Sensitive Chemiluminescence Determination of Three Thiol Compounds Based on Cu(II)-Catalyzing Luminol Reaction in the Absence of an Oxidant

Abstract

A simple and sensitive flow-injection chemiluminescence method was proposed for the determination of three thiol compounds, namely cysteine, acetylcysteine, and glutathione. Weak chemiluminescence was produced directly by the reaction of these mentioned compounds with luminol in an alkaline solution without adding any special oxidants. The chemiluminescence signal could be significantly enhanced by Cu(II). The proposed method allows the determination of 4.0 × 10^?9 to 1.0 × 10^?7 g/mL cysteine, 7.0 × 10^?10 to 1.0 × 10^?7 g/mL acetylcysteine, and 4.0 × 10^?9 to 1.0 × 10^?6 g/mL glutathione with the detection limits of 8 × 10^?10 g/mL, 2 × 10^?11 g/mL, and 7 × 10^?10 g/mL, respectively. The proposed method was applied to the analysis of some commercial formulations containing acetylcysteine.     

Study on a Fluorometric Method for the Determination of Protein in Serum Using Quercetin‐Lanthanum (III)‐Sodium Dodecyl Benzene Sulfonate‐Protein System

Abstract

It was found that the fluorescence intensity of lanthanum (III) (La³⁺)‐quercetin (Qu) complex is greatly enhanced by proteins in the presence of sodium dodecyl benzene sulfonate (SDBS). Based on this finding, a new fluorimetric method for the determination of proteins was developed. Under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins in the range of 2.5×10^?8 to 1.0×10^?5 g/mL for bovine serum albumin (BSA), 5.0×10^?8 to 1.5×10^?5 g/mL for human serum albumin (HSA), and 1.0×10^?7 to 1.5×10^?5 g/mL for egg albumin (EA). Their detection limits (S/N=3) are 5.0×10^?9 g/mL, 7.0×10^?9 g/mL, and 2.1×10^?8 g/mL, respectively. The interaction mechanism was also studied.     

A study of the extraction of plutonium from planchets by Aridus–ICP–SFMS

Two extraction processes of plutonium (Pu) on planchets from alpha spectrometry (AS) have been evaluated by inductively coupled plasma sector field mass spectrometry with a desolvator system (Aridus–ICP–SFMS). The samples were traced with known concentrations of ²³⁹Pu (1.2 × 10³ fg) and ²⁴²Pu (2 × 10³ fg) followed by an electrodeposition in planchets, according to the Hallstadius method. The processes of extraction were carried out with 50 mL of 0.36 mol L^?1 HNO₃ every 30 min up to 180 min in a glass beaker at 60 °C. The first process was on a hotplate and the second used an ultrasonic system. Finally, samples were evaporated to dryness, and resuspended in 10 mL of 0.72 mol L^?1 HNO₃ for evaluation. The results showed that at 120 min, a ~70 % recovery of ²³⁹Pu and a ~80 % recovery of ²⁴²Pu in both processes were obtained. The average recoveries of ²³⁹Pu and ²⁴²Pu at 180 min using the hotplate in plate were 93.4 ± 4.6 and 93.7 ± 4.2 % respectively, and with the ultrasonic system were 96.0 ± 4.3 and 98.2 ± 1.0 % respectively. In conclusion, both processes are suitable for Pu extraction, and Aridus–ICP–SFMS is an essential technique for the reassessments and quantification of Pu. In addition, procedural blanks spiked with 1 × 10² fg mL^?1 U were prepared for each process, in order to study the contribution of the ²³⁸U on the background signal at m/z = 239, which was 0.5 ± 0.2 cps, indicating that the contribution of ²³⁸U on the ²³⁹Pu signal was negligible. Furthermore, this methodology can be applied to sample planchets with environmental, food, biological and nuclear origin, and thereby to avoid repetitive analysis when Pu concentration determined by AS are under minimum detectable activities.     

A sensitive immunosorbent bio-barcode assay based on real-time immuno-PCR for detecting 3,4,3',4'-tetrachlorobiphenyl

A functionalized gold-nanoparticle bio-barcode assay, based on real-time immuno-PCR (IPCR), was designed for the determination of 3,4,3',4'-tetrachlorobiphenyl (PCB77). 15 nm gold nanoparticles were synthesized, and modified with thiol-capped DNA and goat anti-rabbit IgG. The nanoparticle probes were used to replace antibody–DNA conjugate in the IPCR, and were fixed on the PCR tube wall via the immune reaction. Real-time PCR was performed to quantify the DNA signal directly. Under optimized conditions, the new method was used to detect PCB77 with a linearity range from 5 pg L^?1 to 10 ng L^?1, and the limit of detection (LOD) was 1.72 pg L^?1. Real samples of Larimichthys polyactis, collected from the East China Sea, were analyzed. Recovery was from 82 % to 112 %, and the coefficient of variation (CV) was acceptable. The results were compared with GC–ECD, revealing that the method would be acceptable for providing rapid, semi-quantitative, and reliable test results for making environmental decisions.

Flow Injection Post-Chemiluminescence Reaction of Astemizole in N-Bromosuccinimide-Calcein System and Its Application

A flow injection post chemiluminescence (FI-PCL) reaction was found when astemizole was mixed with the CL reaction mixture of N-bromosuccinimide and calcein under alkaline conditions. Based on this observation, a simple and sensitive post chemiluminescence (PCL) technique for the assay of astemizole was described. Under the optimized conditions, the PCL values responded linearly to the concentration of astemizole in the range 1.0 × 10^?3–3.0 µg/mL, with a detection limit of 7.0 × 10^?4 µg/mL. The relative standard deviation was 1.7% for 1.0 × 10^?2 µg/mL astemizole solution (n = 13). It was applied to the determination of astemizole in pharmaceutical preparations with satisfactory results.     

Electrochemical Detection of 2,4,6-Trinitrotoluene Using Interdigitated Array Electrodes

Abstract

We describe the use of interdigitated array gold electrodes (IDAs) for the electrochemical detection of 2,4,6-trinitrotoluene (TNT). Our protocol generates a reversible redox couple (hydroxylamine/nitroso) from the initial reduction of TNT, which can be amplified using redox cycling at IDA electrodes. The IDA electrodes give a limit of detection for TNT at ～6 ng/mL with a linear response (r² = 0.998) between 10 and 10,000 ng/mL for static conditions and between 5 and 200 ng/mL for flow conditions (r² = 0.999).     

Fast and parallel determination of PCB 77 and PCB 180 in plasma using ultra performance liquid chromatography with diode array detection: A pharmacokinetic study in Swiss albino mouse

A simple, sensitive and reproducible ultra‐performance liquid chromatography (UPLC) method has been developed and validated for simultaneous estimation of polychlorinated biphenyl (PCB) 77 and PCB 180 in mouse plasma. The sample preparation was performed by simple liquid–liquid extraction technique. The analytes were chromatographed on a Waters Acquity H class UPLC system using isocratic mobile phase conditions at a flow rate of 0.3 mL/min and Acquity UPLC BEH shield RP₁₈ column maintained at 35°C. Quantification was performed on a photodiode array detector set at 215 nm and PCB 101 was used as internal standard (IS). PCB 77, PCB 180, and IS retention times were 2.6, 4.7 and 2.8 min, respectively, and the total run time was 6 min. The method was validated for specificity, selectivity, recovery, linearity, accuracy, precision and sample stability. The calibration curve was linear over the concentration range 10–3000 ng/mL for PCB 77 and PCB 180. Intra‐ and inter‐day precisions for PCBs 77 and 180 were found to be good with CV <4.64%, and the accuracy ranged from 98.90 to 102.33% in mouse plasma. The validated UPLC method was successfully applied to the pharmacokinetic study of PCBs 77 and 180 in mouse plasma.     

Validation of an HPLC Analytical Method for Determination of Pancuronium Bromide in Pharmaceutical Injections

Abstract

Pancuronium bromide is used with general anesthesia in surgery for muscle relaxation and as an aid to intubation. A high performance liquid chromatographic method was fully validated for the quantitative determination of pancuronium bromide in pharmaceutical injectable solutions. The analytical method was performed on an amino column (Luna® 150 mm × 4.6 mm, 5 µm). The mobile phase was composed of acetonitrile:water containing 50 mmol L^?1 of 1-octane sulfonic acid sodium salt (20:80 v/v) with a flow rate of 1.0 mL min^?1 and ultraviolet (UV) detection at 210 nm. The proposed analytical method was compared with that described in the British Pharmacopoeia.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Chitosan Based Diamond Paste Stochastic Microsensors Modified with Gold Nanoparticles Detect Hepatitis C Virus Core Antigen

Three types of chitosan (chitosan I (n=371–744), chitosan II (n=682–930), and chitosan III (n=868–1365)) as well as gold nanoparticles (10 nm diameter) were used to modify diamond paste for the design of new stochastic microsensors. Hepatitis C virus core antigen was used as model analyte to prove the stochastic behavior of the proposed microsensors. The microsensors cover a linear range of concentration between 40 fg/mL and 4 ng/mL. The highest sensitivity (1.38×10⁵ s^?1/mg/mL) and the lower limit of determination (40 fg/mL) were obtained for chitosan III based microsensor. The hepatitis C virus core antigen was assayed from whole blood samples with recoveries higher than 98.00 %.     

New chemical constituents from the Piper betle Linn. (Piperaceae)

The phytochemical investigation of chloroform extract from Piper betle var. haldia, Piperaceae, leaves has resulted in the isolation of two new chemical constituents which were identified as 1-n-dodecanyloxy resorcinol (H1) and desmethylenesqualenyl deoxy-cepharadione-A (H4), on the basis of spectroscopic data 1D NMR (¹H and ¹³C) and 2D NMR (¹H-¹H COSY and HMBC) as well as ESI-MS, FT-IR and HR-ESI-MS analyses. Compounds H1 and H4 showed excellent antioxidant DPPH free radical scavenging activity with IC₅₀ values of 7.14 μg/mL and 8.08 μg/mL compared to ascorbic acid as a standard antioxidant drug with IC₅₀ value of 2.52 μg/mL, respectively. Evaluation of cytotoxic activity against human hepatoma cell line (PLC-PRF-5) showed moderate effect with the GI₅₀ values of 35.12 μg/mL for H1, 31.01 μg/mL for H4, compared to Doxorubicin^® as a standard cytotoxic drug with GI₅₀ value of 18.80 μg/mL.     

Automated Method for the Total Creatinine Determination in Dehydrated Broths

Abstract

In order to improve the quality control of dehydrated broth, a new automated method was developed to determine total creatinine in dehydrated broths. The sample pretreatment was coupled on‐line with the Flow Injection Analysis (FIA) system for analyte determination by the classical Jaffé reaction, stopped flow methodology, and spectrophotometric detection. The time consumed was reduced from 7 h, which is necessary with the official method, to 25 min. The calibration graph is linear between 0.342–1.368 mg creatinine/100 mL. The relative standard deviation (RSD%) was 1.7%, the sample throughput was 7 h^?1, and the detection limit was 0.185 mg creatinine/100 mL. The validation of the proposed method was carried out with real samples. The obtained results were compared with those obtained from the Association of Official Analytical Chemists (AOAC) reference method.     

Oligonucleotide microarray chip for the quantification of MS2, ΦX174, and adenoviruses on the multiplex analysis platform MCR 3

Pathogenic viruses are emerging contaminants in water which should be analyzed for water safety to preserve public health. A strategy was developed to quantify RNA and DNA viruses in parallel on chemiluminescence flow-through oligonucleotide microarrays. In order to show the proof of principle, bacteriophage MS2, ΦX174, and the human pathogenic adenovirus type 2 (hAdV2) were analyzed in spiked tap water samples on the analysis platform MCR 3. The chemiluminescence microarray imaging unit was equipped with a Peltier heater for a controlled heating of the flow cell. The efficiency and selectivity of DNA hybridization could be increased resulting in higher signal intensities and lower cross-reactivities of polymerase chain reaction (PCR) products from other viruses. The total analysis time for DNA/RNA extraction, cDNA synthesis for RNA viruses, polymerase chain reaction, single-strand separation, and oligonucleotide microarray analysis was performed in 4–4.5 h. The parallel quantification was possible in a concentration range of 9.6?×?10⁵–1.4?×?10¹⁰ genomic units (GU)/mL for bacteriophage MS2, 1.4?×?10⁵–3.7?×?10⁸ GU/mL for bacteriophage ΦX174, and 6.5?×?10³–1.2?×?10⁵ for hAdV2, respectively, by using a measuring temperature of 40 °C. Detection limits could be calculated to 6.6?×?10⁵ GU/mL for MS2, 5.3?×?10³ GU/mL for ΦX174, and 1.5?×?10² GU/mL for hAdV2, respectively. Real samples of surface water and treated wastewater were tested. Generally, found concentrations of hAdV2, bacteriophage MS2, and ΦX174 were at the detection limit. Nevertheless, bacteriophages could be identified with similar results by means of quantitative PCR and oligonucleotide microarray analysis on the MCR 3.     

Rapid and sensitive determination of radiocesium (Cs-135, Cs-137) in the presence of excess barium by electrothermal vaporization-inductively coupled plasma-mass spectrometry (ETV-ICP-MS) with potassium thiocyanate as modifier

An electrothermal vaporization-inductively coupled plasma-mass spectrometric (ETV-ICP-MS) method based on selective volatilization of cesium with KSCN as modifier has been developed for determination of radiocesium, i.e. ¹³⁵Cs and ¹³⁷Cs, in the presence of isobaric barium. A 10000 times excess of barium, which was volatilized at a temperature of 1100?°C, resulted only in a 1% signal increase in the signal of mass 135 amu. The recommended concentration of KSCN is 0.3 mM, and pretreatment and volatilization temperatures are 400?°C and 1100?°C, respectively. A ramp time of 1 s is recommeded for the volatilization step. The achieved limit of detection for ¹³⁵Cs is 0.2 pg/mL (10 μBq/mL) and 4 fg (0.2 μBq) absolute for a sample volume of 20 μL. This means a limit of detection for ¹³⁷Cs of 0.2 pg/mL (0.6 Bq/mL) and of 4 fg (0.01 Bq) absolute. Signal variations of ¹³⁵Cs and ¹³⁷Cs, respectively, in spiked samples with various matrices were investigated.     

P‐Dimethyl Amino Benzaldehyde as a New Chromogenic Reagent for the Determination of Nonsteroidal Anti‐Inflammatory Drug by First‐Order Derivative Spectrophotometry

Abstract

Mefenamic acid reacts with P‐dimethylamino benzaldehyde to give a bluish‐green complex in acidic media after heating for 90 s at 90°C, having maximum absorbance at 597.5 nm. The reaction is selective for mefenamic acid with 0.02 mg/10 mL as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The reaction obeys Beer's Law from 0.02 mg to 2.5 mg/10 mL of mefenamic acid and the relative standard deviation is 0.50%. The quantitative assessment of tolerable amounts of other drugs not interfering has also been studied. First‐order derivative spectrophotometric procedure was applied for the determination of mefenamic acid in pharmaceutical preparations.     

Determination of Three Imidazole Derivatives by Flow-Injection Chemiluminescence

Abstract

A rapid, simple, and sensitive method was developed for the determination of three imidazole derivatives based on their quenching effect on bis(2,4,6-tricholorophenyl) oxalate (TCPO)–H₂O₂ chemiluminescence (CL) in the presence of rhodamine 6 G. Conditions affecting CL intensity were studied. With sodium dodecyl sulfate (SDS) as the additional agent, the relative standard deviation (RSD) was more twice the RSD without SDS. Under optimal conditions, good linear ranges were obtained from 1.0 × 10^?4 g/mL to 1.0 × 10^?6 g/mL, 1.0 × 10^?5 g/mL to 1.0 × 10^?7 g/mL, and 1.0 × 10^?5 g/mL to 7.0 × 10^?7 g/mL, with detection limits of 8.0 × 10^?7 g/mL, 7.0 × 10^?8 g/mL, and 8.0 × 10^?8 g/mL (S/N = 3) for hydrobenzole hydrochloride, thiamazole, and mizolastine, respectively. The RSDs for 13 consecutive injections of 1.0 × 10^?6 g/mL hydrobenzole hydrochloride, thiamazole, and mizolastine were 1.89%, 1.47%, and 1.69%, respectively, and satisfied results were obtained with the method applied to their pharmaceutical preparations. The possible CL mechanism was simply discussed.     

Determination of Hg(II) in Environmental Water Samples Using DLLME Method Prior to GC-FID

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL^?1. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL^?1. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.     

A Novel Fiber with Phenyl-Functionalized MSU (Michigan State University) Coating for Solid-Phase Microextraction Combined with High Performance Liquid Chromatography for Preconcentration and Determination of Trace Polychlorinated Biphenyls in Environmental Water Samples

A novel and robust phenyl-functionalized MSU-1 (Ph-MSU) coated fiber for solid-phase microextraction (SPME) coupled to high performance liquid chromatography (HPLC) was developed for the preconcentration and the determination of 2,4,4′-trichlorobiphenyl (PCB 28), 2,4′,5-trichlorobiphenyl (PCB 31), 2,2′,5,5′-tetrachlorobiphenyl (PCB 52), 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101), 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118), 2,2′,3,4,4′,5′-hexachlorobiphenyl (PCB 138), 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153), and 2,2′,3,4,4′,5,5′-heptachlorobiphenyl (PCB 180) in environmental water samples. Experimental conditions affecting SPME were examined in detail. The Ph-MSU coating provided large porosity and short-range mesostructures necessary for high extraction capacity and rapid mass transfer of PCBs. The Ph-MSU coated fiber exhibited selectivity for PCB 28, PCB 31, PCB 118, and PCB 138 in a limited extraction time. Good linearity for all PCBs was obtained with correlation coefficients from 0.9987 to 0.9994. The recoveries were within 94.3% to 103% for the spiked water with 300 ng · L^?1 per PCB. The relative standard deviations (RSDs) ranged from 3.10% to 6.23% and the limits of detection (LODs) were between 8.73 ng · L^?1 and 13.8 ng · L^?1. The proposed method was applied for the determination of PCBs in real river water and rainwater samples. The median recoveries ranged from 85.6% to 118% with RSDs between 4.23% and 8.78%. The experimental results demonstrated that the Ph-MSU fiber coating could be reused for over 250 times without loss of the extraction efficiency. These results clearly indicate that the Ph-MSU coated fiber was rapid, sensitive, and suitable for the preconcentration and determination of trace PCBs in environmental water samples.     

Determination of Rizatriptan in Human Plasma by Liquid Chromatography Stable Isotope Dilution Electrospray MS�CMS for Application in Bioequivalence Study

A simple, sensitive, selective, rapid, rugged, reproducible and specific liquid chromatography?Ctandem mass spectrometry (LC?CMS/MS) method was used for quantitative estimation of rizatriptan (RZ) in human plasma using rizatriptan-d ₆ (RZD6) as internal standard (IS). Chromatographic separation was performed on Ascentis Express RP Amide C18, 50 × 4.6 mm, 2.7 ??m column with isocratic mobile phase composed of 10 mM ammonium formate:acetonitrile (20:80 v/v) at flow rate of 0.5 mL min^?1. RZ and RZD6 were detected with proton adducts at m/z (amu) 270.2 ?? 201.2 and 276.1 ?? 207.1, respectively, in multiple reaction monitoring (MRM) positive mode. Liquid?Cliquid extraction was used and validated over a linear concentration range of 0.1?C100.0 ng mL^?1 with correlation coefficient r ² ?? 0.9981. The limit of quantification (LOQ) and limit of detection (LOD) were found to be 0.1 ng mL^?1 and 12.5 fg, respectively. Intra- and inter-day precision were within 1.7?C3.1% and 2.8?C3.7%, and accuracy within 96.0?C101.7% and 99.7?C101.4% for RZ. Drug was found to be stable throughout three freeze?Cthaw cycles. The method was successfully employed for analysis of plasma samples following oral administration of RZ (10 mg) in 25 healthy Indian male human volunteers under fasting conditions.     

Novel Sorbent Extraction Technique Using a Chelating Agent Impregnated Porous PTFE Filter Tube: Preconcentration of Rare Earth Elements (REEs) with Bis(2‐Ethyl‐Hexyl)Hydrogen Phosphate (HDEHP) Loaded Porous PTFE Filter Tube Prior to Determination by ICP‐MS

Abstract

Sorbent extraction and elution of rare earth elements (REEs) by using bis(2‐ethyl‐hexyl)hydrogen phosphate (HDEHP) impregnated porous PTFE filter tube were studied. A 100 ng amount of each REEs was quantitatively extracted by filtering 1000 mL of matrix‐free solution under pH 2.0–3.2. For a synthetic seawater sample, extractability of lighter REEs (La–Sm) was lowered; optimum pH range to simultaneously extract all REEs was shifted to 2.9–3.2, and limit of sample volume for quantitative extraction was decreased to 100 mL for La–Sm [although heavier REEs (Eu–Lu) were quantitatively extracted from 1000 mL]. Extracted REEs were quantitatively eluted by filtering through 5 mL of 10 mol/L^?1 hydrochloric acid to the tube. Hence, maximum preconcentration factors were of 200‐ and 20‐fold for Nd–Lu and La–Sm, respectively. Total recovery of 0.5–10 ng of REEs spiked to 300 mL of natural sea salt solution was tested; quantitative recovery (95.9% for Gd–102% for Eu) were obtained for all REEs except La (54.9%). The REEs in the natural sea salt solution were also determined by ICP‐MS after preconcentration with the present method [RSD=16% (La)–1.1% (Yb), n=3].