G Van Der Weken

Applications of Raman spectroscopy in pharmaceutical analysis

As Raman spectroscopy enables rapid, non-destructive measurements, the technique appears a most promising tool for on-line process monitoring and analysis in the pharmaceutical industry. This article gives a short introduction to Raman spectroscopy and presents several applications in the pharmaceutical field.

Chemiluminescence determination of captopril based on a Rhodamine B sensitized cerium(IV) method

Abstract A new Chemiluminescence method for the determination of captopril is described. The method is based on the Chemiluminescence reaction of captopril with cerium(IV) in sulphuric acid medium. Rhodamine B is suggested as a fluorescing compound for the energy-transferred excitation. This sensitized-type of Chemiluminescence emission allows quantitation of captopril concentrations in the 0.1–6.0 μM range with a detection limit of 0.037 μM original concentration. The experimental conditions for the reaction are optimized, the possible reaction mechanism is discussed and a direct application on a commercial drug formulation is given.

Chemiluminescence flow-injection analysis of captopril applying a sensitized rhodamine 6G method☆

A flow-injection analysis with chemiluminescence detection is described for the determination of captopril based on the photochemical reaction with cerium(IV) in sulphuric acid medium yielding a strong chemiluminescent signal which can be sensitized by some fluorescers. The proposed procedure has a linear application range of 1 x 10(-6) - 2 x 10(-4) M (r = 0.997) with a detection limit of 2 x 10(-7) M, an RSD of 2.8% at 1 x 10(-6) M captopril, and a sample measurement frequency of 500 h-1. The method was used for the simple and rapid determination of captopril in a pharmaceutical preparation.

Cerium (IV)-based chemiluminescence analysis of hydrochlorothiazide.

A flow-injection analytical method for the determination of hydrochlorothiazide is presented. The method is based on the chemiluminescence reaction of hydrochlorothiazide with cerium(IV) in sulphuric acid, sensitized by the fluorescent dye rhodamine 6G. The proposed procedure allows quantitation of hydrochlorothiazide in the concentration range of 0.33-130 mumol l(-1) with a detection limit of 0.15 mumol l(-1), an RSD of 2.4% at 10 mumol l(-1) and a sample measurement frequency of 200 h(-1). The method was successfully applied to the determination of hydrochlorothiazide in pharmaceutical preparations containing, amongst others, lactose, maize starch, calcium phosphate, magnesium stearate, potassium chloride and E 110 (disodium-6-hydroxy-5-(4-sulphonatophenylazo) naphthalene-2-sulphonate) as the concomitant species. Apart from the single formulation, hydrochlorothiazide was also determined in tablets combined with the antihypertensive lisinopril.

Application of the restricted-access precolumn packing material alkyl-diol silica in a column-switching system for the determination of ketoprofen enantiomers in horse plasma.

The group of LiChrospher ADS (alkyl-diol silica) sorbents that make part of a unique family of restricted-access materials, have been developed as special packings for precolumns used in the LC-integrated sample processing of biofluids. The advantage of these sorbents lies in the direct injection of untreated biological fluids, that is without sample clean-up, the elimination of the protein matrix with a quantitative recovery together with an on-column enrichment. The present method is based on previous work applying UV detection at 260 nm for ketoprofen determinations. Plasma samples introduced to the ADS precolumn using a 0.1 M phosphate buffer, pH 7.0. After washing with the buffer the ADS column was backflushed with the mobile phase 0.01 M phosphate buffer-6% (v/v) 2-propanol-5 mM octanoic acid at a pH of 5.5, thus transporting the analytes to the chiral-HSA (human serum albumin) (100x4.0 mm) column where the separation of the ketoprofen enantiomers was achieved with a resolution factor of 1.4. The developed column-switching method was fully applicable to plasma injections.

Chemiluminescence determination of some local anaesthetics

Abstract The analytical possibilities of the Chemiluminescence observed from some local anaesthetics on acidic permanganate treatment are investigated. Five drugs belonging to the p-aminobenzoate series gave significant emission and the reagent concentrations for their determination were optimized. The following detection limits were obtained: benzocaine, 30 ng ml−1; butacaine, 20 ng ml−1; butoform, 30 ng ml−1; procaine, 40 ng ml−1 and tetracaine 3 ng ml−1. The application of the reaction to the analysis of some pharmaceutical preparations containing benzocaine and procaine was evaluated.

Detection in the liquid phase applying chemiluminescence

Several chemiluminescence-based reactions are applicable to the determination of various bio-pharmaceutically important analytes, and they can be applied for monitoring chemiluminescence emission using flow injection, liquid chromatographic and capillary electrophoretic analysis, as well as for the development of chemiluminescence-based sensors or in immunoassays. As in general the emission intensity is linearly proportional to the concentration of any of the reagents, the technique allows the analysis of different species involved in the light-producing reaction, amongst which are the chemiluminescent reagent, oxidants, inhibitors, cofactors, catalysts, some fluorophore, etc. The present overview illustrates some important applications of the last decade on this rather unfamiliar luminescence technique to detectional challenges in the liquid phase. The required instrumentation is limited as no external light source is needed. Also, the technique opens perspectives for increasing detection sensitivity in miniaturized flowing streams. On the other hand, several drawbacks still limit full application, eg dependence of the emission signal upon a number of environmental factors forcing the analyst to make a compromise between separating and measuring conditions, a lack of selectivity in specific cases, the critical detection of the signal at strictly defined periods, especially in the case of sharp emission vs time profiles, and the development of detection devices in capillary electrophoresis.

Chemiluminescence detection coupled to liquid chromatography for the determination of penicillamine in human urine

Abstract An on-line liquid chromatography (LC) chemiluminescence detection system is proposed for the determination of penicillamine in human urine. Ion-pair reversed-phase LC using octane sulphonic acid as ion-pairing reagent allows the separation of penicillamine from the urine matrix. The Chemiluminescence reaction of penicillamine with Ce(IV) in sulphuric acid sensitized by quinine is suggested for sensitive penicillamine detection in a post-column mixing set-up. The Chemiluminescence response was linearly related to the concentration of penicillamine in the range 2.0–2000 μmol 1−1 (r = 0.9994, peak height, and 0.9997 peak area, n = 10) with a detection limit ( S N = 3) of 1.0 μ mol 1 −1 (100 pmol per injection). Relative standard deviations were less than 5% (n = 10) for 10–50 μmol 1−1. The excretion rates of penicillamine in human urine of three volunteers after oral penicillamine administration were determined in the present study.

Hplc Determination of N-Acetylcysteine in Pharmaceutical Preparations After Pre-Column Derivatization With ThiolyteR MB Using Fluorescence Detection

Abstract From the three commercially available bimanes, monobromobimane (Thiolyte MB) can be easily used as a fluorescence label for various biomedically important thiols such as acetylcysteine. The optimum reaction conditions for the chemical derivatization reaction applied to acetylcysteine, the reversed-phase chromatographic system and the precautions to be taken for obtaining reproducible analytical data are outlined. RP-18 HPLC occurs using aqueous acetic acid-acetone mixtures with a fluorescence detector installed at 380 nm and 470 nm as excitation and emission wavelengths, respectively. Penicillamine is used as an internal standard, and cysteine and homocysteine can be determined with the same system. Picogram sensitivities can be reached and the influence of potent reducing agents such as sodium borohydride, tributylphosphine and dithioerythritol is discussed. The suggested method allows a specific and sensitive estimation of the mucolytic acetylcysteine in the presence of its disulfide oxidation ...

Chemiluminescence analysis of captopril : comparison between luminol and rhodamine B-sensitized cerium(IV) methods

Two chemiluminescence methods for the determination of captopril are compared in the present paper. The first method is based on the reaction of captopril with the luminol-hydrogen peroxide-copper(II) system, the copper(II) ion acting as a key species in the light-emitting process. The catalytic activity of copper(II) decreases due to complex formation with the sulphhydrylic captopril analyte. Application of this indirect method allows captopril determinations in the 8.0-1.0 microM range as starting concentrations. Similarly, captopril was capable of generating chemiluminescence from acid cerium(IV) solutions, a reaction that could be analytically exploited by the inclusion of the rhodamine B fluorophore yielding a sensitized-type of chemiluminescence emission that allowed quantitation of captopril concentrations in the 0.1-6.0 microM range with a detection limit of 0.037 microM (original concentration). For both types of reaction the experimental conditions were optimized and a direct application was carried out on a commercial drug formulation.