Measurement of mercury species in human blood using triple spike isotope dilution with SPME-GC-ICP-DRC-MS

The measurement of different mercury compounds in human blood can provide valuable information about the type of mercury exposure. To this end, our laboratory developed a biomonitoring method for the quantification of inorganic (iHg), methyl (MeHg), and ethyl (EtHg) mercury in whole blood using a triple-spike isotope dilution (TSID) quantification method employing capillary gas chromatography (GC) and inductively coupled dynamic reaction cell mass spectrometry (ICP-DRC-MS). We used a robotic CombiPAL® sample handling station featuring twin fiber-based solid-phase microextraction (SPME) injector heads. The use of two SPME fibers significantly reduces sample analysis cycle times making this method very suitable for high sample throughput, which is a requirement for large public health biomonitoring studies. Our sample preparation procedure involved solubilization of blood samples with tetramethylammonium hydroxide (TMAH) followed by the derivatization with sodium tetra(n-propyl)borate (NaBPr₄) to promote volatility of mercury species. We thoroughly investigated mercury species stability in the blood matrix during the course of sample treatment and analysis. The method accuracy for quantifying iHg, MeHg, and EtHg was validated using NIST standard reference materials (SRM 955c level 3) and the Centre de Toxicologie du Québec (CTQ) proficiency testing (PT) samples. The limit of detection (LOD) for iHg, MeHg, and EtHg in human blood was determined to be 0.27, 0.12, and 0.16 μg/L, respectively.

Double quantization of CP type orbits by generalized Verma modules

It is known that symmetric orbits in g^* for any simple Lie algebra g are equipped with a Poisson pencil generated by the Kirillov-Kostant-Souriau bracket and the reduced Sklyanin bracket associated to the “canonical” R-matrix. We realize quantization of the Poisson pencil CPⁿ type orbits (i.e. orbits in sl(n + 1)^* whose real compact form is CPⁿ) by means of q-deformed Verma modules.     

Determination of seven arsenic compounds in urine by HPLC-ICP-DRC-MS: a CDC population biomonitoring method

A robust analytical method has been developed and validated by use of high-performance liquid chromatography inductively coupled plasma mass spectrometry with Dynamic Reaction Cell? (DRC) technology that separates seven arsenic (As) species in human urine: arsenobetaine (AB), arsenocholine, trimethylarsine oxide (TMAO), arsenate (As(V)), arsenite (As(III)), monomethylarsonate, and dimethylarsinate. A polymeric anion-exchange (Hamilton PRP® X-100) column was used for separation of the species that were detected at m/z 75 by ICP-DRC-MS (PerkinElmer? SCIEX® ELAN DRCII?) using 10% hydrogen–90% argon as the DRC gas. The internal standard (As) is added postcolumn via an external injector with a sample loop. All analyte peaks were baseline-separated except AB and TMAO. Analytical method limits of detection for the various species ranged from 0.4 to 1.7 μg L^?1 as elemental As. As(III) conversion to As(V) was avoided by adjusting the urine sample to 相似文献   

Potential Use of an Aminopropyl Stationary Phase in Hydrophilic Interaction Capillary Electrochromatography. Application to Tetracycline Antibiotics

We have demonstrated that the aminopropyl stationary phase (APS2) already used for analysis of polar compounds in hydrophilic interaction liquid chromatography can be successfully used in capillary electrochromatography. First, it was shown that the APS2 packing material affords a sustainable electroosmotic flow, the direction and magnitude of which depend on the nature of the electrolyte ions. A triple-layer model is proposed to describe this particular behaviour of the aminopropyl stationary phase. Finally, application to the separation of the tetracycline antibiotics used as test compounds in capillary electrochromatography is described and it is demonstrated that the final separation may be manipulated because of the electromigration and retention properties of the compounds, although migration times cannot be accurately predicted. Revised: 15 March and 6 July 2005     

Liquid chromatography-tandem mass spectrometry method for the determination of dye residues in aquaculture products: development and validation

A method is described for the identification and the quantitative determination of the triphenylmethane dyes, malachite green (MG), crystal violet (CV), brilliant green (BG) and leuco malachite green (LMG) and leuco crystal violet (LCV). The analytes were isolated from the matrix by liquid-liquid extraction with acetonitrile. Determination was performed using LC-MS/MS with positive electrospray ionisation. 4 different deuterated internal standards were introduced to improve the quantitative performance of the method. The method has been validated in line with the EU criteria of Commission Decision 2002/657/EC in accordance with the minimum required performance limit (MRPL) set at 2 μgkg(-1) for the sum of MG and LMG. For all the monitored compounds, accuracy, intra-day and inter-day precision were determined at each level of fortification (0.5, 0.75, 1.0 and 2.0 μgkg(-1)). Decision limits CCα and detection capabilities CCβ were calculated according to the standard ISO 11843-2. A study on the applicability of the method was conducted on various aquacultured species with the aim to assess the matrix effects. The presence of residues of leuco brilliant green in fish has also been confirmed from experimental study performed on trout treated with brilliant green, using LTQ-Orbitrap mass spectrometer.     

Diastereoselectivity in unusual intermolecular tandem Michael reactions

Highly stereoselective consecutive or tandem Michael (MIMI) reactions are reported. A variety of initial nucleophiles react with chiral acylated 1,3-oxazolidin-2-ones to generate a reactive enolate. The enolate then reacts stereoselectively with a second equivalent of the acylated 1,3-oxazolidin-2-one to afford ‘dimeric’ adducts. The adducts have three new contiguous stereogenic centers formed with a high level of control. Single crystal X-ray crystallographic analysis confirmed this controlled formation of novel tandem acyclic conjugate addition or MIMI products in several examples.