RESUMO
Thirteen microelements (Al, As, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Ti, V, and Zn) and four macroelements (Ca, K, Mg, and Na) were determined in the edible muscle tissue of fish in Cienfuegos Bay. Eight species, Albula vulpes, Diapterus rhombeus, Gerres cinereus, Haemulon carbonarium, Haemulon sciurus, Micropogonias furnieri, Kyphosus sectatrix, and Lutjanus cyanopterus were studied. The total concentrations and extracted concentrations using HCl were also determined in sediments. The quality of the analysis was guaranteed by validating the used analytical methods with certified reference materials of fish and sediments. The high content of macroelements confirmed the importance of fish as a valuable source of food for the local population. New information is provided on bioaccumulation of toxic elements As, Cd, Cu, Zn, and Cr in fish of the bay, with concentrations that overcame the local or international maximum allowable levels for human consumption in most samples analyzed. A high correlation between the content of toxic elements As, Cd, Zn, and macroelement K in fish and its concentration extracted from sediments using the HCl extraction method was observed.
Assuntos
Monitoramento Ambiental , Peixes/metabolismo , Oligoelementos/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Baías/química , Sedimentos Geológicos/química , Músculos/metabolismoRESUMO
Advancements in sample preparation for performing trace analysis of inorganic analytes are coming from the dissemination of microwave-assisted procedures, but there is still room for improvements by looking for simple and easily applied procedures. Recently it was proposed a new approach called single reaction chamber with capability for digestions at high pressures and temperatures using simple vials and racks. This was a limitation of former cavity microwave ovens with closed vessels. It was demonstrated here that the use of single reaction chamber approach allows the implementation of efficient digestions using diluted solutions of nitric acid and also allows addressing a critical need of sample preparation for inorganic analysis by running mixed batches of samples. The feasibility of this procedure was demonstrated for organic samples and accuracy was proved by using certified reference materials of apple leaves, bovine liver and whole milk powder. Digestions performed of whole milk powder and bovine liver using 2.0 mol L(-1) nitric acid solution plus concentrated hydrogen peroxide at 240 °C led to residual carbon contents of 0.825 and 1.50% and residual acidities of 1.04 and 0.618 mol L(-1), respectively. These parameters are fully compatible with further measurements using ICP OES or ICP-MS. Al, Cu, Fe, Mn, Mo, Rb, Se, Sr, and Zn were accurately determined by ICP OES or ICP-MS depending on their concentrations in digests.
Assuntos
Carbono/análise , Fígado/química , Malus/química , Metais/análise , Leite/química , Folhas de Planta/química , Animais , Cátions , Bovinos , Concentração de Íons de Hidrogênio , Hidrólise , Micro-Ondas , Ácido Nítrico/química , Pós , Espectrofotometria AtômicaRESUMO
The advantages and shortcomings of focused microwave-induced combustion (FMIC) for digestion of plant samples were studied. The effects of sample mass, absorbing solution, oxygen gas flow-rate, and time of reflux step on recoveries of major, minor and trace metals were systematically evaluated. Afterwards, Al, Ba, Ca, Co, Cr, Cu, Mg, Mn, Ni, Sr, V, and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP OES) and by inductively coupled plasma mass spectrometry (ICP-MS). The main advantages of FMIC when compared to microwave-assisted wet digestion (MAWD) and focused-microwave-assisted wet digestion (FMAWD) are the possibility to digest larger masses of samples (up to 3g) using shorter heating times and diluted nitric acid solution for absorbing all analytes. Using the selected experimental conditions for FMIC, residual carbon content was lower than 0.7% for all samples and relative standard deviation (RSD) varied from 1.5 to 14.1%. Certified reference materials (NIST 1515 apple leaves and NIST 1547 peach leaves) were used for checking accuracy and determined values for all metals were in agreement with certified values at a 95% confidence level. No statistical difference (ANOVA, 95% of confidence level) was observed for results obtained by FMIC, FMAWD, and MAWD. Limits of detection were lower when using FMIC in the range of 0.02-0.15 µg g(-1) for ICP OES and 0.001-0.01 µg g(-1) for ICP-MS, which were about 3 and 6 times lower than the values obtained by FMAWD and MAWD, respectively. It is important to point out that FMIC was a suitable sample preparation method for major, minor and trace metals by both determination techniques (ICP OES and ICP-MS). Additionally, since it allows lower LODs (because up to 3g of sample can be digested) and diluted acid solutions are used (without any further dilution), the use of ICP-MS is not mandatory.
Assuntos
Metais/análise , Plantas/química , Carbono/química , Temperatura Alta , Limite de Detecção , Espectrometria de Massas , Micro-Ondas , Ácido Nítrico/química , Oxigênio/química , Espectrofotometria AtômicaRESUMO
OBJECTIVE: To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. METHODS: One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1 x ST and reaction times to 5 Hz currents were also determined at 2 x ST. RESULTS: Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5 x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22s (0.11 to 0.34) for 5 Hz at 2 x ST. CONCLUSIONS: Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Abeta-fibers, 250 Hz Abeta- or A partial differential-fibers, 5 Hz Abeta-, A partial differential- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.
Assuntos
Estimulação Elétrica/métodos , Fibras Nervosas Mielinizadas/fisiologia , Fibras Nervosas Amielínicas/fisiologia , Tempo de Reação , Tato/fisiologia , Adolescente , Adulto , Estimulação Elétrica/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor/etiologia , Dor/fisiopatologia , Parestesia/etiologia , Parestesia/fisiopatologia , Pressão , Valores de Referência , Limiar Sensorial , Vibração , Adulto JovemRESUMO
OBJECTIVE: The aim of this study was to evaluate the relationship between carpal tunnel syndrome symptoms and compression of the median nerve at the wrist in symptomatic patients. METHODS: A total of 250 patients were selected among those referred for electrodiagnostic evaluation with complaints involving hand or wrist. Primary and secondary symptoms were extracted from the answers to the instrument proposed by Levine et al. [J Bone Joint Surg Am 1993;75:1585]. The association of symptoms and the presence of compression of the median nerve at the wrist were ascertained through a multiple logistic regression test. RESULTS: Secondary symptoms (pain and weakness) were inversely associated with the presence of median nerve compression. Furthermore, primary symptoms (paresthesia, disability and nocturnal symptom) occurred similarly in patients with and without electrophysiologic findings of median nerve compression at the wrist.
Assuntos
Síndrome do Túnel Carpal/diagnóstico , Síndrome do Túnel Carpal/patologia , Neuropatia Mediana/diagnóstico , Neuropatia Mediana/patologia , Condução Nervosa , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor/etiologia , Parestesia/etiologia , Sensibilidade e Especificidade , Punho/inervaçãoRESUMO
A flow injection system with a pre-concentration minicolumn based on a chelating resin was coupled to a flame atomic absorption spectrometer. The focus of this work was the investigation of interference effects and the analytical applicability of the azo-immobilized 8-hydroxyquinoline on controlled-pore glass for the determination of Cr and Mn in mussel and non-fat milk powder. All studied concomitants affected the retention of Cr(III). These effects are probably related to the formation of hydroxo-complexes at the optimum pH range 9.0-10. The positive effect caused by Ca(II) was exploited to increase the retention of Cr(III) species and to improve the slope by 70%. The interferences on Mn(II) retention were less severe. The quantification of Cr and Mn was performed by standard additions. The proposed methodology was validated by analysis of three certified reference materials of mussels (Cr and Mn) and non-fat milk powder (Mn) with a mean relative percent error of <6.5% and mean relative standard deviation of <13%. Chromium and Mn were determined in typical Chilean mussels samples, and Mn was determined in non-fat milk powder samples. Results agreed at the 95% confidence level with those obtained by electrothermal atomic absorption spectrometry (ETAAS) using graphite furnace atomization. The method detection limits for a 30 s pre-concentration time were 0.9 and 1.1 micro g L(-1) for Mn, and 2.2 and 2.5 micro g L(-1) for Cr in acid digested solutions of mussel and non-fat milk, respectively. The methodology is simple, fast (sampling frequency 60-72 h(-1)), reliable, of low cost, and can be applied to the determination of traces of Cr (> or =0.18 micro g g(-1)) and Mn (> or =0.6 micro g g(-1)) in mussel samples, and Mn (> or =0.37 micro g g(-1)) in non-fat milk powder.
Assuntos
Bivalves/química , Cromo/análise , Análise de Injeção de Fluxo/métodos , Manganês/análise , Leite/química , Oxiquinolina/química , Animais , Quelantes , Cromatografia Gasosa , Análise de Injeção de Fluxo/instrumentação , Concentração de Íons de Hidrogênio , Sensibilidade e Especificidade , Espectrofotometria AtômicaRESUMO
A simple method combining slurry sampling after cryogenic grinding and the use of a permanent modification of the integrated platform inside the transversely heated graphite atomizer (THGA) was proposed for the determination of Cd and Pb in foods. Potentialities of the cryogenic grinding were evaluated for grinding different materials of difficult homogenization such as high fat and high fiber tissues. Animal and vegetal samples were cut into small pieces and ground in liquid nitrogen for 2 min. Slurries were prepared directly in the autosampler cup after cryogenic grinding by transferring an exact amount of homogeneous powdered material (5-20 mg) to the cup, followed by 1.00 mL of 0.2% (v/v) HNO3 containing 0.04% (v/v) Triton X-100 and sonication for 30 s, before transferring into the platform previously coated with 250 microg W and 200 microg Rh. Use of a tungsten carbide-rhodium permanent modifier combined with NH4H2PO4 conventional modifier improves tube lifetime and increases the pyrolysis temperature for Cd. Homogeneity tests, carried out by comparing the between- and within-batch precision for each kind of sample, showed no significant differences at the 95% confidence level, indicating good homogeneity for 5-20 mg masses. Detection limits were 3.3 ng g(-1) Cd and 75 ng g(-1) Pb for 1% m/v slurries. Results for determination of Cd and Pb in foods slurries were in agreement with those obtained with digested samples, since no statistical differences were found by the paired t-test at the 95% level.
Assuntos
Cádmio/análise , Análise de Alimentos/métodos , Chumbo/análise , Espectrofotometria Atômica/métodosRESUMO
We reviewed some physiological aspects of the F-wave studies, mainly related to the motoneurone sizes involved in the generation of this potentials and the number of stimuli necessary to analyze the F-wave parameters. F-wave latencies and F-wave conduction velocities obtained in a group of normal volunteers and in a group of diabetic patients are analyzed.
Assuntos
Diabetes Mellitus Tipo 1/fisiopatologia , Condução Nervosa , Tempo de Reação , Nervo Ulnar/fisiopatologia , Adolescente , Estudos de Casos e Controles , Nefropatias Diabéticas/diagnóstico , Nefropatias Diabéticas/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neurônios Motores/fisiologiaRESUMO
Ulnar nerve F-waves were studied in 23 healthy volunteers and 27 diabetic patients. Latencies and chronodispersion were analyzed in each group. In the diabetic group all the parameters were normal in 14 patients (52%) and in 13 (48%) at least one parameter was altered. In these patients the most frequently altered parameter was the maximum latency (92%), followed by mean latency (85%), minimum latency (54%) and chronodispersion (54%). These findings suggest that maximum and mean latencies are better parameters to be analyzed in ulnar F-wave studies than minimum latency.
Assuntos
Diabetes Mellitus Tipo 1/fisiopatologia , Neuropatias Diabéticas/fisiopatologia , Nervo Ulnar/fisiologia , Adolescente , Adulto , Neuropatias Diabéticas/diagnóstico , Eletrodiagnóstico/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tempo de Reação , Valores de Referência , Nervo Ulnar/fisiopatologiaRESUMO
The residual carbon content of a variety of bovine-derived samples and forage was determined by inductively coupled plasma optical emission spectrometry with radial view configuration (ICP-OES) after microwave-assisted digestion under high pressure in a closed vessel. The original carbon concentration in the samples was determined by elemental analysis. The highest amount of original carbon content (64%) was found in viscera. After digestion, up to 75% of it was destroyed. Viscera presented the highest ether extract and blood exhibited a high crude protein content of up to 99%. The efficiency in destroying the organic matter in biological materials seemed to be related to their fat content and showed no significant difficulty for protein-rich samples. The correlation coefficient between the fat content of the samples and the residual carbon after acid decomposition was 0.9173 indicating a fair fit. However, no correlation was observed between % RC and the protein content.