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Propylene Glycol - Science topic

Propylene Glycol is a clear, colorless, viscous organic solvent and diluent used in pharmaceutical preparations.
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I want to estimate freezing point of a mixture made from Ehhanol (H₃CCH₂OH, MW: 46.07 g/mol) , mono propylene glycol (CH₃CH(OH)CH₂OH, MW: 76.1 g/mol) and water. And the ratio of the mixure will vary for example I can start with 1:1:1 and so on. I spent couple of week to google it but not able to figure out how to do that. If someone here have some experience with it or have some suggestion / literature then please help to solve for this problem.
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Dear Dol Lamsal,
The best and simplest choice for the phase-equilibrium calculations and studying such systems (Including Water+Alcohols+Hydrocarbons) is the CPA (Cubic Plus Association) equation of state. I suggest you verify the following references:
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I have developed a syrup at pH 3 of a BCS class II molecule using propylene glycol, beta Cyclodextrin, citric acid, antimicrobial preservative, and sweeting agent. But i every time get precipitation after holding 2 to 3 days. When shake the bottle i found smoke like floating of these precipitation. How can I fix the problem. I am looking forward to your help.
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Thank you sir @phil Geis for your valuable comment. I conducted microbial test and found no growth which made me confirm that it is not from microbial contamination.
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I am optimizing the method of developing natural deep eutectic solvent by using different methods, molar ratio and water content. For heating and stirring method, I used 1:1 Choline chloride:1,2 propanediol. The combination does not form liquid either direct heating or in water bath up-to 2 hours. The temperature is below 100 degree C. I tried to add minimal amount of water (less than 50%). However, the combination does not form homogeneous solution. It only form clear homogeneous solution when I put more water (160%) and its stable at room temperature. My concern is some journals mention the excessive water content may disturb the hydrogen bonds between Choline chloride and 1,2 propanediol. I tried to rotavap to remove water content and it starts recrystallising again. I repeated the experiment by using total dried Choline chloride (freeze dried) after reading some suggestions from previous researchers that had similar issue that caused by wet Choline chloride. However, I obtained similar results 😢. May I have some other suggestions or opinions that may solve the problem? Thanks in advance
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For those arriving at this question: to properly answer this question you have to measure the solid-liquid phase diagram. It will tell you the maximum solubility of choline chloride in 1,2-propanediol at a certain temperature (e.g. 30 ºC). Probably a choline chloride mole fraction of 0.5 (1:1) is higher than the maximum composition at the temperatures you work.
Adding water increases the solubility (lowers the melting point) and can be a solution. Of course also within the thermodynamic limits.
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Dear colleagues,
I'm looking for articles where I can find tests of food attractants used to monitor fruit flies. I am not looking for pheromone-based attractants.
We have already performed a series of tests where we tried to have a glue trap (containing aroma dissolved in propylene glycol) and the raw materials from which the aroma was made were used next to them (eg grapes and grape aroma). Fruit flies almost always chose the raw material itself and they were not interested in the aroma in the glue. Even after removing the raw material itself, the glue trap with aroma did not attract them.
I will be happy for any of your knowledge and articles on the topic.
Thank you.
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Hi, Josef,
take an article about yeast.
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Hello, can someone advise me ordering numbers (the best options are Sigma or Merck, but it could be even some another company) for Ethylen Glycol and Propylene Glycol solutions suitable as cryoprotectants for vitrification of porcine GV oocytes (or at least of some another mammalian species oocytes in general)?
Thank you.
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Hi Matej. I recommend you Syngro Ethylene glycol freeze with Sucroze. I used it for bovine embryo cryopreservation and it worked well.
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Hi, I am working with PEGDA (polyethylene glycol diacrylate) for SLA 3D printing. Parts made from 100% PEGDA are transparent after production, while adding increasing amounts of propylene glycol to the pegda solution makes the final part appearing milky-white. Why does that happen? What causes this phenomenon? Please note that the liquid mixture of PEGDA/propylene glycol is also transparent before 3D printing.
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Dear Carlo: I beleive you have a phase separation problem. The refractive indexes of PEG and PEGDA are 1.4339 and 1.463, respectively. After the 3D printing process, small segregates of PEG are formed. These have to be larger than 300 nm, in order to cause light dispersion, that is milky appeareance.
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Trans-dermal patches contain the drug intended for trans-dermal delivery, along with all kinds of (often petroleum derived) adhesives, plasticizers, inhibitors, and permeability enhancers. I'm trying to find any information about whether any of these other substances, adhesives, enhancers, tackifiers, etc. have been found to also pass through the skin along with the intended drug in small amounts. I have been able to find a lot of information about the composition of various patch systems, as well as trials of how effectively the drug intended for delivery is absorbed, but absolutely nothing about whether any of these other petrochemicals present in the patch matrix also pass through. Is anyone aware of literature on this? Has it just not been studied?
My assumption would be that very minimal trace amounts of the petrochemicals comprising the patch matrix pass into the body along with the drug intended for delivery ~~ but that this has been determined to be a safe amount for relatively short term use. I'm specifically asking this question with transgender people who use hormones in mind. A transgender person who uses HRT as part of transition and chooses trans-dermal delivery, trace amounts of these petrochemicals over a long period of time could cause significant issues...
And as a secondary question, I'm wondering if there are any studies into whether the enhancers//inhibitors in the patch also enable other environmental contaminants to pass through the dermis undigested. To give an example, when I have used trans-dermal patches intended to be worn for 1 week, by the end of the week the patch will regularly get water and soap under the edges, and sometimes the middle as I shower. This from what I've read is normal, and it's suggested to just apply pressure after showering to re-adhere the patch to the skin. So, potentially chemicals that are in shampoos, soaps, and conditioners are coming in contact with the area of skin "prepared" for trans-dermal absorption of xeno-molecules everyday.
Below is a summary of what I've found about the materials used to produce trans-dermal patches:
From what I can gather looking at patents and studies, estradiol trans-dermal patches are generally comprised of 4 main categories of chemical:
(1) The drug intended for delivery ~ Estradiol
(2) An inhibitor such as propylene glycol to disable the role of the dermis in enzymatically digesting xeno-molecules before they enter the body... propylene glycol inhibits the enzymatic reaction that causes oxidation of estradiol into estrone.
(3) An enhancer such as Oleic Acid that is intended to enhance permeability of the skin and facilitate transdermal movement of xeno-molecules
(4) Adhesive polymer, this varies a lot from patch to patch but as an example this is what I was able to find for the Vivelle dot HRT patch ~~~ acrylic adhesive, polyisobutylene, ethylene vinyl acetate copolymer, 1,3 butylene glycol, styrene-butadiene ribber, mineral oil, dipropylene glycol… excerpt from NOVARTIS FDA document https://www.accessdata.fda.gov/drugsatfda_docs/label/2000/20323S23lbl.pdf
And here is a list of the ingredients specific to one brand of Estradiol patch called "Vivelle Dot":
The Vivelle system comprises three layers. Proceeding from the visible surface toward the surface attached to the skin, these layers are (1) a translucent flexible film consisting of an ethylene Page 2 vinyl alcohol copolymer film, a polyurethane film, urethane polymer and epoxy resin, (2) an adhesive formulation containing estradiol, acrylic adhesive, polyisobutylene, ethylene vinyl acetate copolymer, 1,3 butylene glycol, styrene-butadiene rubber, oleic acid, lecithin, propylene glycol, bentonite, mineral oil, and dipropylene glycol, and (3) a polyester release liner that is attached to the adhesive surface and must be removed before the system can be used.
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Hi there! I found the info you provided is important since I am starting a new project "transdermal release". However, I am new in the field and would your guidance to understand the system and technique. All I have is an oily natural product and assigned to study the release from a polyester. Any help would be appreciated regarding the three layers components, sources, procedures ..etc
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Hello,
In the video you can see a drying process of the freshly printed thin layer of the ink, 10x10 mm.
Do you know any work dedicated to the mechanism of such drying procesess? What shape can be layer made with a solid content of the ink?
The ink consists of 2 mass parts of 1,2-propanediol and 8 parts of 1-pentanol and a small percent of a PEIE polymer. The substrate is a glass cover with a oxygen plasma treated ITO.
Tom
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That is a very interesting video. I have been told by polymer experts that during the drying process, certain polymers have an affinity for certain carriers, so they may tend to coalesce around the parts that dry more quickly or more slowly. But I think there may be another explanation as to what created the lines in the first place.
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I'm currently working on a project that involves the simulation of CHT (Conjugated Heat Transfer) problems potentially leading to the evaporation of a water/glycol mixture.
Thus I would need to have the thermal properties (especially the coefficient of volume expansion) of both ethylene glycol (1,2-ethanediol) and propylene glycol (1,2-propanediol) in liquid and gaseous phases.
So far I've managed to find (relatively easily) the properties of the liquid components, but nothing regarding the gaseous components.
Could someone points me in the right direction for such data ?
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The ideal gas approximation can typically be used with reasonable accuracy for sufficiently high molar volume (or low pressure). Otherwise, the gases should be taken as real.
The real gas/vapour density of pure substances or mixtures can often be correlated quite accurately based on the corresponding-states principle. Accordingly the two-parameter principle of corresponding states; for real gases (or vapours), even if saturated, the same compressibility factor (Z) holds for both reduced temperature (Tr = T/Tc) and reduced pressure (Pr = P/Pc).
The compressibility factor can then be read from a generalized compressibility chart, obtained after published data (tables) from a well-known selected reference substance such as dry air or steam, calculated after some chosen equation of state, or estimated from some convenient PVT correlation.
For better accuracy, a three-parameter corresponding state approach is preferred. For saturated vapours, PVT data/predictions should be consistent with vapour pressure data/predictions.
The volumetric thermal expansion for the real gas can be then readily derived from PVT data/predictions, but also depends on the type of thermodynamic process by which temperature changes (e.g. isobaric, isochoric, polytropic).
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  • I am conducting a zeta-potential experiment but it shows I have a poor quality result and my sample conductivity is low. My sample is copper nanoparticles dispersed in propylene glycol.
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Thanks, Alan F Rawle for your suggestions, they are really quite helpful for me. I will consider the options available to increase conductivity.
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Ethanol and propylene glycol are both used to preserve mites, and each have their drawbacks (i.e., evaporation and specimen distortion). Some people add a small amount of glycerol to vials of ethanol to prevent samples from drying out over time if containers prove less than perfectly airtight. Does anyone have experience with the long-term performance of ethanol/propylene glycol mixtures as preservatives for mites, and particularly for oribatids?
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Dear Kara,
The usual concentration for ethanol is 70%. The more percentage makes specimens fragile in long-term even in short-term. About propylene glycol, I should say it may not go to the bottom of vials and it helps to reduce the evaporation of ethanol.
Best, Elaheh
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Propylene glycol has has flash point ~101 degC. What is the wt% of water needed to increase the flash point to ~150degC?
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One of the companies recommends to dissolve their products in 50%/50% mixture of ethanol and propylene glycol and inject 15-75 ul intravenously (or intraperitoneally) in mice.
The stated benefits are high solubility of many compounds, far less inflammation of small vessels than with pure alcohols and a better handling (lower viscosity) than wth pure propylene glycol.
However, as far as I see, the use of this solvent mixture for i.v. injections appears to be almost absent from the literature: so far I've only seen a paper where it was used for i.p. (intraperitoneal) injections.
Does anyone know of this mix (50%/50% EtOH/PG) being used for i.v. injections in practice? If it has these benefits, why is it used so rarely? What are the safety levels and side effects?
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Use of 50:50 ethanol:propylene glycol mixture or 50:50 ethanol :ethylene glycol mixture can be for I.V. injections in mice.
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I have carbonized items in propylene glycol how can I clean it out?
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In the end some solvent did the job, In my case, Acetonitrile caused in the precipitation of the molecules.
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I have tried to derivatize 1-propanol with MSTFA, BSTFA and MTBSTFA. But I can not see any peak other than the blank peaks ( blank were prepared by pyridine and the derivatizing agent).
I derivatized 1,2 propanediol ( 1,2-PD) with MTBSTFA . 1,2 PD has two OH- group and acidic hydrogen was converted to TBDMS.
But what's wrong with the 1- Propanol ? Any idea will be highly appreciated !!!
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You're welcome. I hope some of this will work. 👍
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Hello,
I am looking for PDMS membrane for propylene glycol and glycerol separation. I would highly appreciate if someone could recommend a supplier. 
Thank you
Hripsime
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I have prepared PDMS dense membrane on my own and published a paper
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Hello Friends,
A quick question, can I use RO to separate propylene glycol from water? I am confused because it has low molecular weight and also not sure about the polarity. Can any body help me?
Thank you so much.
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Liquid-liquid extraction (solvent extraction) is better using suitable solvent.
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Actually I have a reproducibility issue.
I have a 7-component microemulsion system consisting of water and propylene glycol as the aqueous phase, ethanol and limonene as the oil phase and Tween60 as the surfactant.
I dissolve a certain amount of my drug at ~40C and then cool it down to 30C. Each time I get different amount of precipitates which means different amount of solubility.
Is it possible to have a range of solubility in microemulsion?
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To start with you may wish to determine the solubility of your drug in each of the individual components (7 components in this case). For that you will need a proper quantitative / analytical assay method (rather than depending on visual observation of drug precipitation). Ideally you would want to have a validated HPLC assay to quantify the drug or at least using UV/Vis spectroscopy (assuming that your drug has a chromophore). You can simply add excess amount of the drug to a fixed volume of each individual component, vortex (mix) at 25 degree Celsius for at least 24 hours (to ensure saturation) and then centrifuge, take a sample from the supernatant, filter and quantify using the assay method that you have developed. That will give you the saturation solubility of your drug in each (individual) component.
You can then repeat the above procedure using the microemulsion formulation.
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The taste on the product is evident. Is it toxic?
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I went through the toxicity profile of PGEE and it doesn't look like to be toxic at those low levels of exposure (literature attached). However, any expert in this field can comment better.
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Hello everyone,
I am in internship in a laboratory to analyze and formulate flavors for e-cigarettes. I have to create a HPLC method to determinate the concentration in sucralose in our products. I already created one, with a protocol of many publications, with water. By the way, I would like to know more about it, and understand how the derivate product is ok for being analyzed in UV. I know that the aromatic chromophore is ok for UV but I would like to know more about it too. Our products are in Propylene glycol, glycerol and nicotina. That's why I can't try to analyze a sample with my standards in HPLC UV, there is no water in and I don't think that if I put water, the sucralose would react with it.
Moreover, I don't understand why I can't see this publication on ScienceDirect, because with my student access I usually can : "Benzoylation of sugars, polyols and amino acids in biological fluids for high-performance liquid chromatographic analysis."
If you have any ideas to try something with my standards and my samples, you can tell me !
Thanks for the help and have a good day,
Alice
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Paper is attached.
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Is it harmful or not?
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Depends on conditions of use and exposure.   A hazards-only based system is perhaps useful for ranking the potencies of similar acting compounds to prioritize which are the most of concern.  However, for actual risk assessment, exposure considerations are just as important as hazards since anything in high enough concentrations can cause toxicity.
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I'm doing research about w/o caffeine micro emulsion (ME). I used 1 ml hot water to dissolve 400 mg caffeine but it crystallized and my ME become unclear or cloudy. I've tried to add 0,5 ml propylen glycol as cosolvent/cosurfactant but it still crystallized. I can't add more water because it can make my ME unstable and become emulsion. What should I do to prevent crystalization caffeine in my ME? Thank you. 
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I took Titus's advice to reduce concentration of caffeine and it works, my microemulsion become stable. Caffeine has character to crystalize, so it doesnt work if I increased temperature to dissolve it because when back to room temperature, it crystalized by itself before I add to ME formulation.
I also have tried to add some methanol and propylen glycol, but it still doesnt enough to dissolve caffeine perfectly.
So, the final result is I dissolve 50 mg caffeine in 1 ml hot water plus 0,2 mL propylen glycol then I put in to my ME.
Thank you for all reserachers who answers my question, it really helpful for my thesis. God Bless You :)
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I have Imidacloprid and Propylene Glycol as contaminant both having 0.4 mM concentrations. I am doing experiment on Fenton process.  I came across with this journal citing that the requirement for H2O2 is 2.12 mg H2O2 per mg COD. I want to know the COD of my concentration without doing COD test. Is this possible?
Thanks.
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Dear Carl,
To calculate Theoretical COD
let us assume this example:
What is the theoretical COD of samples containing 300 mg/L of phenol (C6H5OH)?
The solution:
The theoretical oxidation reaction is as follow:
C6H5OH + 7 O2 ------------ 6 CO2 + 3 H2O
94 gr             224gr
300mg/L      715mg/L
Therefore the COD is 715 mg/L
Good luck
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i am having the data of temperatures, pressures and flow rates before and after the reaction. i need an equation which help me to identify conversion with respect to the change in above known variables.
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Kinetic equations have been solved for difunctional additions in which reaction rates are statistically about equal for all active hydroxyls. Some initiator like acidified water must be used to start the reaction. The ratio of water to propylene oxide determines the final average molecular weight, assuming one molecule of water promotes one molecule of glycols. Reactor needs to be fairly warm to get a reaction in weak acid.
The PO addition is highly exothermic and is likely run out of control making an explosion unless a solvent is used to dilute the chemical potential and help with cooling. Mistakes with propylene oxide might or might not give you a second chance, compared to ethylene oxide which probably doesn't give a second chance. You need to get expert safety advice before using Propylene Oxide, because of possible fire and explosion.
Let me try to remember the formula for ratios of different molecular weight products, from some years ago. Assume all the water and PO reacts, then solvent is removed by boiling, taking the heat with it.   Let f1, f2 and f3 be the mole fractions of mono. di, and tri propylene glycols in a series where f0 is water. Note that some larger molecules are likely if not enough water was used. The mole fractions follow closely to an exponential Maclaurin series expansion based on powers of [-Ln(f1)]. It is the solution of an infinite number of differential equations in series where the rate constants are equal per active hydroxyl group, but reactions are not usually reversible.
Notice that 
e[-Ln(f1)] = 1/f1             and
 ex = 1 + x + x2/2! + x3/3! + ... + xn/n! + ...               then
f2/f1 =  [-Ln(f1)]             and 
f3/f1 =  [-Ln(f1)]2 / 2!           the answers to your question
but there are higher molecular weights in the series, maybe significant amounts if your starting ratios are wrong, or mixing is not good.
The mole fractions add to one.
1 =  f1 + f2 + f3 ...+ fn + ....
1 = f1 + f1[Ln(f1)]  + f1[-Ln(f1)]2 / 2!   + f1[Ln(f1)](n-1)/(n-1)! + ...
Giving your answers from the exponential series.
Ratios of water and PO moles can also be given in series. Product yield is one mole of product per mole of water reacting, hence a refluxing solvent conserves water in the reactor. Moles of PO per mole of product are given.
p = f1 + 2f2 + 3f3 + ... + nfn + ...
p = f1 + 2f1[-Ln(f1)]  + 3f1[-Ln(f1)]2 / 2!   + nf1[-Ln(f1)](n-1)/(n-1)! + ...
As always the actual result differs a bit from the ideal especially in higher molecular weights, but the ideal gives a way to estimate results and select feed ratios.
Notice you can get exactly the same products in the same ratios from reacting acetone in the aldol reaction, but at more severe conditions of temperature and catalyst. Acetone also has potential for strong exothermic polymerization leading to explosion. With acetone there is a series of intermediates called polyacetyls which finally decompose or make glycols unless stabilized by a capping agent. 
If you choose acetone as your solvent then it is not inert, but probably does not permanently alter the product mix unless you have impurities that cap the acetyls.
 PO is added drop wise and only as quickly as its reaction heat Is carried away by reflux condenser.
In no case should PO be allowed to accumulate in the reactor. Also the reactor contents should be prevented from flowing backward  into a PO reservoir.
With these systems start in small scale and protected equipment. Verify the exotherm before proceeding. First get safety advice. Stop when in doubt. Protect people and property from damage.
If you want all mono glycol, water is your reflux solvent.
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I have a Charles River Endosafe PTS machine and I am looking to undertake an Endotoxin test for a chemical dissolved in Propylene glycol. So far I have not been able to find the dilution and what it can be dissolved in, in order to use in the PTS cartridges.  Does anyone have any advice?
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It is necessary to conduct calculations. everything depends on what level B. E. you are going to prescribe for solvent. I can ask my college how to dilute. She is dealing with B.E. very closely.
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i'm wondering why glycerine and propyleneglycol are used as solvents for e- liquids. of course, they are approved for consumation, they steam!
do you know which temperature is reached in the e cigarettes allowing evaporation? 
thanks in advance,
patrick schimpl
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Hello Patrick, 
First of all, glycerine and propyleneglycols are used in e-cigarettes because they are miscible with water - it is necessary to create an aerosol (glycerine and propyleneglycol droplets in water vapour). The temperature in e-cigarettes varies within 100 - 250 °C. Within this range it is no problem to create aerosol, and such a broad range is also convenient to support vaporisation in case your batteries lose voltage (flexibility). 
Ethyleneglycol is also possible (miscible with water and boiling point is even less than that of glycerine), but it is more expensive (because it is a shorter chain alcohol) than the other longer chain alcohols. That is why as Nebelfluid for discos they also use glycerol. Hope it helps. 
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it is polyester synthesized using Adipic Acid, Phthalic Anhydride and Propylene Glycol
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double click the x axis and you will the get the temperature profile added to time as well and then reupload the picture ... you can also check this paper for DSC curve interpretation. You can get the pre-print version from my website.
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Dry or powder Propylene glycol vs its liquid form. Is there is any difference regarding ABSORPTION/METABOLISM?
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Thank you very much dear Ebrahim. However, as you can see in my question, I was asking not about management but about  absorption/metabolism. Could you provide me with any data in this regard?
Thank you very much.
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Hi everybody,
I want to dissolve beta-sitosterol for animal experiment. I try to dissolve it in many solvents such as methanol, ethyl alcohol, polyethylene glycol, propylene glycol, DMSO, ... However, it is unsoluble in these solvents. 
Could everybody know what solvent can dissolve beta-sitosterol ?
Thank you so much
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Hello,
I believe the above answer is based on a misprint.  Beta-sitosterol is INSOLUBLE in water, not soluble as stated in that answer. However it is soluble in ethanol, and most useful, it is soluble in most vegetable oils
Beta-sitosterol | CasNO.83-46-5 - LookChem
www.lookchem.com › Products
Beta-sitosterol is insoluble in water while soluble in chloroform and carbon disulfide.
beta-Sitosterol | 83-46-5 - Chemical Book
www.chemicalbook.com › ChemicalBook › CAS DataBase List
Visit ChemicalBook To find more beta-Sitosterol(83-46-5) information like ... solubility : chloroform: 20 mg/mL, clear, colorless. Water Solubility : INSOLUBLE ...
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Typical pH probes have a temperature limit of 130 C and will see interference from the presence of Ag+ ions in our solution.
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There  is no pH scale for this solution.  You may get a reading With a pH electrode, but it would have no information.
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When collecting freshwater mussels in remote areas, it’s often impractical to use ethanol as a preservative. Especially for amateur collectors without access to laboratories.
Samples collected in the field might need to be stored briefly, then posted to a laboratory. The sample might consist of a snip of mantle tissue (possibly the whole body plus shell). On receipt, the tissue could be transferred to ethanol if necessary.
Some alternatives that have been suggested include  overproof rum, whisky, vodka or other strong spirits, and car antifreeze.
Are there proven options for freshwater molluscs, including freshwater mussels?
This paper describes options for insects (ok for molluscs too?):
Steininger S, Storer C, Hulcr J & Lucky, A. (2015) Alternative preservatives of insect DNA for citizen science and other low-cost applications. Invertebrate Systematics 29, 468–472. Prevention of DNA degradation is essential to conducting molecular analyses of field-captured specimens. This is especially important for projects that incorporate participation of non-specialists in research, such as agency monitoring of pests, or citizen science, where standard methods of preservation may be inaccessible. We examined efficacy of three common alternative products as a substitute for 95% ethanol or pure propylene glycol in preserving DNA: alcohol based hand sanitiser and propylene and ethylene glycol-based automobile antifreeze. We subjected Xylosandrus compactus ambrosia beetles (Coleoptera:  Curculionidae: Scolytinae) to each preservative for two or seven days under direct outdoor exposure and assessed relative quantity of intact DNA by performing real-time polymerase chain reaction amplification of a single-copy nuclear marker. Amplification was observed in all treatments and electrophoresis of the amplified product showed clear bands of the appropriate weight. Successful amplification of the target gene was verified by sequencing the amplified control. No statistically significant differences were found between the cycle threshold values of any treatment. Our results suggest that alcohol-based hand sanitiser and automobile antifreeze can successfully preserve DNA for short-term storage and serve as effective substitutes for laboratory-grade preservatives in citizen science projects, large-scale trapping projects or by professionals.
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NaCl + DMSO is certainly good, but does not solve the problem if something like ethanol must be avoided.
Probably, put the sample in a bucket with  just enough solid salt should be OK. The stuff just need to be shaken from time to time
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Hi,
To investigate management effects on biodiversity I am running a network of emergence and pitfall traps in a long-term conservation agriculture trial in Lilongwe, Malawi.
The climate is tropical and evapouration rates of collecting/preservation fluids in the traps is high.
A quick review of the literature suggests that 30% Propylene glycol should provide a collecting medium that has low evapouration rates and good preservative properties. 
My problem is that is Propylene glycol is very expensive in Malawi. I am wondering if, rather than replacing the P.glycol each trapping round, I can recycle the chemical by topping up the traps with water or a lower % P.glycol to compensate for evapouration? anyone tried this before?
Many thanks,
Pete
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I don't see why you could not do that.   I have used p. glycol pitfall traps over periods of several weeks in Nova Scotia and simply allowed small amounts of rain water to recharge the traps.  I don't think that P. glycol is likely to evaporate, at least not to any significant degree.  What evaporates is the water out of the solution.  Even if all the water in your traps evaporated you are still left with an effective killing solution.  I think the main reason we dilute P. glycol is because its expensive pretty much everywhere, and we stretch it usefulness.  In other words,  fill as many traps as we can, at minimal expense.  However, I've noticed the traps can start to smell pretty foul the more you reuse the same solution.
Best of luck,
Jason
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I have tried till today a lot of protocols (IHC world,...), using isopropanol or propylene glycol or both, but I haven't had any satisfaying results yet...The stain is scattering everywhere out of lipid droplets, red oil is precipitating and the slides end up all dirty. The last protocol I have tried is the following one: fix in formol 10% for ten minutes, then put in 100% propylene glycol for 5 minutes, stain with oil red O 1,8% in isopropanol ( dilution from stock solution 6:4) and then put in 85% propylene glycol for 2 minutes and rinse in deionized water for 1 minutes. I have also tried to later stain with Gill III hematoxylin for 30 seconds, but the results were even worse...  I am quite desperate about it ! Please if anyone met these kind of problems and managed to solve them, I would really appreciate her or his help :) Thanks in advance ! 
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Please check Dr. Lang's above reference as it is very  help full. I simply added a more  detailed account of what we use with some pointers.
We have has good results with the Lillie& Ashburn method of 1942:
Tissue preparation:
Use a dewar flask which has liquid nitrogen in it. Then lower a small metal beaker hooked on a stand and which contains isopentane in to the liquid nitrogen. You can place your muscle  or other tissue on a piece of cork before freezing with OCT to stabilize. When the isopentane is cold, lower your tissue in to it.  If  you do not freeze your tissue right you will get ice crystal artifact.  You can then section your material in the cryostat.(see the book: Muscle Biopsy by Victor Dubowitz). It is important to cut good sections as liver (if it has fat in it) can have this fat spread over the section causing artifact. ie more lipid stained particles. Be sure to clean the knife. This becomes worse at a higher sectioning temperature so keep your temp optimal. 
Stain: Stock solution: Saturated oil red o solution made with isopropanol 99%.  This should be made a few days ahead.                                                                         Working solution: 6 ml stock with 4 ml distilled water. Let stand for ~10 minutes and filter (note you should use a vacuum filter system).  The filtering is very important to remove particles and the vacuum approach helps you work quickly. But if you let this solution stand too long, it reduces the staining ability and will produce particles. So you will have to find the best times etc. . The solution is really unstable and has the tendency to produce the precipitate.
Once you have sections
1. Post fix  tissue in formol calcium,  Typical sections are from 6u to 10u. But you may find it helpful to cut a little thicker when you are beginning to use this stain.        2. Rinse in 60% isopropyl alcohol.                                                                                       3. Place slides in the working solution of ORO and leave aprox 10-30 minutes.  Note: Time may have to be determined by a few attempts.Liver may have large lipid containing vacuoles. These may stain quicker than other tissues. So shorter times may be needed.
4. Some times differentiation is need but you can also lighten the stain itself too much, so be careful. It is best to get the timing right. To differentiate  place in 60% isopropyl alcohol.   It is good to use the microscope at this stage to see what is happening.   
5. Wash well in distilled water.                                                                                               6. You can counter stain also Carrazzi  Haematoxylin.                                                   7.  Mount in glycerol gelatin (This should not be hot or you will destroy the stain).
8. Don't for get the negative control. This will let you know how much precipitate is produced by the stain on a non fatty piece of tissue and will help with interpretation. Also you can look on the part of the slide with no tissue.
good luck                                                                                  
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Dear all..
Kindly suggest the alternate for Propylene glycol which is commonly used as a vehicle control in the experiments (Genotoxicity and  antitumor studies) pertaining to EAC models..and also explain why propylene glycol is the most preferred vehicle control for comparison studies done using chemotherapeutic agents.
I have attached an article for better understanding..
Thank you
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Not really, it depends on your agent and its solubility properties (polarity). This will determine which dissolution vehicle you will use (ethanol,  acetone, DMSO, etc.) It is important to prepare a stock solution so you can keep the concentration of the dissolution vehicle below toxic levels.
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In current scenario, we have Propylene Glycol mixed with proper additive as an antifreeze. But to have freezing point depression by 50 degrees, the Antifreeze to Water proportion needs to be 1:1. I am in search of some chemical which can bring such depression in freezing point even at very low concentrations with water.
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Dear Hari,
This is not possible due to physical properties of solutions. The freezing point depression is given by the molar concentration of the chemical in the given solvent, this is practically not dependent on the chemical properties, and it depends on the number of molecules (or ions) in the volume unit only.
Best regards
Pavel Travnik
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I am planning to treat a rodent species with thyroid hormones (T4 and T3) for 4 weeks using Alzet osmotic pumps (Model 2006). Does anyone have an established protocol or can give me some advice regarding the appropriate solvent (e.g. propylen glycol?) and the stability of the hormones in the pump during implantation. Regards and thanks in advance, yoshi.
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Dear Björn,
thanks for your quick reply (and sorry for my delayed one). I have already checked the list you mentioned beforehand, but there is no reference refering to an administration of thyroid hormones for a duration of 4 weeks with pump model 2006. The technical support at Charles River's was also uncertain..
My main concern is about the stability of the hormones in vivo: 
Is it necessary to replace the hormone solution during treatment, or not? 
Best,
Yoshiyuki
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I need to study the enzyme-solvent interaction and as a start decided to do a zymogram to check the viability of my protease in organic solvents selected (Propylene glycol, Polyethylene glycol and heptane). The problem is the enzyme is commercial and is available as granules which does not dissolve in either of the solvents.They get suspended and settle down in the stacking gel after loading. and also is it fine performing a SDS-PAGE  or a Native PAGE? 
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Sorry to say I wonder if its active in those solvents,  you have mistaken,  the whole biochemistry is affected if it so happens, re check what you mentioned
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What is the solubility of fluocinolone acetonide in propylene glicol (exact ratio)?
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Thank you.
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I have an ingredient list for a method I am interested in trying, but the exact quantities are lacking. If someone has made hydrogel from polyoxyethylene glycol, propylene glycol, urethane polymer and poluoxyalkyleneamine, I would be interested. Thank you.
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thank you Fakhrul Khan!