Determination of alkyltrimethylammonium surfactants in hair conditioners and fabric softeners by gas chromatography-mass spectrometry with electron-impact and chemical ionization

The commercial hair conditioners and fabric softeners were analyzed for the content of alkyltrimethylammonium compounds (ATMACs) by gas chromatography-mass spectrometry (GC-MS) with electron impact (EI) and low-pressure positive-ion chemical ionization (PICI) modes. The method involves mixed diluted samples (adjust pH to 10.0) with potassium iodide to enhance the extraction of iodide-ATMA+ ion pairs by direct liquid-liquid extraction. The iodide-ATMA+ pairs were then demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection-port. A high abundance of ADMAs was detected at the temperature above 300 degrees C in the GC injection-port. The enhanced selectivity of quasi-molecular ion chromatograms of C12-C18-ADMA, obtained using methanol PICI-MS enables ADMAs to be identified. The accuracy and precision of the method was validated and was successfully applied to determine contents of ATMAC in commercial hair conditioners and fabric softeners. The contents of total measured ATMAC ranged from 0.4 to 6.9% for hair conditioners, and from 3.3 to 4.6% for fabric softeners.     

An electron-rich molybdenum-molybdenum quintuple bond spanned by one lithium atom

Take five: A unique quintuply bonded dimolybdenum complex [Mo(2)(μ-Li){μ-HC(N-2,6-Et(2)C(6)H(3))(2)}(3)] (see picture) was synthesized and characterized. The Mo-Mo interaction includes an unexpected bridging Li(+) ion. Calculations indicate the bridging Li(+) ion does not perturb the Mo-Mo bond length (2.0612(4)??), but results in a relatively small effective Mo-Mo bond order of 3.67.     

Environmental radiation detected at Lin Shin hospital in Taichung during the Fukushima nuclear power plant accident

This work is the first evaluation of environmental gamma exposure rates by the Nuclear Medicine Department at Lin Shin Hospital (LSH) in Taichung with Thermoluminescent dosimeter (TLD-100H) during the Fukushima Nuclear Power Plant (FNPP) accident. After the 9.0 M_W strong earthquake hit northern Japan on March 11, 2011, a TLD-100H was used to monitor environmental kerma rate at Taichung (2,500 km away from northern Japan) from Mar-08 to Apr-09, 2011 and evaluated kerma rate due to global fallout of the sever FNPP accidents. Exposure rates varied widely among positions close to the PET/CT facility. Observed kerma rates of up to 4.12 ± 0.62 mSv mo⁻¹ indicated an explicit, heavy leakage of photon through the PET/CT facility. No significant contributions were detected at Taichung, Taiwan. Hence, the health effect cause by the “extra radiation” from FNPP accidents is negligible. As this was a rare case of environmental monitoring during a nuclear power plant accident, its findings are of considerable significance.     

Nickel,copper and manganese hexacyanoferrate with poly(3,4-ethylenedioxythiophene) hybrid film modified electrode for selectively determination of ascorbic acid

The NiHCF-PEDOT, CuHCF-PEDOT and MnHCF-PEDOT films were prepared on glassy carbon electrode (GCE) by multiple scan cyclic voltammetry and characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) techniques. The advantages of these films are demonstrated for selectivity detection of ascorbic acid using cyclic voltammetry and amperometric method. Interestingly, the NiHCF-PEDOT and CuHCF-PEDOT modified electrodes exhibited a wide linear response range (5 × 10⁻⁶−3 × 10⁻⁴ M, R ² = 0.9973 and 1.8 × 10⁻³−1.8 × 10⁻² M, R ² = 0.9924). The electrochemical sensors facilitated the oxidation of AA but not responded to other electroactive biomolecules such as dopamine, uric acid, H₂O₂, glucose. The difference is MnHCF-PEDOT/GCE that no response to AA. In addition, the NiHCF-PEDOT and CuHCF-PEDOT modified electrodes exhibited a distinct advantage of simple preparation, specificity, stability and reproducibility.     

STEREOSELECTIVE SYNTHESIS OF MONOFLUORO-OLEFINS FROM DIISOPROPYL (CARBOETHOXYFLUORO-METHYL)PHOSPHONATE

Abstract

Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate[(i-PrO)₂P(O)CFCO₂Et]^?Li⁺ 2 followed by in siru nucle-ophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH₃)(C0₂Et)C[dbnd]CFCO₂Et 4 or 75% of the E-isomer of a-fluoro-P-vinyl-a,P-unsaturated diester (E,Z)-(CH₂[dbnd]CH)(CO₂C₂H₅)C[dbnd]CFCO₂Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH₃)(CO₂Et)C[dbnd]CFCO₂Et 4 with 79% E-stere-oselectivity. The E/Zratio of (CH₂[dbnd]CH)(CO₂Et)C[dbnd]CFCO₂Et 5 depends on the HMFT or DMPU cosolvents present in the reaction mixture.     

Synthetic approaches to 2-substituted 1-oxo- and 3-oxotetrahydroisoquinolines

2-Substituted homophthalimides 2a-c were reduced regioselectively with sodium borobydride to carbinol-lactam intermediates 3a-c , which were dehydrated, followed by hydrogenation, to give 1-oxo-tetrabydroisoquinolines or 3,4-dihydroisoquinolin-1(2H)ones 5a-c . The isomeric 3-oxo-tetrahydro-isoquinolines or 1,4-dihydroisoquinolin-3(2H)-ones 8a-i were obtained in satisfactory yields via heating 3-isochromanone ( 6 ) with the corresponding amines 7a-i in the presence of aluminum chloride.     

MALDI-mass spectrometry imaging of desalted rat brain sections reveals ischemia-mediated changes of lipids

Ischemia-mediated lipidomic changes in rat brains were explored by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) profiling and imaging after in situ desalting which drastically simplified the spectral presentation of tissue lipids. Removal of interference from the massively changed cations in response to tissue damage permitted the revelation of subtle yet important lipidomic changes. The identities of the detected lipids were confirmed by MALDI tandem mass spectrometry (MALDI-MS/MS). The MALDI-MS imaging (MALDI-MSI) result of lysophosphatidylcholine 16:0 (LPC 16:0) in the desalted brain section appeared essentially identical to that of sodiated LPC 16:0 in the adjacent undesalted section and verified the suitability of the desalting method for the MALDI-MSI studies of lipids in tissue. Other than the consistently decreased phosphatidylcholine (PC) 16:0/18:1, images of PCs containing all saturated, or combined saturated and monounsaturated fatty acyl (MUFA) residues revealed their parenchymal increase by ischemia. Images of PCs containing polyunsaturated fatty acyl (PUFA) residues in normal cortex showed laminated patterns similar to cortical lamina. Ischemia reduced the abundance of PC 16:0/20:4 and PC 16:0/22:6 and disrupted the laminated distribution of the former. However, ischemia increased the subcortical abundance of PUFA-PCs containing stearoyl residue and confined their cortical increase within limited areas. Image of parenchymal sphingomyelin 18:0 (SM 18:0) showed its consistent decrease by ischemia that paralleled the increase of ceramide 18:0-H(2)O in region of moderate to high SM abundance. The above results presented the lipidomic changes largely different from previous MALDI-MSI results and suggested a window of intervention that may benefit the management of cerebrovascular accident and other brain injuries.     

Experimental verification of strong rotational dependence of fluorescence and predissociation yield in the b1Πu(v = 1) level of 14N2

New, rotationally resolved fluorescence-excitation spectra confirm coupled-channel Schro?dinger-equation predictions of strong rotational dependence of the fluorescence and predissociation yields in the b(v = 1) level of (14)N(2).     

A liquid chromatography-tandem mass spectrometry assay for the determination of nemonoxacin (TG-873870), a novel nonfluorinated quinolone, in human plasma and urine and its application to a single-dose pharmacokinetic study in healthy Chinese volunteers

Nemonoxacin (TG‐873870) is a novel C‐8‐methoxy nonfluorinated quinolone with higher activity than ciprofloxacin, levofloxacin and moxifloxacin against Gram‐positive pathogens including methicillin‐susceptible or methicillin‐resistant Staphylococcus aureus and Streptococcus pneumoniae with various resistant phenotypes. A rapid, sensitive and selective liquid chromatography–tandem mass spectrometric (LC‐MS/MS) method was developed and validated to determine the concentration of nemonoxacin in human plasma and urine. Protein precipitation and liquid–liquid extraction were employed for plasma and urine sample preparations, respectively, and extract was then injected into the system. Separation was performed on a C₁₈ reversed‐phase column using acetonitrile–0.1% formic acid as a mobile phase. Both analyte and internal standard (gatifloxacin) were determined using electrospray ionization and the MS data acquisition via the selected reaction monitoring in positive‐ion mode. The lower limit of quantification was 5 ng/mL and the calibration curves were linear in the concentration range of 5–1000 ng/mL. The accuracy, precision, selectivity, linearity, recovery, matrix effect and stability were validated for TG‐873870 in human plasma and urine. The method was successfully applied to a pharmacokinetic study enrolling 12 healthy Chinese volunteers administered nemonoxacin malate capsules. Copyright © 2012 John Wiley & Sons, Ltd.