Pharma
Forum Replies Created
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Don’t add lye or caustic soda
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I see.Now, in that case you’d need about 4 grams of citrate buffer. That is for medium hard tap water and for EVERY LITRE of water coming out of your shower and for every ‘scoop’ of shampoo you use during that particular shower session.As you can see, you don’t stand a snowball’s chance in hell maintaining a pH other than tap water. All you can do is dropping the pH in the bottle and for that, simply adding enough citric acid is all that’s required.
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A: Oil-air contact surface (that’s where rancidity happens fastest) is thousand times greater in a powder than an oil in a bottle. Shelf life drops considerably in a powder blush.B: Blushes often use iron oxides as primary pigment and it’s exactly the iron which accelerates the chemical reaction between oxygen an oil which has the latter turn rancid.-> Solutions would be: drop unsaturated oils, add antioxidants, use coated iron pigments (more expensive) or iron free pigments (which may not exist for your target colour).
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You might want to have a look at THESE.
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Now you have me a bit confused…It is absolutely impossible to tell you how much you’d have to add, even if we knew the starting pH of your product. Many detergents have a pH above or below 7 and even then, they tend to act as buffers themselves. Sugar based surfactants as an example tend to have an alkaline pH (9-11) for stability reasons. Alas, we don’t know how much and what kind of alkali has been added to achieve said pH.The first and foremost question is: Why do you need a buffer? What and why do you want to buffer?From a scientific point of view, it is rather ridiculous to buffer a shampoo because it would require either too much buffer solution or the stuff is self-buffering and all you’d need to do is adjust pH.
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Phytic acid and its salts are highly hydrophilic and do neither penetrate skin nor microbes. Caprylhydroxamic acid is a weak acid and has just the right logP so it can accumulate in microbes but this also means it’s skin permeable.Its weak acidity makes it a less pH dependent chelate but increases the possibility that bound metals become soluble in the oil phase. Given that it forms quite stable metal complexes makes it impossible to predict the pros and cons of the two vs. each other.Healthwise, phytate is certainly safer (it’s something we eat nearly every day since time immemorial).
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Given that you don’t use plain water but rather large amounts of soaps which may not be pH inert, calculating will only give you a hint (apart from the fact that calculating with polyprotic acids is a PITA unless you’re really good with maths or use an app). In the end it’s easier to just add citric acid and then start adding NaOH until you hit pH 5. That would also be a safer way than adding dry NaOH to the formulation and titrating downwards with diluted citric acid as you intend doing (unless I misunderstand your procedure).As a rough estimate which in practical regards is usually more than good enough, 1.5 mole equivalents of NaOH will bring a citric acid solution to a pH slightly below 5 (you could also mix equimolar amounts of citric acid and trisodium citrate to get the same result).
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I’ve worked with hydroxamates and even synthesised some SAHA derivatives. Hydroxamates have been on the drug developers no-no list for years for more or less good reasons (such as mutagenicity) but certain derivatives like vorinostat aka SAHA are now developed as promising drug candidates for example as histone deacetylase inhibitors (cancer therapy). Hydroxamates aren’t harmless compounds and are powerful chelates mainly for zinc and hence, inhibit a broad set of zinc dependent enzymes.Caprylhydroxamic acid is the core structure of several of the mentioned HDAC inhibitors and that’s what makes me wary. Sure, not all hydroxamates are inherently toxic, some are quickly metabolised to their corresponding carboxylic acids. But for now, knowledge and predictability are poor. Cancer treatment is a different story than widespread use as preservative. I don’t dare thinking of what might happen should caprylhydroxamic acid become a replacement for parabens or thiazolinones… my imagination associates that picture with the glyphosat aka Roundup disaster.
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Unfortunately, I can’t help you further. As said, silicate chemistry is not straight forward inorganic chemistry and hence, you’ll just have to try something. For the sake of your skin, go with a more ‘neutral’ quality and just see how it performs. This one is also more likely to give a sandy feeling rather than turning into a hard sheet of smooth glass.
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@Graillotion You can’t raise the flash point by mortal means but have to use black magic. Alas, that one is not approved for cosmetics ;( .@@natiyo123 Partially correct. Good enough for a cosmetic everyday situation.
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Emulgreen L15’s INCI is C15-19 alkanes meaning that some molecules in there does evaporate but rather slowly whilst others nearly don’t.Pentadecane (C15) is liquid at RT and has a high vapour pressure which, like essential oils, lets them evaporate well below its boiling temperature.The other end of the mixtures spectrum is nonadecane (C19) which is solid at RT and has a very low vapour pressure, it does not really evaporate but feels dry (because it’s solid).If you’re looking for faster drying and full evaporation, go with undecane, dodecane, and/or tridecane (C11-13) which evaporate fast and dry quickly or isododecane which has about the same vapour pressure as ethanol and takes longer to fully dissipate. Notably, C4 and C5 have lower vapour pressure but still evaporate.What all these molecules have in common and what seems contradictory to volatility is a high boiling point well above 200°C (if memory serves me right). The reason which greatly contributes to their good volatility is small molecular weights and low intermolecular interactions. Meaning, the lower the number in their INCI name, the faster they evaporate.
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@chemnc Yes
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Break the stored emulsion (heat till separated or centrifuge) to see whether the oil and/or water phase changed colour. Else, it’s simply your emulsion getting old = droplets increase in size and therefore light scattering reduces which reduces the illusion of an emulsion being white.
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Ah, I see. Why not just add some ‘re-fattening’ ingredient such as a plain oil, glyceryl oleate, polyglyceryl-3 oleate or stuff like that?
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PEG-7 or PEG-7 something? PEG-7 has no real use in a shower gel, doesn’t foam or anything, but might act as moisturiser (obviously only if you don’t rinse…).DEA is an additive, not a surfactant leaving Polyquaternium-7 as sole cleansing agent in product N°2 = insufficient cleaning = less stripping = higher perceived hydration.But that’s just a wild guess because your INCI nomenclature does need a serious overhaul…
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An unexplained loss… that could mean anything, from oxidation due to poor formulation over an idiot at the work bench to a greedy boss who’s not coming up for reference substances… make a pick 🙂 .
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You mean mixing two finished products?Well, at first glance it is silly. After second thoughts it may give an entirely new product if you’re lucky, use the right mixing technique, and at least one of the two allows for cold emulsification.Chances for failure are way more likely than for success and that’s just based on physical possibility of mixing, not long-term stability, sensorial profile, or effects.
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Around 7.5-9 at most, depends on what else is in your product and how much you add.
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Your line of thoughts is spot on, susceptibility to oxidation is the main issue. Whether or not the added amount of BHT will suffice, only trial and error will tell.From a theoretical physical point of view (emulsion stability), squalene in a o/w emulsion might be superior to squalane in some regards but may have a negative impact due to a lower melting point of the oil phase and therefore easier droplet fusion.
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Monosodium citrate is acidic, disodium citrate is slightly acidic. Meaning only trisodium citrate will increase pH (obviously, this depends on the starting pH).
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Trisodium citrate is alkaline, it will increase pH.
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Best HLD page to start: https://www.stevenabbott.co.uk/practical-surfactants/
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I have an chicken egg incubator for preliminary tests
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HLB is a stupid and obsolete system which too often doesn’t even work in real life. It was okay back in the day but is utter nonsense these days.It’s only useful for theoretical systems involving water, a PEG-based emulsifier system and an oil. No one produces cosmetics just based on these.A better approach would be HLD; oil industries use it instead of HLB because HLB doesn’t work and one failure in oil drilling easily costs months of work and millions of dollars. Sadly, we from the cosmetic sector don’t have the numbers for most of our ingredients because we are so addicted to HLB that HLD never got a chance. With both systems, the instant you add co-emulsifiers, ‘actives’, rheology-modifiers, and what not, the whole system changes. In that moment, HLB is toast, HLD can still be applied but you’d have to run a small series of tests to re-adjust.Hence, calculating HLB will give you an approximation on where to start but it’s neither a must not ultimate truth. For an o/w emulsion, being above theoretical HLB is by trend better than being below though energy input for emulsification may be higher.I do calculate HLB because I have the values and to see whether or not it matches results. So far, more failures than success. Just looking at the emulsifier’s chemical structure is as accurate and then it’s always trial and error… that’s the weird world of cosmetic product development.
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Most are edible though many ester oils (which are by definition liquid waxes) aren’t digestible and come out on the back the way they got in at the front.Capric/caprylic triglyceride is just fractionated coconut oil, and hence is edible and fully digestible like all mono-, di-, and triglycerides of ‘normal’ fatty acids.I’d be careful with branched-chain fatty acids and fatty alcohols such as isostearyl isostearate and esters of Guerbet alcohols like ethylhexyl and octyldodecyl esters. These are not digestible and usually not metabolisable by humans (only by microbes) though they can still be bioavailable which may render them not so healthy.Esters of propylene glycol and other di- and polyols may be edible or may not be. I’d be hesitant eating for example glycol distearate.