Yield loss during bleaching of pulp of Pinus radiata previously delignified with oxygen.

The pulp bleaching process removes or transforms the chromophore groups in the pulp, so that the final product reaches a desired brightness. However, this chemical treatment inevitably results in yield loss. Therefore, the objective of this work was to quantify the yield loss caused during the bleaching of kraft pulp of Pinus radiata delignified with oxygen. The material was submitted to three distinct ECF sequences (D0(EPO)D1D2, D0(EPO)D1P, and Z/EDP). At the end of each bleaching stage, the pulp brightness and the loss of gravimetric yield of the process were determined, and the generated filtrates were collected. From these filtrates, the pollutant load of the effluent was determined by measuring the content of total dissolved solids, the chemical oxygen demand, the concentration of total organic carbon carbon, and the adsorbable organic halogens. Among the whole sequences, the Z/EDP sequence had the lowest gravimetric yield, the highest pollutant load in the collected filtrate, and lowest potential for adsorbable organic halogens generation. There was good correlation between the loss of yield from the bleaching process and the organic load of the generated effluent; and among the techniques studied, the quantification of total organic carbon was the most appropriate method for the indirect quantification of the yield loss during the bleaching process of the studied material.

Exploring the exocellular fungal biopolymer botryosphaeran for laccase-biosensor architecture and application to determine dopamine and spironolactone.

Laccase was immobilized on a glassy carbon electrode layered with multi-walled carbon nanotubes using a film of botryosphaeran, a fungal (1 → 3)(1 → 6)-ß-D-glucan. This novel biosensing platform was characterized by electrochemical impedance spectroscopy and scanning electron microscopy, and applied for the determination of dopamine. Experimental variables such as enzyme concentration, pH value and operational parameters of the electroanalytical technique were optimized. Using square-wave voltammetry, there was a linear dependence of peak current and dopamine concentration within the range of 2.99-38.5 µmol L-1 with a limit of detection of 0.127 µmol L-1. The biosensor was successfully applied in the determination of dopamine in pharmaceutical injection and synthetic biological samples, and presented good selectivity even in the presence of uric acid and ascorbic acid, as well as other phenolic compounds. The different aspects regarding the operational stability of the laccase biosensor were evaluated, demonstrating good intra-day and inter-day repeatability, and long-storage stability. Furthermore, this biosensor was evaluated in the indirect determination of spironolactone by using the analytical signal of dopamine, presenting a limit of detection of 0.94 µmol L-1. The results obtained in the analysis of spironolactone in commercial pharmaceutical samples were satisfactory.

Indirect determination of formaldehyde by square-wave voltammetry based on the electrochemical oxidation of 3,5-diacetyl-1,4-dihydrolutidine using an unmodified glassy-carbon electrode.

A novel and indirect voltammetric procedure for the selective determination of formaldehyde is described. It is based on the oxidation of 3,5-diacetyl-1,4-dihydrolutidine (DDL) on an unmodified glassy-carbon electrode (GCE), generated by the selective reaction between formaldehyde and acetylacetone. A single oxidation peak of DDL at +0.8 V was observed, while formaldehyde is not electroactive under this condition, showing that this reaction can be used to indirect and selective detection of formaldehyde. Under the optimized conditions, a linear response between 0.4 and 40.0 mg L-1 and a detection limit of 0.13 mg L-1 were achieved, with a relative standard deviation of 0.7% (n = 10, 10 mg L-1). Due to the selectivity of this reaction to formaldehyde, this method is free from interference of other aldehydes. The procedure is a promising alternative for rapid formaldehyde determination in a wide range of samples.

Predicting carcass chemical composition of young Nellore bulls / Predição da composição química da carcaça de machos da raça Nelore

The direct determination of carcass composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Indirect methods have been developed to estimate on quick, simple, economical and reliable ways empty body composition of beef cattle. This study was performed with the objective of developing accurate regression equations to predict carcass composition of Nellore animals using 9-10-11th ribs chemical composition and performance measures as independent variables. Sixty-seven non-castrated Nellore bulls were randomly selected for finishing period in two consecutive years (2008 and 2009) and were finished in individual pens for approximately 100 days, until they reached four millimeters of subcutaneous fat thickness over Longissimus muscle. They were slaughtered at 540 days of average age and body weight at slaughter (BW) and carcass weight (CW) were taken. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946) and weighted (RW). The carcass composition was obtained after grinding, homogenizing, sampling and analyzing the left side of the carcass. Chemical analysis of 9-10-11th ribs cut and carcass were carried for protein (RP and CP), fat (RF and CF), ashes (RA and CA) and water (RWt and CWt). Stepwise and Mallows Cp options were used in PROC GLMSELECT (SAS Inst., Inc., Cary, NC) to determine significant (

O artigo não apresenta resumo em português.

Predicting carcass chemical composition of young Nellore bulls / Predição da composição química da carcaça de machos da raça Nelore

The direct determination of carcass composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Indirect methods have been developed to estimate on quick, simple, economical and reliable ways empty body composition of beef cattle. This study was performed with the objective of developing accurate regression equations to predict carcass composition of Nellore animals using 9-10-11th ribs chemical composition and performance measures as independent variables. Sixty-seven non-castrated Nellore bulls were randomly selected for finishing period in two consecutive years (2008 and 2009) and were finished in individual pens for approximately 100 days, until they reached four millimeters of subcutaneous fat thickness over Longissimus muscle. They were slaughtered at 540 days of average age and body weight at slaughter (BW) and carcass weight (CW) were taken. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946) and weighted (RW). The carcass composition was obtained after grinding, homogenizing, sampling and analyzing the left side of the carcass. Chemical analysis of 9-10-11th ribs cut and carcass were carried for protein (RP and CP), fat (RF and CF), ashes (RA and CA) and water (RWt and CWt). Stepwise and Mallows Cp options were used in PROC GLMSELECT (SAS Inst., Inc., Cary, NC) to determine significant (

O artigo não apresenta resumo em português.