MBL과 컴퓨터 시뮬레이션을 이용한 산·염기 중화 적정에서 적정곡선에 대한 연구

이종백,강대풍,김윤하,김영환,정민재,이상권 한국과학영재교육학회 2019 과학영재교육 Vol.11 No.3

This study is based on Research and Education (R&E) project in Chonnam National University. We explored the variation of the titration curve in the acid-base titration for various acids by both the experiment using the pH meter and MBL tool and the computer simulation. The pH variations in the titration experiment were recorded using pH meter and MBL apparatus by adding the titrant in the titration rate of 0.015mL/sec. The computer simulations were carried out using FORTRAN programming and compared with the experimental data. In the monoprotic strong acid-strong base reaction, the rapid pH variation on the equivalent point in the titration curve is occurred, thus the end point can be found easily in the acid-base neutralization titration experiment. In the monoprotic weak acid-strong base reaction, the rapid pH variation on the equivalent point in the titration curve is also occurred, thus the end point can be found easily. On the contrary, in the diprotic acid-strong base reaction, the pH variation on the equivalent point is dependent on the two acid dissociation constants significantly. For the weak diprotic acid, the evident rapid pH variation on the first equivalent point is generally occurred, whereas the evident rapid pH variation on the second equivalent point is not occurred. Furthermore, for the strong diprotic acid (H2SO4), the rapid pH variation on the equivalent point in the titration curve is occurred only on the second equivalent point. For considered all cases in this study, the computer simulations are significantly consistent with the experimental results, thus can elucidate the pH variations in the equivalent points. Therefore, we suggest that the end point can be found easily and exactly for any acid-base reaction if the computer simulation is carried out before the acid-base neutralization titration experiment. 이 연구는 전남대학교 과학영재교육원 사사과정에 서 진행하는 연구로 수행되었다. 본 연구에서는 산과 염기의 변화에 따른 산・염기 적정곡선의 변화를 pH 센서와 MBL을 이용한 적정 실험과 컴퓨터 시뮬레이션을 통해 살펴보았다. 적정 실험은 실린지 펌프와 MBL을 이용하여 0.015mL/초 간격으로 적정시약을 첨가하면서 적정용액의 pH 변화를 기록하였다. 다음으로 포트란 프로그래밍으로 산・염기 적정시 pH 변화를 시뮬레이션하여 실험결과와 비교하였다. 강산과 강염기의 적정곡선에서는 당량점에서 pH의 매우 급격한 변화가 있기 때문에 적정 실험을 통하여 pH 변화를 기록함으로써 종말점을 쉽게 찾아낼 수 있었다. 약산과 강염기의 적정곡선에서도 당량점에서는 pH 변화가 급격하기 때문에 적정 실험시 pH 변화를 기록함으로써 종말점을 쉽게 찾아낼 수 있었다. 한편, 이양성자산과 강염기의 적정에서는 이양성자산의 단계적 해리상수에 따라 당량점에서의 변화가 많은 영향을 받았다. 이양성자산 약산의 경우 첫 번째 당량점에서의 pH 변화는 대부분의 경우 뚜렷하게 나타나지만 이차 당량점은 산의 해리 상수에 따라 뚜렷하게 나타나지 않는 경우가 많았다. 더구나 황산의 경우에는 이차 당량점에서만 뚜렷한 pH 변화가 있었다. 본 연구에서 수행한 컴퓨터 시뮬레이션은 모든 산・염기 반응에 대해 실험적으로 나타난 산・염기 적정곡선과 매우 잘 일치하였으며 각 당량점에서의 pH 변화를 정확하게 설명할 수 있었다. 따라서 적정 실험을 행하기 전 컴퓨터 프로그래밍을 통해 산・염기 적정곡선을 시뮬레이션한 후 실험을 수행함으로써 당량점을 정확하게 확인할 수 있으리라 기대된다.

포도과즙을 이용하여 제조한 고산도 식초의 품질특성

우승미,여수환,권중호,김선화,정용진 한국식품저장유통학회 2015 한국식품저장유통학회지 Vol.22 No.1

This study was conducted to develop a high-acidity vinegar production (over TA 10%) technology using grape juice to reduce the importation of high-acidity vinegar. The manufacturing condition’s effect on the quality of high-acidity vinegar using pure grape juice without the addition of other nutrients for fermentation was investigated. Twelve percent acidity in vinegar was obtained from grape wine with 6% alcohol content. The acetic-acid yield from grape wine decreased when the wine’s initial alcohol content was high, which extended the induction time. The pH value was similar in all the treatment groups. The sugar content of the 1st-stage fermentation (1st AAF) was proportional to the initial alcohol content whereas in the 2nd-stage fermentation (2nd AAF), the sugar content was highest in the 6%-alcohol treatment. The major organic acids of the high-acidity grape vinegar included tartaric acid, malic acid, and citric acid. The acid content of the high-acidity initial alcohol group was higher than that of the low-acidity initial alcohol group due to the alcohol content added by the fed-batch and acetic-acid yield difference. The ethyl alcohol content was 364~6,091 ppm (the main alcohol while the others had only traces in all the groups). In conclusion, it was possible to manufacture 12% high-acidity vinegar without the addition of an external nutrient source to grape wine containing 6% initial alcohol content. Finally, a complementary study will be required to shorten the fermentation period through the fed-batch-style addition of alcohol for the purpose of industrialization.

Estimating Fruit Characteristics through Image Analysis in ‘Fuji’ Apple Fruits

Hye-Young Sang,Jae-Young Lee,Hae-Woong Jung,In-Myung Choi,Hee-Seung Park 한국원예학회 2005 Horticulture, Environment, and Biotechnology Vol.46 No.2

All observed outer features in ‘Fuji’ apple fruits failed to show certain relationships with Brix degree and their pigment contents also did not exhibit a reliable correlation with it except chlorophyll b content. The distribution of red and green color showed higher significance with Brix degree (r = 0.52 and ?0.44). On the other side, fruit outer features negatively correlated with flesh firmness (r = ?0.70 in fruit weight, ?0.61 in fruit length, and ?0.79 in fruit diameter) and titratable acidity (r = ?0.56 in fruit weight, ?0.46 in fruit length, and ?0.56 in fruit diameter). Flesh firmness and titratable acidity showed negative correlation with anthocyanin content, but had positive correlation with chlorophyll content. However, there was negative correlation of color distribution on fruit skin to flesh firmness and titratable acidity. An index was devised at the basic concept of fruit cross-sectional shape (CS) to improve the evaluation of Brix degree, flesh firmness, and titratable acidity through observing outer fruit appearance. In presuming fruit characteristics by fruit outer features, the introducing CS index generally increased the reliance in estimating Brix degree, but decreased the significance in measuring flesh firmness and titratable acidity.

Proton Affinity Distributions of Humic Acid Extracted from Upland and Paddy Soils

정창윤,박찬원,김정규,임수길,Jeong, Chang-Yoon,Park, Chan-Won,Kim, Jeong-Gyu,Lim, Soo-Kil 한국토양비료학회 1999 한국토양비료학회지 Vol.32 No.4

Potentiometric titration data were collected for some humic acids purified from Korean upland and paddy soils over a range of pH (3.0 - 11.0) with $NaNO_3$ background electrolyte concentrations (0.01, 0.10, 0.50 and 1.00 M). The data were applied to model A and V which included both intrinsic heterogeneity of humic materials and electrostatic interaction influences on binding sites. The elemental analysis were conducted for various type of humic samples. The $E_4/E_6$ ratio proposed negative correlation with the total carboxyl groups ($r^2$= 0.9988). The charge ($cmol_c\;kg^{-1}$) on the humic acids became more negative as the ionic strength increased. In both continuous and batch titrations, the ionic strength effect was greater in Namweon series (pH 6.39) than others at pH 5.00. The effect of ionic strength on surface charge appears to be greater in batch titrations. This could suggest that continuous titrations do not represent an equilibrium state and the effects of electrolyte concentration was not fully realized during the course of titrations. Both models described experimental data obtained from continuous and batch titrations well over a range of ionic strengths. Model A is more simpler than model V but adaptes more fitted parameters. Thus, the observed change in apparent binding constants with surface charge is regarded solely due to electrostatic influences rather than functional group heterogeneity. However, Model V is more mechanistically realistic in a number of discrete ligand binding sites. 토양으로 투입되는 유기물의 종류나 투입된 후의 부식화과정(humification)을 고려하여 선정된 논 밭 토양으로부터 부식간(humic acid)을 추출 정제하였다. 부식간의 유효흡착 부위에 대한 수소이온과 다른 이온간의 흡착 경쟁을 이해하기 위한 첫단계로 수소이온에 대한 친화력(proton affinity)를 전위차적정에 의하여 측정하였다. 또한, 이의 전개양상을 Discrete ligand electrostatic model인 Model A와 Model V로 해석하고자 하였다. 추출 정제된 부식산들은 pH 변화(pH 3~11)에 따라 수소이온 친화력의 분포양상이 서로 차이를 보였으며, 서로 다른 농도의 배경전해질(0.01, 0.10, 0.50 and 1.00 M NaNO3)하에서 이온강도의 증가에 따라 부식산의 표면 음전하량이 증가하였다. 특히 남원통의 경우 증가폭이 pH 6.39 이하에서 상대적으로 컸다. 또한, continuous titration보다 batch titration에서 표면전하에 대한 이온강도에 따른 차이가 확인하였다. 이는 continuous titration시 반응시간의 부족으로 평형상태를 이루지 못해 전해질의 영향을 완전히 반영하지 못하여 이런 결과가 도출된 것으로 생각되어진다. 그러므로, 부식산을 다른 이온종과 반응시키고자 할 때 충분한 반응시간(7일)을 가능케 하는 batch titration이 적절할 것으로 생각된다. 이번 실험에 적용된 Model A와 V는 모두 좋은 예측값 (RSD<$5.46{\times}10-2cmolc\;kg-1$)을 보였다. Model A는 Model V에 비하여 단순하나, 상대적으로 많은 매개변수(fitted parameters)을 필요로 하며, 결합부위인 부식산 관능기들의 겉보기 해리상수(Kapp) 변화는 관능기의 불균일성이라기 보다는 정전기적 인력의 영향이 더 크다고 생각된다. Model V는 관능기들의 해리상수를 중간값과 전개인자로 나타냄으로써 부식산 표면의 불균일성(heterogeneity)을 좀 더 실질적으로 표현해 주고 있다.

포도 ‘캠벨얼리’ 품종의 전엽기 생장조절제 처리가 품질에 미치는 영향

천종필,김병기,배태민,오경영,김진국 경상대학교 농업생명과학연구원 2012 농업생명과학연구 Vol.46 No.6

This study was conducted to increase grape quality by treating plant growth regulator (PGR) in ‘Campbell Early’ grape. Foliar application of gibberellic acid (GA3) at 5 mg·L-1 on flower cluster of ‘Campbell Early’ grape at 3-5 unfolded leaf stage effectively increased columella length, berry weight, soluble solid contents and promoted skin color development. Foliar application of 20 mg·L-1 abscisic acid (ABA) mixed with 5 mg·L-1 of GA3 on flower cluster of ‘Campbell Early’ grape at 3-4 unfolded leaf stage effectively increased skin anthocyanin contents without any detrimental effects on berry enlargement and columella growth. Foliar application of 2.5 mg·L-1 thidiazuron mixed with 5 mg·L-1 of GA3 on flower cluster of ‘Campbell Early’ grape at 3-4 unfolded leaf stage effectively increased fruit quality indices such as higher soluble solid contents and less titratable acidity. 본 연구는 식물생장조절물질을 활용하여 ‘캠벨얼리’ 포도의 품질향상 증진 방안을 마련하기 위하여 실시하였다. 전엽 3∼5엽기에 화방에 대한 지베렐린(GA3) 5 mg·L-1 엽면처리는 ‘캠벨얼리’ 포도의 과경, 과방중, 가용성당함량, 과피의 착색을 증진시켰다. 전엽 3∼4엽기의 화방에 대한 GA3 5 mg·L-1과 ABA 20 mg·L-1 혼용처리는 과립 비대와 과축 신장을 저해하지 않았으며 포도 과피의 안토시아닌 축적에 효과적이었다. ‘캠벨얼리’ 포도의 전엽 3∼4엽기에 화방에 대한 thidiazuron 2.5 mg·L-1과 GA3 5 mg·L-1 혼용처리는 가용성고형물 함량 증진과 산함량 감소를 촉진하여 과실 품질이 증대되었다.

포도의 관능적 품질과 객관적 품질인자 상호간의 상관성

조순덕(Sun-Duk Cho),장민선(Min-Sun Chang),김동만(Dong-Man Kim),김건희(Gun-Hee Kim) 한국원예학회 2010 원예과학기술지 Vol.28 No.4

In order to find correlations between the sensory evaluation and instrumental analysis in ‘Campbell Early’ grape, grapes were divided into three parts. One-half parts were used for the sensory evaluation and the other half were used as samples for instrumental analysis. Relationship between sensory evaluation and instrumental analysis were studied through correlation study using 48-paired data set obtained during storage. Soluble solid content analysis showed that instrumental quality attributes increased along the passage of storage time with increasing temperature. pH and titratable acidity decreased slightly at lower storage temperatures. Correlations between instrumental quality attributes in grapes were found to be very low. Positive correlation was found between pH and soluble solid content, and negative correlation was found between pH and titratable acidity. The relation of sourness and sweetness to sourness was higher than other sensory evaluation factors, and the shape of the grapes was found to have little relation to their sweetness. Texture (r²=0.890) was found to be the most important factor in preference, followed next by sweetness with sourness (r²=0.860). The correlations between the sensory evaluation and instrumental quality attributes were found to be very low, with overall acceptability given to a relatively high content of soluble solid content. Correlations between pH and titratable acidity in terms of overall acceptability were found to be very low.

Facile Titrimetric Assay of Lysophosphatidic Acid in Human Serum and Plasma for Ovarian Cancer Detection

Nazia Tarannum,Deepak Kumar,Ranu Agrawal 대한암예방학회 2023 Journal of cancer prevention Vol.28 No.2

Herein, an instrument free facile acid-base titrimetric methodology is reported for lysophosphatidic acid (LPA) measurement in serum and plasma samples for ovarian cancer detection. The concept is based on the titrimetric method in which alkaline solution was titrated with free fatty acid. Free fatty acid is generated due to action of the lysophospholipase to LPA. A phospholipid derivative known as LPA can function as a signaling molecule. A glycerol backbone serves as the foundation for phosphatidic acid, which also has bonds to an unsaturated fatty acid at carbon-1, a hydroxyl group at carbon-2, and a phosphate molecule at carbon-3. Free fatty acid and glycerol-3-phosphate are formed when LPA reacts with lysophospholipase. The formation of free fatty acid depends on the concentration of LPA. The standard graph of known concentrations of LPA, LPA spiked serum and LPA spiked plasma was plotted. The concentration of LPA in unknown serum and plasma were calculated from the standard graph. The limit of detection of LPA in spiked serum and plasma samples via titrimetric assay was calculated as 0.156 μmol/L. A patient's chance of survival may be outweighed by an early diagnosis of ovarian cancer.

강산과 강염기의 중화 반응에서 BTB 지시약 색 변화 관찰의 한계점 분석 및 개선 방안 제안

김세진,정대홍 한국현장과학교육학회 2024 현장과학교육 Vol.18 No.3

2015 개정 교육과정 통합과학 교과서에 제시된 ‘산과 염기를 섞었을 때 나타나는 변화’ 실험에서는 동일 농도의 산과 염기를 동일 부피로 혼합하였을 때 BTB 용액에 의해 초록색이 관찰되기를 목표로 하지만 실제로 초록색의 관찰은 거의 불가능하고 변색 범위에서 나타나는 다양한 스펙트럼의 초록색에 대한 기준 자료가 없어 액성 판단에 주관성이 크게 관여한다는 한계점이 있다. 본 연구는 초록색 관찰을 가능하게 하는 산과 염기 및 지시약의 농도 조건을 제시하고, UV-Vis 분석법을 바탕으로 종말점과 이론적 중화점 간의 오차를 최소화하는 BTB 용액의 초록색을 제안하고자 한다. 연구 결과 교과서에서 제시된 산과 염기의 농도는 목표로 한 현상을 관찰하기에 지나치게 높았으며 지시약의 농도 및 양에 대한 정보는 불충분하거나 명확한 기준이 없었다. 중화점 부피 6 mL 조건에서 염산과 수산화 나트륨 수용액의 농도 0.010~0.005 M, BTB 용액의 농도 0.08~0.20 % 1방울이 지시약 자체의 영향을 최소화하면서 명확하게 초록색을 판단하기에 적절하였다. 본 연구는 선행된 과학 개념과 일치하는 현상을 관찰할 수 있도록 실험 조건과 참고용 색 가이드라인을 제시하는데 목적이 있다. 궁극적으로는 불일치 상황에서 학생 주도적 탐구를 이끌어내는 안내 자료로 활용될 수 있다. The experiment ‘Changes when mixing acids and bases’ presented in the 2015 revised curriculum integrated science textbook aims to observe the green color of BTB when equal concentrations of acids and bases are mixed in equivalent volumes. However it is almost impossible to observe green color in practice, Aditionally, there is a lack of standard reference materials for the diverse spectra of green color within the discoloration range, leading to significant subjectivity involved in determining acidity. In this study, we propose the concentration conditions for HCl(aq), NaOH(aq) and BTB(aq) that enable the clear observation of the green color. We also provide guidelines for the green color of BTB(aq) that minimizes the error between the end point and the theoretical neutralization point based on UV-Vis analysis. The results indicated that the concentrations of acids and bases given in the textbooks were too high to observe the intended phenomenon, Furthermore, the information on the concentration and amount of indicator was either insufficient or lacked clear criteria. The concentrations of 0.010 to 0.005 M of HCl(aq) and NaOH(aq) and 1 drop of 0.08 to 0.20 % BTB(aq) were adequate for clearly determining green color while minimizing the influence of the indicator itself. The primary purpose of this study is to provide experimental conditions and reference color guidelines for observing phenomena that are consistent with prior scientific concepts. Ultimately, this can be used to guide student-driven inquiry in situations of discrepancy.

Fe(III)-Salicylic acid의 착물 형성에 관한 연구

차기원,박광원,Cha, Ki-Won,Park, Kwang-Won 한국분석과학회 1995 분석과학 Vol.8 No.3

Salicylic acid($C_6H_4(OH)COOH=H_2A$)와 전이금속인 Fe(III) 사이에 형성되는 착물의 안정도상수를 $20^{\circ}C$, 0.1M $KNO_3$ 수용액 중에서 자외-가시선 흡수광도법 및 pH 전위차적정법으로 측정하여 문헌값($logK_f=16.48$)과 비교하였다. $H_2A$의 $pK_{a1}$과 $pK_{a2}$는 $2.92{\pm}0.08$ 및 $12.90{\pm}0.13$이며, Fe(III)-$H_2A$의 1:1 착물의 $logK_f$는 $20^{\circ}C$에서 $11.88{\pm}0.12$였다. The stability constant of the complex between salicylic acid($H_2A$) and Fe(III) ion has been determined using UV-Vis absorption spectrometry and pH titration method in O.1M $KNO_3$ aqueous solution at $20^{\circ}C$ and compared with reference value, $logK_f=16.48$. The $pK_{a1}$ and $pK_{a2}$ of $H_2A$ are $2.92{\pm}0.08$ and $12.90{\pm}0.13$, respectively and the $logK_f$ of 1:1 complex Fe(III)-$H_2A$ system is $11.88{\pm}0.12$ at $20^{\circ}C$.

Gran Plot 적정법을 이용한 U(VI)-AI(III) 용액의 자유산 농도 측정

서무열,이창헌,손세철,김정석,김원호,엄태윤,Suh, Moo-Yul,Lee, Chang-Heon,Sohn, Se-Chul,Kim, Jung-Suk,Kim, Won-Ho,Eom, Tae-Yoon 한국분석과학회 1999 분석과학 Vol.12 No.3

사용후 U-Al 핵연료 용해용액의 자유산 농도 측정에 이용할 수 있는 Gran plot적정법을 개발하였다. 질산을 염기로 적정할 때 미치는 U(VI)과 Al(III)의 영향을 옥살산칼륨 착화제가 함유된 적정매질과 함유되지 않은 적정매질에서 조사하였다. Gran plot방법으로 종말점을 구할 경우 두 가지 매질에서 모두 양의 오차가 있었으며, 착화제가 함유된 매질에서는 U(VI)이 그리고 착화제가 없는 매질에서는 Al(III)이 오차의 원인이었다. 옥살산칼륨 적정매질에 첨가하는 시료량을 조절하여 pH 5.0 이하에서 적정을 시작함으로써 오차를 줄일 수 있었으며, 질산 농도가 0.1 M이고 U(VI) : Al(III) : $H^+$의 몰비율이 2:12:1인 시료의 질산 농도 측정오차는 1%이하였다. 이 방법으로 U:Al의 몰비율이 1:6인 하나로핵연료 용해용액의 질산 농도를 정확하게 측정할 수 있었다. The determination method of free acid in spent U-Al nuclear fuel solutions by Gran plot titration was described. Effect of U(VI) and Al(III) on the alkalimetric titration of nitric acid was investigated in oxalate complexing media as well as in noncomplexing media. Positive biases were observed in both titration media when the end-point was estimated by the Gran plot method. It was found that the cause of the bias was U(VI) in the oxalate complexing media, but Al(III) in the noncomplexing media. The relative error was less than 1% in the titration of 0.1 M $HNO_3$ at a U(VI) : Al(III) : $H^+$ mole ratio of up to 2:12:1 as long as the pH of the oxalate titration media was sustained to be below 5.0 at the beginning of titration. The method was successfully applied to the determination of nitric acid in a solution of HANARO reactor fuel with U:Al mole ratio of 1:6.