Enhancement of chemiluminescence of the KIO4–luminol system by gallic acid,acetaldehyde and Mn2+: application for the determination of catecholamines

Chemiluminescence (CL) from the oxidation of luminol with potassium periodate in strong alkaline solutions was greatly enhanced by the combined effect of gallic acid, acetaldehyde and Mn²⁺. The CL spectra exhibited only one emission band at 425 nm, indicating 3‐aminophthalate as the emitting species. Various scavengers for superoxide anion, hydroxyl radical and singlet oxygen quenched the CL emission very efficiently (74–100%), suggesting the possible involvement of these reactive oxygen species (ROS) in the CL reactions. It is postulated that oxidation of gallic acid and acetaldehyde by periodate catalyzed by Mn²⁺ generates these ROS, which then react with luminol to enhance the CL emission. We also found that the enhanced CL emission was strongly inhibited by catecholamines, probably because of their effective scavenging of ROS. Based on this observation, a simple, rapid and sensitive new CL method was developed for the determination of catecholamines. The detection limits (3σ) for dopamine, l‐ dopa, norepinephrine and epinephrine were 0.63, 1.37, 0.56 and 14.3 nmol/L, respectively. The linear range was 1–10 nmol/L; relative standard deviations were 0.71–1.34% for 0.1 µmol/mL catecholamines. This CL method was applied to the determination of catecholamines in pharmaceutical injections with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence method to detect a β2 adrenergic agonist

A new method for the detection of β₂ adrenergic agonists was developed based on the chemiluminescence (CL) reaction of β₂ adrenergic agonist with potassium ferricyanide–luminol CL. The effect of β₂ adrenergic agonists including isoprenaline hydrochloride, salbutamol sulfate, terbutaline sulfate and ractopamine on the CL intensity of potassium ferricyanide–luminol was discovered. Detection of the β₂ adrenergic agonist was carried out in a flow system. Using uniform design experimentation, the influence factors of CL were optimized. The optimal experimental conditions were 1 mmol/L of potassium ferricyanide, 10 µmol/L of luminol, 1.2 mmol/L of sodium hydroxide, a flow speed of 2.6 mL/min and a distance of 1.2 cm from ‘Y₂’ to the flow cell. The linear ranges and limit of detection were 10–100 and 5 ng/mL for isoprenaline hydrochloride, 20–100 and 5 ng/mL for salbutamol sulfate, 8–200 and 1 ng/mL for terbutaline sulfate, 20–100 and 4 ng/mL for ractopamine, respectively. The proposed method allowed 200 injections/h with excellent repeatability and precision. It was successfully applied to the determination of three β₂ adrenergic agonists in commercial pharmaceutical formulations with recoveries in the range of 96.8–98.5%. The possible CL reaction mechanism of potassium ferricyanide–luminol–β₂ adrenergic agonist was discussed from the UV/vis spectra. Copyright © 2014 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence method for the determination of chloramphenicol based on luminol–sodium periodate order‐transform second‐chemiluminescence reaction

A new chemiluminescence (CL) reaction was observed when chloramphenicol solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate was injected into the reaction mixture of chloramphenicol and alkaline luminol. This reaction is described as an order‐transform second‐chemiluminescence (OTSCL) reaction. The OTSCL method combined with a flow‐injection technique was applied to the determination of chloramphenicol. The optimum conditions for the order‐transform second‐chemiluminescence emission were investigated. A mechanism for OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristics, the UV‐visible spectra and the chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of chloramphenicol over the range 5.0 × 10^?7–5.0 × 10^?5 mol/L with a correlation coefficient of 0.9969 and a detection limit of 6.0 × 10^?8 mol/L (3σ). The relative standard deviation (RSD) for 11 repeated determinations of 5.0 × 10^?6 mol/L chloramphenicol is 1.7%. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

In vitro monitoring sub-nanogram amounts analgin in human urine by its inhibitory of the luminol-periodate chemiluminescence reaction using reagent immobilization release technique

A selective and sensitive as well as rapid chemiluminescence (CL) flow sensor for the determination of analgin is described. The analytical reagents involved in chemiluminescence reaction, luminol and periodate, were both immobilized on an anion-exchange column. The CL signals produced by the reaction between luminol and periodate, which were eluted from the column through water injection, were decreased in the presence of analgin. Analgin was sensed by measuring the decrement of CL intensity, and which was observed linear over the logarithm of analgin concentration range of 0.1 to 50.0 ng mL(-1), and the limit of detection was 0.04 ng mL(-1) (3ó). At a flow rate of 2.0 mL min(-1), including sampling and washing, the detection could be performed in 0.5 min with a relative standard deviation of less than 3.0%. The proposed procedure was applied successfully in the monitoring of analgin in human urine samples without any pre-treatment process. It was found that the analgin concentration reached its maximum after being orally administrated for 4 h, and the analgin metabolism ratio in 10 h was 9.28% in the body of volunteers. The flow sensor offered reagentless procedures and remarkable stability in determination of analgin, and could be easily reused over 80 h.     

Effects of restraint stress on catecholamine concentrations in the glandular stomach of rats

Restraint stress is known to induce gastric ulcers in rats. Peripheral sympathetic activity and catecholamines are involved in the pathogenesis of these gastric ulcers. The aim of the present study was to evaluate the effects of restraint on mucosal and muscle catecholamine concentrations in the glandular stomach of rats. In unrestrained rats, noradrenaline concentration was higher in the muscle than in the mucosa of the glandular stomach (629 +/- 106 vs 18 +/- 3 pg/mg and 217 +/- 37 vs 18 +/- 8 pg/mg, respectively in the corpus and the antrum, p less than 0.01). This can be explained by the existence of an abundant noradrenergic innervation in the muscle layer. After 20 hours of restraint, adrenaline and noradrenaline concentrations were significantly decreased in adrenals, in comparison with unrestrained animals (255 +/- 53 vs 638 +/- 160 ng/mg and 113 +/- 17 vs 198 +/- 37 ng/mg, respectively for adrenaline and noradrenaline, p less than 0.05). In the glandular stomach, noradrenaline and adrenaline concentrations in restrained rats were not significantly different from those in unrestrained rats. However, adrenaline concentrations in the muscle of restrained rats were higher than in the mucosa. Moreover, restraint induced a significant decrease in dopamine concentration in the antral mucosa (from 100 +/- 12 pg/mg in unrestrained rats to 15 +/- 5 pg/mg in restrained rats), suggesting that a depletion in dopamine in the antral mucosa could be one of the pathogenetic factors involved in antral gastric stress-induced ulcers in rats.     

Post‐chemiluminescence determination of chloramphenicol based on luminol–potassium periodate system

A post‐chemiluminescence (PCL) phenomenon was observed when chloramphenicol was injected into a mixture of luminol and potassium periodate after the chemiluminescence (CL) reaction of luminol–potassium periodate had finished. The possible reaction mechanism was proposed based on studies of the CL kinetic characteristics, the CL spectra, the fluorescence spectra and the UV‐vis absorption spectra of the related substances. Based on the PCL reaction, a rapid and sensitive method for the determination of chloramphenicol was established. The linear response range was 6.0 × 10^?7–1.0 × 10^?5 mol/L, with a correlation coefficient of 0.9986. The relative standard deviation (RSD) for 5.0 × 10^?6 mol/L chloramphenicol was 2.3% (n = 11). The detection limit was 1.6 × 10^?7 mol/L. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

A sensitive method for the determination of plasma catecholamines using liquid chromatography with electrochemical detection

Simple and sensitive methods for the determination of plasma catecholamines are of great interest since the level of catecholamines in plasma reflects the activity of the sympatho-adrenal system. In the present work a previously described procedure based on high pressure liquid chromatography with electrochemical detection has been adapted for assay of plasma catecholamines. This method permits simultaneous detection of noradrenaline, adrenaline and dopamine in concentrations down to 0.1 nmol/1 in less than one ml plasma.     

A novel chemiluminescence method for the determination of orciprenaline based on ferricyanide-rhodamine 6G.

A novel flow injection chemiluminescence method for the determination of orciprenaline was developed. The method is based on the chemiluminescence (CL) reaction of orciprenaline with potassium ferricyanide in sodium hydroxide medium, sensitized by the fluorescent dye rhodamine 6G. The proposed procedure allows quantitation of orciprenaline in the concentration range 0.01-1.2 microg/mL, with a detection limit of 7.2 x 10(-3) microg/mL. The relative standard deviation (RSD) is 2.7% for 0.1 microg/mL orciprenaline (n = 9). The sampling frequency was calculated at approximately 120/h. The method was successfully applied to the determination of orciprenaline in pharmaceutical preparations. A brief discussion on the possible CL reaction mechanism is presented.     

Capillary-venous differences of free plasma catecholamines at rest and during graded exercise

Levels of free plasma catecholamines were simultaneously determined in 10 cyclists using capillary blood from one ear lobe and venous blood from one cubital vein. Catecholamine concentrations were higher in the ear lobe blood than in the venous blood at rest and during graded exercise. Average differences amounted to 1.7 nmol X 1(-1) (dopamine), 2.1 nmol X 1(-1) (noradrenaline) and 1.9 nmol X 1(-1) (adrenaline) at rest and increased only to 8.8 nmol X 1(-1) for noradrenaline during exercise. We assume that higher concentrations of dopamine and adrenaline in the capillary blood point to a significant neuronal release of these catecholamines, similar to noradrenaline. Catecholamine concentrations in capillary blood may better reflect sympathetic drive and delivery of catecholamines to the circulation than the concentrations in venous blood.     

Catecholamines increase urine formation in isolated toad (Bufo marinus) kidneys perfused at constant rate

Infusion of catecholamines into isolated kidneys of the toad (Bufo marinus) perfused at constant rate, produced increased arterial pressure accompanied by increased glomerular filtration rate, urine formation rate and sodium excretion. These parameters were all increased by arterial infusion of adrenaline or noradrenaline, or by infusion of adrenaline via the renal portal veins. Portal venous pressure increased slightly after arterial or portal infusion of adrenaline, but decreased after arterial infusion of noradrenaline. Estimation of segmental pressure gradients indicated that the efferent glomerular arterioles were selectively constricted by low concentrations of adrenaline or noradrenaline (3 X 10(-9), 3 X 10(-8) mol l(-1)). Higher concentrations of these amines constricted the preglomerular, as well as the postglomerular vasculature. These results demonstrate that the pericytes and/or endothelial cells which form the walls of the efferent arterioles in B. marinus are capable of active contraction.     

Quantitative determination of bilirubin by inhibition of chemiluminescence from lucigenin.

Bilirubin is a metabolic breakdown product of blood haem, of great biological and diagnostic importance. A new chemiluminescence (CL) method has been developed for the quantification of bilirubin. The method is combined with the flow injection analysis (FIA) technique and based on the inhibition effect of bilirubin on the CL from the lucigenin-hydrogen peroxide system in an alkaline medium. Under the optimum conditions, the decreased CL intensity was proportional to the concentration of bilirubin, in the range 0.0585-58.47 microg/mL. The detection limit estimated from the calibration graph was about 7.8826 ng/mL. The relative standard deviation (RSD) of 10 parallel measurements (1 x 10(-4) mol/L bilirubin) was 2.5%. Recoveries of bilirubin were found to fall in the range 94-97.5% using control sera. The method is interference-free, fast and easy to carry out.     

Performance characteristics of a two-stage dark fermentative system producing hydrogen and methane continuously

The performance of a mesophilic two-stage system generating hydrogen and methane continuously from sucrose (10-30 g/L) was investigated. A hydrogen-generating CSTR followed by an upflow anaerobic filter were both inoculated with anaerobically digested sewage sludge, and ORP, pH, gas output, %H(2), %CH(4) and %CO(2) monitored. pH was controlled with NaOH, KOH or Ca(OH)(2). Using NaOH as alkali with 10 g/L sucrose, yields of 1.62 +/- 0.2 mol H(2)/mol hexose added and 323 mL CH(4)/gCOD added to the hydrogen and methane reactors respectively were achieved. The overall chemical oxygen demand (COD) reduction was 92.6% with 0.90 +/- 0.1 g/L sodium and 316 +/- 40 mg/L residual acetate in the methane reactor. Operation at 20 g/L sucrose and NaOH as alkali led to impaired volatile fatty acid (VFA) degradation in the methane reactor with 2.23 +/- 0.2 g/L sodium, 1,885 mg/L residual acetate, a hydrogen yield of 1.47 +/- 0.1 mol/mol hexose added, a methane yield of 294 mL/gCOD added and an overall COD reduction of 83%. Using Ca(OH)(2) as alkali with 20 g/L sucrose gave a hydrogen yield of 1.29 +/- 0.3 mol/mol hexose added, a methane yield of 337 mL/gCOD added and improved the overall COD reduction to 91% with residual acetate concentrations of 522 +/- 87 mg/L. Operation at 30 g/L sucrose with Ca(OH)(2) gave poorer overall COD reduction (68%), a hydrogen yield of 1.47 +/- 0.2 mol/mol hexose added, a methane yield of 138 mL/gCOD added and residual acetate 7,343 +/- 715 mg/L. It was shown that sodium toxicity and overloading are important issues for successful anaerobic digestion of effluent from biohydrogen reactors in high rate systems.     

Flow injection analysis of riboflavin with chemiluminescence detection using a N-halo compounds-luminol system.

A chemiluminescent method for the determination of riboflavin is described. The method is based on the chemiluminescence (CL) generated during the oxidation of luminol by N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in alkaline medium. It was found that riboflavin could greatly enhance this CL intensity when present in the luminol solution. Based on this observation, a new flow-injection CL method for the determination of riboflavin is proposed in this paper. The detection limits were 7.5 ng/mL and 3.5 ng/mL of riboflavin for the NBS- and NCS-luminol CL systems, respectively. The relative CL intensity was linear, with riboflavin concentration in the range 19-600 ng/mL and 600-2000 ng/mL for the NBS-luminol CL system, and 12-200 ng/mL and 200-2000 ng/mL for the NCS-luminol CL system. The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official method and demonstrated good accuracy and precision.     

Effect of a fall of blood pressure on the release of catecholamines in the hypothalamus

The posterior hypothalamus of anaesthetized cats was superfused through a push-pull cannula and the release of endogenous catecholamines was determined in the superfusate which was continuously collected in 15 min periods. Fall in blood pressure elicited by nitroprusside or bleeding led to an increased rate of release of noradrenaline, adrenaline and dopamine in the hypothalamus. Transection of the brain causal to hypothalamus greatly reduced the rate of resting release of the catecholamines and abolished the enhancing effects of bleeding and nitroprusside. Determination of the catecholamines in samples which were collected in 90 s periods suggested a different pattern of release of the three catecholamines. Further shortening of the collection period (10 s) showed that the fall in blood pressure immediately increased the release of dopamine, while the rates of release of noradrenaline and adrenaline were increased gradually. Hypotension did not influence the rates of release of the catecholamines in the anterior hypothalamus. It is concluded that dopamine, adrenaline and noradrenaline systems of the hypothalamus are involved in the regulation of the arterial blood pressure. The different patterns of release might indicate that dopamine exerts a different function from those of noradrenaline and adrenaline in the normalization of the blood pressure after acute hypotension.     

A study on the micelle-sensitized Ce(IV)-Na2S2O3-norfloxacin chemiluminescence system and its applications.

A new chemiluminescence (CL) flow-injection method was developed for the determination of norfloxacin. The method is based on the CL reaction of norfloxacin with sodium thiosulphate and Ce(IV) in sulphuric acid medium sensitized by sodium dodecylsulphate. Under optimum conditions, the CL intensity is proportional to the concentration of the norfloxacin in the range 3.89 x 10(-8)-7.18 x 10(-6) g/mL. The detection limit (3 s/k) was 2.21 x 10(-9) g/mL for norfloxacin. The method has been applied successfully to the determination of norfloxacin in pharmaceutical formulations and human urine. The mechanism for this chemiluminescence system is discussed.     

Simultaneous radioenzymatic determination of plasma and tissue adrenaline,noradrenaline and dopamine within the femtomole range

A radiometric-enzymatic assay for measuring simultaneously femtomole quantities of adrenaline, noradrenaline and dopamine has been developed. The three catecholamines are first converted to their O-methylated analogues by catechol-O-methyltransferase in the presence of S-adenosyl-methionine-³H and thereafter extracted following addition of sodium tetraphenylborate. This extraction, together with an improved quick chromatographic separation and the oxidation of the adrenaline and noradrenaline derivatives to vanillin, yields an extremely high sensitivity and specificity of the method.The present assay allows the determination of adrenaline, noradrenaline and dopamine in tissue samples with a protein content of 100 μg or less and in plasma volumes of 20 – 100 μl. The amine content of 40 – 50 samples can be determined in two days by one person.Due to the high sensitivity achieved, this method promises to be a valid alternative to the gas chromatography-mass spectrometry technique.     

Analysis of catecholamines and related substances using porous graphitic carbon as separation media in liquid chromatography-tandem mass spectrometry

Capillary porous graphitic carbon (PGC) columns have been utilized for separation of several catecholamines and related compounds (i.e. L-tyrosine, L-DOPA, 3-O-methyl-DOPA, dopamine, 3,4-dihydroxy-phenyl-acetic acid (DOPAC), homovanillic acid, noradrenaline, vanillomandelic acid and adrenaline) on-line with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The use of a mobile phase without ion-pairing agents and with high content of organic modifier facilitated the coupling to the selective and sensitive mass spectrometric detection. Minimum detectable sample concentration (MDC sample) for noradrenaline, dopamine and L-tyrosine in a standard solution was estimated to 3, 10 and 30 nM, respectively (3 S/N corresponds to MDQ for L-tyrosine of approximately 8 x 10(-14)mol). The developed strategy was applied for analysis of brain tissue, i.e. a substantia nigra (ns) sample.     

Chemiluminescence flow-injection analysis of beta-lactam antibiotics using the luminol-permanganate reaction.

A new flow injection chemiluminescence (CL) method has been developed for the determination of six beta-lactam antibiotics, including amoxicillin, cefadroxil, cefoperazone sodium, cefazolin sodium, cefradine and ceftriaxone sodium. When the antibiotic was injected into a stream of KMnO4 with alkaline luminol, a strong CL signal was produced. The method allows the measurements of 0.1-50.0 mg/L amoxicillin, 0.1-80.0 mg/L cefadroxil, 1.0-30.0 mg/L cefoperazone sodium, 1.0-30.0 mg/L cefazolin sodium, 3.0-50.0 mg/L cefradine and 3.0-50.0 mg/L ceftriaxone sodium. The detection limits are 0.05 mg/L for amoxycillin, 0.05 mg/L for cefadroxil, 0.4 mg/L for cefoperazonum sodium, 0.4 mg/L for cefazolin sodium, 0.8 mg/L for cefradine and 0.8 mg/L for ceftriaxone sodium. The relative standard deviations in 11 repeated measurements are 0.6%, 0.8%, 1.5%, 1.2%, 0.4% and 0.3% for 3.0 mg/L amoxicillin, 1.0 mg/L cefadroxil, 10.0 mg/L cefoperazone sodium, 10.0 mg/L cefazolin sodium, 10.0 mg/L cefradine and 10.0 mg/L ceftriaxone sodium, respectively. The method was successfully applied to the determination of amoxicillin in pharmaceutical preparations. A possible CL reaction mechanism is also discussed.     

Reverse micelle-based chemiluminescence system for quinine sulphate.

A new chemiluminescence (CL) method is proposed for the determination of quinine sulphate, which is based on the dichloromethane solvent extraction of the ion-pair complex of tetrachloroaurate (III) with quinine sulphate, and luminol CL detection in a reversed micellar medium formed by the cation surfactant cetyltrimethylammonium bromide in a dichloromethane-cyclohexane (3:7, v/v)-water (0.35 mol/L Na2CO3 buffer solution, pH 11.5). The ion-pair complex of tetrachloroaurate (III) with quinine sulphate produced an analytical CL signal when it entered the reversed micellar water pool. In optimum conditions, CL intensities are proportional to the concentrations of the studied drug over the range 0.015-10 microg/mL, with a detection limit of 1.5 ng/mL. The relative standard deviation (RSD) is 1.38% for 2.5 microg/mL quinine sulphate (n=11). The method has been applied to the determination of the studied drug in biological fluids, with satisfactory results.     

Determination of bisphenol A using a flow injection inhibitory chemiluminescence method.

A new flow injection chemiluminescence (CL) method has been developed for the determination of bisphenol A (BPA), based on the inhibitory effect of BPA on the chemiluminescence reaction between luminol and potassium hexacyanoferrate. Under optimum conditions, the decrease in CL emission intensity was linear with BPA concentration in the range 8.0 x 10(-7)-1.2 x 10(-5) mol/L, and the detection limit was 3.1 x 10(-7) mol/L. The relative standard deviation (RSD) of 11 replicate measurements was 2.6% for 2.0 x 10(-6) mol/L BPA (n = 11). The sampling frequency was calculated to be ca. 120/h. This method has been successfully used to determine the content of BPA in aqueous solution of polycarbonate materials. A brief discussion on the possible chemiluminescence reaction mechanism is presented.