CL Reagent Research Articles

MONO-THIOCYANATO MERCURY (II) CHLORIDE: A NOVEL REAGENT FOR SPECTROPHOTOMETRIC DETERMINATION OF CHLORIDE IN BEERS

The mono-thiocyanato mercuric (II) chloride [Hg(SCN)Cl] reagent was prepared synthetically and implemented for spectrophotometric determination of chloride in beers. In determining chloride, a known aliquot of beer sample was added into Hg(SCN)Cl reagent. The displaced thiocyanate ions were subsequently used to form the red-colored ferric-thiocyanate complex. The absorbance of which was measured at 455-nm was found directly proportional to the concentration of chloride in the beer sample. The experiment was performed by the standard addition method using beer sample and reagent at a time, and further various amount of known chloride was added during the measurement of absorbance. The analysis results show an average standard deviation of 0.02513. The output of this study provides evidence that, the Hg(SCN)2 reagent does not obey Beer’s law, whereas an excellent linearity of absorbance versus concentration of chloride was observed with the ratio of the concentration of Hg(SCN)Cl to chloride is less than 6.66.

A chemiluminescence reagent free method for the determination of captopril in medicine and urine samples by using trivalent silver

A novel flow-injection chemiluminescence (FI-CL) method free of CL reagent was developed for the determination of captopril based on its enhancing effect on the CL derived from diperiodatoargentate(III)-sulfuric acid system. Compared with the conventional CL system, the CL system based on trivalent silver was characterized of good selectivity for the absence of CL reagent. The CL mechanism was discussed through CL spectra and UV–vis absorption spectra. The conditions of the FI-CL system were investigated and optimized. Under the optimal conditions, the relative CL intensity was linear with the captopril concentration in the range of 0.3–15.0μg/mL. The detection limit for captopril was 0.05μg/mL, and the relative standard deviation (n=11) was 2.0% for 5.0μg/mL captopril. The proposed method was applied to the analysis of captopril in tablet and human urine with the recoveries of 83.1%–112.5%, and the relative standard deviations of 0.5%–4.4%. The results obtained by the proposed method agreed well with those obtained from HPLC method. The proposed method is fast, convenient, and cost-effective for the determination of captopril in medicine and biological samples.

Flow injection chemiluminescence determination of lercanidipine based on N‐chlorosuccinimide–eosin Y post‐chemiluminescence reaction

A novel post-chemiluminescence (PCL) reaction was discovered when lercanidipine was injected into the CL reaction mixture of N-chlorosuccinimide with alkaline eosin Y in the presence of cetyltrimethylammonium bromide (CTAB), where eosin Y was used as the CL reagent and CTAB as the surfactant. Based on this observation, a simple and highly sensitive PCL method combined with a flow injection (FI) technique was developed for the assay of lercanidipine. Under optimum conditions, the CL signal was linearly related to the concentration of lercanidipine in the range 7.0 × 10(-10) to 3.0 × 10(-6) g/mL with a detection limit of 2.3 × 10(-10) g/mL (3σ). The relative standard deviation (RSD) was 2.1% for 1.0 × 10(-8) g/mL lercanidipine (n = 13). The proposed method had been applied to the estimation of lercanidipine in tablets and human serum samples with satisfactory results. The possible CL mechanism is also discussed briefly.

Improving the selectivity of non-polar alkanes, alkenes, and aromatic hydrocarbon compounds by the application of acetonitrile as a Cl reagent

Abstract The selective enhancement of membrane introduction mass spectrometry for non-polar alkanes, alkenes, and aromatic hydrocarbon compounds by the application of acetonitrile as a chemical ionization reagent was investigated. Acetonitrile Cl is able to produce specific fragment ions for many of the compounds test and this can be used to identify and quantify the parent neutrals. This method provided relatively high detection limits of the test compounds. This method could potentially be useful for analytical applications such as the detection of non-polar hydrocarbons for environmental studies if CH3CN Cl/MIMS is coupled with a preconcentration method.

A simple microfluidic chlorine gas sensor based on gas–liquid chemiluminescence of luminol-chlorine system

In this work, a microfluidic chlorine gas sensor based on gas–liquid interface absorption and chemiluminescence detection was described. The liquid chemiluminescence reagent-alkaline luminol solution can be stably sandwiched between two convex halves of a microchannel by surface tension. When chlorine gas was introduced into the micro device, it was dissolved into the interfacial luminol solution and transferred to ClO −, and simultaneously luminol was excited and chemiluminescence emitted. The emitted chemiluminescence light was perpendicularly detected by a photomultiplier tube on a certain detection region. The remarkable advantage of the detection system is that both adsorption and detection were carried out at the gas–liquid interface , which avoids the appearance of bubbles. The whole analytical cycle including filling CL reagent, sample injection, CL detection and emptying the device was as short as 30 s. The linear concentration range of chlorine gas detection with direct introduction of sample method is from 0.5 to 478 ppm. The detection limit of this method is 0.2 ppm for standard chlorine gas and the relative standard deviation of five determinations of 3.19 ppm spiked chlorine sample was 5.2%.

Ion-trap tandem mass spectrometric analysis of squalene monohydroperoxide isomers in sunlight-exposed human skin

We previously discovered that squalene monohydroperoxide (SQ-OOH) was produced on human forehead skin and suggested that skin squalene (SQ) may be the principal target lipid for oxidative stress (e.g., sunlight exposure). Because of its six double bonds, SQ peroxidation can yield various positional hydroperoxide isomers. However, the structural characterization of skin SQ-OOH isomers has never been reported. Here, we prepared pure SQ-OOH isomers and developed an analytical method for SQ-OOH isomers using a quadrupole/linear ion-trap mass spectrometer (QTRAP) MS/MS system. Collision-induced dissociation produced specific fragment ions for each SQ-OOH isomer, which permitted discrimination between SQ-OOH isomers by multiple reaction monitoring (MRM). When lipid extract from human forehead skin was subjected to LC-MS/MS with MRM, individual SQ-OOH isomers could be separated and detected with a sensitivity of 0.05 ng/injection. The total concentration of SQ-OOH isomers in forehead skin was approximately 956 microg/g skin lipids, but it increased up to 2,760 microg/g skin lipids after 3 h of sunlight exposure. The LC-MS/MS method was useful for investigating the peroxidation mechanisms of SQ as well as SQ-OOH-mediated skin disorders.

Determination of aromatic compounds by high‐performance liquid chromatography with on‐line photoreactor and peroxyoxalate chemiluminescence detection

This paper describes a novel high-performance liquid chromatographic (HPLC) method for the determination of aromatic compounds with peroxyoxalate chemiluminescence (PO-CL ) detection following on-line UV irradiation. Aromatic compounds were UV irradiated (254 nm, 15 W) to generate hydrogen peroxide, which was determined via PO-CL detection using a mixture of bis(2,4,6-trichlorophenyl)oxalate (aryloxalate) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (fluorophore) as a post-column CL reagent. Generation of hydrogen peroxide from aromatic compounds was confirmed using a flow injection analysis (FIA) system incorporating an enzyme column reactor immobilized with catalase. The conditions for UV irradiation were optimized using benzene and monosubstituted benzenes (phenol, benzaldehyde, nitrobenzene and N,N-dimethylaniline) by an HPLC system to evaluate the analytical performance of the proposed system. The detection limits for benzene and monosubstituted benzenes were in the range 2.1-124 pmol/injection at signal:noise (S:N) ratio = 3. Monocyclic and polycyclic hydrocarbons were also employed to investigate their CL properties. The possibility of PO-CL detection for a wide variety of aromatic compounds was shown for the first time.

Preparation of inorganic–organic pillared montmorillonite using ultrasonic treatment

Montmorillonite (Mt) is a clay mineral with expandable layer structure. Mesoporous pillared montmorillonite can be prepared by introducing gallery templates, such as simple metal cations, quaternary ammonium cations, long chain amines, and hydroxyed inorganic metal ions. In this paper, inorganic–organic pillared montmorillonite intercalated by aluminium and alkyl ammonium chloridize (HDTMA–Cl) was successfully prepared by ultrasonic treatment, and the physicochemical properties of the materials were systematically characterized by XRD, FT-IR, SEM and TEM techniques. The d001 basal spacings and microstructures of Mt–Al–HDTMA were characterized by XRD. The function group, crystal surface morphology, structural and chemical analysis of Mt–Al–HDTMA were measured by FT-IR, SEM, TEM and EDX. The results indicated that ultrasonic method might accelerate the diffusion of the intercalating species, which enhanced the textural properties and the morphologies. The results also suggested that aluminium and HDTMA–Cl reagent entered the interlayer of Mt, and that the crystal structure of the final Mt was preserved.

A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence detection and column switching for determination of MDMA-related compounds in hair

A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence (POCL) detection and column switching has been developed for simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA) and related compounds, for example 3,4-methylenedioxyamphetamine, methamphetamine, and amphetamine, in hair. After digestion of the hair with 1 mol L-1 sodium hydroxide the compounds were extracted with n-heptane and derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. A mixture of hydrogen peroxide and bis(2,4,5-trichloro-6-carbopentoxyphenyl)oxalate in acetonitrile was used as post-column CL reagent. Calibration plots showed linearity was good (r=0.999); detection limits were 0.02-0.16 ng mg-1 hair at a signal-to-noise ratio of 3. The precision of the method, as RSD (n=5), in intra-day and inter-day assays was better than 5.0 and 6.9%, respectively. The proposed method was sufficiently sensitive to detect low ng mg-1 levels of MDMA and related compounds in hair, and could be used for quantification of the compounds in hair samples from patients treated in a chemical dependency unit.

Density functional studies on the reagents Me 3PX 2 (where X=F, Cl, Br and I) in the gas phase and in solution

We report density functional studies at the B3LYP level of theory (with 6-311++g(3d,2p) or DGDZVP basis sets as appropriate) for the title reagents. We located three minima for each X (two for X=F). These correspond to an ion pair (IP), a trigonal structure (TR) and a spoke-shaped charge transfer complex (CT). In the gas phase the trigonal structure is the most stable for X=F, Cl and Br. The CT complex is the most stable for X=I. Our calculations suggest that there is no stable gas-phase CT complex for X=F. For comparison, we also record results for Me 3P +⋯X − (with the ions at infinity). The solvents cyclohexane, dichloromethane and water were modelled using the polarised continuum model. The trigonal structure is the most stable for X=F, whatever the solvent, just as the CT complex is the most stable for X=I whatever the solvent. The X=Cl and Br reagents show intermediate behaviour, depending on the nature of the solvent. Their behaviour is in accord with the common wisdom that polar solvents favour the more ionic species. We suggest that there is no stable CT complex for X=F whatever the solvent, and we agree with the experimental finding that the X=Cl reagent is ionic in dichloromethane, with the possibility that a covalent complex (TR) might also be observed at room temperature.

Characterization of a micro spiral flow cell for chemiluminescence detection

A 5.5 μl spiral micro-flow cell, mounted in front of a photomultiplier, is made from Teflon capillary (75 cm×100 μm ID) with two inlets for the CL reagent and carrier buffer and a waste outlet. It allows the rapid mixing of CL reagent and analyte and simultaneous detection of the emitted light. Using a flow rate of 25 μl/min for a 0.4 mM luminol-8 μM hemin solution (pH 11.6) and 50 μl/min of carrier buffer (pH 11.6), the slight exponential calibration curve for the flow injection–chemiluminescence (FI–CL) determination of H 2O 2 is 2.5–10 μM and the detection limit is 1.5 μM. The detection limit achieved by using a spiral flow cell is 24 times lower than that obtained from a conventional FI system with a low dead volume tee mixer and a 12 μl flow cell in a HPLC fluorometer with the source lamp off. This luminol CL detection method is successfully applied to the enzymatic determination of l-lactate by FI. The lactate sample is mixed with polyethylene glycol (PEG)-stabilized lactate oxidase (LO) enzyme and then injected into the buffered (pH 7.5) carrier stream for CL detection of the H 2O 2 product. Using the optimal conditions of reaction temperature set to 37.5 °C and flow rates of 45 μl/min for the CL reagent and 60 μl/min for the carrier buffer, the calibration range for lactate is 5–50 μM and the detection limit is 2.9 μM. This method is applied to the determination of l-lactate in beer.

ChemInform Abstract: Oxidation Deprotection of Trimethylsilyl Ethers to Carbonyl Compounds by NaBrO3—NH4Cl Reagent in Aqueous Acetonitrile.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sensitive and selective determination of aluminium by peroxyoxalate chemiluminescence detection of the lumogallion complex

For the first time, the feasibility of employing the reaction of bis(2,4,6-trichlorophenyl) oxalate with hydrogen peroxide, i.e. peroxyoxalate chemiluminescence (PO-CL) reaction, for the determination of Al via chemical excitation of the Al-lumogallion complex is demonstrated. Experimental factors that affect the CL signal, such as pH, solvent and buffer compositions, and CL reagent concentrations were investigated. When compared to the use of fluorescence (FL) for the detection of the Al-lumogallion complex or the use of PO-CL reaction for the detection of the Al-8-hydroxyquinoline complex, the use of PO-CL reaction for the detection of the Al-lumogallion complex was found to exhibit higher tolerance towards interferences from a variety of inorganic and organic matrix species. For example, in CL detection, the tolerance limits (defined as the concentration ratio of the matrix ion to Al giving rise to a change in the peak height of the CL or FL signal of the Al working solution by a magnitude of 3% as a certain amount of a matrix species is added) for Fe 3+, Fe 2+ and citrate ions using lumogallion as the chelating agent for the determination of Al were 25, 14 and 170, respectively, whereas in FL detection, the corresponding tolerance limits were 1, 0.1 and 2, respectively. Under optimized conditions, the limit of detection for Al was ca. 0.042 μg l −1 (3 σ) and the calibration plot from 0.582 to 533 μg l −1 was linear ( r=0.999). The applicability of the present CL method was demonstrated for the sensitive and selective determination of trace Al present in natural water samples. The recoveries of Al were found to fall in the range between 90.4 and 109.7% and the average precision was 4.7%.

Exploring the spin–orbit reactivity in the simplest chlorine atom reaction

The reaction of Cl(2P)+H2→HCl+H serves as a benchmark for understanding the abstraction mechanism and has been the subject of numerous experimental and theoretical studies. Despite such intensive investigations, the reactivity of the low-lying spin–orbit excited Cl*(2P1/2) is unknown and has always been assumed to be negligibly small. By exploiting two different sources for generating the Cl(2P) beam, it is now found that the excited Cl*(2P1/2) atom is surprisingly more reactive to H2 than the ground state Cl(2P3/2) reagent, overturning conventional wisdom. By using a technique called Doppler-selected time of flight to directly map out the doubly differential cross sections (angle and speed), the detailed dynamical attributes for both spin–orbit states are also elucidated and contrasted for the first time for any bimolecular reaction.

Determination of dexamethasone in bovine liver by chemiluminescence high-performance liquid chromatography.

A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).

ChemInform Abstract: Oxidation of Benzylic and Secondary Alcohols to Carbonyl Compounds by NaBrO3—NH4Cl Reagent in Aqueous Acetonitrile.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Product State Resolved Study of the Cl + (CH3)3CD Reaction: Comparison of the Dynamics of Abstraction of Primary versus Tertiary Hydrogens

The reaction of Cl atoms with the selectively deuterated isobutane, 2-methylpropane-2-d1, has been investigated under single-collision conditions using state-selective detection of the products by resonance-enhanced multiphoton ionization (REMPI) in a time-of-flight mass spectrometer. The reaction was initiated in a crossed, pulsed flow of the reagents by 355 nm photolysis of Cl2 precursor. The internal state distributions of HCl and DCl products, formed by abstraction of primary and tertiary hydrogen atoms, respectively, from the hydrocarbon reagent are reported. The degree of rotational excitation of both products was found to be very low. By comparison of the intensities of the HCl and DCl REMPI signals, the ratio of the yield of HCl to DCl product was found to be 3.3 ± 0.4. With the known speed and angular distribution of the Cl reagent, it was possible to obtain information on the product center-of-mass angular distributions from measurement of the masses 37 and 38 time of arrival profiles. The DCl product is found to be mainly backward scattered with respect to the incoming Cl atom, while the HCl product is sideways peaked. Inferences on the dynamics of the two possible abstraction pathways from these results are discussed.

Effect of additives to the reaction solvents in a peroxyoxalate chemiluminescence detection system for liquid chromatography

A facile means of optimizing solvent compositions and reagent concentrations for the peroxyoxalate chemiluminescence (PO-CL) detection of fluorescent compounds with bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate (TDPO) and hydrogen peroxide in liquid chromatography (LC) was developed. The reaction time course of CL was easily obtained by changing the PTFE tube lengths in the mixing device in the LC flow system in which the column effluent and CL reagent solution flow. The addition of a phthalate ester to the basic solvent mixture for the chemiluminogenic reagents, ethyl acetate-acetonitrile (50 + 50, v/v) containing TDPO and hydrogen peroxide, resulted in a considerable reduction in the baseline noise level without decreasing the signal of a fluorescent compound, dipyridamole. Phthalate esters having branched-chain moieties were more effective, di-2-ethylhexyl phthalate (DOP) being the best in reducing the baseline noise. A mixture of 0.25 mM TDPO and 25 mM hydrogen peroxide in ethyl acetate-acetonitrile-DOP (50 + 49.75 + 0.25, v/v/v) (1.3 ml min −1 as a chemiluminogenic reagent solution for the eluent [acetonitrile-50 mM imidazole nitrate buffer (pH 6.0) (45 + 55, v/v) (1.0 ml min −1)] was optimum for the detection of amol levels of fluorescent compounds. The detection limit for dipyridamole was 10 amol (signal-to-noise ratio = 2). Under the same conditions, the detection limit for dansylated phenylalanine was 800 amol.