Reference formulas & their QC gates
Standard published formulations (WHO handrub and ORS; classic cosmetic and household bases) presented for education — the same starting points a QC chemist tests against every working day.
WHO Handrub — hydroalcoholic sanitizer
Formula: Ethanol 80% v/v · Glycerol 1.45% · Hydrogen peroxide 0.125% · Purified water to 100%
The WHO Formulation I, published so any pharmacy on Earth can make it. The peroxide isn't for your hands — it kills spores contaminating the bulk itself. Glycerol keeps the alcohol from destroying skin at 80%.
QC gates: Alcohol 75–85% by GC/alcoholometer · peroxide assay · microbial limits · weight-loss (evaporation) on stability
Oil-in-Water Cream Base (vanishing cream)
Formula: Stearic acid ~15% · Glycerin ~8% · Potassium hydroxide ~0.7% · Preservative QS · Water to 100%
Partially neutralizing stearic acid with KOH makes potassium stearate soap in situ — that soap is the emulsifier holding this ancestor of nearly every moisturizer on the shelf together.
QC gates: pH 6–8 · viscosity · centrifuge + freeze-thaw stability · preservative challenge USP <51>
Syndet Liquid Cleanser System
Formula: SLES ~10% active · Cocamidopropyl betaine ~3% · Glycerin 2% · NaCl QS to viscosity · Citric acid QS to pH 5.5 · Preservative QS · Water to 100%
'Syndet' = synthetic detergent: no soap, so no soap-scum and skin-pH friendly. The salt-thickening trick (the 'salt curve') peaks and then collapses — in-process viscosity checks exist because overshooting the peak thins the whole batch.
QC gates: Active matter · pH · viscosity vs the salt curve · foam height · microbial limits
Carbomer Gel Base (clear gel)
Formula: Carbomer ~0.5% · Glycerin 2% · Neutralizer (NaOH/tromethamine) QS to pH ~6.5 · Preservative QS · Water to 100%
Dry carbomer is a curled polymer powder doing nothing; neutralizing uncurls it into a clear gel network. Add the base too fast and you trap lumps ('fisheyes') that never hydrate out — mixing order is a validated step, not a preference.
QC gates: Viscosity after full neutralization · clarity · pH · yield value (does it suspend?)
Anhydrous Ointment Base
Formula: White petrolatum ~95% · Mineral oil QS to consistency (or 100% petrolatum for the simplest base)
No water = almost no microbial risk and no preservative needed — the trade-off is greasiness. This base carries everything from antibiotic ointments to diaper creams.
QC gates: Melting range/congealing point · acid value · peroxide value of oils · homogeneity
Isotonic Saline 0.9%
Formula: Sodium chloride 0.9% w/v · Purified water to 100% (sterile grades: filtered, autoclaved/aseptic)
The simplest formula in the building and the strictest file: for irrigation/sterile grades the tests are the product — sterility, endotoxin, particulates.
QC gates: Chloride assay (argentometric titration) · osmolality ~308 mOsm/kg · USP <71> sterility · USP <85> endotoxin (sterile grades)
Household Bleach (regular)
Formula: Sodium hypochlorite 6% nominal · trace NaOH (stabilizer) · Water to 100%
Strength decays on a clock — roughly 20% per year at room temperature — so the release assay deliberately targets high-in-range and the expiry is calculated from the decay curve.
QC gates: Available chlorine (iodometric titration) · specific gravity · pH > 11 · stability decay trending
Oral Rehydration Salts (WHO ORS)
Formula: Per liter of water: NaCl 2.6 g · Glucose anhydrous 13.5 g · KCl 1.5 g · Trisodium citrate dihydrate 2.9 g
The most life-saving arithmetic on this page. The critical quality attribute is blend uniformity: a pocket of powder heavy on one salt fails the patient it was weighed for.
QC gates: Each salt assayed · blend uniformity (stratified sampling) · osmolality ~245 mOsm/kg · moisture (water activity)
Epsom Bath Soak
Formula: Magnesium sulfate heptahydrate ~100% (optionally fragrance ≤0.5%)
A one-ingredient formula whose entire QC is identity and hydration state: MgSO₄ grabs or loses its seven waters with storage humidity, changing weight per dose without changing appearance.
QC gates: Identity (Mg + sulfate reactions) · complexometric assay · loss on drying/ignition (water of crystallization) · heavy metals
The raw-materials library
36 materials in five functional families. Read any row as the chemist does: what it does, how much goes in, and the test that proves the drum on the dock is really that material.
Bases & solvents
| Raw material | Function | Typical level | QC test |
|---|---|---|---|
| Purified Water | Solvent — the #1 ingredient in the plant | 50–95% | Conductivity, TOC, bioburden (100 CFU/mL action limit) |
| Ethanol | Antiseptic / solvent | 60–95% antiseptic | GC assay, methanol screen |
| Isopropyl Alcohol | Antiseptic / solvent | 70% typical | GC assay, specific gravity |
| Mineral Oil | Emollient / solvent | 1–50% | Viscosity, acid value, PAH limits |
| Petrolatum | Occlusive base | Up to 100% | Melting range, PAH purity (USP grade) |
| Glycerin | Humectant | 1–10% | Identity (IR), specific gravity, DEG/EG limit test |
| Propylene Glycol | Humectant / solvent | 1–15% | GC assay, identity |
Surfactants & emulsifiers
| Raw material | Function | Typical level | QC test |
|---|---|---|---|
| Sodium Lauryl Sulfate (SLS) | Anionic surfactant — foam | 1–30% | Active matter, unsulfated alcohol, pH |
| Sodium Laureth Sulfate (SLES) | Anionic surfactant — milder | 5–15% active | Active matter, 1,4-dioxane limit (GC) |
| Cocamidopropyl Betaine | Amphoteric co-surfactant | 1–10% | Solids, NaCl content, amidoamine limits |
| Polysorbate 20 / 80 | Nonionic emulsifier/solubilizer | 0.5–5% | Saponification & hydroxyl values, peroxide value |
| Cetyl / Cetearyl Alcohol | Emulsion stabilizer | 1–6% | Melting point, hydroxyl value |
| Stearic Acid | Emulsifier / structuring | 1–5% | Acid value, iodine value, titre |
| Glyceryl Stearate | Emulsifier | 1–5% | Acid value, monoglyceride content |
Preservatives & antioxidants
| Raw material | Function | Typical level | QC test |
|---|---|---|---|
| Phenoxyethanol | Preservative | 0.5–1% | GC assay |
| Sodium Benzoate | Preservative (acid systems) | 0.1–0.5% | HPLC assay; works only below ~pH 5 |
| Potassium Sorbate | Preservative (anti-mold) | 0.1–0.3% | HPLC assay |
| Methylisothiazolinone (MI) | Preservative — rinse-off only | ≤0.01% | HPLC; a famous sensitization case study in regulatory limits |
| Tocopherol (Vitamin E) | Antioxidant | 0.1–1% | Assay; peroxide value of the batch |
| BHT | Antioxidant | 0.01–0.1% | GC assay |
| Disodium EDTA | Chelator — disarms metal catalysts | 0.05–0.2% | Complexometric assay |
Thickeners & polymers
| Raw material | Function | Typical level | QC test |
|---|---|---|---|
| Carbomer | Gel network polymer | 0.1–1% | Viscosity after neutralization, residual solvent |
| Xanthan Gum | Natural thickener/suspender | 0.1–1% | Viscosity, microbial limits (it's bacterial-born) |
| Hydroxypropyl Methylcellulose (HPMC) | Tablet binder / gel former | Varies | Viscosity grade verification, substitution pattern |
| Povidone (PVP) | Binder / film former | Varies | K-value (viscosity), peroxide limit |
Actives, acids & minerals
| Raw material | Function | Typical level | QC test |
|---|---|---|---|
| Niacinamide | Skin active (B3) | 2–5% | HPLC assay, related substances |
| Ascorbic Acid | Antioxidant active (C) | 5–20% serums | Assay + color; oxidation trending |
| Salicylic Acid | BHA active | 0.5–2% | Assay, melting point, related substances |
| Urea | Keratolytic / humectant | 2–40% | Assay (nitrogen), biuret limit |
| Citric Acid | pH adjuster / chelator | QS to pH | Acid–base titration assay |
| Sodium Bicarbonate | Antacid / effervescent base | Varies | Alkalinity titration, loss on drying |
| Sodium Chloride | Isotonic agent / viscosity builder | 0.9% saline; QS in cleansers | Argentometric assay |
| Magnesium Sulfate | Bath mineral / osmotic | Up to 100% | Complexometric assay, water of crystallization |
| Zinc Oxide | Skin protectant / UV filter | 5–40% | Assay (complexometric), particle size |
| Titanium Dioxide | Pigment / UV filter | 1–25% | Assay, particle size & coating (photoactivity control) |
| Benzalkonium Chloride | Quat preservative/disinfectant | 0.1–13% by use | Two-phase titration/HPLC homolog profile |
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Shops for bulk raw materials, supplements and lab testing — the supply side of everything above:
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