Enhancement of the fluorescence of the zinc-morin complex by a non-ionic surfactant

A method is described for the fluorimetric determination of zinc, based on formation of a zinc-morin complex in the presence of a non-ionic surfactant. The complex has practically no fluorescence in the absence of surfactant, but the addition of Genapol PF-20 (non-ionic surfactant, ethylene oxide-propylene oxide condensate) makes possible the fluorimetric determination of low concentrations of zinc as it enhances the fluorescence of the complex about 75-fold. Maximum fluorescence is produced at pH 4.7 +/- 0.2 (acetic acid-acetate buffer), with 1.5% surfactant and 0.009% morin. The fluorescence is excited at 433 nm and measured at 503 nm. The calibration graph is linear up to 150 ng/ml zinc concentration and the detection limit is 3 ng/ml. The relative standard deviation (11 replicates) is 2.4% for zinc at 20 ng/ml concentration and 1.7% for 100 ng/ml. Of 29 ions studied, Al(3+), Be(2+), Zr(4+) and Cd(2+) strongly increase the fluorescence of the system, and Fe(3+), Ni(2+), Cu(2+), Ti(IV) and Co(2+) decrease the fluorescence signal.     

Preparation of a novel fluorescence nanoparticles and its application in the determination of Hg(II)

The strong fluorescence 2-vinylnaphthalene and acrylic acid polymer nanoparticles have been prepared under ultrasonic radiation. Based on the fluorescence quenching of polymer by Hg(II), a method for the selective determination of Hg(II) was developed. The reaction conditions between Hg(II) and polymer were investigated in detail. The assay is very few interference stable fluorescence signals (at least 2h), simple instrument (common spectrofluorometer) and simple step. Under optimal experimental conditions, a limit of detection of 0.01 microg ml(-1) was achieved. The calibration curve was linear over the concentration range 0.04-0.1 microg ml(-1) with a correlation coefficient of 0.9927. The proposed method has been applied to the selective quantification of Hg(II) in synthetic samples with the satisfactory results.     

Spectrofluorimetric method for determination of aluminium with chromotropic acid and its application to water samples

A rapid and sensitive method for the trace level determination of aluminium based on the formation of a 1:1 complex with chromotropic acid (1,8-dihydroxynaphthlene-3,6-disulfonic acid) in an methanol medium is reported. The fluorescence intensity of the system was 50 times greater than that of the system without aluminium. This method is very sensitive and selective for the direct determination of aluminium ion. The fluorescence is excited at 346 nm and measured at 370 nm. The optimum conditions are a chromotropic acid concentration of 5.0 ml (1.0x10(-4) M) and pH 4.0+/-0.5 (acetic acid-sodium acetate buffer). The fluorescence intensity is a linear function of the concentration of Al(III) in the range 2-100 ng ml(-1) and the detection limit is 1.0 ng ml(-1). The method has been applied successfully to the determination of trace amount of Al(III) in tap, river and sea-water samples.     

Selective fluorescence determination of chromium(VI) with poly-4-vinylaninline nanoparticles

The strong fluorescence poly-4-vinylaniline nanoparticles (PVN) has been prepared under ultrasonic radiation. Based on the fluorescence quenching of PVN by Cr(VI), a method for the selective determination of Cr(VI), without separation of Cr(III) in water, was developed. The reaction conditions between Cr(VI) and PVN were investigated in detail. The assay is characterized by short reaction time (<1 min even at 0 degrees C temperature), very few interference stable fluorescence signals (at least 2.5 h), simple instrument (common spectrofluorometer) and simplicity (a one-step assay). Under optimal experimental conditions, a limit of detection of 0.02 microg ml(-1) was achieved. The calibration curve was linear over the concentration range 0.1-13.0 microg ml(-1) with a correlation coefficient of 0.9984. The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples and waste-water samples with the satisfactory results.     

A Selective Fluorimetric Method for the Determination of Some β-Lactamic AntibioticsSupported by Natural Science Foundations of China and Shandong province

Abstract

Based on the reaction between acetylacetone-formaldehyde and β-lactamic antibiotics at pH=4.0, in which product can emit strong fluorescence, a selective simple fluorimetric method is described for the determination of both α-aminocephalosporins (namely cepharadine and cefalexin) and 6-aminopenicillanic acid (6-APA) in pure form and in pharmaceutical form. Other β-lactamic antibiotics free from α-amino group do not interfere with the assay. The linear ranges are 1.0×10^?4-8.0×10^?2 mg/ml, 2.0×10^?4-3.0×10^?2 mg/ml and 3.0×10^?4-2.0×10^?2mg/ml for cepharadine, cefalexin and 6-APA, respectively. Their detection limits (S/N=3) are 3.0×10^?5mg/ml, 4.0×10^?5mg/ml and 6.0×10^?5mg/ml.     

微量铽的萤光光度测定——铽与吡啶-2,6-二羧酸螯合物的萤光

铽与吡啶-2,6-二羧酸(以下简称DPA)形成螯合物的萤光有人从生物化学角度作过一些研究^[1],但对测定稀土氧化物中微量铽的研究未见报导。本文系统地研究了Tb³⁺-DPA螯合物萤光产生的条件,拟订了测定稀土氧化物中微量铽的萤光光度法,探讨了螯合物萤光强度与其组成的关系。     

Preparation and application of a novel core/shell organic nanoparticle as a fluorescence probe in the selective determination of Cr(VI)

A novel core/shell organic nanoparticles, anthracene/poly-acrylamide (AN/PAM), has been prepared successfully. Based on the fluorescence quenching of AN/PAM nanoparticles by Cr(VI), a method for the selective determination of Cr(VI), without separation of Cr(VI) in water, was developed. Furthermore, the reaction mechanism between nano-AN/PAM and Cr(VI) was also discussed. The synthesis and reaction conditions were investigated in detail. The assay is characterized by short reaction time, very few interference stable fluorescence signals, simple instruments and sensitivity. Under optical experimental conditions, a limit of detection of 0.02 microg/ml was achieved. The calibration curve was linear over the concentration range 0.04-2.00 microg/ml with a correlation coefficient of 0.9924. The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples and waste-water samples with the satisfactory results.     

Nonextractive spectrofluorimetric determination of aluminium in real, environmental and biological samples using chromotropic acid

An ultra-sensitive and highly selective nonextractive fluorimetric method is presented for the rapid determination of aluminium at nano-trace levels using chromotropic acid as a fluorimetric reagent [lambda(ex) = 360 nm and lambda(em) = 390 nm] in the pH range of 4.1-4.7. The fluorescence intensity of the metal chelate (2:3 complex) reaches a constant value within 1/2 hr and remains unchanged for over 48 hr. The fluorescence intensity aluminium concentration calibration curve is collinear between 1 and 300 ng/ml of Al. A constant fluorescence intensity is obtained over a wide range (1:50-1:1500) of Al:reagent molar concentrations. Large excesses of over 60 cations, anions and complexing agents (like tartrate, oxalate, phosphate, thio-urea, SCN(-), etc.) do not interfere in the Al determination. The developed method was successfully used in assaying aluminium in several standard reference materials (Al-bronze, brass, stainless steel) as well as in some environmental and biological samples. The method is very precise and accurate (S.D = +/-0.001 on 10 ng/ml; 11 determinations).     

Rapid determination of sulphonamides in milk using liquid chromatographic separation and fluorescamine derivatization.

A simple and selective method is presented for the multiple residue determination of eight sulphonamides in consumers' milk. The drugs are sulphisomidine (ID), sulphadiazine (DZ), sulphamerazine, sulphadimidine, sulphamonomethoxine, sulphamethoxazole, sulphadimethoxine and sulphaquinoxaline (SQ). The milk sample was deproteinized with the same volume of 2 M hydrochloric acid and filtered. A 1-ml volume of the filtrate was mixed with 1 ml each of 1.25 M sodium acetate solution and a buffer (pH 3.0) for derivatization with 0.6 ml of 0.02% fluorescamine solution in acetone. A high-performance liquid chromatographic analysis was carried out on a C18 column with a mobile phase of acetonitrile-2% acetic acid (3:5) at 55 degrees C using a fluorescence detector at an excitation wavelength of 405 nm and an emission wavelength of 495 nm. Average recoveries at fortification levels of 2, 5 and 10 ng/ml were 114%, 109% and 106%, respectively. Relative standard deviations were 1-4% at 10 ng/ml for ID, 5 ng/ml for DZ and SQ and 2.5 ng/ml for the other five sulphonamides. The method was applied to 25 milk samples and all appeared to be free from the drugs.     

Spectrofluorometric determination of thallium(III) with pyrogallol red and 3,4,5,6-tetrachlorofluorescein

Summary A spectrofluorophotometric determination of thallium(III) is proposed. It is based on the enhancement of the fluorescence reaction of 3,4,5,6-tetrachlorofluorescein (TCF) with Pyrogallol Red (PR) by thallium(III) in the presence of Swanol (AM 301, lauryldimethyl aminoacetic acid betain) as an amphoteric surfactant. The method was found to be suitable for the determination of thallium(III) down to 4.0 g in 10.0 ml by measuring the difference in the relative fluorescence intensities of a TCF/PR/thallium(III) solution and a TCF/PR solution. The recovery test in artificial urine was satisfactory (96±2%).     

Simultaneous determination of zopiclone and its two major metabolites (N-oxide and N-desmethyl) in human biological fluids by reversed-phase high-performance liquid chromatography

A high-performance liquid chromatographic method has been developed for the simultaneous determination of zopiclone and its main metabolites (N-oxide and N-desmethyl derivatives) in biological fluids. After selective extraction (dichloromethane-2-propanol) these compounds are chromatographed on a column packed with Spherisorb ODS-2 (5 micron) using monobasic sodium phosphate-methanol (45:55, v/v). The eluted compounds are measured by fluorescence detection. The limit of detection of the method is 5 ng/ml for zopiclone in plasma and urine and 10 ng/ml for its two main metabolites (coefficient of variation less than 10%). This method has been successfully applied to pharmacokinetic studies of zopiclone and its two main metabolites in healthy subjects and patients with chronic renal failure.     

Determination of warfarin at trace-levels in water by solid-phase spectrofluorimetry

A new selective and sensitive spectrofluorimetric method for the determination of warfarin at trace levels (0.2–50.0 ng/ml) in water is proposed. Warfarin is fixed on Sephadex QAE A-25 gel (at pH = 7.0) and its fluorescence is measured directly in the solid-phase using a 1-mm silica cell at 312/385 nm with a detection/quantification limit of 0.06/0.2 ng/ml, a relative standard deviation of 2.3% and recoveries between 95 and 105%. The method is applied to the determination of warfarin residues in water.     

Determination of Flecainide in Human Plasma by High Performance Liquid Chromatography with Fluorescence Detection

Abstract

A simple, rapid, selective, and sensitive high-performance liquid chromatographic (HPLC) method for the monitoring of plasma flecainide levels in a therapeutic or research environment is described. The drug is first separated from plasma by a single-step extraction with hexane and then quantitated by HPLC with fluorescence detection. Two linear ranges have been established; 100–2000 ng/ml for drug monitoring in clinical management of patients and 3–300 ng/ml for pharmacokinetic studies. The intra-day variation is less than 6%.     

Selective determination of guanine and its nucleosides and nucleotides by reaction with phenylglyoxal as a fluorogenic reagent

A fluorimetric method is described for determining guanine in its nucleosides and nucleotides. The method is based on the reaction of the compounds with phenylglyoxal as a fluorogenic reagent in a weakly acidic solution (pH 4.0). The fluorescences produced show excitation and emission maxima around 365 and 510 nm, respectively. The conditions established for the reaction do not produce fluorescence from other nucleic acid bases such as adenine, cytosine, uracil and thymine, and their nucleosides and nucleotides. The method is sensitive and selective for guanine and its derivatives, with a detection limit of 47–310 pmol ml^?1 in the reaction mixture.     

Rapid Determination of Propranolol and 4-Hydroxypropranolol in Plasma by High Pressure Liquid Chromatography

Abstract

The resolving power of high pressure liquid chromatography has been combined with the sensitivity of fluorescence detection to develop a method for the determination of propranolol and 4-hydroxypropranolol in plasma. A single selective extraction step precedes chromatography on a high efficiency bonded phase column. The limits of quantitation are approximately 2 ng/ml of plasma for each drug. The analysis of a number of clinical samples has demonstrated the application of the method in pharmacokinetic studies, but the possible interference of other drugs and their metabolites is still under investigation.     

Determination of AJ-3941, a possible agent for the treatment of cerebrovascular disorders, in plasma and brain by means of high-performance liquid chromatography with fluorescence detection.

A sensitive and selective high-performance liquid chromatographic method with fluorescence detection is described for the determination of AJ-3941 (I), a possible agent for the treatment of cerebrovascular disorders, in plasma and brain tissue. A simple hexane extraction was used for plasma, and for brain homogenate the hexane extract was further purified by solid-phase extraction. The determination limit was ca. 3 ng/ml for both plasma (0.5 ml) and 10% (w/v) brain homogenate (1 ml). The method was applied to the determination of I in plasma and brain samples of experimental animals.     

Determination of pyridoxal 5'-phosphate in human serum by reversed phase high performance liquid chromatography combined with spectrofluorimetric detection of 4-pyridoxic acid 5'-phosphate as a derivative

A very sensitive spectrofluorimetric method for the determination of pyridoxal 5'-phosphate (PLP) in human serum is described. The specificity is based on the selective oxidation of PLP to 4-pyridoxic acid 5'-phosphate with potassium cyanide. Separation of the highly fluorescent 4-pyridoxic acid 5'-phosphate is achieved by reversed-phase high-performance liquid chromatography. Specificity is improved by a careful choice of fluorescence filters, maximised at the excitation (325 nm) and emission (418 nm) wavelengths of 4-pyridoxic acid 5'-phosphate. The detection limit for the reaction is 0.22 ng ml(-1). For quantification, the serum is spiked with PLP before protein precipitation with 3.3% m/V trichloroacetic acid. The method can be used for the determination of PLP in serum, even in vitamin B6 deficient patients. The mean value for human serum PLP from 30 healthy adults was found to be 14.6 +/- 4.8 ng ml(-1) (mean +/- standard deviation).     

A Sensitive High Performance Liquid Chromatography Assay for Trospectomycin. An Aminocyclitol Antibiótic,in Human Plasma and Serum

Abstract

This report describes a sensitive, selective and robust assay for the quantification of trospectomycin, an aminocyclitol antibiotic, in human plasma and serum.

This is the first published High Performance Liquid Chramatography (HELC) bioanalytical method for a member of this class of compound.

The method involves the selective solid phase extraction of 6′-n-propyl spectinomycin and the internal standard 6′-n-butyl spectinonycin from 0.5 ml of biofluid, efficient reversed phase high pressure liquid chromatography with post column oxidation, reaction with o-phthaldialdehyde and fluorescence detection. The limit of quantification from 0.5 ml of biofluid is 10 ng/ml.     

Stereoselective determination of R(-)- and S(+)-MK-571, a leukotriene D4 antagonist, in human plasma by chiral high-performance liquid chromatography.

A stereoselective high-performance liquid chromatographic method that utilizes fluorescence detection was developed for the selective and sensitive quantification of R(-)- and S(+)-enantiomers of MK-571 (1), a potent and specific leukotriene D4 antagonist, in human plasma. Racemic 1 was isolated from the acidified plasma using solid-phase extraction and the resulting residue was successfully reacted with isobutyl chloroformate and R(+)-1-(1-naphthyl)ethylamine in triethylamine-acetonitrile medium to form the diastereomer of each enantiomer. A structural analogue of 1 was used as internal standard. The derivatized sample was dissolved in 1,1,2-trichlorotrifluoroethane and an aliquot was chromatographed on a (R)-urea chiral column using a mobile phase containing 89% triethylamine-pentane (3:1000, v/v), 10% 2-propanol, and 1% acetonitrile at a flow-rate of 1.5 ml/min. The fluorescence response (excitation wavelength, 350 nm; emission wavelength, 410 nm) was linear (r2 greater than 0.999) for concentrations of enantiomers of 1 from 0.05 micrograms/ml, the lowest quantitation limit, up to 2.5 micrograms/ml. Intra-day coefficients of variation at 0.05 microgram/ml were 2.4% for the R(-)-isomer and 2.0% for S(+)-isomer. The corresponding inter-day coefficients of variation for R(-)- and S(+)-1 were 2.6 and 3.6%, respectively. The utility of the methodology was established by analysis of plasma samples from male volunteers receiving single intravenous and oral doses of racemic 1.