Validation of a liquid chromatographic-tandem mass spectrometric method for the determination of loperamide in human plasma

A sensitive and selective method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the quantitative determination of loperamide in human plasma. Automated solid-phase extraction (SPE) on disposable extraction cartridges (DEC) is used to isolate the compounds from the biological matrix and to prepare a cleaner sample before injection and analysis in the LC-MS/MS system. After conditioning, the plasma sample is loaded on the DEC filled with endcapped ethyl silica (C2(EC)) and washed twice with water. The analytes are therefore eluted by dispensing methanol. The eluate is then collected and added with ammonium acetate solution in order to inject an aliquot of this final extract in the LC-MS/MS system. On-line LC-MS/MS system using atmospheric pressure chemical ionization (APCI) has been developed for the determination of loperamide. The separation is obtained on a octadecylsilica based stationary phase using a mobile phase consisting in a mixture of methanol and 5mM ammonium acetate solution (25:75, v/v). Clonazepam is used as internal standard (IS). The MS/MS ion transitions monitored are m/z 477--> 266 and 316--> 270 for loperamide and clonazepam, respectively. The most appropriate regression model of the response function as well as the limit of quantitation were first selected during the pre-validation step. These latter criteria were then assessed during the formal validation step. The limit of quantitation (LOQ) was around 50 pg/ml for loperamide. The method was also validated with respect to recovery, precision, trueness, accuracy and linearity.

Sensitive determination of buprenorphine and its N-dealkylated metabolite norbuprenorphine in human plasma by liquid chromatography coupled to tandem mass spectrometry

A highly sensitive method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the quantitative determination of buprenorphine and its active metabolite norbuprenorphine in human plasma. Automated solid phase extraction (SPE) on disposable extraction cartridges (DEC) is used to isolate the compounds from the biological matrix and to prepare a cleaner sample before injection and analysis in the LC-MS/MS system. After conditioning, the plasma sample (1.0 ml) is loaded on the DEC filled with octyl silica (C8) and washed with water. The analytes are, therefore, eluted by dispensing methanol containing 0.1% of acetic acid. The eluate is collected and evaporated to dryness. The residue is dissolved in mobile phase and an aliquot is injected in the LC-MS/MS system. On-line LC-MS/MS system using atmospheric pressure chemical ionization (APCI) has been developed for the determination of buprenorphine and norbuprenorphine. The separation is obtained on a RP-18 stationary phase using a mobile phase consisting in a mixture of methanol and 50 mM ammonium acetate solution (50:50, v/v). Clonazepam is used as internal standard (IS). The MS/MS ion transitions monitored are m/z 468-->468, 414-->414 and 316-->270 for buprenorphine, norbuprenorphine and clonazepam, respectively. The method was validated regarding recovery, linearity, precision and accuracy. The limits of quantification (LOQs) were around 10 pg/ml for buprenorphine and 50 pg/ml for norbuprenorphine.

Development and validation of a liquid chromatographic method for the determination of amlodipine residues on manufacturing equipment surfaces

In the pharmaceutical industry, an important step consists in the removal of possible drug residues from the involved equipment and areas. The cleaning procedures must be validated and the methods to determine trace amounts of drugs have therefore to be considered with special attention. A high performance liquid chromatographic method for the determination of amlodipine residues in swab samples was developed and validated in order to control a cleaning procedure. The swabbing procedure was optimized in order to obtain a suitable recovery of amlodipine from stainless steel. A mean recovery close to 90% was obtained when two swabs moistened with methanol were used. The residual amlodipine was chromatographed at 25 degrees C in the isocratic mode on a RP-18 stationary phase using a mobile phase consisting of acetonitrile, methanol and pH 3.0 triethylamine solution (15:35:50 v/v/v). UV detection was performed at 237 nm. The method was shown to be selective and linear into the concentration range varying from 0.39 to 1.56 microg/ml. Accuracy and precision of the method were also studied. The limits of detection and quantitation were evaluated to be 0.02 and 0.08 microg/ml, respectively. The stability of amlodipine at different steps of the sampling procedure and the precision of the swabbing procedure were also investigated.