector was operated at excitation/emission wavelengths of 275/400 nm. The proposed method allows the determination of DDB within concentration range 0.1–1.5 µg/mL with a limit of detection of 0.032 µg/mL, a limit of quantification of 0.097 µg/mL and a correlation coefficient of 0.9997. The proposed method has been successfully applied for the analysis of DDB in its pills with a percentage recovery of 98.45 ± 0.32. The method was fully validated according to ICH guidelines. Moreover, the high sensitivity of the method permits its use in an in vitro dissolution test for DDB under simulated intestinal conditions. In addition, the proposed method was extended to a content uniformity test according to USP guidelines. Copyright © 2014 John Wiley & Sons, Ltd.     

HPLC fluorescence method for the determination of nizatidine in human plasma and its application to pharmacokinetic study

A sensitive high‐performance liquid chromatographic (HPLC) method was developed for the determination of nizatidine in human plasma. Nizatidine was derivatized by 4‐fluoro‐7‐nitrobenzofurazan (NBD‐F). Chromatographic separation was performed on a Inertsil C₁₈ column (150 mm × 4.6 mm, 5 µm) using isocratic elution by a mobile phase consisting of methanol/water (55:45) at a flow rate of 1.2 mL/min. Amlodipine was used as the internal standard (IS). Fluorescence detector was used operated at 461 nm (excitation) and 517 nm (emission), respectively. The calibration curve was linear over the range of 50–2000 ng/mL. This method was successfully applied to a pharmacokinetic study after oral administration of a dose (150 mg) of nizatidine. Copyright © 2013 John Wiley & Sons, Ltd.     

Fourth‐derivative synchronous spectrofluorimetry and HPLC with fluorescence detection as two analytical techniques for the simultaneous determination of itopride and domperidone

Two simple, rapid and sensitive methods, namely, fourth‐derivative synchronous spectrofluorimetry (method I) and HPLC with fluorescence detection (method II) were developed for the simultaneous analysis of a binary mixture of itopride HCl (ITP) and domperidone (DOM) without prior separation. The first method was based on measuring the fourth derivative of the synchronous fluorescence spectra of the two drugs at Δλ = 40 nm in methanol. The different experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully optimized. Chromatographic separation was performed in < 6.0 min using a RP C₁₈ column (250 mm × 4.6 mm i.d., 5 µm particle size) with fluorescence detection at 344 nm after excitation at 285 nm. A mobile phase composed of a mixture of 0.02 M phosphate buffer with acetonitrile in a ratio of 55 : 45, pH 4.5, was used at a flow rate of 1 mL/min. Linearity ranges were found to be 0.1–2 µg/mL for ITP in both methods, whereas those for DOM were found to be 0.08–2 and 0.05–1.5 µg/mL in methods I and II, respectively. The proposed methods were successfully applied for the determination of the studied drugs in synthetic mixtures and laboratory‐prepared tablets. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel spectrofluorimetric method for the determination of calcitonin in ampules through derivatization with fluorescamine

In this study, a simple, sensitive and selective spectroflourimetric method has been developed for the determination of salmon calcitonin (sCT) in ampules. The method is based on the reaction between sCT and fluorescamine at pH 8.5 in borate buffer, resulting in a highly fluorescent derivative. Fluorescence of derivatized sCT solutions was measured by setting the excitation and emission monochromators and slit widths to 390, 484 and 10 nm, respectively. Sevaral derivatization parameters were optimized. A calibration graph was constructed using standard solutions of the derivatized calcitonin in the range 0.5–6.0 µg/mL. Limit of detection and limit of quantification values were determined to be 0.124 and 0.372 µg/mL, respectively. The proposed method was successfully applied for the determination of sCT in commercially available ampules. High recovery values (101.0–102.0 %), and a low relative standard deviation (RSD %) value (5.3–5.4) proved the accuracy and precision of the proposed method. An isocratic reversed‐phase high‐performance liquid chromatographic (HPLC) method, as a reference, was also developed for the determination of sCT. A reversed‐phase Nucleosil® C₁₈ column (250 mm × 4.6 mm i.d., 10 µm particle size, 120 Å pore size) was used and the detector was set at 210 nm. Statistical comparison of the results of the two methods showed clearly that there was no significant difference between them. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of carbamazepine in human urine and serum samples by high‐performance liquid chromatography with post‐column Ru(bipy)‐Ce(SO4)2 chemiluminescence detection

A novel, sensitive and rapid CL method coupled with high‐performance liquid chromatography separation for the determination of carbamazepine is described. The method was based on the fact that carbamazepine could significantly enhance the chemiluminescence of the reaction of cerium sulfate and tris(2,2‐bipyridyl) ruthenium(II) in the presence of acid. The chromatographic separation was performed on a Kromasil® (Sigma‐Aldrich) TM RP‐C18 column (id: 150 mm × 4.6 mm, particle size: 5 µm, pore size: 100 Å) with a mobile phase consisting of methanol–water‐glacial acetic acid (70:29:1, v/v/v) at a flowrate of 1.0 mL/min, the total analysis time was within 650 s. Under optimal conditions, CL intensity was linear for carbamazepine in the range 2.0 × 10^?8 ~ 4.0 × 10^?5 g/mL, with a detection limit of 6.0 × 10^?9 g/mL (S/N = 3) and the relative standard detection was 2.5% for 2.0 × 10^?6 g/mL (n = 11). This method was successfully applied to the analysis of carbamazepine in human urine and serum samples. The possible mechanism of the CL reaction is also discussed briefly. Copyright © 2012 John Wiley & Sons, Ltd.     

Steady‐state and synchronous spectrofluorimetric methods for simultaneous determination of aliskiren hemifumarate and amlodipine besylate in dosage forms

Aliskiren hemifumarate (ALS) and amlodipine besylate (AML) were simultaneously determined by two different spectrofluorimetric techniques. The first technique depends on direct measurement of the steady‐state fluorescence intensities of ALS and AML at 313 nm and 452 nm upon excitation at 290 and 375 nm, respectively, in a solvent composed of methanol and water (10: 90, v/v) . The second technique utilizes synchronous fluorimetric quantitative screening of the emission spectra of ALS and AML at 272 and 366 nm, respectively using Δλ of 97 nm. Effects of different solvents and surfactants on relative fluorescence intensity were studied. The method was validated according to ICH guidelines. Linearity, accuracy and precision were found to be satisfactory in both techniques over the concentration ranges of 1–15 and 0.4–4 µg/mL for ALS and AML, respectively. In the first technique, limit of detection and limit of quantification were estimated and found to be 0.256 and 0.776 µg/mL for ALS as well as 0.067 and 0.204 µg/mL for AML, respectively. Also, limit of detection and limit of quantification were calculated in the synchronous method and found to be 0.293 and 0.887 µg/mL for ALS as well as 0.034 and 0.103 µg/mL for AML, respectively. The methods were successfully applied for the determination of the two drugs in their co‐formulated tablets. The results were compared statistically with reference methods and no significant difference was found. The developed methods are rapid, sensitive, inexpensive and accurate for the quality control and routine analysis of the cited drugs in bulk and in pharmaceutical preparations without pre‐separation. Copyright © 2014 John Wiley & Sons, Ltd.     

Enantiospecific Analysis of 8‐Prenylnaringenin in Biological Fluids by Liquid‐Chromatography‐Electrospray Ionization Mass Spectrometry: Application to Preclinical Pharmacokinetic Investigations

8‐Prenylnaringenin (8PN) is a naturally occurring bioactive chiral prenylflavonoid found most commonly in the female flowers of hops (Humulus lupulus L.). A stereospecific method of analysis for 8PN in biological fluids is necessary to study the pharmacokinetic disposition of each enantiomer. A novel and simple liquid chromatographic‐electrospray ionization‐mass spectrometry (LC‐ESI‐MS) method was developed for the simultaneous determination of R‐ and S‐8PN in rat serum and urine. Carbamazepine was used as the internal standard (IS). Enantiomeric resolution of 8PN was achieved on a Chiralpak^® AD‐RH column with an isocratic mobile phase consisting of 2‐propanol and 10 mM ammonium formate (pH 8.5) (40:60, v/v) and a flow rate of 0.7 mL/min. Detection was achieved using negative selective ion monitoring (SIM) of 8PN at m/z 339.15 for both enantiomers and positive SIM m/z at 237.15 for the IS. The calibration curves for urine were linear over a range of 0.01–75 µg/mL and 0.05–75 µg/mL for serum with a limit of quantification of 0.05 µg/mL in serum and 0.01 µg/mL in urine. The method was successfully validated showing that it was sensitive, reproducible, and accurate for enantiospecific quantification of 8PN in biological matrices. The assay was successfully applied to a preliminary study of 8PN enantiomers in rat. Chirality 26:419–426, 2014. © 2014 Wiley Periodicals, Inc.     

Enhanced spectrofluorimetric determination of esomeprazole and pantoprazole in dosage forms and spiked human plasma using organized media

A simple, sensitive and rapid spectrofluorimetric method was developed for the determination of esomeprazole (EMZ) and pantoprazole (PRZ) in their pharmaceutical formulations and human plasma. The proposed method is based on the fluorescence spectral behavior of EMZ in methanol in the presence of 0.1 m NaOH containing 0.5% methyl cellulose (MC) at 306/345 nm. The fluorescence intensity of EMZ was enhanced about 1.3‐fold and good linearity in the range 0.4–4.0 µg/mL with a lower detection limit of 0.04 µg/mL and lower quantification limit of 0.14 µg/mL. For PRZ, its methanolic solution exhibited marked native fluorescence at 290/325 nm after enhancement (about 2.1‐ or 1.4‐fold) using either 0.025% sodium dodecyl sulfate (SDS) or 0.05% MC in the presence of 0.2 m borate buffer of pH 9.5. The fluorescence–concentration plots of PRZ were rectilinear over the ranges 0.2–2.0 and 0.3–3.0 µg/mL with lower detection limits of 0.02 and 0.03 µg/mL and lower quantification limits of 0.07 and 0.09 µg/mL using sodium dodecyl sulfate and MC, respectively. The method was successfully applied to the analysis of EMZ and PRZ in their commercial dosage forms and the results were in good agreement with those obtained with the comparison method. Furthermore, in a preliminary investigation, the proposed method was extended to the in vitro determination of the two drugs in spiked human plasma and the results were satisfactory. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of the antihypertensive drug cilazapril and its active metabolite cilazaprilat in pharmaceuticals and urine by solid-phase extraction and high-performance liquid chromatography with photometric detection

A liquid chromatographic method with photometric detection for the determination of cilazapril and its active metabolite and degradation product cilazaprilat in urine and pharmaceuticals has been developed. The chromatographic method consisted of a μBondapak C₁₈ column maintained at 30±0.2°C, using a mixture of methanol-10 mM phosphoric acid (50:50 v/v) as mobile phase at a flow-rate of 1.0 ml/min. Enalapril maleate was used as internal standard. The detection was performed at a wavelength of 206 nm. A study of the retention of cilazapril and cilazaprilat using solid–liquid extraction has been carried out in order to optimise the clean-up procedure for urine samples, which consisted of a solid–liquid extraction using C₈ cartridges. Recoveries greater than 85% are obtained for both compounds. The method was sensitive, precise and accurate enough to be applied to the determination of urine samples obtained from three hypertensive patients up to 24 h after intake of a therapeutic dose (detection limit of 70 ng/ml for cilazapril and cilazaprilat in urine). A comparison of the method developed using photometric and amperometric detection has been carried out.     

Extractionless high-performance liquid chromatographic method for the simultaneous determination of piroxicam and 5′-hydroxypiroxicam in human plasma and urine

A simple and rapid (extractionless) high-performance liquid chromatographic method with UV detection, at 330 nm, was developed for the simultaneous determination of piroxicam and its major metabolite, 5′-hydroxypiroxicam, in human plasma and urine. Acidified plasma and alkali-treated urine samples are used and naproxen is added as internal standard. The separation is performed at 40°C on a C₁₈ Spherisorb column with acetonitrile-0.1 M sodium acetate (33:67, v/v, pH 3.3) as mobile phase. The retention time is 2.2 min for 5′-hydroxypiroxicam, 2.6 min for piroxicam and 3.2 min for naproxen. The detection limit is 0.05 μg/ml using a 100-μl loop.     

A simple and sensitive HPLC fluorescence method for determination of tadalafil in mouse plasma

A simple and sensitive high-performance liquid chromatographic (HPLC) method utilizing fluorescence detection was developed for the determination of the phosphodiesterase type 5 inhibitor tadalafil in mouse plasma. This method utilizes a simple sample preparation (protein precipitation) with high recovery of tadalafil (∼98%), which eliminates the need for an internal standard. For constituent separation, the method utilized a monolithic C₁₈ column and a flow rate of 1.0 mL/min with a mobile phase gradient consisting of aqueous trifluoroacetic acid (0.1% TFA in deionized water pH 2.2, v/v) and acetonitrile. The method calibration was linear for tadalafil in mouse plasma from 100 to 2000 ng/mL (r > 0.999) with a detection limit of approximately 40 ng/mL. Component fluorescence detection was achieved using an excitation wavelength of 275 nm with monitoring of the emission wavelength at 335 nm. The intra-day and inter-day precision (relative standard deviation, RSD) values for tadalafil in mouse plasma were less than 14%, and the accuracy (percent error) was within −14% of the nominal concentration. The method was utilized on mouse plasma samples from research evaluating the potential cardioprotective effects of tadalafil on mouse heart tissue exposed to doxorubicin, a chemotherapeutic drug with reported cardiotoxic effects.     

Simultaneous estimation of levodopa and carbidopa by RP‐HPLC using a fluorescence detector: its application to a pharmaceutical dosage form

A reverse‐phase high‐performance liquid chromatographic (RP‐HPLC) method was developed and validated for the simultaneous estimation of levodopa and carbidopa in bulk and pharmaceutical formulations. Chromatographic separation was achieved by using a C₁₈ reverse‐phase column and a mixture of an aqueous phase (10 mM potassium dihydrogen phosphate buffer, pH 4.0) and methanol (90:10 v/v) as the mobile phase. Quantitative analysis of levodopa and carbidopa was performed using a fluorescence detector at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. The method was linear between 5 and 500 ng/mL for both levodopa and carbidopa. The detection limits for levodopa and carbidopa were 0.30 and 0.60 ng/mL, respectively, whereas the quantitation limit was 0.80 ng/mL for levodopa and 1.2 ng/mL for carbidopa. The method demonstrated good and consistent recoveries (99.63–100.80% for levodopa and 98.97–100.94% for carbidopa) with low interday and intraday relative standard deviation. The validated method was successfully applied to quantify levodopa and carbidopa simultaneously in a pharmaceutical formulation. The method was found to be precise, sensitive and accurate for the simultaneous determination levodopa and carbidopa in bulk and pharmaceutical formulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of cycloserine in human plasma by high-performance liquid chromatography with fluorescence detection,using derivatization with p-benzoquinone

A new method for determining cycloserine in plasma samples is described. This method is based on the derivatization of cycloserine with p-benzoquinone, a reaction that takes place at the same time as the process of plasma deproteinization due to the presence of ethanol as solvent in the solution of the derivatization reagent. Four derivatives are obtained from this reaction. The main derivative is well correlated with the cycloserine concentration. The ratio between the volumes of the plasma sample and the reagent solution is 1:2 for a p-benzoquinone concentration of 1000 μg/mL. Elution from a C₁₈ column was isocratic, using a mobile phase containing (v/v) 85% aqueous 0.1% formic acid solution, and 15% (v/v) of a mixture of methanol and acetonitrile (1:1), with a flow-rate of 1 mL/min, at 25°C. Determinations by fluorescence detection were achieved with excitation at 381 nm and emission at 450 nm, with a detection limit of 10 ng/mL for an injection volume of 5 μL. This method was validated and applied to the determination of cycloserine in blood plasma samples of several healthy volunteers.     

The tissue distribution in mice and pharmacokinetics in rabbits of oxaliplatin liposome

A rapid, sensitive, and simple high-performance liquid chromatographic (HPLC) method with an ultraviolet detector (UV) has been developed for the determination of oxaliplatin in the plasma of rabbits and tissues of mice. The sample preparation was carried out by complexation with 0.5?mL of DETC (diethyl-dithiocarbamate) solution and extracted by ether and chloroform. Then, 20?μL of supernatant was injected into the HPLC system with 0.25?mol/L of sodium chloride solution and methanol (30:70 v/v) as the mobile phase at a flow rate of 1.0?mL/min. Separation was performed with a C₁₈ column at 25°C. The peak was detected at 254?nm. The calibration curve was linear (R²?≥?0.9995) in the concentration range of 0.1~200?μg/mL in plasma and tissues. The intra- and interday variation coefficients were not more than 2.61 and 3.83%, respectively. The limit of detection was 20?ng/mL. The mean recoveries of oxaliplatin were ranged from 97.83 to 104.17% in plasma and tissues. The present method has been successfully applied to the pharmacokinetic study of oxaliplatin liposome in mice and rabbits.     

Simultaneous determination of cefdinir and cefixime in human plasma by RP-HPLC/UV detection method: Method development, optimization, validation, and its application to a pharmacokinetic study

A novel isocratic reversed-phase high performance liquid-chromatography/ultraviolet detection method for simultaneous determination of cefdinir and cefixime in human plasma was developed and validated after optimization of various chromatographic conditions and other experimental parameters. Sample preparation based on a simple extraction procedure consisting of deproteination and extraction with 3 parts of 6% trichloroacetic acid aqueous solution followed by volume make up with the aqueous component of the mobile phase obtained best recoveries of the two analytes. Samples were separated on a Supelco Discovery HS C(18) (150 mm × 4.6 mm, 5 μm) analytical column protected by a Perkin Elmer C(18) (30 mm × 4.6 mm, 10 μm) guard cartridge. The mobile phase, methanol/acetonitrile (50/50, v/v):0.05% trifluoroacetic acid (19:81, v/v), operated at 50°C column oven temperature was pumped at a flow rate of 2.0 mL min(-1) and the column eluents were monitored at a wavelength of 285 nm. When Sample was injected into the Perkin Elmer high performance liquid-chromatography system through Rheodyne manual (or auto-sampler) injector equipped with 20 μL loop, separation was achieved within 4 min. The present method demonstrated acceptable values for selectivity, linearity within the expected concentration range (0.004-5.0 μg mL(-1); r(2)>0.999 for both analytes), recovery (>95% for cefdinir and >96% for cefixime), precision (%RSD<2.0 for cefdinir and <2.2 for cefixime), sensitivity (limit of detection: 1 ng mL(-1) and lower limit of quantification: 4 ng mL(-1) for both analytes), stability of solutions, and robustness. The method was efficiently applied to a pharmacokinetic study in healthy volunteers.     

HPLC法测定牙膏中柚皮苷的含量

建立了高效液相色谱测定牙膏中柚皮苷含量的方法。采用的色谱条件:Hypersil BDS C18色谱柱(250 mm×4.6 mm,5μm);柱温为40℃;以水(A相)和乙腈(B相),梯度洗脱程序为:0～15 min,10%～100%B;流速为1.0 mL/min;检测波长为283 nm;进样量为20μL。结果表明,柚皮苷的质量浓度在14.55～116.40μg/mL范围内与峰面积呈良好的线性关系(r=0.9999),平均加标回收率为97.56%。该方法稳定、准确,重现性好,可作为牙膏中柚皮苷的含量测定和质量控制方法。