We have devoted special attention to sample introduction, to ensure that accurate pipetting can be achieved simply and reproducibly. Simple methods of sample introduction are a requirement for this methodology to be practical in environ- ments where users have little or no laboratory training. Normal pipetting of the sample onto the nitrocellulose pad using disposable polypropylene tips could easily damage the nitrocellulose. We used thin polyethylene tubing (i.d. = 0.28 mm) attached to the needle of a low-cost disposable insulin syringe. This tubing was flexible and thus did not damage the nitrocellulose. A sleeve of elastic silicone tubing was placed around the plunger, which acted as a spring after bringing the slightly pressed syringe into contact with the sample. The sample volume can easily be calculated from the length of the fluid column in the polyethylene tubing. A typical injection volume was 0.3 μL (coefficient of variation = 2.7%, n = 10).