Técnicas de titulación ácido-base: consideraciones metrológicas / Acid-base titration techniques: metrological considerations / Técnicas de titulação ácido-base: considerações metrológicas

Resumen Se evaluaron diferentes sistemas de medición para titulaciones ácido-base, con el propósito de determinar cuál presenta mejores características metrológicas. Estos sistemas incluyen volumetrías y gravimetrías, las cuales se combinaron con diferentes métodos de detección del punto de equivalencia: (i) potenciometría, (ii) indicador ácido-base y (iii) conductividad electrolítica. Este artículo propone una nueva aproximación para la estimación de la incertidumbre de medición asociada a la detección del punto de equivalencia. Los resultados indicaron que, para la determinación del punto de equivalencia, las incertidumbres más bajas se obtienen mediante el método potenciométrico en comparación con el método conductimétrico cuyo sesgo es hasta 78 veces mayor. Sin embargo, se encontró que el método potenciométrico es fuertemente dependiente de la resolución del instrumento y/o la cantidad de agente titulante que se adiciona en la cercanía al punto de equivalencia. También se encontró que la incertidumbre disminuye cerca del 40% empleando métodos gravimétricos en comparación con los volumétricos. Al realizar la evaluación del sesgo de los sistemas de medición acorde con la guía ISO 33:2015, los resultados mostraron que, de los métodos evaluados, el método gravimétrico con detección potenciométrica presentó las mejores características metrológicas, pues se obtuvieron sesgos e incertidumbres menores.

Abstract Different measurement systems for acid-base titrations were evaluated to determine which one had the best metrological characteristics. These systems included volumetric and gravimetric titrations, which were combined with different detection systems: (i) potentiometry, (ii) acid-base indicator, and (iii) electrolytic conductivity. This article proposes a new approach for estimating the measurement uncertainty associated with the detection of the equivalence point. The results showed that, for the determination of the equivalence point, the lowest uncertainties were obtained by the potentiometric method in comparison with the conductometric method, whose bias was 78 times higher. The potentiometric method, however, was strongly dependent on the instrument resolution and/or the titrant amount that is added close to the equivalence point. It was also found that uncertainty decreases about 40% using gravimetric methods as compared to volumetric methods. When performing bias evaluation of the measurement systems according to the ISO 33:2015 guide, results showed that, among the evaluated methods, the gravimetric method with potentiometric detection presented the best metrological characteristics, with the lowest biases and uncertainties.

Resumo Foram avaliados diferentes sistemas de medida para titulações ácido-base, a fim de determinar quais possuem as melhores características metrológicas. Estes sistemas incluem titulações e gravimétricas, que foram combinadas com diferentes sistemas de detecção do ponto de equivalência: (i) potenciometria, (ii) indicador ácido-base e (iii) condutividade electrolítica. Este artigo propõe uma nova abordagem para estimar a incerteza de medição associada à detecção do ponto de equivalência. Os resultados indicaram que, para a determinação do ponto de equivalência, as incertezas mais baixas são obtidas pelo método potenciométrico enquanto que a incerteza do método condutométrico é até 78 vezes maior que a obtida pela potenciometria. Além disso, a potencimetria é altamente dependente da resolução do instrumento e/ou da quantidade de titulante para ser adicionado na proximidade com o ponto de equivalência. Também verificou-se que a incerteza diminui em torno de 40% utilizando métodos gravimétricos. De acordo à guia de norma ISO 33:2015, os resultados mostraram que os métodos de titulação ácido-base avaliados gravimetricamente com detecção potenciométrica proporcionaram as melhores características de metrologia, porque obtiveram os menores distorções e incertezas.

Growth Pattern and Prognostic Factors of Untreated Nonfunctioning Pituitary Adenomas

OBJECTIVE: Pituitary adenomas (PAs) are often detected as incidental findings. However, the natural history remains unclear. The objective of this study was to evaluate the natural history and growth pattern of untreated PAs. METHODS: Between 2003 and 2014, 59 PAs were managed with clinico-radiological follow up for longer than 12 months without any kind of therapeutic intervention. Tumor volumes were calculated at initial and last follow-up visit, and tumor growth during the observation period was determined. Data were analyzed according to clinical and imaging characteristics. RESULTS: The mean initial and last tumor volume and diameter were 1.83±2.97 mL and 13.77±6.45 mm, 2.85±4.47 mL and 15.75±8.08 mm, respectively. The mean annual tumor growth rate was 0.33±0.68 mL/year during a mean observation period of 46.8±32.1 months. Sixteen (27%) PAs showed tumor growth. The initial tumor size (HR, 1.140; 95% confidence interval, 1.003–1.295; p=0.045) was the independent predictive factor that determined the tumor growth. Six patients (11%) of 56 conservatively managed non-symptomatic PAs underwent resection for aggravating visual symptoms with mean interval of 34.5 months from diagnosis. By Cox regression analysis, PAs of last longest diameter over 21.75 mm were a significant prognostic factor for eventual treatment. CONCLUSION: The initial tumor size of PAs was independently associated with the tumor growth. Six patients (11%) of conservatively managed PAs were likely to be treated eventually. PAs of last follow-up longest diameter over 21.75 mm were a significant prognostic factor for treatment. Further studies with a large series are required to determine treatment strategy.

Growth Pattern and Prognostic Factors of Untreated Nonfunctioning Pituitary Adenomas

OBJECTIVE: Pituitary adenomas (PAs) are often detected as incidental findings. However, the natural history remains unclear. The objective of this study was to evaluate the natural history and growth pattern of untreated PAs.METHODS: Between 2003 and 2014, 59 PAs were managed with clinico-radiological follow up for longer than 12 months without any kind of therapeutic intervention. Tumor volumes were calculated at initial and last follow-up visit, and tumor growth during the observation period was determined. Data were analyzed according to clinical and imaging characteristics.RESULTS: The mean initial and last tumor volume and diameter were 1.83±2.97 mL and 13.77±6.45 mm, 2.85±4.47 mL and 15.75±8.08 mm, respectively. The mean annual tumor growth rate was 0.33±0.68 mL/year during a mean observation period of 46.8±32.1 months. Sixteen (27%) PAs showed tumor growth. The initial tumor size (HR, 1.140; 95% confidence interval, 1.003–1.295; p=0.045) was the independent predictive factor that determined the tumor growth. Six patients (11%) of 56 conservatively managed non-symptomatic PAs underwent resection for aggravating visual symptoms with mean interval of 34.5 months from diagnosis. By Cox regression analysis, PAs of last longest diameter over 21.75 mm were a significant prognostic factor for eventual treatment.CONCLUSION: The initial tumor size of PAs was independently associated with the tumor growth. Six patients (11%) of conservatively managed PAs were likely to be treated eventually. PAs of last follow-up longest diameter over 21.75 mm were a significant prognostic factor for treatment. Further studies with a large series are required to determine treatment strategy.

Comparision between Brain Atrophy and Subdural Volume to Predict Chronic Subdural Hematoma: Volumetric CT Imaging Analysis / 대한신경손상학회지

OBJECTIVE: Brain atrophy and subdural hygroma were well known factors that enlarge the subdural space, which induced formation of chronic subdural hematoma (CSDH). Thus, we identified the subdural volume that could be used to predict the rate of future CSDH after head trauma using a computed tomography (CT) volumetric analysis. METHODS: A single institution case-control study was conducted involving 1,186 patients who visited our hospital after head trauma from January 1, 2010 to December 31, 2014. Fifty-one patients with delayed CSDH were identified, and 50 patients with age and sex matched for control. Intracranial volume (ICV), the brain parenchyme, and the subdural space were segmented using CT image-based software. To adjust for variations in head size, volume ratios were assessed as a percentage of ICV [brain volume index (BVI), subdural volume index (SVI)]. The maximum depth of the subdural space on both sides was used to estimate the SVI. RESULTS: Before adjusting for cranium size, brain volume tended to be smaller, and subdural space volume was significantly larger in the CSDH group (p=0.138, p=0.021, respectively). The BVI and SVI were significantly different (p=0.003, p=0.001, respectively). SVI [area under the curve (AUC), 77.3%; p=0.008] was a more reliable technique for predicting CSDH than BVI (AUC, 68.1%; p=0.001). Bilateral subdural depth (sum of subdural depth on both sides) increased linearly with SVI (p<0.0001). CONCLUSION: Subdural space volume was significantly larger in CSDH groups. SVI was a more reliable technique for predicting CSDH. Bilateral subdural depth was useful to measure SVI.

Radiation Pneumonitis after Adjuvant Radiotherapy for Breast Cancer: A Volumetric Analysis Using CT Simulator / 한국유방암학회지

PURPOSE: To assess clinical factors and volumetric parameters associated with clinically significant symptomatic radiation pneumonitis (RP), which requires steroid medication after radiotherapy (RT). METHODS: Medical records of 204 irradiated breast cancer patients were reviewed. Percent lung volume (PLV) receiving more than 20 Gy was measured from CT-based treatment plan and was correlated with the central lung distance (CLD) of local and regional fields. PLV was also evaluated as a predictive factor of symptomatic RP, along with other previously reported clinical factors. RESULTS: Average (+/-standard deviation) actual irradiated lung volume and PLV for breast/chest wall irradiation were 169 (+/-50.6) cm3 and 14.9 (+/-3.8)%, respectively. Addition of regional irradiation resulted in increase of 183 (+/-80.2) cm3 in actual irradiated lung volume and 16.5 (+/-6.2)% in PLV. The correlation between CLD of the local fields and PLV was significant, with 1 cm of CLD corresponding to approximately 6% of PLV. CLD of the regional field was also significantly associated with PLV: a CLD of 3 cm corresponds to a PLV of approximately 13%; a CLD of 4 cm, approximately 17%; and a CLD of 5 cm, approximately 21%. RP developed in 11 patients (5.4%). There was an increased incidence of RP among patients who underwent local RT vs local and regional RT (2.4% vs 12.1%, p=0.0192). In terms of PLV, total PLV > or =23% was associated with the development of RP (p=0.0467). Previously reported clinical factors failed to show statistically significant association. CONCLUSION: Correlation between CLD and PLV for local and regional fields was significant on volumetric analysis. Although symptomatic RP requiring steroid medication was a rare complication, regional irradiation increased the incidence of RP, and such relationship can be expressed with a volumetric parameter of PLV.

Determination of Potassium Chloride in Compound Sodium Chloride Injection by Sodium Tetraphenylborate Volumetric Method / 中国药房

OBJECTIVE:To establish sodium tetraphenylborate volumetric method in place of gravimetric analysis method for the determination of the content of potassium chloride in compound sodium chloride injection.METHODS:The contents of potassium chloride in compound sodium chloride injection were determined by sodium tetraphenylborate volumetric method and sodium tetraphenylborate gravimetric method respectively,the results of which were compared.RESULTS:The average recovery of volumetric method was99.75%(RSD=0.46%,n=9),there was no significant difference in the t-test comparison between the determination results of volumetric method and that of the gravimetric method.CONCLUSION:The sodium tetraphenylborate volumetric method is simple,fast and accurate,which can take the place of gravimetric method for the deter?mination of contents of potassium chloride in compound sodium chloride injection.

Prediction of Late Enophthalmos by Volumetric Analysis of Blowout Fractures using Orbital CT

The purpose of this study was to determine whether orbital volume assessment by CT could provide additional information for the initial evaluation of orbital blowout fractures and guide optimal treatment. The medical records of 26 patients with orbital blowout fractures, either surgically or conservatively managed, were retrospectively reviewed. Orbital volumetric analysis was then determined from digitized CT scans. Fracture-related volume expansion relative to the unaffected fellow orbit was correlated with degree of enophthalmos. Early Hertel's measurements[4 weeks] were obtained in 13 nonrepaired fractures and in 3 of 13 surgically repaired patients[late presentation;16 patients]. When seen at more than 4 weeks, 4[80%] of 5 patients with> OR =13% orbital volume expansion manifested significant enophthalmos[>2 mm] compared with 2[18.2%] of 11 patients with<13% orbital expansion[p<0.01]. CT measurements of orbital volume can predict the final degree of late enophthalmos and may facilitate the planning of surgical intervention.