Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 23
Filter
Add more filters










Publication year range
1.
Nature ; 508(7494): 72-5, 2014 Apr 03.
Article in English | MEDLINE | ID: mdl-24670644

ABSTRACT

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur--that is, one of a class of small objects orbiting primarily between Jupiter and Neptune--with an equivalent radius of 124 ± 9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

2.
Biomed Chromatogr ; 27(6): 757-64, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23225623

ABSTRACT

Nowadays, there is increasing interest in natural antioxidants from food by-products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra-high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by-products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard-column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile-methanol (containing 0.05 m ammonium acetate)-dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low-density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions.


Subject(s)
Chromatography, High Pressure Liquid/methods , Food Packaging , Penaeidae/chemistry , Shellfish/analysis , Animals , Limit of Detection , Polyethylene/chemistry , Reproducibility of Results , Xanthophylls/analysis
3.
Biomed Chromatogr ; 24(4): 387-92, 2010 Apr.
Article in English | MEDLINE | ID: mdl-19650149

ABSTRACT

A simple and specific analytical method was developed and tested for the determination of sulforaphane in broccoli by-products. The method includes the optimization of the conversion of glucoraphanin to sulforaphane, followed by purification of extracts using solid-phase extraction and high-performance liquid chromatography (HPLC) analysis. The response surface methodology was used to find optimum conditions for the preparation and purification procedure. Chromatographic conditions for reversed-phase HPLC with UV photodiode array detection were as follows: column, Exil ODS C(18), 25 x 0.46 cm, 5 microm; column temperature, 36 degrees C; mobile phase, a 30 : 70 (v/v) mixture of acetonitrile:water; flow rate, 0.6 mL/min. The detection wavelength was UV 202 nm. Under these conditions, excellent linearity was obtained (r(2) = 1), and the overall recovery was 97.5 and 98.1% for fresh florets and lyophilized florets, respectively. The precision results showed that the relative standard deviation of the repeatability for florets fresh and lyophilized was 3.0 and 4.0%, respectively. Sulforaphane contents were determined in the edible portion of fresh broccoli, and broccoli crop remains.


Subject(s)
Brassica/chemistry , Chromatography, High Pressure Liquid/methods , Thiocyanates/analysis , Glucosinolates/chemistry , Hydrogen-Ion Concentration , Imidoesters/chemistry , Isothiocyanates , Oximes , Reproducibility of Results , Solid Phase Extraction , Sulfoxides , Thiocyanates/chemistry
4.
Article in English | MEDLINE | ID: mdl-18243075

ABSTRACT

A new, simple, and reproducible isocratic high-performance liquid chromatography (HPLC) method has been developed for the determination of free and total tyrosine and tryptophan in a protein concentrate. To determine total amino acids, the method involves alkaline hydrolysis of the proteins with sodium hydroxide at 120 degrees C for 4h in the absence of air. Best results were achieved with a SS Exil ODS column 5microm (25cmx0.46cm i.d.), with an eluent of methanol: 40mM sodium acetate buffer (adjusted to pH 4.5 with acetic acid; 20:80, v/v), a flow rate of 0.80mL/min at 26 degrees C, and with programmable fluorescence detection. Under optimum conditions excellent linearity was obtained, and the overall recovery was 90.5, and 95.9% for total tryptophan and tyrosine, respectively. The precision results showed that the relative standard deviation of the repeatability and reproducibility were < or =4.78 and < or =4.65, respectively. This method was used to quantify the cited analytes in the protein concentrate obtained during the lactic acid fermentation of shrimp waste.


Subject(s)
Penaeidae/chemistry , Proteins/analysis , Shellfish/analysis , Tryptophan/analysis , Tyrosine/analysis , Waste Products/analysis , Animals , Chromatography, High Pressure Liquid , Fermentation , Food Handling , Hydrolysis , Reference Standards , Reproducibility of Results , Spectrometry, Fluorescence
5.
J Chromatogr Sci ; 45(4): 195-9, 2007 Apr.
Article in English | MEDLINE | ID: mdl-17504567

ABSTRACT

This work presents a high-performance liquid chromatography (HPLC) method for the quantitation of glucosamine in chitin. The method includes an acid hydrolysis of chitin. The chromatographic separation is achieved using a Hypersil ODS 5-microm column (250 x 4.6 mm) at 38 degrees C, with precolumn derivatization with 9-fluorenylmethyl-chloroformate and UV detection (lambda = 264 nm). The mobile phase is a mixture of mobile phase A [30 mM ammonium phosphate (pH 6.5) in 15:85 methanol-water (v/v)], mobile phase B [15:85 methanol-water (v/v)], and mobile phase C [90:10 acetonitrile-water (v/v)], with a flow rate of 1.2 mL/min. The HPLC method proposed showed adequate repeatability (relative standard deviation, 5.8%), accuracy (92.7% recovery), and sensitivity, with a detection limit of 2 microg/mL. The method is successfully applied to the quantitation of glucosamine for the determination of the purity of chitin from shrimp waste.


Subject(s)
Chromatography, High Pressure Liquid/methods , Crustacea , Glucosamine/analysis , Animals , Reproducibility of Results , Sensitivity and Specificity , Spectrophotometry, Ultraviolet
6.
Biomed Chromatogr ; 20(10): 981-4, 2006 Oct.
Article in English | MEDLINE | ID: mdl-16802328

ABSTRACT

In the present study, a simple and rapid reversed-phase HPLC method for the determination of astaxanthin in shrimp waste hydrolysate has been developed and validated. The analytical procedure involves the direct extraction of astaxanthin from the lipid fraction with methanol. The analytical column, SS Exil ODS, was operated at 25C. The mobile phase consisted of a mixture of water:methanol:dichloromethane:acetonitrile (4.5:28:22:45.5 v/v/v/v) at a flow rate of 1.0 mL/min. Detection and identification were performed using a photodiode array detector (lambda(detection) = 476 nm). The proposed HPLC method showed adequate linearity, repeatability and accuracy.


Subject(s)
Chromatography, High Pressure Liquid/methods , Penaeidae/chemistry , Animals , Penaeidae/metabolism , Reproducibility of Results , Xanthophylls/analysis
7.
J Chromatogr A ; 1105(1-2): 106-10, 2006 Feb 10.
Article in English | MEDLINE | ID: mdl-16439254

ABSTRACT

This work presents an HPLC method for the quantification of free amino acids in lyophilized protein fraction from shrimp waste hydrolysate which is obtained by acid lactic fermentation and analyzed using pre-column derivatization with 9-fluorenylmethyl-chloroformate. The amino acids were separated in a Hypersil ODS 5 microm column (250 mm x 4.6 mm) at 38 degrees C. The mobile phase was a mixture of phase A: 30 mM ammonium phosphate (pH 6.5) in 15:85 (v/v) methanol/water; phase B: 15:85 (v/v) methanol/water; and phase C: 90:10 (v/v) acetonitrile/water, with flow rate 1.2 ml/min. Fluorescence detection was used at an excitation wavelength of 270 nm and an emission wavelength of 316 nm. Method precisions for the different amino acids were between 4.4 and 7.1% (relative standard deviation, RSD); detection limits were between 23 and 72 ng/ml; and the recoveries were between 89.0 and 95.0%. The amino acid present at the highest concentration was tyrosine.


Subject(s)
Amino Acids/analysis , Chromatography, High Pressure Liquid/methods , Fermentation , Protein Hydrolysates/chemistry , Waste Products/analysis , Animals , Aquaculture , Fluorenes/chemistry , Penaeidae/growth & development
8.
J Chromatogr A ; 1105(1-2): 111-4, 2006 Feb 10.
Article in English | MEDLINE | ID: mdl-16439255

ABSTRACT

A high-performance liquid chromatography method for the microscale determination of alpha- and gamma-tocopherol in leaves, flowers and fresh beans from Moringa oleifera is reported. The method includes microscale saponification and extraction with n-hexane. Optimized conditions for reversed-phase HPLC with UV detection were as follows: column, 25 cm x 0.46 cm, Exil ODS 5-microm; column temperature, 25 degrees C; mobile phase, a 20:80 (v/v) mixture of methanol:acetonitrile; flow rate, 1.0 ml/min. With these conditions, method precision (relative standard deviation) was 5.6% for alpha-tocopherol and 4.9% for gamma-tocopherol. We used this method to measure alpha- and gamma-tocopherol in samples from M. oleifera as part of nutritional studies in edible plants cultivated in the Northwest México.


Subject(s)
Chromatography, High Pressure Liquid/methods , Moringa oleifera/chemistry , alpha-Tocopherol/analysis , gamma-Tocopherol/analysis , Flowers/chemistry , Plant Leaves/chemistry , Reproducibility of Results , Seeds/chemistry , Spectrophotometry, Ultraviolet
9.
J Chromatogr A ; 1105(1-2): 135-9, 2006 Feb 10.
Article in English | MEDLINE | ID: mdl-16439259

ABSTRACT

This study presents an HPLC method for the simultaneous quantification of retinol, alpha-tocopherol, and cholesterol in shrimp waste hydrolysate lipid fraction. The method includes microscale saponification and extraction with n-hexane. Liposoluble vitamins and cholesterol were quantified by HPLC with UV detection (HPLC-UV), on a 25 cm x 0.46 cm SS Exil ODS 5 microm column, mobile phase 68:28:4 (v/v/v) methanol:acetonitrile:water; flow rate 1.4 ml/min; column temperature 36 degrees C. The detection was operated using two channels of a diode-array spectrophotometer, 325 nm for retinol and 208 nm for alpha-tocopherol and cholesterol. With these conditions, the overall recovery was 95.7, 100.8, and 98.0% for retinol, alpha-tocopherol, and cholesterol, respectively. The method precision (relative standard deviation) was 1.83% for retinol, 2.32% for alpha-tocopherol, and 1.98% for cholesterol. This method was used to quantify the cited analytes in the hydrolysate obtained during lactic acid fermentation of shrimp waste. This hydrolysate may be a valuable supplement of nutrients in fish production.


Subject(s)
Cholesterol/analysis , Chromatography, High Pressure Liquid/methods , Vitamin A/analysis , Waste Products/analysis , alpha-Tocopherol/analysis , Animals , Aquaculture , Penaeidae/growth & development , Spectrophotometry, Ultraviolet
10.
Biomed Chromatogr ; 18(3): 183-90, 2004 Apr.
Article in English | MEDLINE | ID: mdl-15103705

ABSTRACT

This study presents an HPLC method for the quantification of sterols in edible seaweeds. Sterols were identified by HPLC/mass spectrometry (HPLC-MS) in positive APCI mode. The samples were saponified by refluxing with 1 m ethanolic KOH, and the non-saponifiable fraction was extracted with hexane. Sterols were quantified by HPLC with UV detection (HPLC-UV), on a 15 x 0.4 cm Kromasil 100 C(18) 5 micro m column (mobile phase 30:70 v/v methanol:acetonitrile; fl ow rate 1.2 mL/min; column temperature 30 degrees C; detection wavelength 205 nm). Method repeatability for fucosterol was good (coefficient of variation 2.4%). Sterol contents were determined in canned or dried brown seaweeds (Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca) and red seaweeds (Palmaria sp., Porphyra sp.). The predominant sterol was fucosterol in brown seaweeds (83-97% of total sterol content; 662-2320 micro g/g dry weight), and desmosterol in red seaweeds (87-93% of total sterol content; 187-337 micro g/g dry weight).


Subject(s)
Chromatography, High Pressure Liquid/methods , Seaweed/chemistry , Sterols/analysis , Mass Spectrometry , Reproducibility of Results , Spectrophotometry, Ultraviolet
11.
Biomed Chromatogr ; 18(2): 90-7, 2004 Mar.
Article in English | MEDLINE | ID: mdl-15039960

ABSTRACT

A high-performance liquid chromatographic (HPLC) method is described for determination of the ratio of beta-d-mannuronic acid to alpha-l-guluronic acid (M/G ratio) in dietary fibre of edible seaweeds. Total dietary fibre (TDF) content was determined gravimetrically. The TDF fraction was hydrolysed with 12 m and 1 m H(2)SO(4), then neutralized with AG 4 x 4 resin. The uronic acids were separated in a Tracer Extrasil SAX 5 micro m column (25 cm x 4 mm) at 35 degrees C, with 2 mm KH(2)PO(4) containing 5% methanol as mobile phase at a fl ow rate of 1.5 mL/min. The detection wavelength was UV 210 nm. The chromatographic identifications of beta-d-mannuronic acid and alpha-l-guluronic acid were confirmed by liquid chromatography-mass spectrometry (LC-MS). The method precision was 1.4% for beta-d-mannuronic acid and 3.5% for alpha-l-guluronic acid. The method was used to determine M/G ratio in canned seaweeds (Saccorhiza polyschides and Himanthalia elongata) and in dried seaweeds (H. elongata, Laminaria ochroleuca, Undaria pinnatifida, Palmaria sp. and Porphyra sp.).


Subject(s)
Chromatography, High Pressure Liquid/methods , Dietary Fiber/analysis , Seaweed/chemistry , Uronic Acids/analysis , Mass Spectrometry , Spectrophotometry, Ultraviolet
12.
J Chromatogr Sci ; 42(3): 117-20, 2004 Mar.
Article in English | MEDLINE | ID: mdl-15023245

ABSTRACT

This study presents a high-performance liquid chromatography (HPLC) method for simultaneous determination of thiamine and riboflavin and the results of its application to a number of edible seaweeds that are sampled in dried form (Himanthalia elongata, Laminaria ochroleuca, Undaria pinnatifida, Palmaria sp., and Porphyra sp.) or as canned food (H. elongata and Saccorhiza polyschides). Samples are prepared by acid and enzymatic hydrolysis. Optimized conditions for reversed-phase HPLC with fluorescence detection are as follow: column, Kromasil 100 C18; column temperature, 35 degrees C; mobile phase, a 72:28 (v/v) mixture of 0.005 M ammonium acetate (pH 6.7)-methanol; and flow rate, 1.35 mL/min. With these conditions, recovery is 95.52% for thiamine and 90.08% for riboflavin, and the method precision (relative standard deviation) is 2.66% for thiamine and 2.21% for riboflavin. On a dry weight basis, thiamine contents range from 0.14 microg/g in dried H. elongata to 2.02 microg/g in dried Porphyra and riboflavin contents from 0.31 microg/g in canned H. elongata to 6.15 microg/g in dried Porphyra.


Subject(s)
Chromatography, High Pressure Liquid/methods , Riboflavin/analysis , Seaweed/chemistry , Thiamine/analysis , Quality Control , Spectrometry, Fluorescence
13.
Food Addit Contam ; 20(3): 291-9, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12623655

ABSTRACT

The behaviour of two commercial oxygen-scavenging products with respect to migration of active ingredients into foodstuffs was investigated. Migrants were identified, and by using appropriate analytical methods, migration was determined in a variety of liquid, solid or gelled food simulants and foods. Simulants were chosen to cover a range of water activities and viscosities. Foods and the gelled food simulant agar were packed with and without vacuum, and with the oxygen scavenger in various locations relative to the packed food. The main migrants, as identified by X-ray fluorescence spectrometry, infrared spectroscopy and scanning electron microscopy with energy-dispersive spectrometry were Na(+) and Cl(-) in non-acidic aqueous simulants, and Na(+), Cl(-) and Fe(2+) in 3% acetic acid. Migration into aqueous simulants exceeded the current European Union limit for total migration from plastic materials (assumed to be currently applicable to these systems) and was probably excessive by any reasonable standard. However, neither oxygen scavenger appeared to release significant quantities of migrants into solid foods when the scavenger was properly located in the package and the packing process does not favour the contents becoming wet by water released from the food.


Subject(s)
Food Contamination/analysis , Food Packaging/methods , Food Preservation/methods , Acetic Acid/chemistry , European Union , Food Analysis/methods , Food Packaging/legislation & jurisprudence , Free Radical Scavengers/chemistry , Iron/chemistry , Legislation, Food , Sodium Chloride/chemistry , Water/chemistry
14.
J Chromatogr A ; 976(1-2): 277-84, 2002 Nov 08.
Article in English | MEDLINE | ID: mdl-12462619

ABSTRACT

A high-performance liquid chromatographic (HPLC) method for the microscale determination of alpha-tocopherol in macroalgae is reported. The method includes microscale saponification and extraction with n-hexane. The presence of alpha-tocopherol in macroalgae samples was confirmed by HPLC-MS. Alpha-tocopherol levels as determined in samples by HPLC with UV and fluorescence detection did not differ significantly; however, fluorescence detection has a higher sensitivity (detection limit 10.4 ng/ml, vs. 104 ng/ml with UV detection), as well as good precision (relative standard deviation 1.81%) and recovery (94.3%). Fluorescence detection is also faster. We used this method to determine the alpha-tocopherol contents of four commercial macroalgae products from northwest Spain as part of nutritional studies in dehydrated Himanthalia elongata and Laminaria ochroleuca, and also in canned Himanthalia elongata and Saccorhiza polychides.


Subject(s)
Chromatography, High Pressure Liquid/methods , Eukaryota/chemistry , alpha-Tocopherol/analysis , Reference Standards , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet
15.
Conscientia ; 3(2): 93-96, abr.-jun.1999.
Article in Spanish, English, Portuguese | Index Psychology - journals | ID: psi-18528

ABSTRACT

Um dos pressupostos básicos da conscienciologia é a pluriexistencialidade ou serialidade existencial, condição a que está submetida a consciência durante seu processo evolutivo caracterizada pela alternância contínua entre o estado de consciência intrafísica (conscin) e o de consciência extrafísica (consciex) (AU)

16.
Conscientia ; 3(1): 21-27, jan.-mar.1999.
Article in Portuguese | Index Psychology - journals | ID: psi-18530

ABSTRACT

Neste artigo encontram-se registrados os resultados de uma investigação desenvolvida no Laboratório da Sinalética Energética, do Centro de Altos Estudos da Consciência (CEAEC). Participaram deste estudo 12 pesquisadores, durante quatro semanas consecutivas, incluindo auto-experimentos no laboratório e debates técnicos. Esta imersão evidenciou a importância da sinalética energética-parapsíquica como instrumento para a realização da assistencialidade inter-consciencial, potencializando a percepção do intercâmbio multidimensional que já ocorre no cotidiano dos experimentadores(AU)


Subject(s)
Humans
17.
Conscientia ; 3(1): 50-54, jan.-mar.1999.
Article in Portuguese | Index Psychology - journals | ID: psi-18538
18.
Conscientia ; 2(4): 161-170, out.-dez.1998.
Article in Spanish, English, Portuguese | Index Psychology - journals | ID: psi-18910

ABSTRACT

A programação existencial (proéxis) é um tema de estudo de grande relevância para todas as conscins que participaram dos cursos intermissivos. Para apoiar as pesquisas em Proexologia foi instalado no centro de altos estudos da consciência (CEAEC) o laboratório da proéxis. Neste artigo, expõem-se o funcionamento deste laboratório e os recursos que oferece ao pesquisador, que englobam textos de esclarecimento, testes conscienciométricos e planilhas de auto-análise, indicando seu potencial para a pesquisa em Proexologia (AU)

19.
Conscientia ; 2(4): 189-189, out.-dez.1998.
Article in Portuguese | Index Psychology - journals | ID: psi-18918

ABSTRACT

Na existência humana, o conhecimento e domínio da bioenergética possui importância fundamental para a consciência ampliar sua lucidez e a qualidade das suas manifestações (AU)

20.
Conscientia ; 2(3): 103-110, jul.-set.1998.
Article in English, Portuguese | Index Psychology - journals | ID: psi-18928

ABSTRACT

Os laboratórios Conscienciais são câmaras multidimensionais preparadas cientificamente segundo a conscienciologia, reunindo condições físicas e extrafísicas que favorecem a realização de experimentos relativos à consciência. Apresenta-se, neste trabalho, uma proposta para a pesquisa da consciência através dos laboratórios conscienciais, descrevendo-se suas características básicas, analisando-se algumas possibilidades que oferecem para a pesquisa da consciência, com base nas informações proporcionadas pelos laboratórios do CEAEC (AU)

SELECTION OF CITATIONS
SEARCH DETAIL
...