J. Den Hartigh

High-performance liquid chromatographic determination of the antitumor agent mitomycin c in human blood plasma

A high-performance liquid chromatographic method for the determination of the antitumor drug mitomycin C in blood plasma samples of cancer patients is described. The drug is extracted from the plasma with chloroform–2-propanol (1+1, ww) and chromatographed on a reversed-phase column with u.v. detection at 365 nm. The detection limit of the determination is 1 ng ml-1 for 0.2–1.0 ml plasma samples. Preliminary results of a pharmacokinetic study show that the sensitivity and selectivity of the assay are adequate for drug monitoring in clinical practice. The results obtained from multiwavelength detection suggest the existence of metabolites.

Polarographic analysis for corticosteroids: Part 1. The electroanalytical properties of corticosteroids

Abstract The electroanalytical behaviour of corticosteroids has been studied in different supporting electrolytes. The reduction patterns are established by examining pH profiles, by constant-potential coulometry, fast-sweep voltammetry, potentiometry with ion-selective electrodes and differential pulse polarography. Dimerization and alcohol formation take place with the reduction of the C-3 keto group resulting in one or two peaks, depending on the number of double bonds in the A-ring and the pH. The C-20 keto group is reduced to an alcohol. Both reduction steps can be used for analytical purposes. The differential pulse peak height is linear with the concentration down to 10 -6 M steroid.

Electrochemistry of potentially bioreductive alkylating quinones Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents

The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the result of a change in the electron density of the quinone moiety, pre- or post-protonation of substituents, hydrogen bond formation, tautomerization reactions and steric interactions between the quinone moiety and substituents. The information obtained was of benefit in the elucidation of the reduction mechanisms of quinoid antitumour agents such as aziridnylquinones and mitomycins.

Polarographic reduction and determination of nalidixic acid

Abstract Protonated and uncharged forms of nalidixic acid (1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid) ans its 7-hydroxymethyl derivative are reduced at the dropping mercury electrode in two one-electron waves, whereas their anions are reduced in a single one-electron wave. Reduction of nalidix acid results in hydrogenation of the ethylenic bond in the azinone ring. Protonated and uncharged forms of the propyl ester of the nalidix acid are reduced in a single one-electron wave. In acidic media, the CO bond in the 7-hydroxymethylnalidixic acid is also reduced. Structural effects on the properties of the acid—base equilibria are discussed. Based on these studies, a differential pulse polarographic method for the determination of 10 −5 –10 −6 M nalidixic acid and its metabolite, the 7-hydroxymethyl derivative, in urine was developed; only a simple extraction is needed.

Ion-exchange liquid chromatographic analysis of bisphosphonates in pharmaceutical preparations

A simple, fast and uniform method has been developed for the quantitative determination of bisphosphonates in the quality control of pharmaceutical preparations. The method is based on ion-exchange liquid chromatography with conductivity detection. Separation is performed on a Waters IC-PAK Anion column using 2 mM nitric acid or 25 mM succinic acid as the mobile phase. Retention of the bisphosphonates can be influenced by pH and the anion concentration of the mobile phase. Sensitivity and selectivity are sufficient for the assay of bisphosphonates in bulk drug and pharmaceutical preparations. Sample preparation comprises dissolution or dilution of the sample in the mobile phase followed, if necessary, by filtration prior to HPLC analysis. Since the method is stability indicating, it is also well suited for shelf-life studies of bisphosphonate pharmaceutical preparations. Validation of the analytical method for the assay of pamidronate injection indicated an intra-day reproducibility of 1.7% (n = 6) and an inter-day reproducibility of 2.7% (n = 6). A linear relationship between response and concentration was found in the concentration range studied from 200 ng to 10 micrograms pamidronate per 20 microliters injected. The lower limit of detection (signal-to-noise ratio = 3) of pamidronate was about 100 ng.

Qualitative aspects of the degradation of mitomycins in alkaline solution.

The major degradation product in alkaline solution of mitomycin A, mitomycin C and porfiromycin is the corresponding 7-hydroxymitosane. The isolation and the physico-chemical and analytical properties of these compounds and their derivatized analogues are discussed. Data are presented on the degradation of mitomycin C at extremely high pH values.

Quantitative aspects of the degradation of mitomycin C in alkaline solution.

The alkaline hydrolysis of mitomycin C has been studied over a wide range of pH/H_(7-15). A stability-indicating high-performance liquid chromatographic (HPLC) method was used to separate the degradation products from the parent drug. The quantitative effects of temperature and buffers on the degradation of mitomycin C in alkali have been determined. A profile of log k(obs) against pH/H_ was constructed after corrections had been made for buffer effects and after extrapolation to 25 degrees C by application of the Arrhenius equation.

Handling of biological samples in the determination of the anti-neoplastic drug mitomycin C

A study to ascertain suitable conditions for handling biological samples from patients, treated with the antibiotic mitomycin C (MMC), with the objective of improving the accuracy and reliability of the determination is described. Situations frequently occurring in medical practice are simulated to optimize procedures for reliable and reproducible sampling, sample treatment and determination of MMC. Continuation of drug partitioning in whole blood after sampling can be prevented by immediate cooling in ice before the separation of plasma from cells. The adjustment of the pH of urine samples is shown to be particularly important since a low urinary pH causes decomposition of MMC; moreover, it may decrease extraction recovery. Furthermore, long-term exposure of samples to daylight induces drug decomposition. Frozen storage of plasma and urine samples for periods greater than 3 weeks is to be avoided as this results in a considerable drop in MMC concentration. Repeated cycles of freezing and thawing are shown to have no effect upon the analytical results (6 cycles tested). The analysis of extracts of biological samples may take place up to at least 24 h after their preparation without measurable loss of analyte.

Valence state of technetium in technetium methylene diphosphonate at tracer concentrations, measured by amperometry

Abstract The valence state of technetium-99 in technetium methylene diphosphonate complexes was determined at tracer concentrations. 10−7 to 10−8 M of 99TcO4− was titrated with Sn(II) in 10−1 M MDP solutions, similar to practical conditions for preparations of the radiopharmaceutical 99mTc-MDP. Sensitive detection was performed by normal pulse amperometry. A valence state of Tc(IV) has been confirmed.

Optimization of an Electrochemical Detector Using a Static Mercury Drop Electrode in High-Performance Liquid Chromatography. Analysis of the Anticancer Agent Mitomycin C in Plasma

An electrochemical detector using a static mercury drop electrode has been optimized for combination with high-performance liquid chromatography. Parameters like pump noise, oxygen in mobile phase and sample solution, nozzle, flow rate, working potential in the d.c. — and the d.p.p.— mode, have been examined. The application of the method in routine analysis has been illustrated by the analysis of the anticancer agent mitomycin C in plasma.