Study of Spectral Character of Alkali Metals Using Microwave Plasma Torch Simultaneous Spectrometer

IntroductionIn the past decades, alkali metals were widely ap-plied in many fields, such as applied catalysis[1,2],surface science[3,4], and molecular biology[5]. Micro-wave plasma torch(MPT), developed and improved byYu and coworkers[6,7], is a novel dev…     

Separation and Quantification of Key Starting Materials of Irbesartan Using Liquid Chromatography–Mass Spectrometry as a Separation and Identification Tool

Abstract

A liquid chromatography–mass spectrometry (LC-MS) method was developed and validated for determining the levels of 4-methyl-2-cyano biphenyl and 4-bromomethyl-2-cyano biphenyl, which are key starting materials of an antihypertensive drug substance, irbesartan. An active pharmaceutical ingredient of irbesartan was synthesized by using these two starting materials for its therapeutic use. We have explicated the LC-MS method to separate and quantify these two compounds in irbesartan at nanogram levels. The method was capable of separating irbesartan and its starting materials, which were monitored for their absence in the finished product of irbesartan. The separation was carried out at 40°C on a 150- × 4.6-mm cyano column by using the mobile phase containing 60 volumes of water adjusted to pH 3.2 with formic acid and 40 volumes of acetonitrile. The detection wavelength was 220 nm. The MS involved an electrospray ionization (ESI) probe and ion-trap analyzer and was validated with respect to its specificity, accuracy, and precision.     

Determination of Tetracyclines in Honey Using Liquid Chromatography with Ultraviolet Absorbance Detection and Residue Confirmation by Mass Spectrometry

A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction （SPE）, while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C 18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 μg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% （n= 18）. Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey （2-50 ng/g） was realized by liquid chromatography-tandem mass spectrometry （LC/MS/MS）. The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r〉 0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey.     

Simultaneous Multi-Wavelength UV-Visible Detection for HPLC Using a Diode-Array Spectrophotometer—A Versatile Software Package

Abstract

A BASIC program was developed to monitor absorbance simultaneously at various wavelengths using an HP8451A Diode Array Spectrophotometer linked to a HPLC system and equipped with a flow cell. The program measures a maximum of ten wavelengths and takes a maximum of 240 measurements for each wavelength, using only 16K of memory and a dual disc drive. The program includes the options of replotting using a different ordinate scale and saving the numerical data on disc.     

Determination of Biogenic Amines in Cheese Using Simultaneous Derivatization and Microextraction Method Followed by Gas Chromatography–Mass Spectrometry

Microwave-assisted extraction and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry as a sensitive and efficient method was applied to extract and determine four biogenic amines (BAs) in Iranian Lighvan cheese samples. Carrez solutions were used for the sedimentation of proteins. Effective factors on the performance of microextraction were studied and optimized. The proposed method showed good linear ranges from 5 to 500 ng mL^?1, with the coefficients of determination higher than 0.9929. Average recoveries were between 97 and 103%. Limits of detection for all analyzed BAs ranged from 5.9 to 14.0 ng g^?1, and limits of quantitation ranged between 19.7 and 46.2 ng g^?1. Compared with previous methods, the proposed method is simple, fast, accurate, and precise and gives low detection limits for investigating trace amounts of BAs in Iranian Lighvan cheese samples. The levels of four BAs were determined in five Lighvan cheese samples. Cadaverine was found as prevailing amine in the cheese samples. Putrescine, tyramine, and histamine were present at the second, third, and fourth highest levels, respectively.     

Prediction of Early Atherosclerotic Plaques Using a Sequence-Activated Fluorescence Probe for the Simultaneous Detection of γ-Glutamyl Transpeptidase and Hypobromous Acid

Atherosclerosis is a lipoprotein-driven disease, and there is no effective therapy to reverse atherosclerosis or existing plaques. Therefore, it is urgently necessary to create a noninvasive and reliable approach for early atherosclerosis detection to prevent initial plaque formation. Atherosclerosis is intimately associated with inflammation, which is accompanied by an excess of reactive oxygen species (ROS), leading to cells requiring more glutathione (GSH) to resist severe oxidative stress. Therefore, the GSH-hydrolyzed protein γ-glutamyl transpeptidase (GGT) and the ROS-hypobromous acid (HBrO) are potential biomarkers for predicting atherogenesis. Hence, to avoid false-positive diagnoses caused by a single biomarker, we constructed an ingenious sequence-activated double-locked TP fluorescent probe, C-HBrO-GGT, in which two sequential triggers of GGT and HBrO are meticulously designed to ensure that the probe fluoresces in response to HBrO only after GGT hydrolyzes the probe. By utilization of C-HBrO-GGT, the voltage-gated chloride channel (CLC-1)-HBrO-catalase (CAT)-GGT signaling pathway was confirmed in cellular level. Notably, the forthcoming atherosclerotic plaques were successfully predicted before the plaques could be observed via the naked eye or classical immunofluorescent staining. Collectively, this research proposed a powerful tool to indicate the precise position of mature plaques and provide early warning of atherosclerotic plaques.     

Effective Separation and Simultaneous Quantification of Permethrin Isomers in Household Products by Validated TLC—Densitometric Method

JPC – Journal of Planar Chromatography – Modern TLC - Permethrin is widely used in household pests and insect-controlling products. A sensitive and robust TLC-densitometric method for...     

Simultaneous Determination of Associated α- and Glucoamiuse Using Cross-Linked Amylose

Abstract

The method described consists in the simultaneous determination of the action of the amylolytic preparations containing the associated α- and glucoamylase, upon native amylose (a substrate for both α- and glucoamylase) and upon cross-linked amylose (a substrate for α-amylase). In order to know the percentage of α- and glucoamylase respectively of the total amylolytic activity, the fallowing relations are proposed: %α = 2.31 A_x/A. 100 and % glucoamylase = 100 - %α, where A and A_x are the hydrolytic activity of the amylolytic preparation on nonmodified amylose and on cross-linked amylose respectively, The present method has an error of no more than 11%.     

Thin-Layer Chromatography—Image Analysis Method for the Simultaneous Quantification of Andrographolide and Related Diterpenoids in Andrographis paniculata

JPC – Journal of Planar Chromatography – Modern TLC -     

Structural Characterization of Anhydroicaritin Glycosides Using ESI—FT—ICR Mass Spectrometry

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to determine the structures of anhydroicaritin glycosides by the MS/MS experiments of anhydroicaritin glycosides and their methylated derivatives,With high accuracy FT-ICR-MS provides much information about the structures of compounds ,FT-ICR-MS shows the great potential application in the structural characterization of unknown compounds.     

Fast Quantification of Salivary 8-Hydroxy-2′-deoxyguanosine as DNA Damage Biomarker Using CE with Electrochemical Detection

The aim of this study was to investigate the correlation between levels of a marker of oxidative DNA damage, 8-hydroxy-2′-deoxyguanosine (8-OHdG), in human saliva and urine, and to explore its potential application in fast diagnosis of many diseases (especially cancer) associated with oxidative damage. A simple and time-efficient method, based on capillary electrophoresis with electrochemical detection, was developed for the determination of salivary and urinary 8-OHdG. Under the optimum conditions, 8-OHdG and its coexisting analytes could be well separated within 16 min at a voltage of 14 kV in 60 mmol L^?1 borax running buffer (pH 8.2). A good linear relationship was established between peak current and concentration of analytes over three orders of magnitude with detection limits (S/N = 3) ranging from 0.41 × 10^?7 to 2.50 × 10^?7 mol L^?1 for all analytes.     

Detection of Antibacterial and Antioxidant Compounds in the Essential Oil of Schizonepeta annua (Pall.) Schischk. Using High-Performance Thin-Layer Chromatography—Direct Bioautography and Gas Chromatography—Quadrupole Time-of-Flight Mass Spectrometry

JPC – Journal of Planar Chromatography – Modern TLC - Schizonepeta annua (Pall.) Schischk. is an endemic annual plant from the Lamiaceae family and it has been employed to cure...     

A New Method for Decreasing Mass Limit of Detection and Increasing Number of Theoretical Phates in Capillary Electrophoresis with Amperometric Detection

A new method aws developed to decrease the mass limit of detection (LOD) and increase the number of theoretical plates(N)in capillary electrophoresis with amperometric detcction.When the single microcylinder electrode,the 10 μm ID capillary with the etched detection end and the in-capillary alignment were used,the mass LOD for phenol was reduced 124 times and N was increased 36 times in comparison with the normal situation.     

Simultaneous Quantification of Anandamide and Other Endocannabinoids in Dorsal Vagal Complex of Rat Brainstem by LC–MS

A quantitative method has been developed and validated for the simultaneous determination of anandamide (AEA), docosatetraenylethanolamide (DEA) and N-arachidonyldopamine (NADA) in dorsal vagal complex (DVC) of rat brainstem by liquid chromatographic-electrospray ionization mass spectrometry. The analytes were extracted from the tissue samples of rat brainstem by a single step liquid extraction technique using acetonitrile. The chromatographic separation was conducted on a C18 column using a gradient mobile phase consisting of methanol and water at a flow rate of 0.3 mL min^?1. The analytes were quantified by positive electrospray ionization mass spectrometry with selected ion monitoring (SIM) mode. The limits of detection (LOD) for AEA, DEA and NADA were 0.5, 1 and 0.5 ng mL^?1, respectively. This method required only simple processing of the samples and could be applied to monitor the change in the level of these compounds in DVC of the rat brain tissue. Time dependent (10–70 min) accumulation of the endocannabinoids (AEA, DEA, and NADA) in brain tissue was also studied, which included a novel examination of the accumulation of DEA as a function of time in rat brain tissue after decapitation.     

LC–MS–MS Assay for Simultaneous Quantification of Fexofenadine and Pseudoephedrine in Human Plasma

A rapid, sensitive, and simple HPLC–MS–MS method, with electro-spray ionization and cetirizine as internal standard (IS), has been developed and validated for simultaneous quantification of fexofenadine and pseudoephedrine in human plasma. The analytes were isolated from plasma by solid-phase extraction (SPE) on Oasis HLB cartridges. The compounds were chromatographed on an RP 18 column with a mixture of ammonium acetate (10 mm, pH 6.4) and methanol as mobile phase. Quantification of the analytes was based on multiple reaction monitoring (MRM) of precursor-to-product ion pairs m/z 502 → 466 for fexofenadine, m/z 166 → 148 for pseudoephedrine, and m/z 389 → 201 for cetirizine. The linear calibration range for both analytes was 2–1,700 ng mL⁻¹ (r = 0.995), based on analysis of 0.1 mL plasma. Extraction recovery was 91.5 and 80.88% for fexofenadine and pseudoephedrine, respectively. The method was suitable for analysis of human plasma samples obtained 72 h after administration of a drug containing both fexofenadine and pseudoephedrine.     

Ion-Pairing Liquid Chromatography Coupled with Mass Spectrometry for the Simultaneous Determination of Nucleosides and Nucleotides

Adenosine and its corresponding nucleotides adenosine 5'-monophosphate (AMP), adenosine 5'-diphosphate ( ADP ) and adenosine 5'-triphos-phate (ATP) are important biomolecules that provide energy and substrates for various cellular bio-chemical processes. There have been strong     

Ion-Pairing Liquid Chromatography Coupled with Mass Spectrometry for the Simultaneous Determination of Nucleosides and Nucleotides

Adenosineanditscorrespondingnucleotidesadenosine 5′monophosphate (AMP) ,adenosine 5′diphosphate (ADP)andadenosine 5′triphosphate(ATP)areimportantbiomoleculesthatprovideen ergyandsubstratesforvariouscellularbiochemicalprocesses[1] .Therehavebeenstrongde…