Chemiluminescence Determination Research Articles

Chemiluminescent determination of total reducing capacity of phenolic compounds and analysis of oxidizable compounds in infusions with Oxone® decomposition

Tea consumption has grown significantly due to its well-documented health benefits, including the prevention of cardiovascular and neurodegenerative diseases. These benefits are primarily attributed to the antioxidant properties of polyphenolics and other compounds. So, bringing information on the nutritional properties in herbal infusions has become relevant to promote consumer choices. Leveraging the luminescence generated by the catalytic decomposition of Oxone®, we developed a chemiluminescent procedure to measure the total reducing capacity (TRC) of phenolic compounds and quantify the total content of oxidizable compounds (TCOC) in teas and infusions. TRC values of ten phenolic compounds were quantified and expressed in Trolox®, while TCOC values from twelve tea and infusion samples were determined and expressed in gallic acid. The TCOC values were compared with total polyphenol content and total antioxidant capacity. No correlation was observed between TRC values and the number or position of hydroxyl or other groups. However, strong correlations were identified between TCOC values and polyphenol content (r=0.860) and antioxidant capacity (r=0.788) in the analyzed samples, suggesting the polyphenolic content contributes to both TCOC and total antioxidant activity. These findings increase awareness of the nutritional and medicinal value of infusions, reinforcing their role as functional foods.

Single-holed cobalt - nitrogen - carbon hollow structure with oxidase-mimicking activity for the chemiluminescence determination of β - galactosidase activity.

A single-holed cobalt - nitrogen - carbon (Co - N - C) hollow structure nanozyme has been fabricated by in situ growth of zeolitic imidazolate framework (ZIF - 67) on the polystyrene (PS) sphere and following treatment by high-temperature carbonization. The Co - N - C nanostructure mimics the activity of oxidase and can activate O2 into reactive oxygen species (ROS), giving a remarkable enhancement on the chemiluminescence (CL) signal of luminol - O2 reaction. The Co - N - C oxidase mimic has further been exploited in the biosensing field by the determination of the activity of β - galactosidase (β - gal). The CL method for β - gal activity has a linear range of 0.5mU·L-1 to 5.0 U·L-1, a detection limit of 0.167mU·L-1, and the precision of 3.1% (5.0 U·L-1, n = 11). This method has been employed to assess inhibitor screening of β - gal and determine activity of β - gal in spiked human serum samples.

Flow injection chemiluminescence determination of acetochlor and cartap-HCl in freshwater samples using an acidic KMnO4 -rhodamine-B reaction system.

A flow injection (FI) methodology using the acidic potassium permanganate (KMnO4 )-rhodamine-B (Rh-B) reaction with chemiluminescence (CL) detection was established to determine acetochlor and cartap-HCl pesticides in freshwater samples. Experimental parameters were optimized, and Chelex-100 cationic exchanger mini column and solid-phase extraction (SPE) were used as phase separation techniques. Linear calibration curves were observed for the standard solutions of acetochlor and cartap-HCl over the ranges 0.005-2.0mg L-1 [y= 1155.8x+ 57.551, R2 =0.9999 (n= 8)] and 0.005-1.0mg L-1 [y= 979.76x+ 14.491, R2 =0.9998 (n= 8)] with LODs and LOQs of 7.5×10-4 and 8.0×10-4 mg L-1 (3σ blank) and 2.5×10-3 and 2.7×10-3 mg L-1 (10σ blank), respectively, with an injection throughput of 140 h-1 . These methods were used to estimate acetochlor and cartap-HCl with or without the SPE procedure, respectively, in spiked freshwater samples. Results obtained were not significantly different at a 95% confidence level to those of other reported methods. Recoveries for acetochlor and cartap-HCl were obtained over the ranges 93-112% (RSD = 1.9-3.6%) and 98-109% (RSD = 1.7-3.8%), respectively. The most probable CL reaction mechanism was explored.

Design of a New Bioluminescence Sensor Using an Arduino Device Linked to Bluetooth Mobile Phone and USB Computer to Measure Triglycerides

In this work, a new device is designed for measuring the light intensity of the Bioluminescence reaction between Luminol with Hydrogen peroxide that is produced as an activity of Triglycerides Phosphate Oxidase. The project includes the use of a homemade and semi-automated device for the determination of Chemiluminescence (CL) and Bioluminescence light by direct reaction analysis of Luminol with oxidant and using a Mobile –phone as a recorder which is employed in chemistry with Arduino and applied this device into the enzymatic reaction for determine Triglyceride by this new methods. The method is easy, simple, and rapid with high sensitivity for the determination of hydrogen peroxide. The light of the Bioluminescence reaction of Luminol (5-amino-2,3-dihydro-1,4_phthalazinedione) with oxidant (H2O2) was sensed by photocell and the signal was sent to Mobile. The method used to determine glycerol and compare the results of the device with real value to give high accuracy, Triglyceride was determined in its kit. It gave 99.2 and ±0.1 of Recovery and RSD, respectively.

Cholesterol 7α-Hydroxylase Gene-204A/C Polymorphism in Normal and Gestational Diabetic Pregnancies

To investigate the cholesterol 7α-hydroxylase gene ( CYP7A1)-204A/C single nucleotide polymorphism and its relationship with the blood lipid levels of pregnant women with gestational diabetes mellitus (GDM) and normal pregnant women. The genotype and allele frequencies of CYP7A1-204A/C gene polymorphism of 1037 normal pregnant women, the normal controls, and 627 pregnant women with GDM were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and blood glucose (Glu) were measured by enzymatic assay. Chemiluminescence determination of plasma insulin (Ins) was conducted. Apolipoproteins A1 (apoA1) and B (apoB) were measured by the turbidimetric immunoassay. Allele frequencies of A and C at the CYP7A1-204A/C polymorphic locus were 0.586 and 0.414, respectively, in the GDM group and 0.557 and 0.443, respectively in the control group. The distribution of genotype frequencies in both groups showed conformity with the Hardy-Weinberg principle. There was no significant difference in allele and genotype frequencies between the GDM group and the control group. In the control group, carriers of the genotype AA were associated with significantly higher concentrations of apoA1 and lower levels of Ins and homeostatic model assessment of insulin resistance (HOMA-IR) compared with those with genotype CC (all P<0.05). In the non-obese subgroup of the control subjects, carriers of the genotype CC were associated with significantly higher plasma TG or apoA1 levels compared with those with genotype AA ( P<0.05). In the GDM group, carriers with genotype AA of CYP7A1-204A/C polymorphism had elevated levels of gestational weight gain (GWG) compared with those with genotype CC ( P<0.05). These results suggest that 204A/C polymorphism in the CYP7A1 gene is not associated with GDM, but may be closely associated with gestational weight gain in pregnant women with GDM. Variants in this locus are strongly associated with plasma apoA1, Ins, and HOMA-IR levels in the controls and elevated plasma TG levels in non-obese controls.

Strong chemiluminescence intensities of bis-acridinium esters under neutral and alkaline conditions

Four novel bis-acridinium esters were synthesized using common methods, and their chemiluminescence properties were investigated at pH 7−10. In the chemiluminescence of bis-acridinium esters, the introduction of fluorine at the 2-position of the phenyl ring and methyl groups at the 2,7-positions of the acridine ring changed greatly the chemiluminescence intensities. Pentane-1,5-diyl bis(2-fluoro-4-(2,7,10-trimethylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) showed strong chemiluminescence and long-lasting chemiluminescence under both neutral and alkaline conditions. Pentane-1,5-diyl bis(2-fluoro-4-(10-methylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) was applied for highly sensitive chemiluminescence determination of hydrogen peroxide and catalase activity. The linear calibration ranges of hydrogen peroxide and catalase activity were 5–1000 μM (R = 0.999) and 0.05−1 U/mL (R = 0.998), respectively.

Online chemiluminescence determination of the hydroxyl radical using coumarin as a probe.

The hydroxyl radical (˙OH) is one of the strongest oxidizing species, which can react with a variety of organic and inorganic chemicals. Although ˙OH is widely used for degradation of environmental pollutants, detection of ˙OH remains a major challenge due to its high reactivity and short lifetime, especially online detection. In this study, a novel method for online detection of ˙OH by flow oxidization chemiluminescence (F-OCL) using coumarin as a probe was established. The concentrations of ˙OH determined by this new method were consistent with those determined by HPLC analysis. Because the new method has a short response speed, it was successfully used to quantify the dynamic change of ˙OH in the TiO2 photocatalytic process and Fenton reaction in real time. Furthermore, a combination of two chemiluminescence systems was developed to track the dynamics of ˙OH and hydrogen peroxide (H2O2) in homogeneous or heterogeneous Fenton reactions occurring in soil slurry. The proposed method and strategy have good application potential in online ROS monitoring of both natural and engineered systems.

Development of a Selective Assay of Tyrosine and Its Producing and Metabolizing Enzymes Utilizing Pulse-UV Irradiation-Induced Chemiluminescence.

A new pulse UV irradiation-induced chemiluminescence (CL) determination method was developed for l-tyrosine using the luminol derivative L-012. The proposed method depends on the formation of reactive oxygen species (ROS) upon pulse UV irradiation of l-tyrosine; then, these ROS react with L-012 producing strong CL. The proposed method showed excellent sensitivity and ultraselectivity toward l-tyrosine. The mechanism of the developed CL method was studied using ROS scavengers, HPLC, and mass spectrometry. The method was linear for l-tyrosine in the range of 0.03-50 μM. Minor changes in the l-tyrosine structure, including hydroxylation, dehydroxylation, phosphorylation, or decarboxylation, were found to lead to a strong decrease in CL. Using the excellent selectivity of the proposed method for l-tyrosine, we have developed a CL assay for measuring alkaline phosphatase activity in the range of 0.02-15 U/L with the limit of detection (LOD) of 4 mU/L using the nonchemiluminescent O-phospho-l-tyrosine as a substrate. Furthermore, the CL reaction was applied for tyrosinase activity assay as this enzyme can convert l-tyrosine to the nonchemiluminescent l-dopa. The decrease in CL is correlated with the tyrosinase activity in the range of 0.025-0.75 U/mL with an LOD of 1.5 mU/mL. Moreover, the tyrosinase activity assay was successfully applied for the determination of IC50 of the tyrosinase inhibitors kojic acid and benzoic acid. Therefore, our novel pulse UV irradiation CL method for the determination of l-tyrosine was not only suitable for the determination of this vital amino acid but also extended to the successful determination of its producing and metabolizing enzymes and their inhibitors.

Flow injection chemiluminescence determination of ethion and computational investigation of the adsorption process on molecularly imprinted polymerized high internal phase emulsion

The lack of sufficient selectivity is the main limitation of chemiluminescence (CL) methods; because the CL reagent is not restricted to a specific analyte. This study investigated the preconcentration and determination of ethion using a flow injection CL (FIA-CL) method using a molecularly imprinted poly high internal phase emulsion (MIP-polyHIPE) adsorbent. Preliminary studies showed that ethion could be determined with high sensitivity in the Ru(bipy)3 2+ -acidic Ce(IV) CL system. A MIP-polyHIPE adsorbent was synthesized and used for preconcentration to increase the selectivity and sensitivity of the method. The adsorption of ethion on the adsorbent was investigated using density functional theory (DFT) and molecular dynamics (MD), UV-vis and FTIR spectrophotometry and liquid chromatography-tandem mass spectrometry (LC-MS-MS). Response surface methodology (RSM) and central composite design (CCD) were used to find optimized concentrations of variables. The linear dynamic range (LDR) and limit of detection (LOD) for ethion in the FIA-CL method were calculated 1.0 ⨯ 10-9 to 2.0 ⨯ 10-7 and 6.0 ⨯ 10-10 mol L-1 , respectively. The percentage of relative standard deviation for five repetitive measurements of 5.0 ⨯ 10-8 mol L-1 ethion was 4.2%. The proposed method was successfully used to separate and preconcentrate ethion from drinking and surface water sources.

One-Step Chemiluminescent Determination of Glucose by a Functionalized Graphene Nanocomposite

A chemiluminescence (CL) nanosensing platform was constructed by using reduced graphene oxide (rGO) as the carrier, which was loaded with N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as the signaling molecule, hemin as the catalyst, and glucose oxidase (GOx) as the enzyme. The loading efficiency of GOx was determined to be 0.64 mg GOx/mg rGO. The nanosensing platform achieved one-step determination of glucose without pre-incubation steps. When glucose is added to the CL nanosensing platform, the GOx on the nanocomposite catalyzes the reaction between glucose and O2 to produce H2O2 which oxidizes ABEI to emit light with the catalysis of hemin. When glucose was mixed with the nanocomposite, a growth-type CL profile was observed and the maximum signal was obtained approximately 6 min after the addition of glucose to the nanocomposite. The CL nanosensing platform exhibited a linear enhanced response for glucose from 10 μM to 1 mM. The detection limit for glucose was 2.6 μM. The proposed glucose CL sensing platform also exhibited good selectivity and specificity. Furthermore, it was successfully applied in the determination of glucose in serum, and satisfactory recoveries were obtained, signifying its potential in clinical diagnosis.

Ascorbic acid as an alternative coreactant for luminol reaction and sensitive chemiluminescence determination of ascorbic acid in soft drinks

Ascorbic acid can serve as an efficient coreactant for luminol chemiluminescence (CL) reaction. An observable CL emission is produced when mixing ascorbic acid with luminol in an alkaline condition. The CL signal is further dramatically enhanced by cobalt(II) ions. This CL system was exploited as a new method for direct determination of ascorbic acid with a flow injection mode. A good linear response is acquired between the CL signal and ascorbic acid concentration in 5.0–1000.0 ng/mL range with a detection limit of 1.3 ng/mL. The relative standard deviations are 2.3% for intra–day (n = 11) and 3.7% for inter–day (n = 3) by parallel determination of 0.5 μg/mL ascorbic acid solution. The method has good selectivity for ascorbic acid since no obvious responses are observed for a variety of inorganic ions and biological substances. The practicability of the method has been demonstrated by the analysis of ascorbic acid in some soft drinks.

In English

The properties of heteropoly acids and of their complexes with cationic surfactants at the trace level have been studied by ESR spectroscopy, UV-VIS spectrophotometry, NMR and FTIR spectroscopy, by the method of chemiluminescence analysis applied in aqueous solutions and on the cellulose surface. For elucidation of the mechanism of chemiluminescence reactions of heteropoly acids with luminol kinetic methods, diffuse reflectance spectroscopy and liquid chromatography have been applied. For the first time one-electron reduction of heteropoly acids by luminol was confirmed by registration of diffuse reflectance spectra of reduced heteropoly acids on cellulose surface. It has been suggested that the mechanism of heteropoly acids immobilization on cellulose includes combination of Coulomb and hydrophobic interactions. A scheme of heteropoly acids immobilization on the surface was proposed based on ion exchange processes on cellulose or diethylaminoethyl cellulose surface. It has been shown that ionic associates heteropoly acid – cationic surfactant react with an alkaline solution of luminol with light emission similarly to heteropoly acids themselves. For the first time, heterogeneous chemiluminescence, namely, the chemiluminescence of heteropoly acids immobilized on cellulose, with luminol, has been used for examining the composition of ionic associates heteropoly acid - cationic surfactant. By using Bjerrum’s method it has been found that in strongly acidic media (at pH 1.0) vanadomolybdophosphoric acid forms with cationic surfactant, namely, with dodecylpyridinium bromide, not tetra-substituted but triply substituted ionic associate. This result can be explained by the fact that the fourth proton in H4PVMo11O40 is weakly dissociated; it is more strongly bound to heteropoly anion and is localized on the oxygen atom of the Mo–O–Mo angular bond. Ionic associates of heteropoly acids were used as analytical forms for highly sensitive chemiluminescence determination of P, As, Si, Ge in waters of different types. Detection limits for P, As, Si, Ge are 0.02–0.07 µg/L. Due to the high sensitivity of the method, phosphorus was successfully determined in surface water and ultrapure water, arsenic – in river and mineral water, silicon – in ultrapure water and vapor condensate of electric power stations, germanium – in water of electronic industry.

A molecularly imprinted polymerized high internal phase emulsion adsorbent for sensitive chemiluminescence determination of clopidogrel

A molecularly imprinted polymerized high internal phase emulsion (MIP-polyHIPE) adsorbent was used for selective separating and preconcentrating the anti-plaque drug, clopidogrel. For the first time in this study, chemiluminescence (CL) methods were evaluated for the determination of clopidogrel. The synthesis of adsorbents by the emulsion templating method showed that the sensitivity of the method can be increased up to 42 times. The determination of clopidogrel was evaluated by Ru(phen)32+-Cerium (IV), KMnO4-H2SO4, KMnO4-H2SO4-Na2SO3, and luminol-H2O2 CL systems. According to the results, only the Ru(phen)32+-Cerium (IV) CL system showed a reasonable sensitivity for clopidogrel. Using MIP-polyHIPE adsorbent, the linear range, the limit of detection, and relative standard deviation for clopidogrel in this system were respectively 1.0 × 10−9–8.0 × 10−8 mol L−1, 3.0 × 10−10 mol L−1, and 6.3% (n = 4, 1.0 × 10−8). The proposed method was employed for determining clopidogrel in pharmaceuticals and blood serum samples. The results showed the good sensitivity and accuracy of the proposed method.

A novel luminol-based chemiluminescence method for detecting acetylcholine

Aim. To develop а new simple non-enzymatic method for the determination of acetylcholine (ACh) by the chemiluminescent reaction of luminol under conditions of the enzymatic hydrolysis of acetylcholine (pH 8.5).Experimental part. The method proposed is based on the perhydrolysis reaction of ACh by the excess ofhydrogen peroxide with the formation of peracetic acid. The latter was further determined by the activation effect of the luminol chemiluminescent oxidation reaction in the presence of hydrogen peroxide. The analytical signal was the summary luminescence (Σ) registered within certain time.Results and discussion. The pH range of the analytically applicable system was from 8.2 to 8.5. The effect of ACh + H2O2 incubation period on the reaction progress was also studied. The increase of the incubation period enhanced the sensitivity of the method (the limit of detection (LOD)), but because of practical reasons (especially the detection speed) and practical experience the incubation period was set to 30 min. The linear dependence was observed in the acetylcholine chloride concentration range of (0.8 – 2.8) × 10-4 mol/L. While determining acetylcholine chloride in the concentration range of (1.1 – 2.2) × 10-4 mol/L the relative standard deviation (RSD) did notexceed 3 % ((X – μ) × 100 %/μ = –0.5…+0.5 %). The Limit of Quantitation (LOQ, 10S) was 7.7 × 10-5 mol/L.Conclusions. A new non-enzymatic kinetic method for the chemiluminescent determination of ACh in aqueous solutions and the pharmaceutical formulation Acetylcholinchlorid Injeel® has been proposed. This method is simple, fast, inexpensive, and thus appropriate for the routine ACh quality control in the laboratories of hospitals, pharmaceutical industries and research institutions.Key words: acetylcholine; chemiluminescence method

Stir flat sheet membrane liquid phase microextraction for the selective chemiluminescence determination of ofloxacin and fleroxacin in human urine

Stir flat sheet membrane liquid phase microextraction procedure for the chemiluminescence determination of polar antibiotics (ofloxacin and fleroxacin) in human urine samples was developed. The microextraction procedure assumed simultaneous ion-pair complex formation between antibiotic and anionic dye in acidic medium, dispersion of extraction solvent by rotation of a stir flat sheet microporous membrane unit, mass-transfer of complexes from sample into microdroplets of extraction solvent followed by extract collection into the unit. After preconcentration the unit was immersed in alkaline aqueous solution for analytes re-extraction based on ion-pair complex decomposition followed by the chemiluminescence analysis of obtained aqueous phase. The developed microextraction procedure allowed to exclude matrix effects for the selective, simple, and rapid chemiluminescence determination of ofloxacin and fleroxacin in urine samples. The calibration graphs were linear over the concentration ranges of 0.1–25 mg L−1 for ofloxacin and fleroxacin. The LOD values, calculated from the blank tests based on 3σ, were 30 µg L−1 for ofloxacin and fleroxacin. The procedure was conveniently applied to the determination of fluoroquinolones in urine samples.

In situ encapsulation of horseradish peroxidase in zeolitic imidazolate framework-8 enables catalyzing luminol reaction undernear-neutral conditions for sensitive chemiluminescence determination of cholesterol.

HRP@ZIF-8 nanocomposite was prepared by in situ encapsulation of horseradish peroxidase (HRP) in the frame of zeolitic imidazolate framework-8 (ZIF-8) with a simple one-pot method. The HRP@ZIF-8 nanocomposite displays outstanding thermal stability and efficiently catalyzes the chemiluminescence (CL) reaction of luminol with hydrogen peroxide (H2O2) under near-neutral pH condition (pH 7-8). This CL system has a good response to H2O2 with a linear range of 0.1-100.0μmolL-1. The limit of detection (LOD) is 0.06μmolL-1 H2O2. By marriage with cholesterol oxidase, cholesterol is determined with a linear range from 0.1 to 100.0μmolL-1 and a LOD of 0.04μmolL-1. The relative standard deviations (RSD) are 1.7% and 2.5%, respectively, in 11 repeated measurements of 50.0μmolL-1 solutions of H2O2 and cholesterol, indicating excellent precision of the method. The method shows good selectivityand has been applied to the determination of total cholesterol in real serum samples. No significant difference has been observed between the results obtained by this method and thecholesterol oxidase-peroxidase coupling method. Graphical abstract Schematic presentation of in situ one-pot synthesis of horseradish peroxidase@zeolitic imidazolate framework-8 (HRP@ZIF-8) nanocomposite and chemiluminescence determination of cholesterol with HRP@ZIF-8 catalyzing luminol-H2O2 system.

A dual-functional smartphone-based sensor for colorimetric and chemiluminescent detection: A case study for fluoride concentration mapping

Reliable field techniques for sensing and mapping environmental contamination has the potential to revolutionize environmental monitoring, among which smartphone-based sensors (SPSs) are playing an increasing role owing to the low cost and the widespread ownership of smartphone. How to integrate more functions on SPSs has been a hot field of research. In this study, a dual-functional SPS for colorimetric and chemiluminescence detection were developed through simple and efficient light path design within an integrated 3D-printed attachment, and the smartphone application design makes it possible for simpler analysis, storage and transmission of data. In colorimetric detection, due to the use of white LED and diffraction grating, this sensor could determinate samples in various color, and five contaminants, including fluoride, ammonia nitrogen, orthophosphate, turbidity, and chlorine, were detected with good reliability. The chemiluminescence determination of H2O2 indicated broader potential application fields. As a successful case study, this SPS was used to map the fluoride concentration of surface water in Suzhou (China) with good sensitivity (0.06 mg/L limit of detection, 0.1∼2 mg/L linear range). In summary, the dual-functional and on-site sensing capabilities of this SPS show prospects in the field of environmental monitoring, even in medical diagnosis, food safety and so on.

Cobalt-doped hydroxyapatite nanoparticles as a new eco-friendly catalyst of luminol-H2O2 based chemiluminescence reaction: Study of key factors, improvement the activity and analytical application.

In this study, a novel catalyst based on hydroxyapatite doped by cobalt for chemiluminescence reaction of luminol oxidation by H2O2 was suggested for the first time. The catalyst nanoparticles were synthesized by a hydrothermal method and characterized by various methods including density functional theory calculations. The impact of nanoparticles sizes, surface composition, contact efficiency and crystallinity on chemiluminescence intensity were investigated. The maximum chemiluminescence intensity was obtained for polycrystalline nanoparticles. This phenomenon was studied in detail and applied for chemiluminescence analysis for the first time. The chemiluminescence determination of sulfonamides as model analytes was considered. The sensing was based on sulfonamides-dependent quenching of the chemiluminescence intensity in the presence of novel catalyst existed as an aqueous suspension.

Trapping and preconcentration of volatile organic sulfur compounds in water samples by portable and battery-powered trapping device prior to gas chromatography-sulfur chemiluminescence determination

A simple, portable and battery-powered trapping device (iTrap) consisting of a purification tube, a trapping unit and a miniature air pump was developed for the pre-concentration of volatile organic sulfur compounds (VOSCs). The tested VOSCs, including methanthiol (MT), ethanethiol (ET), dimethyl sulfide (DMS), diethyl sulfide (DES) and dimethyl disulfide (DMDS), were firstly purged from water samples and then in situ pre-concentrated with the iTrap prior to their analysis by thermal desorption gas chromatography coupling with a sulfur chemiluminescence detector (TD-GC-SCD). Twenty-six adsorbents were studied to find the most suitable adsorbent for the efficient pre-concentration of VOSCs. Under optimal conditions, limits of detection of 6, 8, 6, 2 and 3 ng L−1 were obtained for MT, ET, DMS, DES and DMDS, respectively. The precisions were better than 5.3% (relative standard deviations, RSDs). The iTrap was successfully applied for the analysis of VOSCs in Certified Reference Materials, several surface water, underground water and wastewater samples collected from Pengzhou city, Sichuan, China. Moreover, the VOSCs trapped in the iTrap were much more stable than those directly stored in water samples and the recoveries for all samples could be maintained at acceptable levels (>73%), even their preservation time as long as 8 h.

New Reusable Solid Biosensor with Covalent Immobilization of the Horseradish Peroxidase Enzyme: In Situ Liberation Studies of Hydrogen Peroxide by Portable Chemiluminescent Determination.

Herein, we reported a chemiluminescent biosensor based on the covalent immobilization of the horseradish peroxidase (HRP) enzyme on a polydimethylsiloxane (PDMS) support to quantify in situ hydrogen peroxide (H2O2). The chemiluminescent reaction based on the use of luminol as an oxidizable substrate, with HRP as the catalyst, has been used in order to quantify H2O2 as the oxidizing agent. The performance of the proposed biosensor has been demonstrated to determine H2O2 liberated by cells in a culture medium and for evaluating the delivery of H2O2 from denture cleaner tablets, as examples of application. For both analyses, the results indicated that the biosensor is cost-effective, sensitive, and selective with a detection limit of 0.02 μM and good linearity over the range 0.06–10 μM. Precision was also satisfactory (relative standard deviation, % RSD < 6). The strength of this biosensing system is the simplicity, portability, and reusability of the devices; it can be applied up to 60 times with 90% of its activity maintained.