Enthalpy and Entropy Contributions to the Solubility of Sulphamethoxypyridazine in Solvent Mixtures Showing Two Solubility Maxima

The solubility of sulphamethoxypyridazine was measured at several temperatures in mixtures of water: ethanol and ethanol: ethyl acetate. Sulphamethoxypyridazine was chosen as a model drug to compare the solvation effects of proton donor-proton acceptor (water and ethanol) and proton acceptor (ethyl acetate) solvents and mixtures of these solvents because this drug contains functional groups capable of Lewis acid-base interaction. A plot of the mole fraction solubility against the solubility parameter (δ₁) of these solvent mixtures showed two solubility maxima, one at δ₁ = 30·87 MPa^1/2 (20:80 v/v water: ethanol) and another at δ₁ = 20·88 MPa^1/2 (30:70 v/v ethanol: ethyl acetate) at all the temperatures under study. The enthalpies and entropies of mixing as well as the enthalpies and entropies of transfer of sulphamethoxypyridazine from ethanol to water:ethanol and ethanol:ethyl acetate mixtures were calculated to compare solvation characteristics of the solvent mixtures toward the drug. As ethanol is added to water, the entropy increases and the structure of the solvent mixture became less ordered, favouring the interaction of the drug with the solvent mixture. On the other hand, in the case of the ethanol: ethyl acetate mixture, solubility is favoured by the more negative enthalpy values. This way, the same result, i.e. a solubility maximum, is obtained by different routes. In the ethanol: water mixtures, the dissolution process is entropy-controlled while enthalpy is the driving force in the case of ethanol: ethyl acetate mixtures. The two solvent systems show enthalpy-entropy compensation. Water deviates from the linear relationship due possibly to its hydrophobic effect.     

Solubility behavior of polymorphs I and II of mefenamic acid in solvent mixtures

The dissolution profile and solubility of two polymorphic forms of mefenamic acid were studied in solvent mixtures of ethanol-water and ethyl acetate-ethanol. The solubility parameter (delta) was used to study the effect of polarity on the solubility behavior of the two polymorphs. Differential scanning calorimetry and infrared spectroscopy were performed on the original powders and on the solid phases after contact with the solvent systems for the characterization and identification of the polymorphs. The dissolution rates of both polymorphs is greater in the less polar mixtures (ethyl acetate-ethanol) of lower solubility parameter values. Form II showed larger dissolution rates and saturation concentrations than Form I in all the solvent systems studied. The solid phase of Form II converts totally to Form I after equilibration with the solvents. The rate of conversion was faster in the least polar mixtures. The solubility of both polymorphs reaches a single maximum at 80% ethyl acetate in ethanol, delta = 20.09 MPa1/2. The modified extended Hildebrand method was used to predict the solubility profile of each polymorph. A single equation was obtained for both polymorphs which includes the solubility parameter of the mixtures and the logarithm of the solubility mole fraction of each polymorph in water. The Hildebrand solubility parameter of mefenamic acid is independent of the crystalline form and was determined from two methods giving quite similar values, delta 2 = 20-21 MPa1/2.     

Solubility and phase separation of benzocaine and salicylic acid in 1,4-dioxane-water mixtures at several temperatures

The solubilities of benzocaine and salicylic acid were determined in water-dioxane mixtures at several temperatures (5-40 degrees C for benzocaine and 10-40 degrees C for salicylic acid). The solubility curves as a function of dioxane ratio showed a maximum at 90% dioxane at all temperatures. Above 25 degrees C, the homogeneous mixture splits into two liquid immiscible phases. For benzocaine, the initial dioxane concentration range at which phase separation takes place increased with temperature (50-60% at 25 degrees C, 50-70% at 30-35 degrees C and 40-70% at 40 degrees C). For salicylic acid, the dioxane concentration required for phase separation (40-60% dioxane) did not change with temperature. Phase separation was not related to solid phase changes (polymorphism or solvates). The phase composition and drug extraction at the drug-rich phase were determined. The apparent enthalpies of the solution process were a nonlinear function of the dioxane ratio for both drugs. The apparent enthalpy of solution of benzocaine was larger than that expected at the upper limit of phase separation (70% dioxane), whereas for salicylic acid the apparent enthalpy of solution decreased abruptly at the region corresponding to phase separation (40-70% dioxane). Both drugs showed a nonlinear pattern of enthalpy-entropy compensation.     

Enthalpy-entropy compensation for the solubility of drugs in solvent mixtures: paracetamol, acetanilide, and nalidixic acid in dioxane-water

In earlier work, a nonlinear enthalpy-entropy compensation was observed for the solubility of phenacetin in dioxane-water mixtures. This effect had not been earlier reported for the solubility of drugs in solvent mixtures. To gain insight into the compensation effect, the behavior of the apparent thermodynamic magnitudes for the solubility of paracetamol, acetanilide, and nalidixic acid is studied in this work. The solubility of these drugs was measured at several temperatures in dioxane-water mixtures. DSC analysis was performed on the original powders and on the solid phases after equilibration with the solvent mixture. The thermal properties of the solid phases did not show significant changes. The three drugs display a solubility maximum against the cosolvent ratio. The solubility peaks of acetanilide and nalidixic acid shift to a more polar region at the higher temperatures. Nonlinear van't Hoff plots were observed for nalidixic acid whereas acetanilide and paracetamol show linear behavior at the temperature range studied. The apparent enthalpies of solution are endothermic going through a maximum at 50% dioxane. Two different mechanisms, entropy and enthalpy, are suggested to be the driving forces that increase the solubility of the three drugs. Solubility is entropy controlled at the water-rich region (0-50% dioxane) and enthalpy controlled at the dioxane-rich region (50-100% dioxane). The enthalpy-entropy compensation analysis also suggests that two different mechanisms, dependent on cosolvent ratio, are involved in the solubility enhancement of the three drugs. The plots of deltaH versus deltaG are nonlinear, and the slope changes from positive to negative above 50% dioxane. The compensation effect for the thermodynamic magnitudes of transfer from water to the aqueous mixtures can be described by a common empirical nonlinear relationship, with the exception of paracetamol, which follows a separate linear relationship at dioxane ratios above 50%. The results corroborate earlier findings with phenacetin. The similar pattern shown by the drugs studied suggests that the nonlinear enthalpy-entropy compensation effect may be characteristic of the solubility of semipolar drugs in dioxane-water mixtures.     

Thermodynamic origin of the solubility profile of drugs showing one or two maxima against the polarity of aqueous and nonaqueous mixtures: niflumic acid and caffeine

The purpose of this work was to investigate the origin of the different solubility profiles of drugs against the polarity of solvent mixtures with a common cosolvent. Niflumic acid and caffeine where chosen as model drugs. The solubilities were measured at five or six temperatures in aqueous (ethanol-water) and nonaqueous (ethyl acetate-ethanol) mixtures. The enthalpies of solution were obtained at the harmonic mean of the experimental temperature. Solid phase changes were analyzed using differential scanning calorimetry and thermomicroscopy. A single solubility maximum was obtained for niflumic acid against the solubility parameter of both mixtures that is not related to solid phase changes. In contrast, caffeine displays two maxima and anhydrous-hydrate transition occurs at the solubility peak in the amphiprotic mixture. The apparent enthalpies of solution of both drugs show endothermic maxima against solvent composition that are related to hydrophobic hydration. A general explanation for the cosolvent action in aqueous mixtures is proposed. The dominant mechanism shifts from entropy to enthalpy at a certain cosolvent ratio dependent on the hydrophobicity and the solubility parameter of the drug. Niflumic acid and caffeine show enthalpy-entropy compensation in ethanol-water, and this relationship is demonstrated for the first time in nonaqueous mixtures. The results support that enthalpy-entropy compensation is a general effect for the solubility of drugs in solvent mixtures. The shape of the solubility curves is correlated with the compensation plots. The solubility peaks separate different enthalpy-entropy relationships that also differentiate the solubility behavior of the hydrate and the anhydrous forms of caffeine.     

Phase equilibria and thermodynamics of p-hydroxybenzoic acid

The prevalence of phases and associated solubilities of p-hydroxybenzoic acid have been investigated in methanol, acetonitrile, acetic acid, acetone, water, and ethyl acetate at temperatures from 10 to 50 degrees C. Thermodynamic data was acquired through determination of van't Hoff enthalpy of solution, enthalpy of fusion, and melting temperature. Indications of polymorphic enantiotropy were found primarily through solubility analysis and FTIR-ATR. A comprehensive thermodynamic investigation disclosed correlation between the van't Hoff enthalpy of solution and the solubility in different solvents. A higher solubility is linked to a lower van't Hoff enthalpy of solution. A thermodynamic analysis to discriminate between different solid phases is presented.     

The effect of vehicle on the diffusion of salicylic acid through hairless mouse skin

The solubilities of salicylic acid in, and the fluxes through, hairless mouse skin from isopropyl myristate, 1-octanol, 1-propanol, propylene glycol, and formamide have been determined experimentally. Values for permeability coefficients (Kp) corresponding to the respective fluxes were determined from: flux/solubility = Kp. These values were then compared with values for the respective partition coefficients (P) which were calculated from the known solubility parameters for the vehicles (delta v), salicylic acid (delta i), and skin (delta s). Two different delta i values were used to calculate theoretical P values, one based on the peak solubility method and the other based on calculation from group contributions (11 and 14.4 (cal/cm3)1/2, respectively). There was good correlation between the values for theoretical log P - 1.42 and experimental log Kp for the delivery of salicylic acid from vehicles exhibiting solubility parameters in the range of delta v = 10-18 (cal/cm3)1/2, when delta i was assumed to be 14.4 (cal/cm3)1/2. There was also a good correlation between the values for theoretical log P - 2.09 and experimental log Kp for vehicles exhibiting solubility parameters in the range of delta v = 7.6-10 (cal/cm3)1/2, when delta i was assumed to be 11 (cal/cm3)1/2. Two different delta i values were used because salicylic acid apparently behaves like a polar molecule in polar vehicles and a nonpolar molecule in nonpolar vehicles. Qualitatively, fluxes and permeability coefficients were found to be inversely dependent on drug solubility in the vehicles, with a minimum that corresponded approximately to the point where delta v = delta i, and the minimum within the theoretical P curve.(ABSTRACT TRUNCATED AT 250 WORDS)     

Polymorphism and thermodynamics of m-hydroxybenzoic acid

Solution and solid-state properties of m-hydroxybenzoic acid have been investigated. Two polymorphs were found where the monoclinic modification exhibits a higher stability than the orthorhombic form. The solubility of the monoclinic polymorph was determined between 10 and 50 °C in methanol, acetonitrile, acetic acid, acetone, water and ethyl acetate. The solubility of the orthorhombic polymorph was determined between 10 and 50 °C in acetonitrile, acetic acid, acetone and ethyl acetate. A thermodynamic analysis revealed a marked correlation between the molar solubility and the van’t Hoff enthalpy of solution at constant temperature. In addition, in each solvent increased temperature resulted in increased van’t Hoff enthalpy of solution. It is shown that the solubility data can be used to estimate melting properties for both polymorphs. The solubility ratio of the two forms and the DSC thermogram of the orthorhombic form strongly suggest that the system is monotropic. However, according to the polymorph rules of Burger and Ramberger, the estimated higher melting enthalpy and lower melting temperature of the orthorhombic form points towards an enantiotropic system. Hence, this system appears to be an exception to the Burger and Ramberger melting enthalpy rule, and the probable reason for this is found in the difference in the heat capacity of the two solid forms.     

Determination of salicylic acid and aspirin in multicomponent tablets by liquid chromatography on a nonionic resin

Aspirin and free salicylic acid were determined in combinations containing caffeine, phenacetin, salicylamide, and acetaminophen by liquid chromatography on poly(methyl methacrylate) resin. Precision and accuracy were +/- 2% for salicylic acid, the latter at levels corresponding to 0.02% of the aspirin content.     

复方乙酰水杨酸片质量标准研究

目的:完善复方乙酰水杨酸片的质量标准,提高其质量控制水平.方法:采用《中华人民共和国药典》2015年版四部相关方法和拟定标准方法,对复方乙酰水杨酸片拟定的质控项目进行检验,建立复方乙酰水杨酸片的薄层色谱鉴别方法,建立HPLC同时测定HPLC鉴别(1)、游离水杨酸、溶出度、含量均匀度和含量测定的方法,同时以3个主成分为目...     

Effects of solvent medium on solubility. V: Enthalpic and entropic contributions to the free energy changes of di-substituted benzene derivatives in ethanol:water and ethanol:cyclohexane mixtures

The solubility at four different temperatures in water, cyclohexane, and mixtures of water and ethanol and ethanol and cyclohexane of nine derivatives of the structure pX1-C6H4-X2, together with their heats of fusion are reported. The enthalpy and entropy of mixing (delta HM and delta SM, respectively), and also the excess free energy (delta GE) for pure solvents and several compositions of solvent mixtures were calculated. The enthalpic and entropic contribution to the free energy of transfer for water:solvent mixtures was also calculated for each compound. Solvent systems may be classified by means of the enthalpic-entropic relationships exhibited by the series in each case.     

Superoxide radical scavenging and antibacterial activities of different fractions of ethanol extract of Mentha spicata (L.)

Mentha spicata is a well-known spice that has a variety of biological properties and is abundantly available throughout the world. This study was designed to investigate the superoxide radical scavenging and antibacterial properties of different fractions (hexane, chloroform, ethyl acetate, and aqueous) of the ethanol extract of Mentha spicata. In addition, xanthine oxidase generated uric acid inhibition, reducing potential and iron chelating activity, also was investigated. Ethyl acetate fraction exhibited the highest (≤84%) superoxide radical scavenging and inhibition of uric acid formation at 40 μg/ml compared with the standard quercetin (≤81%) at 30 μg/ml. The highest reducing potential also is observed in ethyl acetate and aqueous fractions, which were comparable to the reducing potential of quercetin and ascorbic acid. Iron chelating activity of solvent fractions was found to be better than standard of EDTA (79% at 3 mg/ml). In addition, all fractions showed effective antibacterial activity against five human pathogenic bacteria among the ten samples used. However, aqueous fraction showed maximum growth inhibition zone (≤36 mm diameter at 6 μg/per disc) against Shigella boydii. Hence, we conclude that the ethyl acetate and aqueous fractions of ethanol extract of Mentha spicata exhibited higher superoxide radical scavenging and antibacterial activities.     

Additional routes in the metabolism of phenacetin

omega-Hydroxylation of the ethyl moiety of phenacetin by rabbit-liver microsomal preparations was slow, but was increased 10-fold by pretreatment of the animals with phenobarbitone (PB), and was decreased 2.8-fold by treatment with 3-methylcholanthrene (3-MC) or beta-naphthoflavone (beta-NF). N-[4-(2-hydroxyethoxy)phenyl]acetamide (beta-HAP), the omega-hydroxylation product, which was detected in trace amounts only in the urine of rabbits injected with phenacetin, was converted into [4-(acetylamino)phenoxy]acetic acid (4-APA) by the microsomal and cytosolic fraction of liver homogenate and NADP+ or NAD+. Rabbits excreted 56% of a dose of beta-HAP as 4-APA in the 48 h urine. Phenacetin, injected i.p. into rabbits previously treated with PB, was excreted in the urine as 4-APA (12.2% of dose). beta-HAP formed endogenously or added as substrate in vitro was recovered as the O-acetyl derivative, when ethyl acetate was used for extraction of metabolites from microsomal incubation mixtures. (omega-1)-Hydroxylation of the ethyl moiety of phenacetin, which gave 4-acetamido-phenol, occurred rapidly with rabbit-liver microsomal preparations, and was not increased significantly after pretreatment of animals with either PB or 3-MC. omega-Hydroxylation of the acetic moiety of phenacetin by rabbit-liver preparations to give N-(4-ethoxyphenyl)glycolamide (4-GAP) was slow, but was increased three-fold after pretreatment of animals with 3-MC or beta-NF, whereas PB had no effect. 4-GAP was detected in trace amounts only in the urine of rabbits injected i.p. with phenacetin. N-Hydroxylation of phenacetin by rabbit-liver microsomal preparations was slow, but increased three-fold after treatment of animals with 3-MC, and was unchanged by PB. N-Hydroxylation of phenacetin by hepatic microsomes from 3-MC-treated rabbits was 26 times slower than that of 2-acetylaminofluorene; no N-hydroxy derivatives of N-(4-chlorophenyl)acetamide and propanil were detected in vitro.     

Ethno-medicinal study of Artemisia ordosica Krasch.(traditional Chinese/Mongolian medicine) extracts for treatment of allergic rhinitis and nasosinusitis

OBJECTIVE To evaluate the in vivo anti-inflammatory and allergic rhinitis(AR) alleviating effect as well as in vitro antimicrobial activities of Artemisia ordosica Krasch.(AOK) extracts to verify its ethno-medicinal claims.METHODS Crude extracts(methanol/95%-ethanol/ethyl acetate) of AOK root/stem/leaf and fractions(petroleum ether/ethyl acetate/n-butanol/aqueous) of AOK root extractwere prepared. Xylene-induced ear swelling model in mouse and ovalbumin(OVA)-induced AR model in guinea pig were established. Ear swelling degrees of mice were measured. The numbers of rubbing movement and sneezes of guinea pigs were counted to evaluate the symptoms of AR. The serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1 were measured by ELISA assay. The histological changes of nasal mucosa were investigated by light microscope after H&E staining. Antimicrobial activities of AOK extracts were also tested.LC-MS/MS analysis was performed to characterize the constituents of active extract and molecular docking was conducted to predict the biological mechanism. RESULTS In ear-swelling model, extract(100.00 mg·kg~(-1)) from the ethyl acetate layer of 95% ethanol(100.00 mg·kg~(-1)) showed better swelling inhibition in mice than positive control(dexamethasone,191.91 mg·kg~(-1)). In AR model, extract from the ethyl acetate layer of 95% ethanol significantly alleviated the AR symptoms in guinea pigs, decreased the serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1, and reduced the infiltration of eosinophil in nasal mucosa. For Staphylococcus aureus, the ethyl acetate extract of AOK stem showed the highest inhibition(MIC=1.25 g·L~(-1)), for Escherichia coli, n-butanol layer of 95% ethanol extract of AOK root showed the highest inhibition(MIC=15.00 g·L~(-1)), for Candida glabrata, 95%-ethanol extract of AOK stem showed the best inhibition(MIC=0.064 g·L~(-1)),while ethyl acetate and n-butanol layers showed similar inhibition on MRSA(MIC=7.50 g·L~(-1)). LC-MS/MS characterization showed that dicaffeoylquinic acids account for more than 30% of ethyl acetate layer of AOK extract. Dicaffeoylquinic acids bind with histamine-1 receptor with high affinities and interesting modes. CONCLUSION Extracts from AOK had interesting anti-inflammatory activity in mice, alleviating effect against OVA-induced AR in guinea pigs, and antimicrobial activities in vitro, which support the ethno-medicinal use of it. The main constituents in ethyl acetate layer of AOK root extract are dicaffeoylquinic acids and could bind with histamine-1 receptor well. These findings highlighted the importance of natural product chemistry study of AOK.     

Predicting the Solubility of Drugs in Solvent Mixtures: Multiple Solubility Maxima and the Chameleonic Effect

Abstract— An approach to reproduce the solubility profile of a drug in several solvent mixtures showing two solubility maxima is proposed in this work. The solubility of sulphamethoxypyridazine was determined at 25°C in several mixtures of varying polarity (hexane: ethyl acetate, ethyl acetate:ethanol and ethanol: water). Sulphamethoxypyridazine was chosen as a model drug because of its proton-donor and proton-acceptor properties. A plot of the mole fraction of the drug vs the solubility parameter of the solvent mixtures shows two solubility peaks. The two peaks found for sulphamethoxypyridazine demonstrate the chameleonic effect as described by Hoy and suggest that the solute-solvent interaction does not vary uniformly from one mixture to another. The different behaviour of the drug in mixtures of two proton-donor and proton-acceptor solvents (alcohol and water), and in mixtures of one proton acceptor (ethyl acetate) and one proton donor-proton acceptor (ethanol) is rationalized in terms of differences in the proton donor-acceptor ability of the solvent mixtures. An approach based on the acidic and basic partial solubility parameters together with the Hildebrand solubility parameter of the solvent mixtures is developed to reproduce the experimental results quantitatively. The equation predicts the two solubility maxima as found experimentally, and the calculated values closely correspond to the experimental values through the range composition of the solvent mixtures. These results show that the chameleonic effect can be described in a quantitative way in terms of Lewis acid-base interactions; this approach can assist the product formulator to choose the proper solvent mixture for a new drug. A good solvent blend should result in a solubility parameter close to that of the drug; the acidic and basic partial solubility parameter values should provide maximum acid-base interaction of the mixed solvent with the drug. The failure in one of these conditions results in decreased solubility. Solubility parameters as well as the acidic and basic parameters are tabulated or they can be obtained from group contribution methods, making easier the evaluation of the best solvent mixture for a drug.     

HPLC法同时测定人血浆中的对乙酰氨基酚、水杨酸和咖啡因的含量

目的建立同时测定人血浆中对乙酰氨基酚、水杨酸和咖啡因浓度的HPLC法,并将其应用于阿咖酚胶囊复方制剂的人体药动学研究。方法以甲醇-四氢呋喃-10 mmol.L-1醋酸盐缓冲液(含体积分数为0.1%的冰醋酸溶液)(体积比为23∶2∶77)为流动相,茶碱为内标,采用krom asil苯基柱分离,在237 nm处进行检测。结果血浆中对乙酰氨基酚、水杨酸和咖啡因测定方法的线性分别为0.203~16.2、0.503~80.4、0.103~8.24μg.L-1;方法的准确度?RE?分别为-4.2%~0.5%、-9.2%~-0.5%、-7.8%~1.9%;日内精密度?RSD?分别小于5.2%、6.5%、7.0%;日间精密度?RSD?分别小于8.1%、5.2%、6.2%。结论建立的HPLC方法可用于阿咖酚胶囊复方制剂的人体药动学研究。     

复方乙酰水杨酸片灼烧物中止泻成分研究

从复方乙酰水杨酸片(APC)灼烧物中分离出六个化合物,其中五个化合物分别鉴定为阿斯匹林(Ⅰ),非那西丁(Ⅱ),水杨酸(Ⅲ),水杨酸乙酯(Ⅳ)及水杨酸苯酯(Ⅴ)。第六个化合物系苯酰苯胺衍生物,命名为 N-(4-乙氧苯基)-2-羟基苯酰胺(益肤酰胺,Ⅵ)。药理实验结果表明,化合物(Ⅰ),(Ⅴ)及 APC 片灼烧物具有明显的胃肠道蠕动抑制作用;益肤酰胺(Ⅵ)具有较强的免疫抑制作用。     

Towards an understanding of the molecular mechanism of solvation of drug molecules: a thermodynamic approach by crystal lattice energy, sublimation, and solubility exemplified by paracetamol, acetanilide, and phenacetin

Temperature dependencies of saturated vapor pressure for the monoclinic modification of paracetamol (acetaminophen), acetanilide, and phenacetin (acetophenetidin) were measured and thermodynamic functions of sublimation calculated (paracetamol: DeltaGsub298=60.0 kJ/mol; DeltaHsub298=117.9+/-0.7 kJ/mol; DeltaSsub298=190+/-2 J/mol.K; acetanilide: DeltaGsub298=40.5 kJ/mol; DeltaHsub298=99.8+/-0.8 kJ/mol; DeltaSsub298=197+/-2 J/mol.K; phenacetin: DeltaGsub298=52.3 kJ/mol; DeltaHsub298=121.8+/-0.7 kJ/mol; DeltaSsub298=226+/-2 J/mol.K). Analysis of packing energies based on geometry optimization of molecules in the crystal lattices using diffraction data and the program Dmol3 was carried out. Parameters analyzed were: (a) energetic contribution of van der Waals forces and hydrogen bonding to the total packing energy; (b) contributions of fragments of the molecules to the packing energy. The fraction of hydrogen bond energy in the packing energy increases as: phenacetin (17.5%)相似文献   

醋酸氯地孕酮平衡溶解度及表观油水分配系数的测定

目的:测定醋酸氯地孕酮(CA)的平衡溶解度及表观油水分配系数,为CA新剂型的体外评价进行处方前研究。方法:采用高效液相色谱法测定CA在水及不同pH(1·2、2·0、3·0、4·5、5·5、6·8、7·4、8·0)介质及常用9种有机溶剂(包括甲醇、乙醇等)中的平衡溶解度;采用摇瓶法测定其在正辛醇与水及各pH介质组成的体系中的表观油水分配系数(P)。结果:37℃时,CA在水及9种pH值介质中的平衡溶解度依次为0·473、0·533、0·423、0·056、0·309、0·428、0·447、0·428、0·448μg·mL-1,在甲醇、乙醇等中的平衡溶解度为7320·61～344248·70μg·mL-1;CA在水中的lgP值为4·05,不同pH条件下的lgP值差别不大(4·11～4·25)。结论:CA不溶于水,易溶于有机溶剂,在弱酸环境下有一定程度的降解;且其lgP值较大,提示在制剂研究中需采用适当的增溶手段。     

HPLC测定复方乙酰水杨酸片中3组分的含量

目的同时测定复方乙酰水杨酸片中乙酰水杨酸、咖啡因、非那西丁的含量。方法采用HPLC,色谱柱：Symmetry C18柱（4．6mm×150mm,5um）,流动相为pH6．5的磷酸二氢钾缓冲液-乙腈（78：22）,流速为1．0mL·min^-1,检测波长为270nm。结果3组分分别在8．80～70．42ug·mL^-1（r=0．9999）、1．42～11．34ug·mL^-1（r=0．9999）、6．12～48．92ug·mL^-1。（r=0．9999）内成良好线性关系,平均回收率分别为101．2％（RSD=0．7％,n=6）、99．1％（RSD=0．8％,n=6）、100．3％（RSD=0．7％,n=6）。结论本法可不经分离,直接测定复方乙酰水杨酸片中3组分的含量。