Spectrofluorimetric determination of levofloxacin in tablets, human urine and serum

A spectrofluorimetric method to determine levofloxacin is proposed and applied to determine the substance in tablets and spiked human urine and serum. The fluorimetric method allow the determination of 20–3000 ng ml⁻¹ of levofloxacin in aqueous solution containing acetic acid–sodium acetate buffer (pH 4) with λ_exc=292 and λ_em=494 nm, respectively. Micelle enhanced fluorescence improves the sensibility and allows levofloxacin direct measurement in spiked Human serum (5 μg ml⁻¹) and urine (420 μg ml⁻¹), in 8 mM sodium dodecyl sulphate solutions at pH 5.     

Spectrofluorimetric determination of moxifloxacin in tablets, human urine and serum

A spectrofluorimetric method to determine the antibiotic moxifloxacin is proposed and was applied to pharmaceuticals, human urine and serum. The fluorimetric method allows the determination of 30-300 ng mL-1 moxifloxacin in aqueous solution containing phosphoric acid-phosphate buffer (pH 8.3) with lambda exc = 287 nm and lambda em = 465 nm. Detection and quantification limits were 10 and 30 ng mL-1, respectively, with a relative standard deviation (n = 10) of 2%. This method was applied to the determination of moxifloxacin in three Spanish commercial pharmaceutical formulations. Another variant of the method in micellar medium allows the direct measurement of moxifloxacin in human serum and urine by standard additions. The enhanced fluorescence of moxifloxacin in 8 mM sodium dodecyl sulfate (SDS) solution at pH 4.0 (acetic acid-acetate buffer) for lambda exc = 294 nm and lambda em = 503 nm shows the same linear range as the aqueous method with a 25% lower slope (with detection and quantification limits of 15 and 60 ng mL-1, respectively, and a relative standard deviation of 1.3%), but permits the background fluorescence for urine and serum blanks to be minimized. Hence, sufficient sensitivity is reached to determine therapeutic concentrations of the drug in urine (average recovery 102 +/- 2%) and serum (average recovery 105 +/- 2%) samples.     

Spectrofluorimetric determination of cisatracurium and mivacurium in spiked human serum and pharmaceuticals

Spectrofluorimetric methods to determine cisatracurium and mivacurium are proposed and applied to the determination of both substances in human serum and to the determination of mivacurium in pharmaceuticals. The fluorimetric methods allow the determination of 5-500 ng ml(-1) of mivacurium in aqueous solutions and 5-500 ng ml(-1) of cisatracurium in water-acetonitrile solutions, both containing acetic acid-sodium acetate buffer (pH 5.5) with lambda(exc)=230 nm and lambda(em)=324 nm.     

Spectrofluorimetric determination of triethylenethiophosphoramide in blood

The method is based on a reaction of the ethyleneimine group with sodium sulfide, taurine and o-phthalaldehyde to give a fluorescent product. Triethylenethiophosphoramide (thioTEPA) can be determined in the range 9.4–945 ng in 100 μl of 1-propanol with a relative standard deviation of 2.3–4.7%. The method is applied to the determination of thioTEPA in rabbit blood plasma. The use of Extrelut 3 proved to be efficient for the clean-up of thioTEPA in plasma samples.     

Spectrofluorimetric method for the determination of uric acid in human serum

A new spectrofluorimetric method is described for the determination of uric acid (UA), that can remarkably reduce the fluorescence intensity of the enoxacin (ENX)-terbium ion (Tb³⁺) complex at 545 nm. The reduced fluorescence intensity of Tb³⁺ ion at pH 5.7 is proportional to the concentration of UA. Optimum conditions for the determination of UA have been investigated. The linear range and detection limit for the determination of UA are 6.0 × 10^?7–3.0 × 10^?5 M and 1 × 10^?7 M, respectively. The relative standard deviation (RSD) was 0.4% for 6 × 10^?6 M UA (n = 11). The method is simple, practical and relatively free of interferences. It has been successfully applied to assess UA in serum at the level of 3 × 10^?4 M with an RSD of 5–7% (n = 3). The results were evaluated by comparison with a common clinical spectrophotometric method using phosphotungstic acid as developer.     

Spectrofluorimetric determination of human serum albumin using a doxycycline-europium probe

A new spectrofluorimetric method is proposed for determination of human serum albumin (HSA) with the limit of detection at ng levels. Using doxycycline (DC)-europium (Eu³⁺) as a fluorescent probe, in a buffer solution of pH 10.2, HSA can remarkably enhance the fluorescence intensity of the DC-Eu³⁺ complex at 612 nm and the enhanced fluorescence intensity of Eu³⁺ is proportional to the concentration of HSA. Optimum conditions for the determination of HSA are also investigated. The linear ranges for HSA are 0-9.2 and 9.2-34.5 μg ml⁻¹ with limits of detection of 64 and 115 ng ml⁻¹, respectively. This method is simple, practical and relatively free of interference from coexisting substances, as well as much more sensitive than most of the existing assays. The determination results for human serum and urine samples are identical to those by the AOAO method, with relative standard deviations of five determinations of 1.1-3.6%. By the Rosenthal graphic method, the binding number and association constant of human serum albumin with the probe are 1.8 and 3.71×10⁵ l mol⁻¹, respectively.     

Spectrofluorimetric determination of tetracycline and anhydrotetracycline in serum and urine.

A spectrofluorimetric method, involving alkaline degradation and formation of a magnesium complex, is described for the determination of tetracycline (TC) and anhydrotetracycline (ATC) in their mixed solution. Tetracycline is degraded and determined in alkaline solution. This treatment of ATC produces almost no fluorescence, but a fluorescent magnesium complex forms at pH 7.5. Several synthetic samples of TC and ATC, with TC:ATC ratios ranging from 50:1 to 1:50, were analysed. The recoveries of TC and ATC are about 71-76 and 61-63% in serum, respectively, and are all about 100% in urine.     

Spectrofluorimetric determination of acrivastine in spiked human urine and pharmaceuticals

A spectrofluorimetric method to determine acrivastine is proposed and applied to its determination in human urine and pharmaceuticals. The fluorimetric method allows the determination of 58-2000 ng ml(-1) of acrivastine in aqueous solutions containing acetic acid-sodium acetate buffer (pH 6.5) with lambda(exc)=230 nm and lambda(em)=380 nm.     

Voltammetric determination of cholesterol in human blood serum

Cholesterol has a number of important functions in a human body. The disorders of cholesterol biosynthesis increase the risk of the development of cardiovascular diseases and worsens the function of the immune system. This study is devoted to the development of a method for determining the concentration of cholesterol in blood serum using voltammetry. We selected the following working conditions for the determination of cholesterol: a phosphate buffer solution with pH 6.86 was a supporting electrolyte; potential sweep rate was W = 30 mV/s; and recording was carried out in the constant-current mode. An organomodified electrode was used as a working electrode. The peak was observed at +0.98 V. The dependence of the electrooxidation current of cholesterol on its concentration was linear in the range of 0.1–50 μM with a limit of detection of 0.01 μM. The results of the determination of cholesterol in blood serum by voltammetry were compared to those obtained by the fluorimetric method.     

Spectrofluorimetric determination of magnesium in blood serium with calcein blue

Magnesium was determined in blood serum by fluorimetry with calcein blue (CB) in alkaline solution (0.01 M KOH). Four separate procedures for masking of iron, copper, zinc and calcium were applied. Complete masking was obtained with a mixture of ethylene glycol-O,O′-bis(2-aminoethyl)-N,N,N′,N′-tetraacetic acid, triethanolamine and triethylenetetramine. The mean value of magnesium in a 40-μl sample of quality control serum was within the appropriate limits of the reference sample. The effects of pH, masking agents and matrix of serum on the fluorescence of CB were investigated.     

Spectrofluorimetric determination of paroxetine hydrochloride in its formulations and human plasma

A sensitive spectrofluorimetric procedure for the determination of paroxetine-HCl in pharmaceutical formulations and human plasma has been described. The native fluorescence of the drug has been studied under different conditions. Maximum fluorescence intensity was obtained in methanol at 340 nm using 290 nm for excitation. Different surfactants showed negative effect on the fluorescence intensity of paroxetine-HCl. Regression analysis of Beer's plot showed good correlation (r=0.9999) between fluorescence intensity and concentration over the range of 0.05-0.40 microg ml-1 with lower limit of detection (LOD) of 0.015 microg ml-1. The drug was successfully determined in its tablets with average % recovery of 98.00+/-0.99% which was in accordance with those given by a compendial method. The method was also applied to the determination of paroxetine-HCl in spiked human plasma with average recovery of 77.70+/-1.06%.     

Spectrofluorimetric determination of benzodiazepinooxazoles

Summary A study of fluorescence properties of Cloxazolam and Oxazolam has been carried out. pK_a-values were calculated and a spectrofluorimetric method was developed in acidic hydroalcoholic medium for the determination of the drugs. The fluorescence intensity was linear with the concentration up to at least 6.00×10^–6 mol/l for Cloxazolam and 5.17×10^–6 mol/l for Oxazolam. Detection limits obtained were 2.91×10^–8 mol/l and 4.56×10^–8 mol/l for Cloxazolam and Oxazolam, respectively. Spectrofluorimetric methods were applied to the determination of both drugs in pharmaceuticals and errors lower than 2.5% were obtained. Spectrophotometric determination methods were also developed.     

Capillary isotachophoretic determination of cysteinyl leukotrienes.

The cysteinyl leukotrienes (LTs) C4, D4 and E4 are among the most potent lipid mediators of anaphylaxis and inflammation. A capillary isotachophoretic method is described for the determination of these cysteinyl LTs. The method is based on anionic separation and detection using UV (254 nm) and conductivity detectors. The total analysis time is of the order of 30 min. The limit of detection of the method was determined to be 0.5 nmol of LTE4. Despite of similar chemical structures, all three cysteinyl LTs can be determined simultaneously.     

On-line SFE-GC for determination of PCBs in human milk and blood serum

On-line coupled supercritical fluid extraction and gas chromatography (SFE-GC) has been utilized for the determination of PCBs and other organochlorine compounds in human milk and blood serum. The procedure involved preconcentration of the sample on C₁₈-silica sorbent in an extraction cell: after precipitation of the proteins up to 20 ml of human milk was concentrated on 0.5 g of sorbent. Serum (up to 5 ml) was applied to the C₁₈ material without pretreatment. Basic alumina was utilized as a selective adsorbent for lipids in the on-line SFE-GC system. The method was used to analyze milk and serum spiked with 0.5 and 10 ng of Aroclor 1260 and the results compared with those obtained by liquid–liquid extraction of serum.     

Spectrofluorimetric study of the beta-cyclodextrin-ibuprofen complex and determination of ibuprofen in pharmaceutical preparations and serum

The inclusion complexation of ibuprofen in beta-cyclodextrin (beta-CD) has been examined by means of spectrofluorimetry at both acid and alkaline pH. The results suggest that stable 1:1 complexes are formed in both media. The analysis of the pK(a) values for ibuprofen in both the absence and presence of beta-CD (4.12 and 4.66, respectively) suggests that in the inclusion complex the carboxylic group is located outside the cyclodextrin (CD) but interacting with it. Further structural characterization of the complex was carried out by means of am1 semiempiral calculations. Based on the obtained results, a spectrofluorimetric method for the determination of ibuprofen in the presence of beta-CD at 10 degrees C was developed in the range of 4.7-58 mug ml(-1). Better limits of detection (1.6 mug ml(-1)) and quantification (4.7 mug ml(-1)) were obtained in this latter case with respect to those obtained in the absence of beta-CD. The method was satisfactorily applied to the quantification of ibuprofen in pharmaceutical preparations. A novel spectrofluorimetric determination of ibuprofen in the presence of beta-CD was also developed for serum samples at concentration levels between 5 and 70 mug ml(-1). It uses second-order fluorescence excitation-emission matrices coupled to an algorithm based on self-weighted alternating trilinear decomposition (SWATLD), and avoids resorting to separative instrumental analyses.     

Spectrofluorimetric flow-injection determination of cyanide

The spectrofluorimetric determination of cyanide (0.1–20 μg ml^?1) with pyridoxal and pyridoxal-5-phosphate by a normal flow-injection method and a stopped-flow procedure is reported. The large number of interfering species in the normal method is significantly decreased by the use of the stopped-flow method. The relative standard deviation is <2%.     

Spectrofluorimetric determination of 1,4-thienodiazepines

The fluorescence characteristics of four 1,4-thienodiazepines in aqueous and methanolic solutions and the effect of pH on fluorescence intensity are described. The pK_a values are calculated. Fluorimetric methods with limits of detection between 3 and 38 ng ml^?1 were developed, and applied for determinations of one drug in tablets, and the others in serum after extraction with a Sep-Pak C₁₈ cartridge.