Credit mostly goes to DVap. I modified his 'simplified' method, to use readily available supplies, and avoid having to dilute very strong HCl. See end of post for links. This is the test I use, and you can assemble your own kit for about $20. The Reason: Since there are no true production standards, and people like to mix their own liquids, this will allow you to test liquid for nicotine levels easily. The Kit: .12N Sulfuric Acid Bromothymol Blue Distilled Water 10mL Graduated Cylinder, .1mL markings is optimum A paper towel The Test: Pour some distilled water in the cylinder, swirl it, dump it out. Repeat step 1. Repeat step 1. Dry cylinder with a sliver of paper towel. Put 1mL of eLiquid in the cylinder Add 2 drops blue Fill cylinder to the 3mL mark with distilled water Swirl to mix Add a drop of acid Swirl to mix If the color of the solution didn't turn pale yellow, repeat 8-9 Measure the final volume Subtract 3 from the number you read in step 12 Multiply the result of step 13 by 19.4712 The resulting number is the mg/mL Notes on measuring: Always measure from the center of the liquid, where its at its lowest point. Never measure from the high point on the sides. Notes on adding to the cylinder: Avoid dribbling liquids down the sides, as it will skew results, since some will add to the amount when you swirl to mix. For an accurate end result, exactly 1mL eliquid must be used. Note on step 10: Over several drops, the color will go from blue to bluish-green to green, and when you've reached the 'magic drop', it will suddenly all turn yellow. Note on final result: If the manufacturer added acids for preservatives, it should not skew the results enough to matter, as they use very minute amounts. Also, as most DIY'ers can't read volumes to several decimals, bear in mind there is a small margin of error. I tested 12 different bottles, 10 of the results were within 1mg of their rated, all just slightly low, probably due to flavoring being added. Car, Caution, Cleanup: The .12N sulfuric acid and blue are designed for use by average home owners. They are quite safe to use. The acid is very diluted, so it won't eat holes in things. If spilled, the blue will stain. The distilled water has several safety concerns, if you're unaware, please see the many dangers it poses at the Dihydrogen Monoxide Research Division. Since this may catch someone who truly doesn't get it, think H2O. The real danger of testing is posed by the e-liquid. If you're testing high nicotine content liquid, a mL would be enough to kill childrens, pets, animals, even you. If you're working with very high strength, I'd caution you to use latex, rubber, or vinyl gloves. Disposal of solution after test should be as you would dispose of e-liquid. The most toxic part is the nicotine content. Unless you just poured out bleach or drain-o, you should be fine pouring it in the drain, so long as you flush the drain after with some water. After liquid disposal, rinse your testing equipment clean with plain old tap water, shake off excess water, and let air dry. The liquid does get sticky, and gets hard to clean if left to dry on. Example: Cylinder is rinsed well. 1mL of liquid labeled 24mg is added to the empty cylinder. 2 drops of blue are added Distilled water is added until its at 3mL The solution is swirled A drop of acid is added, then its swirled, and this is repeated ... The solution turns yellow after several 'drop and swirl's The final volume is measured at just over 4.2mL Subtract 3 to get 1.2 Multiply this by 19.4712 to get ~23.3, which is the actual mg/mL Where to get supplies: The acid and blue you can find in a local pool chemical supply store, in the test kit refill section. Both will be labeled with their actual chemical names. The magic number '19.4712' requires that the acid be .12N acid. Also, do not buy 'total alkalinity indicator' as its not the right chemical (the acid is usually right next to it). Distilled water must be distilled water, not mineral, not filtered, not tap, not carbonated. You can find it at the grocery store. Cylinders you can buy in hobby shops, for chemistry set piece replacements. If you want a handy little bottle for putting the water in, you can buy clean, sterile 60mL dropper bottles from tattoo supply shops for about $1 each. Just make sure you give it at least 3 rinses with distilled water before filling it. For those that don't have the options available to them that those in big cities have, and rely on internet ordering, here's a few links for you... Inexpensive lab equipment for DIY chemistry... 10mL Glass .1mL-Graduated Cylinder Taylor pool testing chemical supplies... .12N Sulfuric Acid Bromothymol Blue Reference The original 'simplified' method by DVap can be found here. The original 'expanded' method, also by DVap, can be found here.