Search PubMed⌕ Search

Biomedical subjects

C Gooijer

Publications and source records attributed to C Gooijer.

30 records · Page 2Linked to original sources
PubMed1998

On-line dialysis solid-phase extraction coupled to capillary electrophoresis.

A fully automated dialysis solid-phase extraction (SPE) sample preparation procedure is coupled on-line to capillary electrophoresis (CE) for the first time. The system is used to determine sulfonamides in serum and urine. The dialysis unit serves to remove proteins and particulate matter. Reconcentration of the analytes is performed with a small SPE column while (in)organic salts and other interferences are removed simultaneously. Finally, the analytes are desorbed and injected, via a homemade interface, into the CE system. Limits of detection (LOD) of 0.05-0.1 and 0.05-0.3 microg/mL are obtained in urine and serum, respectively. The within-day and between-day precisions are in the range of 2-6% and 3-8%, respectively, for a concentration of five times the LOD. The dialysis SPE-CE system was used over a period of six months for the analysis of over 500 serum and urine samples without problems such as clogging of the CE capillary or SPE column.

Body Fluids↗
PubMed1997

Evaluation of phytic acid as a buffer additive for the separation of proteins in capillary electrophoresis.

The use of phytic acid to improve protein analysis by capillary electrophoresis (CE) is becoming more and more popular. Due to its size and number of negative charges (up to 12) it provides a high ionic strength combined with a low conductance resulting in an efficient decrease of wall adsorption for proteins. Because of its twelve acidic groups, phytic acid can be used as a buffer over a wide pH range (pH 2-11). The limited wall adsorption of proteins using phytic acid-containing buffers is observed for buffers with a pH of 5.5 and higher. With a monoprotic buffer, most of the investigated proteins show wall adsorption at the pH values studied. In case of a phytic acid buffer, wall adsorption is reduced by a factor of 2-4. The use of phytic acid both as a modifier and as a pH buffer results in more pronounced differences between the various protein mobilities compared with the use of monoprotic buffers. As a result this feature can be used to improve resolution in protein separations.

Buffers↗
PubMed1995

Determination of the anticancer drug metabolite WR1065 using pre-column derivatization and diode laser induced fluorescence detection.

A liquid chromatographic (LC) procedure using alumina as stationary phase in both the pre- and the analytical column, is reported for the determination of WR1065, the active metabolite of the amino- and thiol-containing anticancer drug WR2721. After pre-column derivatization of the thiol group, the analyte is determined by LC with diode laser induced fluorescence detection in the near-infrared. Selective removal of excess label is achieved by means of column switching; it allows the detection of 5 x 10(-9) M WR1065 in water and 10-fold diluted, deproteinated plasma samples. The detection limit is determined by the derivatization reaction and not by the fluorescence detection of the labelled analyte. Endogeneous thiols do not interfere.

Antineoplastic Agents↗
PubMed1990

Low-level interferences in peroxyoxalate chemiluminescence.

The role of interferences at concentrations lower than 10(-3) M in peroxyoxalate chemiluminescence is examined based on experimental results available in the literature. Implications for fluorophore and for hydrogen peroxide determinations are discussed. An interpretation in terms of the reaction mechanism is proposed.

Chromatography, High Pressure Liquid↗
PubMed1989

Lanthanide luminescence quenching as a detection method in ion chromatography. Chromate in surface and drinking water.

Dynamic quenching of Eu(III) and Tb(III) luminescence by inorganic anions as a detection method in ion chromatography was investigated. To obtain a high luminescence intensity, lanthanide(III) complexes are formed with ligands which make indirect excitation of the ions possible. Only a few anions (e.g., nitrite, chromate) induce efficient dynamic luminescence quenching. Chromate is an efficient quencher of Tb-acac luminescence. Samples of tap water and surface water, spiked with chromate, were injected into a high-performance liquid chromatographic system with post-column addition of the luminescent complex. In this way, a detection limit of 1.1 . 10(-7) M (13 ppb) of chromate could be obtained.

Chromates↗
PubMed1989

On the mechanism of peroxyoxalate chemiluminescence. Quenched chemiluminescence as a detection method in HPLC.

Several analytes such as the inorganic anions bromide, iodide, sulphite and nitrite and organic compounds as substituted anilines and sulphur compounds cause quenching of peroxyoxalate chemiluminescence. A detection method for liquid chromatography based on the quenching phenomenon has been developed. It makes use of an immobilized luminophore, i.e. 3-aminofluoranthene covalently bound via an alkyl-spacer on controlled pore glass, packed in the detector cell. The mechanism behind the quenching has been elucidated by investigating the roles of luminophores (both in the liquid and in solid state) and oxalates in peroxylate CL with respect to quenchers. Most probably the quencher destroys the radical ion pair produced after electron transfer in the last stage of the CIEEL reaction scheme, thus preventing the formation of electronically excited luminophore.

Chromatography, High Pressure Liquid↗
PubMed1987

HPLC detection of choline and acetylcholine in serum and urine by an immobilized enzyme reactor followed by chemiluminescence detection.

A method using HPLC has been developed for the detection of choline (Ch) and acetylcholine (ACh) using an immobilized enzyme reactor which converts Ch and ACh into hydrogen peroxide and betaïne. The formed H(2)O(2) is quantified by means of a solid-state peroxyoxalate chemiluminescence detector based on an immobilized fluorophore and addition of oxalate from a solid bed. The conditions necessary for chemiluminescence detection are obtained by using a make-up flow of acetonitrile after the enzyme reactor. Precipitation problems due to the poor solubility of salts in the final acetonitrile-water mixture are circumvented by adding a crown ether to the make-up flow. The reproducibility of the method was calculated to be 3.4-3.7% RSD. Detection limits are in the sub-picomole range and a linear range of at least three orders of magnitude is found. Measurements in urine and serum reveal no matrix effects.

Journal Article↗
PubMed1983

Room temperature phosphorescence as a liquid chromatographic detection method for polychlorinated naphthalenes and biphenyls in complex matrices.

Quenched and sensitized room temperature phosphorescence techniques have been used for the detection of PCNs and PCBs after liquid chromatographic separation. The usefulness of these techniques to fingerprinting of commercial Aroclor and Halowax mixtures in complex matrices has been shown. The complementary nature of these detection modes yield valuable information in addition to UV detection. a signal inverter is proposed for linearization of the quenched RTPL signals. In this way linear calibration plots over more than two orders can be obtained. Detection limits are generally in the low nanogram or subnanogram concentration region. The application of RTPL detection techniques to the analysis of commercial PCN and PCB mixtures in surface water and urine is demonstrated. Pre-columns can be used to advantage for pre-concentration and clean-up of this type of samples.

Chemical Phenomena↗
PubMedDate not supplied

Capillary electrophoresis of the collagen crosslinks HP and LP utilizing absorbance, wavelength-resolved laser-induced fluorescence and conventional fluorescence detection.

A capillary electrophoretic (CE) method is presented for the determination of the collagen crosslinks hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP). Various detection techniques are compared, i.e. UV-Vis diode-array absorbance detection (DAD) and fluorescence detection both in the laser-induced fluorescence (LIF) and the conventional fluorescence mode. LIF detection was performed using a frequency-doubled Rhodamine dye laser pumped by an excimer laser, for excitation at 290 and 325 nm. The emission was measured with an intensified diode-array detector mounted on a spectrograph to obtain wavelength-resolved spectra. Relevant concentration detection limits were achieved only by using LIF detection, i.e. 200 nM of HP and LP in a 30 mM phosphate buffer (pH 2.0). Linear calibration curves were obtained from the detection limits up to the maximum concentration available, 23 microM for HP and 4.2 microM for LP, respectively for both fluorescence modes. The identity of the migrating compounds was confirmed by on-line recording of both the absorption and the fluorescence spectra.

Buffers↗
PubMedDate not supplied

Trace analysis of 3-hydroxy benzo[a]pyrene in urine for the biomonitoring of human exposure to polycyclic aromatic hydrocarbons.

Determination of benzo[a]pyrene (BaP) metabolites in urine can provide direct insight into recent exposure to BaP integrated from all uptake routes. In order to detect 3-OH BaP in human urine after exposure to BaP at the workplace, extremely sensitive methods need to be developed. In this paper, a new extraction method is presented, and two laser-based fluorescence techniques are evaluated. Using HPLC with laser-induced fluorescence detection, a detection limit of 8 ng/L was obtained. With laser-excited Shpol'skii spectrometry after chemical derivatization, 3-OH BaP could be detected at even a 0.5-ng/L concentration. In a pilot study, urine samples from coke-oven workers and from occupationally nonexposed control persons were analyzed. In the control samples, the average 3-OH BaP concentration was 8.3 ng/L; the 3-OH BaP concentrations were found to be highly correlated (r2 = 0.89) with urinary 1-OH pyrene, a widely used biomarker for polycyclic aromatic hydrocarbon (PAH) exposure. Significantly elevated 1-OH pyrene concentrations were measured in urine samples from coke-oven workers, but in most samples a corresponding increase of 3-OH BaP was not observed. Possible explanations for this discrepancy are discussed.

Benzopyrenes↗