Comparison between titrimetric and spectrophotometric methods for quantification of vitamin C.

Vitamin C is usually quantified by titrimetric or chromatographic methods. However, these methods have limitations: food color interferes with the titrimetric method and the chromatographic method is costly. The aim of this study was to compare a spectrophotometric method, based on reduction of cupric ions in the presence of cuproine complex, with a titrimetric method, based on reduction of 2,6-dicholorophenolindophenol. Linearity, precision, accuracy, and limits of detection (LOD) and quantification (LOQ) were evaluated using a standard vitamin C solution. Both methods were also applied for AA quantification in industrialized orange and pineapple juices. The methods were precise and accurate when applied to the standard solution. The spectrophotometric method was more sensitive, with lower values for LOD (0.002mgmL-1) and LOQ (0.010mgmL-1), and more accurate with error less than 5% while results from the titrimetric method were affected by the juice color, which generated errors in excess of 15%.

Mixture of alkaline tetrasodium EDTA with sodium hypochlorite promotes in vitro smear layer removal and organic matter dissolution during biomechanical preparation.

AIM: The aim of this study was to determine the following: (i) the quantity of free chlorine in mixtures of equal proportions of sodium hypochlorite (NaOCl) with trisodium ethylenediaminetetraacetic acid (EDTAHNa3 ) and alkaline tetrasodium ethylenediaminetetraacetic acid (EDTANa4 ); (ii) organic matter dissolution; and (iii) the time necessary to remove the smear layer by these irrigants alone and when mixed. METHODOLOGY: The solutions were mixed in a 1 : 1 ratio and then iodometrically titrated over time to determine the quantity of free available chlorine. The capability of organic matter dissolution by the solutions alone and the mixtures of irrigants was analysed by weighing bovine muscle tissue specimens before and after submission to the following groups (n = 10): G1 - 0.9% saline solution (control), G2 - 2.5% NaOCl, G3 - 17% EDTAHNa3 , G4 - 10% EDTANa4 , G5 - 20% EDTANa4 , G6 - 5% NaOCl + 17% EDTAHNa3 , G7 - 5% NaOCl + 10% EDTANa4 and G8 - 5% NaOCl + 20% EDTANa4 . The times necessary for smear layer removal were determinated on discs of bovine dentine with a standardized smear layer produced with SiC papers using a scanning electron microscope that did not require the samples to be sputter coated. The dentine discs were submitted to the same experimental groups previously described (n = 10) over several time periods, and the photomicrographs acquired were scored for the presence of smear layer. The parametric data of tissue dissolution were analysed using two-way anova and one-way anova with Tukey's post hoc tests (α < 0.05), whilst nonparametric data of smear layer removal were analysed by Friedman test (α < 0.05) and the Kruskal-Wallis test with Dunn's post hoc (α < 0.05). RESULTS: EDTAHNa3 caused an almost complete and immediate loss of free available chlorine from NaOCl, whilst EDTANa4 promoted a slow and concentrat-ion-dependent decline. The organic matter was not dissolved in the control group, EDTA groups or the mixture of NaOCl + 17% EDTAHNa3 group (P > 0.05). NaOCl alone and the associations of NaOCl + EDTANa4 dissolved tissue at all periods analysed (P < 0.05). The smear layer was not removed in the control and NaOCl groups (P > 0.05). The smear layer was removed at 1 min in the NaOCl + 17% EDTAHNa3 group (P < 0.05); 2 min in 17% EDTAHNa3 group (P < 0.05); and 5 min in 10% EDTANa4 , 20% EDTANa4 , 5% NaOCl + 10% EDTANa4 and 5% NaOCl + 20% EDTANa4 groups (P < 0.05). CONCLUSIONS: Alkaline EDTANa4 was slower in removing the smear layer than EDTAHNa3 , but when mixed with NaOCl during biomechanical canal preparation promoted organic matter dissolution and smear layer removal simultaneously. However, the mixing of NaOCl and EDTANa4 should be performed immediately before use to prevent the reduction of free available chlorine.

Adrenergic alpha2A receptor gene and response to methylphenidate in attention-deficit/hyperactivity disorder-predominantly inattentive type.

An association between ADRA2A -1291 C > G polymorphism and response to methylphenidate in inattentive symptoms was previously suggested in children with ADHD. No investigation specifically assessed this association in ADHD-inattentive type (ADHD-I). In this naturalistic pharmacogenetic study, 59 subjects with ADHD-I from a non-referred sample were treated with short-acting methylphenidate and genotyped for ADRA2A -1291 C > G polymorphism. The primary outcome measure was the inattentive subscale of the SNAP-IV applied by a child psychiatrist blinded to genotype at baseline and first month of treatment. Children and adolescents with the G allele showed significantly lower inattentive scores with MPH treatment at the first month of treatment than subjects without the G allele (n = 59; F = 6.14; p = 0.016). We extended to ADHD-I previous findings suggesting the influence of the G allele at the ADRA2A -1291 C > G polymorphism on the improvement of inattentive symptoms with methylphenidate in children with all ADHD subtypes.