Flow-injection chemiluminescence determination of chloroquine using peroxynitrous acid as oxidant

A new flow-injection chemiluminescence (CL) method for determination of chloroquine is proposed based on a stronger chemiluminescence of chloroquine in hydrogen peroxide-nitrite-sulfuric acid medium. The proposed method allows the measurement of chloroquine over the range of 3.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹. The detection limit is 8.6×10⁻⁸ mol l⁻¹, and the relative standard deviation for 1.0×10⁻⁶ mol l⁻¹ chloroquine (n=11) is 1.6%. The CL mechanism is also discussed.     

Determination of levodopa by capillary electrophoresis with chemiluminescence detection

A rapid and simple method using capillary electrophoresis (CE) with chemiluminescence (CL) detection was developed for the determination of levodopa. This method was based on enhance effect of levodopa on the CL reaction between luminol and potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]) in alkaline aqueous solution. CL detection employed a lab-built reaction flow cell and a photon counter. The optimized conditions for the CL detection were 1.0 × 10⁻⁵ M luminol added to the CE running buffer and 5.0 × 10⁻⁵ M K₃[Fe(CN)₆] in 0.6 M NaOH solution introduced postcolumn. Under the optimal conditions, a linear range from 5.0 × 10⁻⁸ to 2.5 × 10⁻⁶ M (r = 9991), and a detection limit of 2.0 × 10⁻⁸ M (signal/noise = 3) for levodopa were achieved. The precision (R.S.D.) on peak area (at 5.0 × 10⁻⁷ M of levodopa, n = 11) was 4.1%. The applicability of the method for the analysis of pharmaceutical and human plasma samples was examined.     

Improvement on Simultaneous Determination of Cr(III) and Cr(VI) by Capillary Electrophoresis and Chemiluminescence Detection

Chromiumexistsindifferentoxidationstatesingroundwater,industrialwastewater,seawater,andsoilofourenvironment1,2.Chromium(III)isanessentialtraceelementforhumans,requiredforthemaintenanceofnormalglucose,cholesterol,andfattyacidmetabolism.Ontheotherhand,watersolublechromium(VI),intheformCr2O72-orCrO42-,ishighlyirritatingandtoxictohumansandanimals3.Itsacutetoxiceffectsincludeanimmediatecardiovascularshockandlatereffectsonkidney,liver,andblood-formingorgans.Therefore,itisnecessaryforriskassessme…     

Flow-injection chemiluminescence determination of fluoroquinolones by enhancement of weak chemiluminescence from peroxynitrous acid

A flow-injection chemiluminescence (CL) method is described for the determination of fluoroquinolones including ciprofloxacin, norfloxacin and ofloxacin. The method is based on the enhancement by these compounds of the weak CL from peroxynitrous acid. The linear ranges are 1.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹ for ciprofloxacin and norfloxacin, and 3.0×10⁻⁷ to 3.0×10⁻⁵ mol l⁻¹ for ofloxacin, respectively. The detection limits (S/N=3) are 4.5×10⁻⁸ mol l⁻¹ ciprofloxacin, 5.9×10⁻⁸ mol l⁻¹ norfloxacin and 1.1×10⁻⁷ mol l⁻¹ ofloxacin, respectively. The proposed method was applied to the determination of fluoroquinolones in pharmaceutical preparations.     

Microdialysis sampling and high-performance liquid chromatography with chemiluminescence detection for in-vivo on-line determination and study of the pharmacokinetics of levodopa in blood

A simple, reliable, and reproducible method for in-vivo on-line separation and determination of levodopa has been based on microdialysis then high-performance liquid chromatography with chemiluminescence detection. The perfusate is perfused at a flow rate of 5 L min^–1. The concentration of levodopa in the dialysate is determined on line with a chemiluminescence system. The dialysate sample volume is approximately 20 L. The response of the system is linearly related to the concentration of levodopa in the range 1×10^–8 to 1×10^–6 g mL^–1 (r²=0.9995) with a detection limit (3) of 3×10^–9 g mL^–1 and sample throughput of 12 h^–1; RSD is 2.8% (n=11). The method has been successfully used to study the pharmacokinetics of levodopa in vivo; the values of the pharmacokinetics parameters C_max, AUC_0–t and T_max were 16.60, 20.92 ng mL^–1, and 90 min, respectively.     

Continuous chemiluminescence determination of formaldehyde in air based on Trautz-Schorigin reaction

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5 L min⁻¹ (absorption liquid flow rate of 336 μL min⁻¹). The limit of detection (S/N = 3) is 0.60 μg m⁻³ HCHO (0.49 ppb). The calibration graph is linear up to 300 μg m⁻³ HCHO (244 ppb). The relative standard deviations of chemiluminescence method for 1 × 10⁻⁶ and 5 × 10⁻⁶ M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.     

Simultaneous operation of plural separation modes in capillary electrophoresis with a chemiluminescence detector possessing a micro-space area for reaction/detection

Analysis of alpha-amino acids, proteins, and phenolic compounds was simultaneously performed using three capillaries in capillary electrophoresis with chemiluminescence detection, taking advantage of the micro-space area for reaction/detection at the tip of the capillary. The three capillaries included usual, polymer-containing, and sodium docley sulfate (SDS)-containing migration buffers for separation. The eluted samples from the capillaries, which were inserted into the chemiluminescence detection cell, were mixed with chemiluminescence reagent at the tips of the capillaries to generate visible light. The specific micro-space area for reaction/detection at the tips of the capillaries enabled the simultaneous operation of the three separation modes in the present system.     

Protein microarrays enhanced performance using nanobeads arraying and polymer coating

A nanosize material composed of 330 nm glass beads coated with a copolymer of N,N-dimethylacrylamide (DMA), N,N-acryloyloxysuccinimide (NAS) and [3-(methacryloyl-oxy)propyl]trimethoxysilane (MAPS) was developed to improve the protein immobilization on biochips. The developed material, bearing rabbit-IgG proteins, was arrayed as 150 μm spots trapped at the surface of a poly(dimethylsiloxane) elastomer (PDMS), and compared to copoly(DMA-NAS-MAPS)-coated glass slides and latex beads based biochips. Evidences were made through scanning electron microscopy that the newly developed material based microarray exhibited surface irregularities at the submicron level leading to high specific area.The combination of such large immobilization area with the highly efficient protein immobilization of the copoly(DMA-NAS-MAPS) polymer, enabled the achievement of microarrays exhibiting good performances both in pure media and complex samples (human sera). Indeed, high specific/non-specific signal ratio was found using this optimized immobilization procedure.Chemiluminescent detection of anti-rabbit-IgG was obtained through peroxidase labeled antibodies in the 5 μg/l to 10 mg/l range. Application of the developed system to real samples was achieved for the detection of rheumatoid factor (RF) through a capture assay. Interesting results were obtained, with a RF detection over the 5.3-485 IU/ml range and without measurable matrix effect or non-specific signal.     

Determination of phenolic compounds using high-performance liquid chromatography with Ce-Tween 20 chemiluminescence detection

A novel method for the simultaneous determination of phenolic compounds such as salicylic acid, resorcinol, phloroglucinol, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, and m-nitrophenol by high-performance liquid chromatography (HPLC) coupled with chemiluminescence (CL) detection was developed. The procedure was based on the chemiluminescent enhancement by phenolic compounds of the cerium(IV)-Tween 20 system in a sulfuric acid medium. The separation was carried out with an isocratic elution or with a gradient elution using a mixture of methanol and 1.5% acetic acid. For six phenolic compounds, the detection limits (3σ) were in the range 1.40-5.02 ng/ml and the relative standard deviations (n=11) for the determination of 0.1 μg/ml compounds were in the range 1.9-2.9%. The CL reaction was well compatible with the mobile phase of HPLC, no baseline drift often occurred in HPLC-CL detection was observed with a gradient elution. The method has been successfully applied to the determination of salicylic acid and resorcinol in Dermatitis Clear Tincture and p-hydroxybenzoic acid in apple juices.     

Detection of paracetamol by capillary electrophoresis with chemiluminescence detection

Indirect detection of paracetamol was accomplished using a capillary electrophoresis-chemiluminescence (CE-CL) detection system, which was based on its inhibitory effect on a luminol-potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]) CL reaction. Paracetamol migrated in the separation capillary, where it mixed with luminol included in the running buffer. The separation capillary outlet was inserted into the reaction capillary to reach the detection window. A four-way plexiglass joint held the separation capillary and the reaction capillary in place. K₃[Fe(CN)₆] solution was siphoned into a tee and flowed down to the detection window. CL was observed at the tip of the separation capillary outlet. The CL reaction of K₃[Fe(CN)₆] oxidized luminol was employed to provide the high and constant background. Since paracetamol inhibits the CL reaction, an inverted paracetamol peak can be detected, and the degree of CL suppression is proportional to the paracetamol concentration. Maximum CL signal was observed with an electrophoretic buffer of 30 mM sodium borate (pH 9.4) containing 0.5 mM luminol and an oxidizer solution of 0.8 mM K₃[Fe(CN)₆] in 100 mM NaOH solution. Under the optimal conditions, a linear range from 6.6 × 10⁻¹⁰ to 6.6 × 10⁻⁸ M (r = 0.9999), and a detection limit of 5.6 × 10⁻¹⁰ M (signal-to-noise ratio = 3) for paracetamol were achieved. The relative standard deviation (R.S.D.) of the peak area for 5.0 × 10⁻⁹ M of paracetamol (n = 11) was 2.9%. The applicability of the method for the analysis of pharmaceutical and biological samples was examined.