pinkanga, I have to dispute that a single dose of MDMA is completely eliminated in 24 hours.
Without going into first order kinetics, compartmental models or distribution factors, a more probable time frame for a person with an average metabolism is around 4 to 5 days. Erowid says perhaps 3-5 here
ask Erowid
Regarding urine tests and what constitutes a probable positive, this is also greatly dependant upon the type of test used. As mentioned in the above link, MDMA also has metabolites which have much longer half lives, and which are likely to significantly extend the time required for a “complete clear”.
If you have MDMA in multiple doses you will also increase the plasma half life, particularly of the R isomer, which rises steadily in ratio to the S isomer with repeated doses (up to a maximum of ~7:1). In other words elimination of the R isomer is slower (& non-linear), much more so for 2 hourly spaced pills compared to 2 taken at once. Also, any renal insufficiency or low 2D6 count is likely to increase redistribution and further slow elimination.
Increased urination and body fluid intake (not too much during the roll, but regular water intake the days following) coupled with good exercise, will all greatly aid in increasing elimination. If you are sensible, the careful use of ammonium chloride can also help considerably, although you should first check with your Dr and or pharmacist, and don't go over the recommended dosage!
THC is a different matter. Ammonium Chloride will likely slow elimination of the acidic metabolites of THC. Once you’re over the amphetamines, you can look at THC by using an alkaliser as apposed to an acidifier to hasten excretion of the lipophilic conjugated THC metabolites. A suitable urinary alkaliser is baking soda, (or a Ural) but again NOT TOO MUCH
Altering urinary pH can be a rather savage means of speeding up body function. Any predisposition with urinary or hepatic problems, or upping the dose could make this practice highly dangerous, so please always check with your Dr. first.
If you are to supply the test yourself, or know which test it is, the simplest method is to test yourself first. An all clear today should ensure an all clear tomorrow. Just have a quiet night in between