Indirect Fluorimetric Detection Research Articles

Determination of D- and L-Amino Acids in Pharmaceutical Preparations by Indirect Chiral HPLC and Fluorimetric Detection

An indirect chiral HPLC method based on the derivatization reaction with o-phthaldialdehyde and N-acetyl-L-cysteine and fluorimetric detection is applied to determine the enantiomeric purity of amino acids in pharmaceutical preparations. Three samples, vanim™ 14, tebetane, and tulgrasum were analized and their enantiomeric contents were determined. Sample preparation did not require cleanup. The validity of the method was established. The D-AA content is not always specified in the labels of these pharmaceutical preparations.

Estimation of log Pow values for neutral and basic compounds by microchip microemulsion electrokinetic chromatography with indirect fluorimetric detection (μMEEKC-IFD)

Microchip microemulsion electrokinetic chromatography with indirect fluorimetric detection (μMEEKC-IFD) was used to obtain log P octanol/water (log P ow) values for neutral and basic compounds. Six compounds, with log P ow values between 0.38 and 5.03, were used to create a calibration curve relating the log of retention factors (log k) obtained from μMEEKC-IFD with the known log P ow values. The log P ow values for six additional compounds were determined using the log k values obtained by μMEEKC-IFD and the linear relationship between log P ow and log k established for the standard compounds. The μMEEKC-IFD buffer was composed of 50 mM 3-[cyclohexylamino]-1-propane-sulfonic acid (CAPS) buffer (pH 10.4) containing 1.2% n-heptane (v/v), 2% sodium dodecylsulfate (w/v), 8% 1-butanol (v/v) and 4 μM 5-carboxytetramethyl-rhodamine (TAMRA) as the fluorophore probe for indirect detection. The μMEEKC-IFD provided an accurate method for estimating log P ow values and also a means for analyzing compounds that are non-fluorescent.

A Review of Instrumentation and Measurement Techniques for Ground-Based and Airborne Field Studies of Gas-Phase Tropospheric Chemistry

ABSTRACT The development, applications and intercomparisons of instrumentation and measurement techniques for ground-based and airborne field studies of gas-phase tropospheric chemistry are reviewed. Filter radiometry, chemical actinometry and scanning spectroradiometry for j-NO2 and j-(O1D) are described. Detection of OH using L-POAS/DOAS, MOAS, LIF/FAGE and CIMS is discussed. Observations of NO3 using DOAS, MIESR and CRDS, and of HO2 and RO2 with CA, CIMS/IMR-MS, MIESR, and LIF/FAGE are also reviewed. GC-FID, GC-ECD and GC-MS analyses of NMHCs and alkyl, peroxyacyl and bi-functional organic nitrates are described, together with applications of CIMS/PTR-MS, DOAS and LIF. CO measurements utilising GFC, GC-HgO/UV, VUV-RF and TDLAS are presented. Measurements of O3 using UV photometry, chemiluminescence, electrochemistry, LIDAR/DIAL and DOAS are discussed. Chemiluminescence and LIF detection methods for NO with photochemical and thermal convertors for NO2 and NOy are also discussed, as are TDLAS, MIESR, DOAS, CRDS and other approaches for NO2. HONO measurements using DOAS, CIMS, CRDS, TDLAS, denuder systems, chemiluminescence and on-line analyses of NO2 − are described. For HONO2, filter packs, denuder systems, chemiluminescence methods, mist chambers, TDLAS, CIMS and LIF are presented. Direct and indirect fluorimetric, chromatographic and spectroscopic detection techniques are discussed for CH2O and higher carbonyls. Observations of H2O2 and ROOH utilising colorimetry, chemiluminescence, fluorescence, HPLC and TDLAS are also described.

Use of eosin as a fluorophore in capillary electrophoresis with laser detection

Eosin has been used to generate the background signal for indirect fluorimetric detection of inorganic and organic ions, simultaneously separated by capillary zone electrophoresis (CZE). This reagent provides constant fluorescence over the pH range of 5–10 and is compatible with the excitation by an argon ion laser at 488 nm with emission at 520 nm. The use of esosine as fluorophore, H 3BO 3, and Na 2B 4O 7 as electrolyte and diethylentriamine as modifier of the electroosmotic flow in CZE were optimised. The analytical potential of the studied buffer was tested on a group of 12 anions, used as model compounds. Both, hydrodynamic and electrokinetic injection mode were optimised. The detection limits determined by the last injection mode, were in the range 0.008–0.037 mg l −1. By using this method, the quantitation of the common anions in tap and mineral water has been carried out successfully.

Indirect fluorimetric detection of proteins via postcolumn mixing with fluorescence probe in size-exclusion chromatography

Proteins were visualized by postcolumn mixing with 2-p-toluidinyl-6-naphthalene sulfonate or 1-anilino-8-naphthalene sulfonate in size-exclusion chromatography. The indirect detection is based on fluorescence enhancement of the fluorescence probe owing to hydrophobic interaction with proteins. Bovine serum albumin gave the highest signal intensity among the proteins examined.

Utilization of fluorescein sodium salt for the indirect fluorimetric detection in micellar electrokinetic chromatography

The potential of fluorescein sodium salt to generate a background signal in indirect fluorimetric detection in micellar electrokinetic chromatography (MEKC) has been studied by using a sample test containing various alcohols (methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-1-ol, pentan-3-ol, 2-methylbutan-1-ol, 3-methylbutan-1-ol), acetaldehyde, acetone and ethyl acetate. In order to optimize sample test resolution and detection sensitivity, we have studied different parameters: sodium dodecyl sulfate concentration, electrolyte ionic strength, applied voltage as well as that of the addition of an organic cosolvent within the running electrolyte. Although the micellar pseudo-phase was not able to be saturated with the fluorophore in order to obtain the maximal detection sensitivity, the detection thresholds were satisfactory. By way of example, the detection threshold reached for 3-methylbutan-1-ol is 0.03% (v/v). The quantitative aspect was approached with ethanol titration in a commercial white wine. Finally the repeatability relating to, on the one hand, the effective electrophoretic mobilities and, on the other hand, the corrected areas has also been studied.

Indirect Fluorimetric Detection of Cyclodextrins via Postcolumn Mixing with 2-p-Toluidinyl-6-naphthalenesulfonate in Liquid Chromatography

Cyclodextrins (CD's) were visualized by postcolumn mixing with 2-p-toluidinylnaphthalene sulfonate (TNS) in liquid chromatography. The indirect detection is based on fluorescence enhancement due to the formation of an inclusion complex between TNS and CD's. β-CD gave larger signal intensity than α- and γ-CD. Different selectivities were observed for alkyl-bonded silica stationary phases with different chain length.

Improved method for simultaneous determination of ascorbic acid and dehydroascorbic acid, isoascorbic acid and dehydroisoascorbic acid in food and biological samples

The total vitamin C amount in different food and plasma samples was determined by a dual detection system, after HPLC separation, with direct detection of ascorbic acid and indirect fluorimetric detection of dehydroascorbic acid after a post-column O-phenyldiamine derivatisation. The two active forms of vitamin C and their d-isomers were separated within 10 min. The repeatability was determined by measurement of several fruits and vegetables and ranged from 0.3 to 1.9% (relative standard deviation) for vitamin C. The reproducibility, based on double determinations, ranged from 1.9 to 3.6% for vitamin C, depending on the matrix. The reproducibility, based on several determinations of reference materials, ranged from 2.4 to 3.7% for ascorbic acid and from 4.3 to 5.8% for dehydroascorbic acid, again depending on the matrix.

Optimization of the indirect fluorimetric detection for the simultaneous analysis of inorganic anions and polycharged organic anions by capillary electrophoresis

Until no w, fluorescein sodium salt has been used to gener ate the background signal for indirect fluorimetric detection of inorganic cations or mono-charged organic anions separated by Capillary Zone Electrophoresis (CZE). In this paper , we extend the use of fluorescein sodium salt to the simultaneous CZE analysis of inor ganic anions (Cl - , NO - 2 , NO - 3, SO 2- 4 , F - ) and poly- charged or ganic anions (oxalate and citr ate). The electroosmoti c flow was reversed by using tetradecyltrimethylammonium bro- mide (TTAB) or hexadimethrin e. The specific problems linked to the simultaneous utilization of fluorescein sodium salt and a positively char ged capillary were studied and resolved by reducing the fluorescein/TTAB interactions and by optimizing the fluo - rophore concentration in the electrolyte . The study of r eproducibility and the quantitati ve approach led to very good results. In such conditions the quantification of Cl - , NO - 3 and SO 2- 4 , in dif ferent mineral and spring waters, has been successfully realized . In addition, the detection thresholds reached the range of one hundred to a f ew hundred ppb. Key wo rd s . C ap i l l a r y zone electro p h o resis - indirect fl u o ri m e t r ic detection - fl u o rescein sodium salt - inorganic anions - polycharged or ganic anions.

Utilization of fluorescein sodium salt in laser-induced indirect fluorimetric detection II. Application to organic anions

Previously, we have used the fluorescein sodium salt to generate the background signal in the indirect fluorimetric detection of inorganic cations (alkaline, alkaline earth metals and transition metals) separated by capillary zone electrophoresis (CZE). In this work, we report that the use of fluorescein sodium salt can be extended to the detection of organic anions. A study of the detection thresholds and of reproducibility (elution times and effective electrophoretic mobilities) was performed. As samples we used, on the one hand, a mixture of n-alkane sulfonates (from C 1 to C 10) and, on the other hand, a mixture of carboxylic acids (from C 1 to C 18). Under the optimal conditions, detection thresholds of about 700 to 800 ppb were obtained and the reproducibility of effective electrophoretic mobilities was characterized by a relative standard deviation of about 0.5%. Calibration curves were also established (correlation coefficients were found to be between 0.995 and 0.9998). Finally, we compared the evolution of the experimental response coefficients of these two series of samples as a function of alkyl chain length with theoretical response coefficients obtained from findings reported by Ackermans et al. [J. Chromatogr., 549 (1991) 345].

Utilization of fluorescein sodium salt in laser-induced indirect fluorimetric detection of ions separated by capillary zone electrophoresis

Indirect detection, the principles of which were demonstrated some years ago, has attracted renewed interest in both UV-visible and fluorimetric detection. This paper reports the implementation of laser-induced indirect fluorimetric detection using a commercially available detector and its association with high-performance capillary electrophoresis for the determination of inorganic ions. In order to optimize the response sensitivity, the fluorescent agent being fluorescein sodium salt, the influence of the fluorescein sodium salt concentration, the ionic strength, the electrolyte pH and the gain on the signal-to-noise ratio were studied successively, the injection mode being either electrokinetic or hydrodynamic. In the case of a 75 μm I.D. fused-silica capillary, detection limits were in the ppb range or about 10 ppb for alkali metal cations using injection in the electrokinetic or in the hydrodynamic mode, respectively. As the detection system used had its maximum sensitivity at basic pH, the use of a complexing agent was required in order to perform the determination of alkaline earth metal cations, because they precipitate or are adsorbed at basic pH. Therefore, using ethylenediaminetetraacetic acid sodium salt (EDTA), it is possible to analyse at pH 7.5, in less than 5 min, a mixture containing three alkaline earth metal cations (Ba 2+, Ca 2+ and Mg 2+) and three transition metal cations (Fe 3+, Zn 2+ and Cu 2+) in addition to the previously mentioned alkali metal cations (Li + and K +).

Indirect fluorimetric detection of alkali and alkaline earth metal ions in capillary zone electrophoresis with cerium(III) as carrier electrolyte

It is shown that cerium(III) sulphate is a useful electrolyte for the determination of ammonium and alkali and alkaline earth metal ions using capillary zone electrophoresis with indirect fluorimetric detection. The limits of detection are in the low micromolar range. The separation can be influenced by adding 18-crown-6 to the electrolyte solution to change the retention behaviour of the analyte ions. Some examples of separations of standard solutions and practical applications are given to demonstrate the possibility of qualitative and quantitative analyses.

Indirect fluorimetric detection and quantification in capillary zone electrophoresis of inorganic anions and necleotides

The combination of indirect fluorescence detection and separation by capillary zone electrophoresis is discussed. Differences in instrument configuration, compared with earlier experiments, resulted in a reversed peak elution order. Separation of a 5′-triphosphate nucleotide from its corresponding diphosphate and monophosphate homologues can be accomplished in 5 min by this method. A quantitative comparison is made between the injection methods of electromigration and injection by gravity flow for samples of inorganic anions diluted in water with varying total concentrations. With injection of electromigration, the amount of sample injected varies significantly with the total ionic concentration of the sample.

Indirect fluorimetric detection of non-electrolytes in thin-layer chromatography

Indirect fluorimetric detection of non-electrolytes in thin-layer chromatography

Optimization of single-column anion chromatography with indirect ultraviolet photometric and fluorimetric detection

Optimization of single-column anion chromatography with indirect photometric and indirect fluorimetric detection is described. A simplex algorithm is used for signal maximization with eluent concentration, pH and flow rates as dependent variables. Absolute detection limits obtained for chloride, nitrite, nitrate and sulphate by indirect photometric detection were 1.0, 1.2, 1.4, and 2.0 ng, respectively. The use of single-beam indirect fluorimetric detection of these anions is also demonstrated. The method was applied to the detection of anions arising from gaseous acids or atmospheric aerosols.