Development and validation of an HPLC stability-indicating method for identification and assay of elemental iron(II) in pharmaceutical drug products using reversed-phase HPLC

Ferrous sulfate tablets are a supplementary iron source for people who suffer from iron deficiency anemia. A simple, fast, and QC-friendly HPLC method was developed and validated to determine elemental iron in ferrous sulfate drug products. A TSK-GEL Super octadecylsilyl column (50 x 4.6 mm id, 2 microm particle size) with a mobile phase consisting of 0.06 M methanesulfonic acid in water-acetonitrile (40 + 60, v/v) and UV detection at 282 nm were used for this method. Separation of the elemental iron peak from the matrix was achieved within 5 min. This method was successfully validated according to International Conference on Harmonization guidelines, and shown to be stability-indicating for the shelf-life samples of ferrous sulfate tablets, as well as selective for the analyte of interest.     

A change of variables formula for mappings in

A change of variables formula for mappings in is obtained, where the usual jacobian is replaced by the determinant of the approximate differential.

     

Mechanism of base-catalyzed autooxidation of corticosteroids containing 20-keto-21-hydroxyl side chain

Corticosteroids and related compounds containing the 20-keto-21-hydroxyl side chain such as betamethasone, betamethasone 9,11-epoxide, dexamethasone, and dexamethasone 9,11-epoxide have been found to undergo facile autooxidation on the 1,3-dihydroxyacetone side chain of their D-rings under strong alkaline conditions to yield five main degradants (17-formyloxy-17-acid, 17-acid, 21-aldehyde, 20-hydroxy-21-acid, and 17-ketone). The rate of the autooxidation was correlated with the strength and concentration of the base used in the reaction. A novel mechanism for the observed autooxidation is proposed, in which the facile oxidation of the presumed enolate (resulting from the carbanion at the 21-position) by molecular oxygen is the key step. The proposed autooxidation mechanism, supported by LC-MS isotope experiments using ¹⁸O₂ as the oxidant, can satisfactorily explain the oxidative degradation patterns observed for corticosteroids containing the 20-keto-21-hydroxyl side chain.     

Determination of acetaminophen in human plasma by ion-pair reversed-phase high-performance liquid chromatography. Application to a single-dose pharmacokinetic study

The determination of acetaminophen in biological samples of humans who have ingested normal and overdosage of the drug is necessary to understand the clinical pharmacokinetics of acetaminophen and to determine its distribution and toxicokinetic parameters. This paper describes a rapid, simple, and sensitive high-performance liquid chromatographic method for determining acetaminophen in human plasma. Acetaminophen is isolated from plasma by adding approximately 200 microL of acetonitrile and 50 mg of solid zinc sulfate to each milliliter of plasma. A short column (60 mm x 4.6 mm) slurry packed with 5.0-microns PRP-1 particles is used with an isocratic elution of 5.0 mM dibasic potassium phosphate and 5.0 mM tetrabutylammonium hydroxide/methanol, 70:30 (v/v). The flow rate is 1.0 mL/min. The acetaminophen peak is detected with a variable wavelength ultraviolet/visible detector at 250 nm and 0.50 to 0.002 AUFS. The analysis time of the assay is less than 15 min, and the limit of detection is 20 ng/mL for an 80-microL injection volume. The pharmacokinetics of acetaminophen in plasma from a subject who had orally ingested 975 mg of the drug in tablet form is conducted using this method, and various pharmacokinetic parameters are determined.     

Assay of ibuprofen in human plasma by rapid and sensitive reversed-phase high-performance liquid chromatography:application to a single dose pharmacokinetic study

A rapid and sensitive reversed-phase high-performance liquid chromatography (HPLC) method is developed to determine the concentration of ibuprofen in human plasma. Ibuprofen is isolated from plasma by adding 0.50 mL of acetonitrile to 1.0 mL of plasma. The endogenous substances precipitated by acetonitrile are separated by centrifugation. The supernatant is saturated with ammonium sulfate to salt-out the acetonitrile. The salted-out acetonitrile is injected directly into the HPLC system. A 150-mm x 4.6-mm column packed with 3-microns reversed-phase octadecylsilane particles (C18) is used for the method finally developed. The mobile phase is a 1:1 ratio of acetonitrile-phosphoric acid (pH 2.2). Ibuprofen is monitored with a UV-visible detector at 220 nm and 0.10-0.002 absorbance units full scale (A.U.F.S.). The mean percent of relative standard deviations for within-day and between-day analyses are less than 3. The limit of detection for ibuprofen (in human plasma) is 25 ng/mL for a 100-microL injection volume. Quantitation of ibuprofen in human plasma at 100 ng/mL can be achieved with a relative standard deviation of less than 5%. The completion time of assay is less than 20 minutes.     

Determination of 5-fluorouracil in plasma and whole blood by ion-pair high-performance liquid chromatography

5-Fluorouracil in blood or plasma was determined by extraction and column liquid chromatography. Acetonitrile was added to blood or plasma and the mixture was stirred and centrifuged. Zinc sulfate addition was followed by stirring and centrifuging. The acetonitrile was salted out with ammonium sulfate, and an aliquot was evaporated with nitrogen. The residue was dissolved in mobile phase and chromatographed. The stationary phase was a styrene-divinylbenzene copolymer, and the mobile phase was 10 mM tetrabutylammonium hydroxide-methanol (74:26). 5-Fluorouracil was detected by UV absorption at 266 nm. Time of the assay was less than 30 min. The detection limit was 10 ng/ml and the relative standard deviation was 4 to 10% depending on the concentration.     

Separation of the two enantiomers of T-3811ME by normal-phase HPLC using modified amylose as chiral stationary phase

A normal-phase enantioselective high-performance liquid chromatographic method is developed for the separation of the undesired enantiomer from T-3811ME and quantitaion of the undesired enantiomer at low levels using a Chiralpak AD-H column (4.6 x 150 mm) packed with modified amylose stationary phase. The 2% water-modified 2-propanol is used for the method development activities, including exploration of various organic modifiers, optimization of additive acid concentration, column screening, and column temperature optimization. The final optimized method separated the undesired enantiomer from T-3811ME and is proven to be robust, sensitive, linear, accurate, and precise.