Pitfalls and Practical Solutions
Joseph Chamberlain in The Analysis of Drugs in Biological Fluids, 2018
Traces of water can be removed from organic phase by the adding a pinch of anhydrous sodium sulfate. Even visible amounts of water can be mopped up by this reagent and the dried solvent can be readily poured off, the hydrated salt sticking in clumps to the sides of the vessel. Alternatively the organic extract can be simply filtered through anhydrous sodium; if there are only trace amounts of water, simply passing the phase through dry filter paper will be adequate with less potential of losing drug by adsorption to the solid salt. For example, calcium chloride added to the extract was shown to cause loss of oxprenolol in an assay for this compound.1406 Immediate storage of dried-down samples in a desiccator is recommended to remove last traces of water or to preserve the anhydrous condition of samples. Reid1407 suggests that silica gel, rather than phosphorous pentoxide, should be used as a desiccant; the latter reagent will overdry the atmosphere and cause volatilization of drug from the sample. A similar effect may also be noted in freeze-drying procedures; during the process of freeze-drying the sample will remain cold, but if the process is allowed to continue after the water has been removed, the temperature of the sample will rise to ambient and loss of sample may occur.1408
Autoradiography
Howard J. Glenn, Lelio G. Colombetti in Biologic Applications of Radiotracers, 2019
Another method has been described by Stumpf and Roth;29, 30 Frozen sections are taken at a low temperature (usually below −50° C). The sections are collected in the cryostat and then transferred to a freeze-dryer, without raising the temperature. After freeze-drying for about 20 hr, the sections are brought to room temperature in a desiccator. In a darkroom, the sections are transferred to teflon slides. These are then pressed against emulsion-covered slides, to which the sections will adhere. Exposure is carried out at −15° C. The slides are then allowed to reach room temperature. Before the photographic processing, the slides are breathed upon so that the moisture of the breath secures adherence between section and emulsion during development and fixation. A gentle handling is also needed to achieve this goal. An alternative method presented by Stumpf30 is to pick up cryostat sections on emulsion-covered slides and then thaw the sections onto the emulsions by immediately bringing the slides to room temperature. The method appears to give good results for substances such as steroid hormones, which are relatively tightly bound to their cellular receptors, but it is questionable whether the method may be used for more freely diffusable compounds.
Engineering Stable Spray-Dried Biologic Powder for Inhalation
Anthony J. Hickey, Sandro R.P. da Rocha in Pharmaceutical Inhalation Aerosol Technology, 2019
Small chambers can be used for accelerated and cyclic stability studies, whereas long-term stability studies may be performed in walk-in chambers engineered to provide a uniform temperature exposure; these may be fitted with temperature readouts and alarms [310]. In preliminary laboratory work, spray dried powder can be stored over saturated salt solution in a desiccator to control relative humidity and the desiccator placed in the stability chamber at a set temperature [237]. Relative humidity ranges for saturated salt solutions are available in the literature [314,315]. However, this method can require much storage space and does not test the effect of interactions of the powder with the container, for example, those associated with leachables and extractables, which should be tested [41,309]. Additionally, the ability of the proposed packaging to protect against humidity should be tested [309].
Comparison of properties of dust in alveolar of rats and the workplace
Published in Experimental Lung Research, 2021
Xu Zhang, Zheng Zhang, Peng Wang, Shuyu Xiao, Ke Han, Yali Tang, Heliang Liu, Yuping Bai, Yulan Jin, Jinlong Li, Xiaoming Li, Qingan Xia, Fuhai Shen
We plotted the standard curve of mass and absorbance of alpha-SiO210.00 mg of standard α-SiO2 and 990.00 mg KBr were weighed thoroughly in a dry environment to prepare a mixed sample, which was a 10 μg/mg α-SiO2 working sample. The working samples of 10 μg/mg alpha-SiO2 were weighed at 0 mg, 10 mg, 30 mg, 50 mg, 80 mg, and 100 mg respectively, and KBr was added to 200 mg. The mixture was ground thoroughly in a dry environment and tablets were prepared with a tablet press at 20 kPa for 1 minute. It was put in the desiccator for later use. The wavelength range of 400 cm−1 to 4000 cm−1 was selected, and the absorbance was measured by infrared spectrophotometer. We record the absorbance of the sample at 694 cm−1, 780 cm−1, and 800 cm−1 wavelengths by excel. Then we draw the standard working curves at 694 cm−1, 780 cm−1, and 800 cm−1 wavelengths and obtain the standard curve equation (1).
Aqueous extract of large cardamom inhibits vascular damage, oxidative stress, and metabolic changes in fructose-fed hypertensive rats
Published in Clinical and Experimental Hypertension, 2021
Kanthlal SK, Arya VS, Bindhu Paul–Prasanth, Vijayakumar M, Rema Shree AB, Uma Devi P
The large cardamom fruit used in this study was obtained from the Spices Board of India. The fruit was processed as per the standard guidelines and regulations of the board. A voucher specimen (ASP/Cog08S) was deposited at the School of Pharmacy, Amrita Vishwa Vidyapeetham, AIMS Kochi, Kerala. The plant name was checked with The Plant List (TPL) database http://www.theplantlist.org/tpl1.1/record/kew-219503 the website being accessed on February 3, 2019. Using a mixer grinder, the dried fruit was pulverized and passed through mesh no. 400 to get a dry, coarse powder. In a 250 mL sterile Erlenmeyer flask, 5 grams of large cardamom powder was soaked for 30 minutes in 100 ml of distilled water. The flask was stoppered with cotton (sterile) and boiled until 1/4th (25 mL) volume was reached (23). The solution was filtered through a muslin cloth. Using an IKA-RV-10 rotary vacuum evaporator (55°C at 7 mbar), the concentrated extract was then evaporated for dryness. Throughout the course of the experiment, the extract was maintained in the desiccator.
Formulation of sustained release bioadhesive minitablets containing solid dispersion of levofloxacin for once daily ocular use
Published in Pharmaceutical Development and Technology, 2019
Ahmed Abd El-Bary, Howida Kamal Ibrahim, Balqees Saeed Haza’a, Ibrahim Al Sharabi
Stability studies were carried out on the optimized ocular minitablets formulation according to the International Conference on Harmonization (ICH) guidelines (ICH 2003). Minitablets from of the optimized formulation were stored in a glass desiccator for a period of six months at 40 °C/75%RH. Saturated solution of sodium chloride was used to initiate and maintain the relative humidity inside the desiccator which placed in an oven at 40 °C. Samples of the minitablets were taken when fresh and at the end of three and six months, and subjected to visual observation to detect any physical changes, friability testing, determination of drug content, and in vitro drug release profiles. Drug content was evaluated using the stability indicating HPLC assay described previously (CARAS 2012). The similarity factor (ƒ2) was used to compare the dissolution data.
Related Knowledge Centers
- Desiccant
- Cobalt(Ii) Chloride
- Glovebox
- Schlenk Line
- Abderhalden'S Drying Pistol
- Silica Gel
- Calcination
- Molecular Sieve
- Phosphorus Pentoxide
- Calcium Chloride