You can't buy 100% Nicotine without a commercial license... I think the highest concentrations you can buy for personal use is 10% (100mg/ml), which can be purchased in 100% VG base, or PG base, or a mixture of the two. Comp is giving good advice about buying your Nicotine in a 100% VG base, so it will make it much easier to mix and calculate your end result of PG/VG ratios of your juices.