• Carbon letters
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• 제22권
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• pp.14-24
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• 2017

Carboxylated multi-wall carbon nanotubes (MWCNTs-COOH) have been used as efficient adsorbents for the removal of picric acid from aqueous solutions under stirring and ultrasound conditions. Batch experiments were conducted to study the influence of the different parameters such as pH, amount of adsorbents, contact time and concentration of picric acid on the adsorption process. The kinetic data were fitted with pseudo-first order, pseudo-second-order, Elovich and intra-particle diffusion models. The kinetic studies were well described by the pseudo-second-order kinetic model for both methods. In addition, the adsorption isotherms of picric acid from aqueous solutions on the MWCNTs were investigated using six two-parameter models (Langmuir, Freundlich, Tempkin, Halsey, Harkins-Jura, Fowler-Guggenheim), four three-parameter models (Redlich-Peterson, Khan, Radke-Prausnitz, and Toth), two four-parameter equations (Fritz-Schlunder and Baudu) and one five-parameter equation (Fritz-Schlunder). Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were applied to determine the best fit isotherm. The error analysis showed that the models with more than two parameters better described the picric acid sorption data compared to the two-parameter models. In particular, the Baudu equation provided the best model for the picric acid sorption data for both methods.

• 약학회지
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• 제37권2호
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• pp.119-123
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• 1993

A spectrophotomertic method is proposed for the determination of antihistamines. The method is based on solvent extraction of the ion pair formed between antihistamines and colored picric acid into chloroform. The binding state of antihistamines-picric acid complexes were presumed by IR and $^{1}$H-NMR spectra as intermolecular hydrogen bonding. This method was applicable to the determination of antihistamines in the pharamaceutical preparations.

• 약학회지
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• 제42권3호
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• pp.243-247
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• 1998

A method for the determination of basic drugs based on their reaction with picric acid to form an ion-association complex extractable into several plasticizers was developed. Ba sic drugs-picric acid complexes in acid medium could be extracted quantitatively into several plasticizers except phosphates. For example, the chlorpromazine-picric acid complex showed maximum absorbance at near 410nm and was applied to extraction spectrophotometric determination of chlorpromazine. The calibration curves are linear (r>0.998) within a range from $10^{-6}to\;5{\times}10^{-4}M$ and the precision of the method was acceptable because RSD was less than 2.6% (n=7). The factors affecting the extraction system was discussed.

• 한국염색가공학회지
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• 제26권4호
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• pp.277-282
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• 2014

Two tert-butyl substituted phthalocyanines(Pcs), in metal-free and metallated forms, were synthesized and the fluorescence responses toward various nitro derivatives, including picric acid(PA), 2,4-dinitrotoluene(DNT), 1,4-dinitrobenzene(DNB), 4-nitrotoluene(NT), nitrobenzene(NB), 1,4-benzoquinone(BQ), and nitromethane(NM) were investigated. Among the various nitro derivatives, current Pc derivatives exhibited efficient and exclusive fluorescence quenching in the presence of picric acid, which was readily observed by a naked eye. Quenching efficiency was estimated by the Stern-Volmer relationship, in which quenching constant, KSV, was calculated to be in the range of $10^4M^{-1}$. It was also found out that the aggregational behaviors of these Pcs are heavily dependent on the nature of solvent systems, subsequently affecting the quenching efficiency.

• 한국식품영양과학회지
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• 제17권2호
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• pp.136-143
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• 1988

발효단백질 중의 유리아미노산을 효과적으로 정량하기 위하여 정량방법(추출조건, 제단백(除蛋白) 및 발색법)에 따른 영향을 검토하였다. 낙농발효품의 수용성 유리아미노산은 $75^{\circ}C$, 40분, 대두발효품은 $40^{\circ}C$, 3시간에서 효과적으로 추출되었다. 여러 침전방법(95% ethanol 처리, $100^{\circ}C$, 3분 가열 및 1% picric acid phthaldialdehyde로 발색시켜 D.L.-lysine을 표준아미노산으로 삼아 정량, 계산하였을 때가 아미노산자동분석기에 의한 결과에 가장 접근하였으나 ethanol로 침전시킨 뒤 OPDA로 발색시킨 결과도 이와 유사하였다. TNBS(2,4,6-trinitrobenzensulfonic acid)에 의한 발색정량에는 ethanol 침전처리가 가장 효과적이었으나 종래의 동감법(銅監法)(copper salt method, Spies and Chamber, 1958.)에 의한 결과는 다른 비색정량 및 아미노산자동분석기에 의한 결과에 비하여 시료에 따른 과소의 차이가 심하였고 재현성이 결여되었다.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2819-2822
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• 2009

• 대한화학회지
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• 제49권1호
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• pp.35-46
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• 2005

• 약학회지
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• 제35권3호
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• pp.182-189
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• 1991

Systematic study on the extraction of ion pair by the use of picric acid (PCA) as an ion pair forming reagent to the aliphatic amines has not be done by spectrophotometric method. The extraction of ion pair by the use of PCA and 23 kinds of the aliphatic amines was examined. The procedure is as follows; Elving's buffer solution (pH 1.3~10, ionic strength 0.5) each amine solution, and PCA solution were taken into a test tube. The mixture was shaken mechanically with chlorform. The organic phase was filtered through a filter paper to remove water droplets. The absorbance was examined at $\lambda_{max}$ against a reagent blank. Primary and secondary whose carbon number were more than 7 or 6, respectively, are extractable as ion pairs with PCA, while tertiary amines and quaternary ammonium salts are also extractable without the correlation of carbon number. It was considered that the ion pair extraction of primary and secondary amines was affected by the number of carbon of amines, but its extraction of tertiary amines or quaternary ammonium salts was affected by kind of aliphatic amines rather than pKa values or carbon number of amines.

• 약학회지
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• 제31권5호
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• pp.322-329
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• 1987

A rapid and sensitive spectrophotometric method has been developed for quantitation of some phenothiazine derivatives (PTZDS). The method depends on the formation of insoluble yellow complexes between PTZDS and picric acid (PCA) in aqueous layer. These complexes are quantitatively extracted from aqueous phase into chloroform. The binding ratio of PTZDS-PCA complexes were presumed as PTZDS-1 to PCA-1 by means of mole ratio and continuous variation methods. The complexes are stable for more than 24hours in chloroform layer at room temperature. Most of compounds associated with pharmaceutical preparation of PTZDS do not interfere with this method. However, chlorpheniramine and diphenhydramine interfere with the riaethod. The binding state of PTZDS-PCA complexes were presumed by IR and $^1$H-NMR spectra as intermolecular hydrogen bonding.

• 한국분말재료학회지
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• 제28권4호
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• pp.317-324
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• 2021

High-strength low-alloy (HSLA) steels show excellent toughness when trace amounts of transition elements are added. In steels, prior austenite grain size (PAGS), which is often determined by the number of added elements, is a critical factor in determining the mechanical properties of the material. In this study, we used two etching methods to measure and compare the PAGS of specimens with bainitic HSLA steels having different Nb contents These two methods were nital etching and picric acid etching. Both methods confirmed that the sample with high Nb content exhibited smaller PAGS than its low Nb counterpart because of Nb's ability to hinder austenite recrystallization at high temperatures. Although both etching approaches are beneficial to PAGS estimation, the picric acid etching method has the advantage of enabling observation of the interface containing Nb precipitate. By contrast, the nital etching method has the advantage of a very short etching time (5 s) in determining the PAGS, with the picric acid etching method being considerably longer (5 h).