Even by reducing duration and power setting it was impossible to control the temperature within the test-tubes, and clearly the sample-volume ratios, test-tube/bottle size would need to be optimised and tailored to each expeimental situation. The next step was to investigate extraction in an ultra-sonic bath as this technique has been described by several authors, though in some cases long extraction times are reported . Samples (50 mg) were weighed into 10 mL test-tubes with 5 mL water or 70 % aqueous methanol, and placed in the ultrasonic bath at the lowest settings for 30 minutes. Again, it proved difficult to ensure uniform heating; adding ice to the ultra-sonic bath failed to maintain an even temperature, and the variation in heating among samples resulted in poor repeatability of extraction. Furthermore, in some cases, the rapid rise in temperature caused the methanol to evaporate resulting in sample loss. Given this difficulty, the more conventional rotary mixing was compared to ultrasonic extraction. Samples were mixed for 15 minutes on a rotary mixer and then either a further 15 more minutes on the rotary mixer or 15 minutes' sonication. There was little difference between the two extraction methods so rotary mixing was adopted, which has the added advantage of enabling several samples to be extracted simultaneously.