Determination of Trace Copper by Fluorescence Spectrophotometry Based on Cu(DP)2+ and Cu‐4.0‐Generations Polyamidoamine Dendrimers Catalyze Cu2+ to Oxidize Fluorescein

Abstract

Fluorescein can emit strong and stable fluorescence. Cu²⁺ can oxidize fluorescein, which causes the fluorescence signal to diminish. Cu(DP)²⁺ (DP refers to α,α′‐dipyridyl) and Cu‐GPD‐4.0 (GPD‐4.0 refers to 4.0‐generations polyamidoamine dendrimers) both can catalyze Cu²⁺ to oxidize fluorescein, which causes the fluorescence signal to diminish sharply. The ΔF is directly proportional to the content of copper. Based on the facts above, a new catalytic fluorescence spectrophotometry for the determination of trace copper using Cu(DP)²⁺ and Cu‐GPD‐4.0 was established. The linear range of this method is 0.040–28 pg mL^?1. The regression equation for working curve is ΔF=209.5+14.39 C_Cu ²⁺ (pg mL^?1), n=7; correlation coefficient is 0.991. The detection limit of this method is 1.0×10^?14 g mL^?1. After replicate measurement times, RSDs are 3.1% and 4.2% for samples containing 0.040 and 28 pg mL^?1 Cu²⁺, respectively. This method is rapid and precise with high sensitivity and good repeatability. The method has been applied to the determination of trace copper in tea and human hair with satisfactory results. Meanwhile, the mechanism for the determination of trace copper by catalytic fluorescence spectrophotometry using Cu(DP)²⁺ and Cu‐GPD‐4.0 was also discussed.     

Determination of Total Chromium in Biological Samples by Automated Reagent Injection Chemiluminescence Analysis

A sensitive method for the determination of total chromium in real samples by flow injection–chemiluminescence (FI–CL) analysis was proposed. It was found that the CL intensity from luminol–lysozyme reaction could be markedly quenched, and the decrease of CL intensity was linear with the logarithm of Cr(III) concentrations over the range of 5.0 to 4000 pg mL^?1 with a detection limit of 2.0 pg mL^?1 (3σ) and relative standard deviations (RSDs) of 3.0, 2.6, and 2.0% for 10, 100, and 1000 pg mL^?1 Cr(III) (n = 7), respectively. At a flow rate of 2.0 mL min^?1, the whole process including sampling and washing could be accomplished within 36 s. The proposed CL method was successfully applied to the determination of total chromium in pharmaceutical capsules, a dietary supplement, and spiked human serum samples, with recoveries from 92.2 to 108.4% and RSDs of less than 4.0%. Using the homemade FI–CL model, the binding constant (K = 4.38 × 10⁶ L mol^?1) and the binding sites (n ≈ 1) of Cr(III) to lysozyme were given.     

Domoic acid at trace levels in lagoon waters: assessment of a method using internal standard quantification

Domoic acid (DA) is a neurotoxin produced by different algae, including pennate diatoms, principally from the genus Pseudo-nitzschia, and it is the main cause of amnesic shellfish poisoning. Determination of this toxin in seawater samples is fundamental to define the real contamination risks for aquatic species. We have developed two very sensitive instrumental methods using hydrophilic interaction liquid chromatography coupled using tandem mass spectrometry in positive and negative polarity modes. Instrumental detection limits were 9 pg mL^?1 for positive and 19 pg mL^?1 for negative ionisation. A procedural method based on solid-phase extraction for the determination of dissolved DA present in seawater has been developed, and an extraction procedure was employed for the determination of the toxin in the particulate fraction. DA quantification was performed using the internal standard method to account for signals fluctuations and random errors during sample treatment. To our knowledge, this is the first study to use this quantification method for DA determination. Trueness, extraction yield, matrix effects, repeatability and procedural detection limits were evaluated during method validation. Procedural detection limits of 0.3 pg mL^?1 (positive mode) and 0.6 pg mL^?1 (negative mode) were found for the dissolved fraction, and absolute limits of 0.4 pg (positive mode) and 6.0 pg (negative mode) for particulate samples were obtained. The most sensitive method in positive mode was applied to define DA occurrence in the Venice Lagoon. Trace concentrations of domoic acid ranging from 1.5 to 16.2 pg mL^?1 were found for the first time in the Venetian environment.

Chemiluminometric Determination of the Pesticide Pirimicarb by a Flow Injection Analysis Assembly

Abstract

A flow injection (FI) method is described for the determination of pirimicarb. It was found that an enhanced chemiluminescence (CL) signal is obtained when employing the luminol–H₂O₂–horseradish peroxidase (HRP) system. Under the optimum experimental conditions, the enhanced CL intensity was linear with the concentration 4.25–30.75 ng mL^?1 (r = 0.997, n = 8) with a relative standard deviation of 0.99%, containing 12.75 ng mL^?1 (n = 8). The limit of detection of the investigated compound was 0.12 ng mL^?1. The method shows a moderate selectivity against other pesticides (Amitrole, Atrazine, 2,4,5-T, Dichlorprop, and Metamidophos).The proposed method was sensitive, simple, rapid, and successfully applied to the determination of pirimicarb when it is applied in freshwater; the mean recoveries were 98.3–118.5%.     

Flow-injection chemiluminescence determinations for human blood lead using controlled reagent release technology

A flow-through CL method for the determination of lead combined with controlled-reagent-release technology has been developed. Chemiluminescence (CL) reagents luminol and potassium permanganate were immobilized on anion exchange resin by electrostatic interaction. Lead ion was determined by its enhancing effect on the CL reaction between luminol and potassium permanganate. Both luminol and potassium permanganate were eluted from the anion exchange resin column by sodium phosphate solution. The linear range of the system was 10 μg mL^?1, and the detection limit was 5?×?10^–9 g mL^?1 lead (3σ). A complete analysis could be performed in 1 min with a relative SD 3.2% (1.0?×?10^–7 g mL^?1, n?=?9). The column shows remarkable stability and can be reused over 350 times and 21 days. The method has been applied to determine lead in human blood samples.     

Validation of an Analytical Biomarker Approach for the Detection of Nandrolone Abuse in the Porcine

The use of anabolic steroids as growth promoting agents in food production is prohibited under European Union legislation, but there is currently no internationally accepted method for detecting the abuse of the anabolic steroid nandrolone in the porcine. Therefore, an analytical biomarker approach based on gas chromatography-tandem mass spectrometry (GC-MS-MS) analysis of the major urinary free fraction nandrolone metabolite 19-noretiocholanolone was developed and validated. The lower and upper limits of quantification of the assay were 25 and 3,000 pg mL^?1 respectively. The limit of detection was calculated as 13.2 pg mL^?1, which is significantly lower than previously reported methods. When applied to a population of untreated animals, 19-noretiocholanolone distributions in boars and gilt were bimodal, with a small number of concentrations in each sex at around the 1,000 pg mL^?1 region and the majority of concentrations closer to the lower end of the calibration range. Statistical analysis of the data was carried out in order to suggest screening and confirmatory threshold approaches for this steroid in the urine of boars and gilts. The adopting of particular screening thresholds would be at the discretion of the individual regulating authorities, but at a false non-compliance rate of 1 in 10,000 of the normal population, the suggested confirmatory thresholds (7,501.6 pg mL^?1 for boars and 19,200.4 pg mL^?1 in gilts) are able to detect the abuse of nandrolone for several weeks following administration of this steroid.     

A Rapid Determination of Taurine in Human Plasma by LC

Taurine is an amino acid which is not incorporated into proteins but found in the cytosol of many mammalian cells, in high concentrations (2–30 mM). Increase in plasma taurine concentration has already been reported after surgical trauma, X-radiation, muscle necrosis, carbon tetrachloride-induced liver damage, and paracetamol overdose. Plasma taurine concentration was measured using LC with fluorescence detection following derivatization by o-phtalaldehyde plus 3-mercapto-propionic acid and α-aminobutyric acid as internal standard. Under these conditions the retention time of taurine was 10 min. This method was sensitive enough, to quantify 150 pg mL^?1 and detect 50 pg mL^?1 of taurine ranging normally between 65 and 179 mmol L^?1 (8–22 μg mL^?1). The validated method allowed simple determination of human plasma taurine in pharmacokinetic and biomarker studies.     

Ultrasensitive Assay of Gatifloxacin at Picogram Level Based on its Enhancing Effect on the Myoglobin‐Luminol Chemiluminescence Reaction

Abstract

Picogram‐level gatifloxacin was determined based on its significantly catalyzed effect on myoglobin‐luminol chemiluminescence (CL) reaction in the flow injection system. The enhanced chemiluminescence intensity was linear with gatifloxacin concentration in the range from 50 ngl^?1–10 µg l^?1 (r²=0.9995), and the detection limit was 20 ng l^?1 (3σ). At a flow rate of 2.0 ml min^?1 for each line, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 4.0% (n=7). The proposed method was applied successfully in the determination of gatifloxacin in tablets, human serum and urine samples with the recovery from 97.4–104.5%.     

Assessment of immobilized yeast for the separation and determination of platinum in environmental samples by flow-injection chemiluminescence and electrothermal atomic absorption spectrometry

The yeast Saccharomyces cerevisiae immobilized in calcium alginate beads was used for separation and subsequent determination of Pt in environmental samples by flow-injection chemiluminescence (FI-CL) and electrothermal atomic absorption spectrometry (ETAAS). The application of a yeast column resulted in an increase in the tolerable matrix ions concentration compared to direct measurements by both detection techniques. The developed FI-CL method of Pt determination based on the catalytic effect of Pt(IV) ions on luminol oxidation in alkaline medium is characterized by a low limit of detection (0.15 ng mL^?1), and good sensitivity and precision, and can be used for analysis of Pt in water samples. Determination of Pt in more complex environmental samples can be carried out by ETAAS (LOD?=?6 ng mL^?1) after introduction of a column clean-up step with 10 mM nitric acid. The accuracy of the method was confirmed by analyzing the certified reference material of platinum ore (SARM-7), spiked grass, and road dust samples.     

Artificial Enzyme Mimics for Catalysis and Double Natural Enzyme Co-immobilization

This work presents a new chemiluminescent (CL) probe array assay. The new type CL probe array is based on enzyme mimics of Co₃O₄–SiO₂ mesoporous nanocomposite material, which not only have an excellent catalytic effect on the luminol–H₂O₂ CL reaction in an alkaline medium but also can be used for the immobilization of enzymes. The linear range of the lactose concentration is 3.0?×?10^?7 to 1.0?×?10^?5 g mL^?1 and the detection limit is 6.9?×?10^?8 g mL^?1. β-Galactosidase and glucose oxidase were selected as a model for enzyme assays to demonstrate the applicability of Co₃O₄–SiO₂ mesoporous nanocomposite material in multienzyme immobilization. The novel bifunctional CL probe array has been successfully applied to the determination of lactose in milk.     

Determination of Piribedil in Human Serum, Urine and Pharmaceutical Dosage Form by LC-DAD

A rapid, selective and sensitive reversed-phase liquid chromatographic (LC) method was developed for the determination of piribedil in human serum, urine and pharmaceutical dosage form. LC analysis was carried out using reversed-phase isocratic elution with a C₁₈ column and a mobile phase of 0.01 M phosphate buffer-acetonitrile (50:50, v/v). The chromatograms showed good resolution and sensitivity with no interference of human serum and urine. Piribedil concentrations were determined using diode array detection at 240 nm. Sildenafil citrate was used as internal standard. The limit of quantification (LOQ) and limit of detection (LOD) concentrations were 107.2 and 321.6 pg mL^?1, 96.6 and 290.4 pg mL^?1, 161.7 and 53.9 pg mL^?1 for urine, serum and pharmaceutical dosage forms, respectively. The method was validated for its linearity, precision and accuracy and applied to the tablets, urine and human serum. In addition, the results were compared to those obtained from UV-spectrophotometry.     

A New Flow‐Injection Chemiluminescence Method for the Determination of Acyclovir and Gancyclovir

Abstract

A rapid and sensitive flow‐injection chemiluminescence (FI‐CL) method, which is based on the CL intensity that generated from the redox reaction of Ce(IV)‐rhodamine B in H₂SO₄ medium, for the determination of acyclovir and gancyclovir is described. For acyclovir, the determination range is 3×10^?8 g mL^?1–7×10^?5 g mL^?1, with 1.56×10^?8 g mL^?1 as its determination limit. During 11 repeated measurements for 1×10^?6 g mL^?1 acyclovir, the relative standard deviation was 2.08%. For gancyclovir, the determination range was 5×10^?8 g mL^?1–7×10^?5 g mL^?1, with 2.35×10^?8 g mL^?1 as its determination limit. The relative standard deviation is 2.83% with 11 repeated measurements of 1×10^?6 g mL^?1 gancyclovir. This method can be successfully used to determine the content of acyclovir and gancyclovir in injections, acyclovir in eye drops, and, maybe, also for other ciclovirs.     

Determination of Sugars by LC with On-Line Electrogenerated Cu(HIO6)2]5−–Luminol Chemiluminescence Detection

A novel method was developed for the determination of sugars such as glucose, fructose and lactose by column liquid chromatography coupled with chemiluminescence detection. The LC separation used a Kromasil NH₂ column (250 × 4.6 mm, i.d.: 5 μm, pore size, 100 Å) with a mobile phase consisting of acetonitrile and water. The chemiluminescence detection was based on the enhancement effect of the selected sugars on the chemiluminescence intensity between luminol and [Cu(HIO₆)₂]^5?, which was on-line electrogenerated by constant current electrolysis. The limits of detection for determination of glucose, fructose and lactose were 4, 3 and 20 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of glucose and fructose in grape samples and lactose in milk samples.     

Automated Sequential‐injection Chemiluminescence Determination of Glucosamine Sulphate via Luminol‐Hydrogen Peroxide System

A highly sensitive automated sequential‐injection chemiluminescence (SIA‐CL) method for determination of glucosamine sulphate (GLS) was developed. The goal of the present work is the evaluation of the enhancement effect of the investigated drug glucosamine sulphate on the chemiluminescence reaction between luminol and H₂O₂ in alkaline medium of 1.0 × 10^?2 mol L^?1 sodium hydroxide at pH 11. The experimental conditions affecting the CL reaction such as the sequence of the reagents, concentrations, flow rate and aspirated volumes of reactants were systematically investigated and optimized. Under optimum conditions 50 μL of 1.0 × 10^?3 mol L^?1 luminol, 30 μL of a GLS test solution and 50 μL of 1.0 × 10^?2 mol L^?1 H₂O₂ were used and the luminescing zone was pushed into the detector at a flow rate 100 μL s^?1. The proposed method recorded high sensitivity, accuracy and simplicity that could be clarified as linear concentration range 1.0‐2000 ng mL^?1 with rectilinear part (r = 0.9992, n = 9) and limit of detection 0.3 ng mL^?1, along with relative standard deviation 1.3%. It was found that the developed method can be used directly to determine the investigated drug GLS in its pharmaceutical dosage forms and in spiked serum and urine by diluting the samples for a 1000 fold. The obtained results were statistically analyzed and compared with those obtained by the reported method.     

On the Effect of Hydrogen Peroxide on the Flow‐Injection Determination of Platinum Based on Luminol Chemiluminescent Reaction

Abstract

A flow‐injection chemiluminescent (CL) method for the determination of trace amounts of Pt(IV) based on the oxidation reaction of luminol in alkaline solution is proposed. The effect of Pt(IV) on the oxidation of luminol was studied in the absence and in the presence of hydrogen peroxide. The positive effect of hydrogen peroxide as well as chloride ions on the sensitivity of measurements was observed. The developed method is characterized by a low limit of detection of Pt (LOD=0.06 ng mL^?1) and good reproducibility (RSD=2.2%). The addition of hydrogen peroxide to the reaction medium resulted in decreasing of platinum detection limit to 0.03 ng mL^?1.     

Simple and rapid surface-enhanced Raman Spectroscopy assay for safranine T and its application in highly sensitive determination of mercury (Ⅱ)

A simple and sensitive surface-enhanced Raman spectroscopy (SERS) method for the detection of safranine T (ST) and Hg²⁺ using silver nanoparticles (AgNPs) as substrate was developed. ST can absorb on the surface of AgNPs through electrostatic interaction, the electromagnetic effect combined with chemical adsorption effect give a notable Raman enhancement for ST. The presence of Hg²⁺ well decreased the absorbed ST molecules on AgNPs, leading to a significant decrease of SERS signals thus enabling to detect Hg²⁺. The determination conditions for SERS, including the amount of AgNPs, the concentration of NaCl, the concentration of HCl, the concentration of ST and the reaction time, were optimised. Under the optimised experimental conditions, good linear responses were obtained for ST and Hg²⁺ in the concentration ranges of 0.01–4.0 μmol L^?1 (3.5–1403.4 ng mL^?1) and 0.01–2.0 μmol L^?1 (2.0–401.2 ng mL^?1), the limit of detection were 3.0 nmol L^?1 (1.1 ng mL^?1) and 2.0 nmol L^?1 (0.4 ng mL^?1), respectively. The present method was subsequently applied to the determination of ST in tomato sauces and Hg²⁺ in environmental waters, the recoveries of ST and Hg²⁺ in spiked samples are 95.5–107.8% and 91.4–110.8 %, respectively.     

Label-Free Electrochemiluminescent Determination of DNA Using Luminol and Hemin Functionalized Nanoparticles

Luminol and hemin dual-functionalized silica nanoparticles were synthesized using a typical reverse water-in-oil microemulsion protocol. The obtained nanoparticles were further characterized by transmission electron microscopy, scanning electron microscopy, atomic absorption spectrometry, chemiluminescence, and electrochemiluminescence. The results indicated that the luminol and hemin dual-functionalized silica nanoparticles exhibited significantly higher chemiluminescence and electrochemiluminescence intensities than those of luminol functionalized silica nanoparticles due to the catalytic effect of hemin on the chemiluminescence and electrochemiluminescence of luminol. Furthermore, a simple and sensitive label-free electrochemiluminescence DNA biosensor was developed based on the chitosan modified luminol and hemin dual-functionalized silica nanoparticles and a single-stranded DNA probe. The chitosan modified luminol and hemin dual-functionalized silica nanoparticles were immobilized on the surface of an indium-doped tin oxide electrode and the single-stranded DNA probe was immobilized on the surface of the nanoparticles through electrostatic interactions between single-stranded DNA and chitosan, which allowed hybridization with the target DNA sequences. The hybridization events were evaluated by electrochemiluminescence, and only the complementary sequence formed double-stranded DNA with the DNA probe to give strong electrochemiluminescence signals. Finally, the electrochemiluminescence intensity was found to be linearly related to the concentration of the complementary sequence at concentrations from 1.0?×?10^?12 to 1.0?×?10^?6?mol·L^?1 with a detection limit of 5.0?×?10^?13?mol·L^?1.     

A Multicommuted Flow‐based System for Hydrogen Peroxide Determination by Chemiluminescence Detection Using a Photodiode

Abstract

A simple, rapid, and automated assay for hydrogen peroxide in pharmaceutical samples was developed by combining the multicommutation system with a chemiluminescence (CL) detector. The detection was performed using a spiral flow‐cell reactor made from polyethylene tubing that was positioned in front of a photodiode. It allows the rapid mixing of CL reagent and analyte and simultaneous detection of the emitted light. The chemiluminescence was based on the reaction of luminol with hydrogen peroxide catalyzed by hexacyanoferrate(III).

The feasibility of the flow system was ascertained by analyzing a set of pharmaceutical samples. A linear response within the range of 2.2–210 µmol l^?1 H₂O₂ with a LD of 1.8 µmol l^?1 H₂O₂ and coefficient of variations smaller than 0.8% for 1.0×10^?5 mol l^?1 and 6.8×10^?5 mol l^?1 hydrogen peroxide solutions (n=10) were obtained. Reagents consumption of 90 µg of luminol and 0.7 mg of hexacyanoferrate(III) per determination and sampling rate of 200 samples per hour were also achieved.     

In vitro monitoring of picogram levels of risperidone in human urine via luminollysozyme flow injection chemiluminescence

The anti-schizophrenic drug risperidone (RSP) exerts an inhibitory effect on the chemiluminescence (CL) of the luminol-lysozyme system. This finding forms the basis for a sensitive flow injection method for its determination at picogram levels. RSP binds to Trp62 in the lysozyme, and this leads to a conformational change upon which the CL of the system is quenched. The decrease in CL is proportional to the logarithm of the concentration of RSP, and the calibration graph is linear in the range from 0.1 pg?mL^?1 to 1.0 ng?mL^?1, with relative standard deviations of <5.0%, and a detection limit of 0.05 pg?mL^?1 (3σ). At a flow rate of 2.0 mL?min^?1, the whole process including sampling and washing is completed within 20 s. The method was successfully applied to monitoring RSP in human urine after incorporation of 2 mg of RSP, with a total excretion of 16.6% within 8.5 h.

Determination of Gallic Acid by Flow Injection Analysis Based on Luminol‐AgNO3‐Ag NPs Chemiluminescence System

A novel flow injection procedure has been developed for the determination of gallic acid based on the enhancement function for luminol‐AgNO₃‐Ag NPs chemiluminescence (CL) system by gallic acid. The enhancement mechanism was proposed for the reinforcing effect of the gallic acid on the CL system. The UV‐vis absorption spectrum and CL emission spectrum were applied to confirm the mechanism. The method is simple, rapid and sensitive with a detection limit of 5×10^?10 g·mL^?1 and a linear range of 8.0×10^?10–1.0×10^?7 g·mL^?1. The relative standard deviation (RSD) is 1.3% for eleven measurements of 5×10^?8 g·mL^?1 gallic acid. The method has been successfully applied to the determination of gallic acid in Chinese proprietary medicine–Jianmin Yanhou tablets and synthesized samples.