Biomedical subjects

G K Yin

Publications and source records attributed to G K Yin.

17 recordsLinked to original sources

PubMed1997

[Determination of rate order for degradation of drugs with nonisothermal stability experiment].

By a theoretical investigation of simulated nonisothermal data, the inability to determine the rate order for degradation of drugs with ordinary nonisothermal experiment was discussed. Results indicate that both rate order n and activation energy E can change the curvature of the c-t curve and the change caused by higher n can be compensated by higher E in ordinary nonisothermal experiments. That means a suitable E can always be assessed to fit each of the definite n (0, 1, or 2 in our study) very well. As a result, a same set of c-t data can be well fitted by different combinations of n and E. This is why the rate order cannot be assessed in ordinary nonisothermal experiments. To overcome this deficiency, it is important that there have both temperature rising and lowering parts in one nonisothermal experiment. A new heating model, temperature rising and lowering program, was presented. With this new heating model, the kinetic parameters, including the rate order, can be obtained in one nonisothermal stability experiment. The ability of the new heating model to determine rate order is almost the same as that of isothermal experiments.

Drug Stability↗

PubMed1995

[Study on shelf-life prediction of drugs under indoor natural light irradiation].

The photodegradation of drugs under natural light and various lamp light irradiation was studied and the shelf-life of drugs under indoor natural light irradiation was predicted with hydroxyprogesterone caproate injection as an example. The equivalent influences of different light sources on the photostability of the above drug were obtained. Therefore, the natural light photostability and the shelf-life of drugs under indoor natural light irradiation can be studied with lamp light exposure experiment. The photodegradation of hydroxyprogesterone caproate injection obeys zero order kinetics: C = C0-kEt, and its shelf-life under indoor natural light irradiation is about 1.9 years.

17 alpha-Hydroxyprogesterone Caproate↗

PubMed1993

[Study on the degradation kinetics of vitamin K3 powder].

The effect of temperature and humidity on the rate of discoloration and degradation of vitamin K3 powder was studied via accelerated test under isothermal, constant humidity and dark conditions. The photodegradation of vitamin K3 powder was studied under room temperature and constant humidity. The changes of color and concentration of vitamin K3 were monitored by diffuse reflectance spectroscopy and high performance liquid chromatography, respectively. At temperatures 50-90 degrees C and relative humidities 50-93%, the rate equation of discoloration is -dR/dt = KRR, that of degradation is d(c(o)-c)/dt = kc (c(o)-c)1/2, and that of photodegradation is -dR/dt = kp (Ro-R)-1, where Ro and R are initial relative reflectance and relative reflectance at time t, respectively, c(o) and c are initial concentration and concentration at time t, respectively, kR, kc and kP are apparent rate constants of discoloration, degradation and photodegradation, respectively. The general equation of the relationship between the apparent rate constant k, absolute temperature T and relative humidity RH is k = k' exp (-Ea/RT) exp (m' RH), where Ea is apparent activation energy, k' and m' are constants. Within the ranges of experimental temperatures and humidities, the average apparent activation energies of discoloration and degradation are 105.51 and 130.72 kJ/mol, respectively.

Color↗

PubMed1992

[A study on the decomposition kinetics of vitamin C tablet].

Under the condition of relative humidity less than the critical relative humidity, the discoloration rate and decomposition rate of vitamin C tablet and the discoloration rate of vitamin C tablet in solution were studied at temperatures 60-90 degrees C and relative humidities 60%-80%. The general equation of the relationship between the apparent rate constant k, absolute temperature T and relative humidity RH is: k = k' exp(-E/RT) exp(mRH), where k' and m are constants, E is apparent activation energy. The values of k', m and E for discoloration, decomposition and discoloration in solution are different.

Ascorbic Acid↗

PubMed1992

[Obtaining natural light photostability of drugs from lamp light exposure experiments].

The photostability of vitamin B2, vitamin K3, zinc sulfadiazine and vesnarinone, and the equivalent influences of different light sources on the photostability of the above drugs were studied under natural light and lamp lights. From this study, the photostability of drugs under different light sources can be converted to each other, and the natural light photostability of drugs can be conveniently obtained from lamp light exposure experiments. The relationship between the surface reflectance of the above drugs and the cumulative illumination of different light sources can be formulated as R = A + B(Et) + C/(Et + D) accurately, and the cumulative illumination of different light sources irradiated on the above drugs can be converted to each other equivalently.

Drug Stability↗

PubMed1990

[A study on the decomposition kinetics of vitamin C powder].

The effect of temperature and humidity on the discoloration and degradation of vitamin C powder was studied via accelerated test under isothermal and constant humidity conditions. The changes of color and concentration of vitamin C were monitored by diffuse reflectance spectroscopy and iodimetry respectively. Under the condition of relative humidity less than the critical relative humidity, the apparent rate constant of discoloration of Kc of vitamin C powder is: kc = 'exp (-Ea/RT) exp (m 'RH), where k' and m' are constants, RH is relative humidity and Ea is activation energy, when RH less than 70%, Ea = 104.33 kJ . mol-1. The degradation curve of vitamin C powder under various temperatures and humidities can be expressed by C = N/(1 + Btn), the rate equation of degradation of vitamin C powder is: -dC/dt = kdC(1 + 1/n) (N-C)(1 - 1/n), where kd is the apparent rate constant of degradation, B and n are constants, N is the initial content of vitamin C and C is the content of vitamin C at time t. When RH are 97, 93, and 79.5%, Ea are 86.87, 88.22 and 202.64 kJ.mol-1, respectively.

Ascorbic Acid↗

PubMed1989

[Kinetics of solid-state decomposition of aspirin].

The kinetics of the solid-state decomposition of aspirin was studied at 85 degrees, 80 degrees, 75 degrees, 70 degrees C and various relative humidities. Decomposition percentage of aspirin (x) and time (t) could be described by the equation: x = ktn where k is a constant which depends on the temperature and relative humidity. The water vapour pressure effected on the solid-state decomposition of aspirin may be presented by the Arrhenius equation: k = A.exp (-E/RT).Ps where T is the absolute temperature, P is water vapour pressure, s is a constant, R is the gas constant, A is another constant, E is the activation energy. From this equation, the activation energy of the decomposition of aspirin is calculated to be 122.17kJ.mol-1 (29.2 kcal.mol-1).

Aspirin↗

PubMed1988