Intra-source separation

Taylor and colleagues [98] at the Mayo Clinic published a method for the simultaneous analysis of urinary cortisol and cortisone. They used 2H4 cortisol as an internal standard and took a 0.5-ml urine sample. An API 2000 with Turboion-spray source was used in the positive-ion mode. Chromatography was conducted on a standard-bore C18 column with Q8 precolumn filter. MRM was conducted in the positive-ion mode monitoring m/z 363—>121 for cortisol, 367—>121 for 2TL, cortisol, and 361— -121 for cortisone. Cortisol and cortisone were separated and both were eluted within 2 min. Inter- and intra-assay variation for both compounds was < 9% for amounts above 2 pig/dl. The values obtained agree well with those of other studies, such as ours (Table 5.3.2) [62]. They found a range for cortisol for adult males of 4.2-60 pg/24 h and for adult females 3.0-43 pg/24 h. In summary, the 3-min run time of their method has allowed the Mayo group to completely transfer their cortisol and cortisone workload from RIA and HPLC to MS/MS. 

A sensitive, simple, and specific liquid chromatographic method coupled with electrospray ionization-mass spectrometry for the determination of donepezil in plasma was developed, and its pharmacokinetics in healthy, male, Chinese was studied [34]. Using loratadine as the IS, after extraction of the alkalized plasma by isopropyl alcohol-n-hexane (3 97, v/v), solutes are separated on a Cig column with a mobile phase of methanol-acetate buffer (pH 4.0) (80 20, v/v). Detection is performed with a TOF mass spectrometer equipped with an electrospray ionization source operated in the positive-ionization mode. Quantitation of donepezil is accomplished by computing the peak area ratio (donepezil [M + H](+) m/z 380-loratadine [M + H](+) mlz 383) and comparing them with the calibration curve (r = 0.9998). The linear calibration curve is obtained in the concentration range 0.1-15 ng/ml. The limit of quantitation is 0.1 ng/ml. The mean recovery of donepezil from human plasma is 99.4 6.3% (range 93.4-102.6%). The inter- and intra-day RSD is less than 15%. After an oral administration of 5 mg donepezil to 20 healthy Chinese volunteers, the main pharmacokinetic parameters of donepezil are as follow T(max), 3.10 0.55 h tV2j 65.7 12.8 h C(max), 10.1 2.02 ng/ml MRT,... 

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