Search results for "ARDS"
showing 10 items of 1705 documents
Microscale synthesis of phosphatidyl-[3H]choline from 1,2-diacylglycerol. Assessment of isomerization by reversed-phase high-performance liquid chrom…
1995
The synthesis of rac-1-palmitoyl-2-oleoylglycero-3-phospho-[3H]choline of high specific activity was carried out on a microscale by making 7 mumol of rac-1-palmitoyl-2-oleoylglycerol react first with an equimolar amount of POCl3 and then of [3H]choline. After purification by thin-layer chromatography and normal-phase high-performance liquid chromatography and normal-phase high-performance liquid chromatography (HPLC), the yield of the synthesis of [3H]phosphatidylcholine (120 microCi/mumol) was 22%. rac-1-Palmitoyl-2-oleoylglycerol was purified before use by reversed-phase HPLC under conditions which were nonisomerizing and allowed the separation of 1,2- and 1,3-isomers of diacylglycerol. E…
Determination of pyrethroid pesticide residues in fatty materials by solid-matrix dispersion partition, followed by mini-column size-exclusion chroma…
1999
The method studied uses a combination of a solid-matrix dispersion partition (SMDP) followed by high-performance size-exclusion chromatography on a minicolumn (HPmSEC) of 7.8 mm I.D. for the separation of pyrethroid (PYR) residues from fatty material. The solid-matrix dispersion extraction is carried out by absorbing a fat solution onto an Extrelut-3 cartridge (filled with a macroporous diatomaceous material) and extracting the PYR residues with acetonitrile. Up to 1 g of fatty material can be extracted with 15 ml acetonitrile. The small amount (mean +/- S.D. = 12.4 +/- 5.9 mg) of fatty material which is eluted into the acetonitrile is further removed by HPmSEC. PYR pesticide residues are c…
Determination of organochlorine pesticide residues in honey from the central zone of Portugal and the Valencian community of Spain
2004
In this study nine organochlorine pesticide residues ([alpha]-, [beta]-, and [gamma]-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), aldrin, p,p'-DDE, p,p'-DDD, o,p'-DDT, and p,p'-DDT) in forty nine samples of honey collected from markets of Portugal and Spain during 2001 and 2002, respectively, were evaluated. For this evaluation, three analytical procedures were studied. The analytical procedure, based on LLE extraction with ethyl acetate followed by gas chromatography-electron-capture detection (GC-ECD) for quantification, and mass spectrometry (GC-MS) for confirmation, has been selected. Recoveries of spiked samples ranged from 68%, for [beta]-HCH, and 126% for p,p'-DDT, for forti…
Processing of Generator-Produced 68Ga for Medical Application
2007
The (68)Ge/(68)Ga generator provides an excellent source of positron-emitting (68)Ga. However, newly available "ionic" (68)Ge/(68)Ga radionuclide generators are not necessarily optimized for the synthesis of (68)Ga-labeled radiopharmaceuticals. The eluates have rather large volumes, a high concentration of H(+) (pH of 1), a breakthrough of (68)Ge, increasing with time or frequency of use, and impurities such as stable Zn(II) generated by the decay of (68)Ga, Ti(IV) as a constituent of the column material, and Fe(III) as a general impurity.We have developed an efficient route for the processing of generator-derived (68)Ga eluates, including the labeling and purification of biomolecules. Prec…
Univariate method for background correction in liquid chromatography–Fourier transform infrared spectrometry
2007
An univariate method is proposed for background correction in on-line gradient liquid chromatography-Fourier transform infrared (LC-FTIR) spectrometry using acetonitrile:water as mobile phase components. The method is based on the calculation of the ratio of absorbances (AR) at two characteristic wavenumbers for each spectrum. This parameter is subsequently used to locate the most appropriated eluent spectrum within a reference spectra matrix (RSM) to be subtracted from each spectrum included in the sample chromatogram. To correct minor changes in eluent spectra intensity during the elution of analytes, a correction factor (Kf), defined as the ratio of the absorbance of the sample and the s…
Extraction of clenbuterol from calf urine using a molecularly imprinted polymer followed by quantitation by high-performance liquid chromatography wi…
2002
A method for the extraction of clenbuterol from calf urine samples using a molecularly imprinted polymer (MIP) has been developed. The aim was that the final extracts from the MIP should allow quantitation of clenbuterol down to 0.5 ng/mL urine using HPLC with UV detection. The MIP was produced using brombuterol as a template and the selectivity of the MIP, for clenbuterol, was tested against a non-imprinted polymer (produced without template) and was found to be high. After loading of 5 mL diluted centrifuged urine, selective binding was established in acetonitrile-acetic acid (98:2). For further elution of interferences, 0.5 M ammonium acetate buffer pH 5 and 70% acetonitrile in water was…
Determination of busulfan in human plasma using high-performance liquid chromatography with pre-column derivatization and fluorescence detection.
1999
A rapid, sensitive and reproducible high-performance liquid chromatographic assay for busulfan in human plasma was developed. After extraction of plasma samples with acetonitrile and methylene chloride, busulfan and the internal standard [1,5-bis(methanesulfonyloxy)pentane] were derivatized with 8-mercaptoquinoline to yield fluorescent compounds which were detected with a fluorescence detector equipped with filters of 360 nm (excitation) and 425 nm (emission). Calibration graphs showed a linear correlation (r>0.9990) over the concentration range of 20-2000 ng/ml. The recovery of busulfan from plasma standards was 70+/-5%. The detection and quantification limits for busulfan in plasma sample…
Emerging approaches to estimate retention factors in high performance liquid chromatography.
2004
The retention factor is one of the most universally used parameters in chromatography. The errors associated with the conventional ways to determine the retention factor of compounds in liquid chromatography are studied and compared with those corresponding to new approaches. The later avoid the use of extra-column time and hold-up time values, which have proven to be tedious and ambiguous. Simulations and real data, used to examine the accuracy of four different approaches (two classic and two new), suggest that the new approaches could be considered more satisfactory than the classic ones.
Development of standard operation procedures for the manufacture of n-octadecyl bonded silicas as packing material in certified reference columns for…
2004
The development of standard operation procedures for the manufacture of a n-octadecyl bonded spherical silica packing from partially condensed tetraethoxysilane as silica source is described. The synthesis comprises five intermediate products and six synthesis steps which were examined according to their reproducibility and robustness. The results led to the optimisation of the manufacturing process for a n-octadecyl bonded silica. Correlations were drawn between the dynamic viscosity of the poly(ethoxy)siloxane (PES), the synthesis parameters, the resulting pore structural properties and particle size distribution of the silicas. Validated procedures were developed to manufacture spherical…
Identification of diterpenes in canvas painting varnishes by gas chromatography-mass spectrometry with combined derivatisation.
2004
A derivatisation method that combines the formation of ethyl esters from the carboxylic groups and trimethylsilyl ethers from hydroxyl groups of the components of diterpenic resins is presented in this paper. This methodology involves two experimental steps: (1) formation of ethyl esters using ethyl chloroformate; and (2) the esterified compounds are lead to react with trimethylsilylimidazole to form the corresponding trimethylsilyl ethers. The main advantage of the proposed method is the possibility of performing simultaneously the analysis of amino acids from proteins, fatty acids from drying oils, and diterpenic compounds from natural resins usually found in works of art. This methodolog…