Guía internacional para una dosificación más segura de la clozapina en adultos mediante el uso de 6 titulaciones personalizadas de dosis basados en la etnicidad, la proteína C reactiva y los niveles de clozapina / An international adult guideline for making clozapine titration safer by using six ancestry-based personalized dosing titrations, CRP, and clozapine levels

Esta guía internacional propone mejorar los prospectos de la clozapina en todo el mundo mediante la inclusion de información sobre la titulación del fármaco en función de la ascendencia del paciente. Las bases de datos de reacciones adversas a medicamentos (RAM) sugieren que la clozapina es el tercer fármaco más tóxico en los Estados Unidos de América (EE. UU.) y que produce una mortalidad por neumonía en todo el mundo 4 veces mayor que la correspondiente a la agranulocitosis o la miocarditis. El rango terapéutico de referencia para las concentraciones séricas estables de clozapina es estrecho, de 350 a 600 ng/ml, con potencial de toxicidad y reacciones adversas más fecuentes a medida que aumentan las concentraciones. La clozapina se metaboliza principalmente por CYP1A2 (las mujeres no fumadoras requieren la dosis más baja y los hombres fumadores la dosis más alta). A través de la conversión fenotípica, la prescripción conjunta de inhibidores del metabolismo de la clozapina (incluidos los anticonceptivos orales y el valproato), la obesidad o la inflamación con elevaciones de la proteína C reactiva (PCR), pueden convertir al paciente en un metabolizador lento/pobre (MP). Las personas de ascendencia asiática (de Pakistán a Japón) o los habitantes originarios de las Américas tienen menor actividad de CYP1A2 y requieren dosis más bajas de clozapina para alcanzar concentraciones de 350 ng/ml. En los EE. UU. se recomiendan dosis diarias de 300-600 mg/día. La dosificación personalizada lenta puede prevenir RAM tempranas (incluidos el síncope, la miocarditis y la neumonía). La esencia de esta guía se fundamenta en 6 esquemas de titulaciones personalizadas para pacientes hospitalizados...(AU)

This is the Spanish translation of an international guideline which proposes improving clozapine package inserts worldwide by using ancestry-based: 1) dosing and 2) titration. Adverse drug reaction (ADR) databases suggest clozapine: 1) is the third most toxic drug in the United States (US), and 2) produces worldwide pneumonia mortality four times greater than that of agranulocytosis or myocarditis. For trough steady-state clozapine serum concentrations, the therapeutic reference range is narrow, from 350 to 600 ng/mL with the potential for toxicity and ADRs as concentrations increase. Clozapine is mainly metabolized by CYP1A2 (female non-smokers require the lowest dose and male smokers the highest dose). Poor metabolizer (PM) status through phenotypic conversion is associated with co-prescription of inhibitors (including oral contraceptives and valproate), obesity or inflammation with C-reactive protein (CRP) elevations. People with ancestry from Asia (Pakistan to Japan) or the Americas’ original inhabitants have lower CYP1A2 activity and require lower clozapine doses to reach concentrations of 350 ng/ml. Daily doses of 300-600 mg/day are recommended in the US. Slow personalized titration may prevent early ADRs (including syncope, myocarditis and pneumonia). The core of this guideline consists of six personalized titration schedules for inpatients...(AU)

La edad y el uso de máscara oronasal se asocian con menor calidad en la titulación con CPAP autoajustable en domicilio en pacientes sin adaptación / Age and Oronasal Mask are Associated with Lower Quality in Automatic CPAP Titration at Home in Patients without Previous Adaptation

Introducción: se considera aceptable (TitAcept) una prueba con CPAP automático en domicilio (APAP) cuando su uso es ≥ a 4 horas/noche y el índice de apneas residuales (IAHr) ≤ 10 eventos/hora (AASM). Sin embargo, todas las variables relacionadas con la calidad de este procedimiento no se conocen completamente. Objetivo: evaluar la cali-dad de la titulación con APAP en el domicilio. Material y métodos: estudio retrospectivo en pacientes "naïve" de CPAP. El criterio de TitAcept seleccionó dos grupos y la regresión logística múltiple identificó predictores de prueba no aceptables. Resultados: incluimos 1325 TitAcept; 941 hombres (71%), edad: 57 ± 12,4 años, IMC: 32,3 ± 8,8 kg/m2, IAH: 34,2 ± 19 ev/h. La titulación alcanzó 3,4 ± 3,5 noches, adherencia: 379 minutos/noche; pre-sión efectiva: 8,7 ± 1,7 cm H2O, IAHr; 3,1 ± 2,4 ev/h y fugas 16,1 ± 8,7 litros/min. Fueron predictores; edad ≥ 50 años; OR: 1,62 (IC95%: 1,23-3,46), p: 0.0005 y máscara orona-sal; OR: 2,49 (IC95%: 1,79-3,46), p: 0.0001. Conclusiones: una significativa proporción de pacientes que realizaron una titulación no vigilada con APAP en domicilio no alcan-zaron criterios de calidad adecuada. La edad ≥ 50 años y el uso de máscara oronasal se asocian con menor calidad en la prueba, de acuerdo a criterios preestablecidos. (AU)

Introduction: automated CPAP (APAP) titration at home is considered acceptable (Tit-Accept) when its device is used ≥ 4 hours/night and the residual apnea index (AHIr) es ≤ 10 events/hour (AASM). However, all the variables related to quality of this procedure are not fully known. Objective: to assess the quality of the titration with APAP at home.Material and Methods: retrospective study in CPAP "naïve" patients. The TitAccept criteri-on selected two groups and multiple logistic regression identified predictors of non-ac-ceptable titration. Results: we included 1325 TitAccept; 941 men (71%), age: 57 ± 12.4 years, BMI: 32.3 ± 8.8 kg/m2, baseline AHI: 34.2 ± 19 ev/h. The titration reached 3.4 ± 3.5 nights, adherence: 379 minutes/night; effective pressure: 8.7 ± 1.7 cmH2O, AHIr; 3.1 ± 2.4 ev/h and leaks 16.1 ± 8.7 liters/min. The predictors were; age ≥ 50 years; OR: (AU)

A low-cost automated titration system for colorimetric endpoint detection.

An auto titrator system was developed to accurately and precisely detect colorimetric endpoints for spectrochemical titrations. This system was constructed using inexpensive components such as a Raspberry Pi® single-board computer, 3D-printed components, and a commercially available spectral sensor. The auto titrator was evaluated by performing a standard method for determination of water hardness. Regardless of analyst experience, the auto titrator performed better than the traditional titration approach that involves manual dosing of titrant and visual detection of the endpoint. Inter-day, intra-day, inter-instrumental, and intra-instrumental validation studies were performed to establish the accuracy and precision of endpoint detection. The auto titrator eliminates the subjective bias in color perception and produces accurate and precise endpoint results.

A hybrid strategy combining solution NMR spectroscopy and isothermal titration calorimetry to characterize protein-nanodisc interaction.

NMR is a powerful tool for characterizing intermolecular interactions at atomic resolution. However, the nature of the complex interactions of membrane-binding proteins makes it difficult to elucidate the interaction mechanisms. Here, we demonstrated that structural and thermodynamic analyses using solution NMR spectroscopy and isothermal titration calorimetry (ITC) can clearly detect a specific interaction between the pleckstrin homology (PH) domain of ceramide transport protein (CERT) and phosphatidylinositol 4-monophosphate (PI4P) embedded in the lipid nanodisc, and distinguish the specific interaction from nonspecific interactions with the bulk surface of the lipid nanodisc. This NMR-ITC hybrid strategy provides detailed characterization of protein-lipid membrane interactions.

Electrochemical Performance of Na3V2(PO4)2F3 Electrode Material in a Symmetric Cell.

A NASICON-based Na3V2(PO4)2F3 (NVPF) cathode material is reported herein as a potential symmetric cell electrode material. The symmetric cell was active from 0 to 3.5 V and showed a capacity of 85 mAh/g at 0.1 C. With cycling, the NVPF symmetric cell showed a very long and stable cycle life, having a capacity retention of 61% after 1000 cycles at 1 C. The diffusion coefficient calculated from cyclic voltammetry (CV) and the galvanostatic intermittent titration technique (GITT) was found to be ~10-9-10-11, suggesting a smooth diffusion of Na+ in the NVPF symmetric cell. The electrochemical impedance spectroscopy (EIS) carried out during cycling showed increases in bulk resistance, solid electrolyte interphase (SEI) resistance, and charge transfer resistance with the number of cycles, explaining the origin of capacity fade in the NVPF symmetric cell. Finally, the postmortem analysis of the symmetric cell after 1000 cycles at a 1 C rate indicated that the intercalation/de-intercalation of sodium into/from the host structure occurred without any major structural destabilization in both the cathode and anode. However, there was slight distortion in the cathode structure observed, which resulted in capacity loss of the symmetric cell. The promising electrochemical performance of NVPF in the symmetric cell makes it attractive for developing long-life and cost-effective batteries.

Comparison of prenatal anti-D titration testing by gel and tube methods: A review of the literature.

BACKGROUND: Antenatal titration testing is traditionally performed using a manual tube test. Tube testing has limitations; it is a manual, time-consuming method with wide interobserver variability. Gel-based testing is an attractive alternative because it is more precise and can be automated. This study's objective was to summarize the published literature that assessed the relationship between titrations performed by tube and gel for anti-D alloimmunized pregnancies. STUDY DESIGN AND METHODS: A comprehensive literature search was performed. Articles were selected if research was original and compared at least five pairs of anti-D titration tests performed by gel and tube. Differences in the number of dilutions between gel and tube methods were compared overall by study and cell type using linear models. RESULTS: A total of 512 articles were identified; eight were included, and titer data from 384 tube and gel pairs were abstracted. The median anti-D titer in tube was 8 (range 0-2048) and by gel was 64 (range 0-4096). Anti-D gel titration results were 2.1 (95% CI; 1-3.3) additional dilutions greater than in tube. Most studies utilized double-dose reagent cells for testing. At a tube titer of 16, the sensitivity and specificity of gel titrations is maximal (91% and 94% respectively) at a gel titer of 64. CONCLUSION: Overall, titrations performed by gel were two dilutions higher than the corresponding tube titer. For titrations, double-dose reagent cells should be considered to standardize practice. A rigorous prospective study is needed to compare tube titrations with gel titrations using a standardized process.

Similar glycaemic control and risk of hypoglycaemia with patient- versus physician-managed titration of insulin glargine 300 U/mL across subgroups of patients with T2DM: a post hoc analysis of ITAS.

AIMS: The Italian Titration Approach Study (ITAS) demonstrated comparable HbA1c reductions and similarly low hypoglycaemia risk at 6 months in poorly controlled, insulin-naïve adults with T2DM who initiated self- or physician-titrated insulin glargine 300 U/mL (Gla-300) in the absence of sulphonylurea/glinide. The association of patient characteristics with glycaemic and hypoglycaemic outcomes was assessed. METHODS: This post hoc analysis investigated whether baseline patient characteristics and previous antihyperglycaemic drugs were associated with HbA1c change and hypoglycaemia risk in patient- versus physician-managed Gla-300 titration. RESULTS: HbA1c change, incidence of hypoglycaemia (any type) and nocturnal rates were comparable between patient- and physician-managed arms in all subgroups. Hypoglycaemia rates across subgroups (0.03 to 3.52 events per patient-year) were generally as low as observed in the full ITAS population. Small increases in rates of 00:00-pre-breakfast and anytime hypoglycaemia were observed in the ≤ 10-year diabetes duration subgroup in the patient- versus physician-managed arm (heterogeneity of effect; p < 0.05). CONCLUSIONS: Comparably fair glycaemic control and similarly low hypoglycaemia risk were achieved in almost all patient subgroups with patient- versus physician-led Gla-300 titration. These results reinforce efficacy and safety of Gla-300 self-titration across a range of phenotypes of insulin-naïve people with T2DM. CLINICAL TRIAL REGISTRATION: EudraCT 2015-001167-39.

THE MAKING OF A FOOTPRINT IN PROTEIN FOOTPRINTING: A REVIEW IN HONOR OF MICHAEL L. GROSS.

Within the past decade protein footprinting in conjunction with mass spectrometry has become a powerful and versatile means to unravel the higher order structure of proteins. Footprinting-based approaches has demonstrated the capacity to inform on interaction sites and dynamic regions that participate in conformational changes. These findings when set in a biological perspective inform on protein folding/unfolding, protein-protein interactions, and protein-ligand interactions. In this review, we will look at the contribution of Dr. Michael L. Gross to protein footprinting approaches such as hydrogen deuterium exchange mass spectrometry and hydroxyl radical protein footprinting. This review details the development of novel footprinting methods as well as their applications to study higher order protein structure. © 2020 The Authors. Mass Spectrometry Reviews published by John Wiley & Sons Ltd. Mass Spec Rev.

Titration of Recombinant Adeno-Associated Virus (rAAV) Genome Copy Number Using Real-Time Quantitative Polymerase Chain Reaction (qPCR).

This protocol is used to determine the concentration of DNase-resistant vector genomes (i.e., packaged in the capsid) in purified recombinant adeno-associated virus (rAAV) preparations. The protocol begins with treatment of the vector stock with DNase I to eliminate unencapsidated AAV DNA or contaminating plasmid DNA. This is followed by a heat treatment to heat-inactivate DNase I, to disrupt the viral capsid, and to release the packaged vector genomes for quantification by real-time polymerase chain reaction (PCR) using a set of standards (linearized plasmid used for vector production) containing known copy numbers. To accomplish high-throughput titration, the primer and probe sets used in real-time PCR are usually designed to target common elements present in most rAAV genomes, such as promoters and poly(A) signals. This strategy significantly reduces the number of PCRs, controls, and turnaround time. Several important controls should be included in the assay as follows: The first two controls should have a known copy number of the rAAV genome plasmid treated or not treated with DNase I. This control tests the effectiveness of DNase treatment. To control for potential cross-contamination between samples during the preparation process, a blank control containing nuclease-free water only should be processed and tested in parallel. A validation vector sample with a known titer should be included in every assay to monitor interassay variability. Finally, for the PCR run, a no-template control (NTC) is included to indicate cross-contamination during PCR setup.

Zika Virus Isolation, Purification, and Titration.

Zika virus (ZIKV) is an important pathogen transmitted to humans by the mosquito vector Aedes aegypti. ZIKV is able to infect several tissues and organs and, importantly, has been associated with microcephaly and central nervous system abnormalities in fetuses and newborn babies of mothers exposed to ZIKV during pregnancy, as well as neurological diseases such as Guillain-Barré syndrome in adults. There is currently no vaccine or drug licensed to prevent or treat ZIKV infections. The use of ZIKV isolation in disease diagnosis has been largely replaced by new techniques. However, virus isolation is still considered as a gold standard for the detection of ZIKV and is usually performed in research and reference laboratories for characterization, sequencing, and a variety of research experiments including pathogenesis, drug susceptibility, and vaccine efficacy. The experimental procedures presented here describe the most common techniques used for ZIKV isolation, propagation, purification, and quantification.

Late administration of caffeine affects cardiac maturation in chick embryos: a combined two and threedimensional morphogenetic and gene analyses

Cardiac malformations are very prevalent and can be caused both by defective genes and envi-ronmental teratogens. Among the latter, caffeine causes malformations when exposed during early cardiac development, whereas its later effects are still unclear. We exposed three-day incubated (D3) chick embryos to 2 mg caffeine and analyzed them at D5, D7 and D9. The embryos were serially sec-tioned and analyzed two-dimensionally. Alternatively, the sections of D9 embryos were reconstructed three-dimensionally using Amira® software and analyzed volumetrically. The expres-sion of genes involved in endothelial-mesenchymal transformation (EMT) was studied by real-time PCR. Interestingly, caffeine treatment at D3 em-bryos did not induce cardiac malformations, but did delay growth, in particular that of the ventricles and ventricular trabeculae. Furthermore, it affected EMT in the endocardial cushion and atrioventricu-lar valves. Gene-expression analysis revealed that caffeine had a progressively deleterious effect on the expressions of GATA4, MMP2, SNAIL1, TWIST1, and VIMENTIN. The effect of late caf-feine administration on the chicken embryos would provide suggestive evident towards a possible heart developmental defect in humans, particularly heavy caffeine consumers during pregnancy

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Human Serum Albumin Binding in a Vial: A Novel UV-pH Titration Method To Assist Drug Design.

The knowledge on human serum albumin (HSA) binding is of utmost importance as it affects pharmacokinetic behavior and bioavailability of drugs. In this article, we report a novel method to screen for ionizable molecules with high HSA binding affinity based on pKa shifts using UV-pH titration. We investigated the HSA binding of 27 drugs and compared the results to experimental data from conventional methods. In most cases, significant shifts (ΔpKa > 0.1) were observed for drugs with high HSA binding, while no change could be detected for low-affinity binders. We showed the pivotal role of ionization centers in the formation of strong interactions between drug and HSA using molecular docking studies. We also verified our findings by testing five modified analogues designed by structural considerations. Significant decreases in their HSA binding proved that the UV-pH titration method combined with an in silico support can be used as a medicinal chemistry tool to assist rational molecular design.

An environment-friendly spot test method with digital imaging for the micro-titration of citric fruits.

A new method to determine the total titratable acidity of orange, lemon and passion fruit, based on a spot test obtained from digital images and using anthocyanins as the biodegradable indicator, is presented for the first time. The colorimetric reactions were carried out by acid-base titration on a microscale, employing anthocyanin with a microplate for spot test purposes, with detection by digital imaging. To obtain highly precise data, a chamber based on a diffuser was developed to control the illumination supplied by the light emitting diodes, and coupled to a smartphone to acquire adequate digital images. High precision was obtained with a relative standard deviation of 0.758% for n = 95. The RGB values were extracted from the digital images and used as analytical signals, the values being correlated with the micro-volume of the titrant and used to construct the titration curves and obtain the first and second derivatives, respectively. For comparative purposes, the official AOAC (Association of Official Analytical Chemists) and MAPA (Ministry of Agriculture, Livestock and Food Supply of Brazil) methods were used and the results compared by applying the paired t-test at the 95% confidence level (n = 3). No difference was found between the values and the relative errors were less than 2.8%. The micro-titrimetric method was fast, uses anthocyanins as the natural indicator, is practical, and permits a reduction of 922 times or 99.9% of the volume required in a conventional titration. It is therefore ideal for routine analyses leading to a reduction in the waste generated, according to the principles of green chemistry.

Análise volumétrica e linear do tecido ósseo em camundongos Knockout para receptores AT1 e AT2 da Angiotensina II / Volumetric and linear analysis of bone tissue in Angiotensin II AT1 and AT2 receptor Knockout mice

O osso é um tecido conjuntivo mineralizado que além de fornecer uma estrutura para o corpo, funciona como um órgão endócrino. Há diversas doenças que podem envolver o metabolismo ósseo, como a doença periodontal que é um processo inflamatório multicausal. O Sistema ReninaAngiotensina, que tem como principal modulador a Angiotensina II, está envolvido com o equilíbrio eletrolítico e a inflamação. A Angiotensina II interage principalmente com dois receptores, tipo 1 (AT1) e tipo 2 (AT2). Este trabalho objetivou realizar uma análise volumétrica e linear do tecido ósseo de camundongos em animais saudáveis e submetidos a um modelo experimental de doença periodontal: influência dos receptores AT1 e AT2 da angiotensina II. Foram utilizados seis grupos, três controles e três experimentais, com dez animais cada um, utilizando três linhagens distintas de camundongos: selvagem (WT), knockout AT1 e knockout AT2. A doença periodontal foi induzida através de ligadura, com fio de nylon 5.0, e após quinze dias os animais foram submetidos à eutanásia. Com o intuito de analisar se as variações genéticas teriam influência sobre as características fenotípicas do tecido ósseo foram realizadas análises de amostras da coluna vertebral e do fêmur dos animais das três linhagens utilizadas. A perda óssea foi avaliada através das análises volumétricas e linear através de MICRO-CT. Os resultados obtidos a partir das amostras de coluna vertebral demonstraram houve diferença significativa na densidade óssea entre o grupo WT e o AT1 (p < 0,05). Em relação ao número e separação entre as trabéculas houve diferença significativa entre os grupos WT e AT1(p < 0,01) e WT e AT2 (p < 0,05), para ambas as análises. Não houve diferença significativa entre as linhagens knockout. O modelo utilizado foi eficaz gerando perda óssea e diferenças significativas entre os controles e doentes (WT e AT1: p < 0,001; AT2: p < 0,01). Na análise das amostras de maxila não houve diferenças significativas entre as linhagens que foram submetidas à doença periodontal. O nocaute dos genes dos receptores de angiotensina II promoveu alterações no fenótipo ósseo dos animais, tendo, nesses grupos, uma redução da densidade e qualidade óssea. A presença exclusiva do receptor AT1 não foi indutora de uma maior perda óssea, nem a presença exclusiva do receptor AT2 se mostrou protetora, mas parece ser determinante para o metabolismo ósseo (AU).

Bone is a mineralized connective tissue that in addition to providing a structure for the body, functions as an endocrine organ. There are several diseases that can involve bone metabolism, such as periodontal disease, which is a multicausal inflammatory process. The Renin-Angiotensin System, whose main modulator is Angiotensin II, is involved with electrolyte balance and inflammation. Angiotensin II interacts mainly with two receptors, type 1 (AT1) and type 2 (AT2). This work aimed to carry out a volumetric and linear analysis of the bone tissue of mice in healthy animals and submitted to an experimental model of periodontal disease: influence of angiotensin II AT1 and AT2 receptors. Six groups were used, three controls and three experimental, with ten animals each, using three different lines of mice: wild (WT), knockout AT1 and knockout AT2. Periodontal disease was induced by ligation, with 5.0 nylon thread, and after fifteen days the animals were euthanized. In order to analyze whether genetic variations would influence the phenotypic characteristics of bone tissue, analyzes of samples from the spine and femur of the animals of the three strains used were performed. Bone loss was assessed using volumetric and linear analysis using MICRO-CT. The results obtained from the spine samples showed a significant difference in bone density between the WT and AT1 groups (p <0.05). Regarding the number and separation between the trabeculae, there was a significant difference between the groups WT and AT1 (p <0.01) and WT and AT2 (p <0.05), for both analyzes. There was no significant difference between the knockout strains. The model used was effective in generating bone loss and significant differences between controls and patients (WT and AT1: p <0.001; AT2: p <0.01). In the analysis of the maxilla samples, there were no significant differences between the strains that were submitted to periodontal disease. The knockout of the angiotensin II receptor genes promoted changes in the bone phenotype of the animals, having, in these groups, a reduction in bone density and quality. The exclusive presence of the AT1 receptor did not induce greater bone loss, nor did the exclusive presence of the AT2 receptor prove to be protective, but it seems to be determinant for bone metabolism (AU).

The enzyme-modified comet assay: Enzyme incubation step in 2 vs 12-gels/slide systems.

The enzyme-modified comet assay is a commonly used method to detect specific DNA lesions. However, still a lot of errors are made by many users, leading to dubious results and even misinterpretations. This technical note describes some critical points in the use of the enzyme-modified comet assay, such as the enzyme concentration, the time of incubation, the format used and the equipment. To illustrate the importance of these conditions/parameters, titration experiments of formamidopyrimidine DNA glycosylase (Fpg) were performed using the 2 gels/slide and the 12 minigels/slide formats (plus the 12-Gel Comet Assay Unit™). Incubation times of 15 and 30 min, and 1 h were used. Results showed that the 12 minigels/slide system requires a lower volume and concentration of Fpg. A longer time of incubation has a bigger impact when using such format. Moreover, the paper describes how to perform and interpret a titration experiment when using the enzyme-modified comet assay.

[Improvement of the Non-aqueous Titration Method in the Japanese Pharmacopoeia for a Purpose of Advancement in Experimental Safety Using Alternative Solvents].

In this study, we attempted to improve the non-aqueous titration method using N,N-dimethylformamide (DMF) in the Japanese Pharmacopoeia seventeenth edition (JP XVII) for advancement in experimental safety. As an alternative solvent for DMF, we demonstrate titrations using dimethyl sulfoxide (DMSO), which has similar properties as and much higher safety than DMF. Five drugs (i.e., acetohexamide, glibenclamide, sulfamethoxazole, tranilast, and furosemide) listed in JP XVII use DMF as a solvent for titrations with sodium hydroxide standard solution. For these drugs, we examined whether DMF can be replaced with DMSO in quantitative analyses. As a result, a quantification similar to that of the Pharmacopoeia protocol is possible by simply replacing DMF with DMSO or using a mixed solvent of DMSO and water.

Miniaturized Potentiometric Titration for Improving Portability and Accuracy in the Determination of Total Acid in Squeezed Fruit Juice.

To determine the total acidity in freshly squeezed fruit juice, we miniaturized the potentiometric titrations and achieved better accuracy compared with titrations from a conventional pH probe. The improvement was the result of a higher jump in pH at the endpoint due to a reduction in the dilutions of both the titrand and titrant. A conventional pH probe requires more than 50 mL of titrand, which can lead to a 25000-fold dilution of the titrant when adding the titrant at 2 µL intervals. Conversely, when the volume of the titrand can be reduced to 1 mL, the dilution is only 500-fold, which results in a higher jump in pH at the endpoint. The concentration of the titrant, NaOH, was optimized by titrating sample solutions containing 25 and 50 mM of citric acid. The addition of 5 M NaOH in intervals of 2 µL led to a more accurate endpoint for both 25 and 50 mM citric acid solutions. Miniaturization of the titration process is advantageous in terms of portability, accuracy, and in requiring less consumption of a sample, thereby simplifying the process of repeat measurements that are helpful in evaluating the precision of analytical results. Practical samples of squeezed fruit juices were titrated via three methods that showed no significant differences: classic titrimetry with an indicator, conventional potentiometry, and miniaturized potentiometry. This process would be effective for use in the field and in developing countries. PRACTICAL APPLICATION: The total acidity of fruits and fruit juices is an important indicator of quality and is generally expressed in terms of the citric acid content. However, a standard potentiometric titration requires a large sample volume, which makes it difficult to assess dispersion of the acidity for individual fruits. The results of this study indicate that the use of miniaturized potentiometric titration could benefit food chemistry in many developing countries in addition to opening new fields of food chemistry such as on-site quality control of citrus fruit and evaluation of variations in quality.

Rapid evaluation of bioactive Ti-based surfaces using an in vitro titration method.

The prediction of implant behavior in vivo by the use of easy-to-perform in vitro methods is of great interest in biomaterials research. Simulated body fluids (SBFs) have been proposed and widely used to evaluate the bone-bonding ability of implant materials. In view of its limitations, we report here a rapid in vitro method based on calcium titration for the evaluation of in vivo bioactivity. Using four different titanium surfaces, this method identifies that alkaline treatment is the key process to confer bioactivity to titanium whereas no significant effect from heat treatment is observed. The presence of bioactive titanium surfaces in the solution during calcium titration induces an earlier nucleation of crystalline calcium phosphates and changes the crystallization pathway. The conclusions from this method are also supported by the standard SBF test (ISO 23317), in vitro cell culture tests using osteoblasts and in vivo animal experiments employing a pelvic sheep model.

Capillary electrophoretic apparatus for the endpoint detection in microtitration methods.

Titration methods are routinely used in the laboratories for the quantification of acids and bases, for the complexometric determination of metal ions and for the ion-pair titrations of drugs in pharmaceutical control. They also find application in a wide variety of chemical and biochemical studies. However, conventional titration methods (CTM) require large amounts of samples that are not always available. In absence of micro-titrator devices, the application of these methods for expensive samples and for small batch sizes is not possible. In this work, it was demonstrated that the commercial capillary electrophoretic apparatus (CEa) can be used, in a quick and easy way, for the end-point detection in a microtitration process. The proposed methodology exploits the change of the solutions conductivity during the titrations. The equivalent points can be easily located by plotting the change in electrical current as a function of the titrant volume added. More interestingly, only 1.1-1.5 mL of analyte solutions are required to establish the titration curves. The advantages and the limitations of the procedure are discussed in detail.