Surflan AS is sold as a 40.4% solution of oryzalin (the active ingredient, or AI). The AI oryzalin is only slightly water-soluble (2.6 mg/L). The formulation contains carriers (solvents) that will increase this solubility. As a result, I would not expect DMSO to be needed if you are beginning from a Surflan formulation. The formulation should already be compounded to enhance penetration of the oryzalin through plant tissues --- Surflan IS an herbicide, remember.
There is a very wide range of Surflan concentrations which are in use throughout the plant breeding community. Tony Avent (Plant Delights, NC) uses either a 1:100 or a 1:200 dilution on hostas (among other species). Kevin Vaughn (USDA, MS) uses a 10 uM (micromolar) solution on daylilies. Arthur Evans (AR) uses a 0.005% oryzalin solution on oriental and Asian lilies.
How do these different ways of expressing calculations compare? This can get very confusing.
0.005% is a 1:20,000 dilution. 0.005% is 0.00005 as a decimal. 1 / 0.00005 equals 20,000. This is the dilution IF you base the calculation on the FORMULATION, i.e. 0.005% Surflan. This is very different from a 0.005% oryzalin, which if you start from the 40.4% Surflan AS formulation, is actually a 1:8,000 dilution (or 0.5 mL Surflan AS in 4L water, as Arthur Evans describes it). This second perspective (1:8,000) is BASED ON THE ACTIVE INGREDIENT ORYZALIN.
In any case, 0.005% oryzalin is a 1:8,000 dilution of Surflan AS. This is 80X more dilute than 1:100. Yet, both concentrations are effective. There are two possible reasons: 1) more is NOT necessarily better. Oryzalin is barely water-soluble: throwing more in the bucket does not mean that more will dissolve; and 2) oryzalin may have a broad effective range, and although more may not be better, it may also not be worse.
Surflan AS is only 40.4% oryzalin. Therefore, 1 kg of Surflan AS contains 40.4% oryzalin, or 404 g oryzalin. The remainder is solvent. I estimate that the density of Surflan AS is about 1.2 (meaning 1 mL Surflan would have a mass of 1.2 g). One mL of Surflan AS is about 1.2 g of formulation, and would contain 40.4% x 1.2, or 0.48 g oryzalin. 0.48 g equals 480 mg (actually 484.8 mg). One mL Surflan would contain 484.8 mg oryzalin.
0.5 mL Surflan AS would contain half of this, or 242.4 mg oryzalin. Dissolving 242.4 mg in 4 L (or 4,000 mL) would give you a solution of about 0.000175 M. Or 174.96 micromolar. This is about 20X the amount of oryzalin that will normally dissolve in water. The carrier solvents help keep the oryzalin in solution.
[NOTE: If my estimated density is in error, and it might be, the rest of the calculation will change, too. However, this will have no impact on the preparation of the working solutions. When I remember to bring the Surflan formulation into the lab, I will accurately weigh / measure the mass of 1 mL. That should allow me to accurately determine the density. If it varies greatly from d = 1.2 g/mL, I will let you know immediately.]
A 1:100 dilution would be 10 mL Surflan AS in 1 L water. 10 mL Surflan contains 1.4 g or 1,400 mg oryzalin. Dissolving 1.4 g oryzalin into 1 L of water would make a 0.004 M solution, which is a 4,000 uM solution. This is just about 23X more concentrated than a 175 uM solution.
A 10 uM solution (just a little bit over the solubility of pure oryzalin in water) requires 3.46 mg of oryzalin dissolved in 1 L of water.
SUMMARY TABLE:
| molar (M) | percent (%) | dilution* | |
| 0.005% oryzalin | 175 uM | 0.005% | 1:8,000 |
| 1:100 Surflan dilution | 4,000 uM | 1% | 1:100 |
| 10 micromolar sol'n | 10 uM | 0.0003% | 1:140,000 |
From this information, I am guessing that the most likely effective range is going to be between 10 uM and 100 uM. Preparation of working solutions for both of these concentrations is given below, and using relatively easy-to-locate measuring tools.
CAUTION: Although Surflan is more safe than colchicine, it is a HIGHLY TOXIC POISON. Please be prepared to handle it safely, or do not handle it at all. Wear gloves. Throw the gloves away after use. Wear safety glasses. Wash the safety glasses after use, wearing CLEAN gloves.
TOOLS AND SUPPLIES NEEDED:
TO MAKE A ORYZALIN STOCK SOLUTION (about 100 mM, or
0.1 M)
Measure 9 mL water into the graduated cylinder. Leave this solution
in the graduated cylinder.
Using an eye dropper or small pipette, add Surflan AS to the graduated cylinder until a total of 10 mL are contained in the cylinder. You will be adding formulation until the total reaches the 10 mL line (9 + 1 = 10). The graduated cylinder should now contain 9 mL water plus 1 mL Surflan AS formulation.
[NOTE: You can also use an analytical balance to measure the formulation. Place the small bottle (or a disposable pan) on the balance. Tare the bottle. Measure 0.857 g of the Surflan AS formulation into the bottle (or pan). If you use a disposable pan, be sure to rinse it into the bottle with some of the water from the 9 ml in the graduated cylinder.]
Pour the contents of the cylinder into the small bottle. Cap (close) the bottle, and shake vigorously. Oryzalin is barely water-soluble.
Slowly uncap the bottle, and pour the solution back into the graduated cylinder. Repeat transfer from cylinder to bottle and back again three or four times.
Cap the bottle of stock solution. The concentration of this stock solution is 100 millimolar (or 0.1 M). Each mL of stock solution contains 0.034636 g oryzalin, or 34.64 mg oryzalin.
Label the bottle of stock solution: "STOCK SOLUTION - 100 millimolar (100 mM). DILUTE 1,000X to 10,000X BEFORE USE".
Return to Credits and Intro
TO MAKE WORKING SOLUTIONS (10 uM
and 100 uM)