placed into the automated immunoassay machine once the test has begun the u201c multi gripper u201d comprising an aluminium arm inside the machine comprising two bars defining a series of gripper slots is moved downwards onto the dipsticks and the grippers grab the upper portions 12 of the dipsticks the dipsticks are lifted by the arm from the starting slots and may be initially moved to the back of the machine that is to the end slots where they can be read by an optical reader to establish a background signal for each dipstick the dipsticks are moved to u201c tube one u201d which contains the sample to be tested for a predetermined period of time which for the salmonella test is typically twenty minutes at this stage the dipsticks may be raised and lowered inside the tubes to u201c jiggle u201d them and ensure that the contents of the tube are mixed in the case of a salmonella test this also ensures that the buffer additive initially located in tube one is mixed into the sample which is added to tube one the arm is then raised and the dipsticks are moved out of u201c tube one u201d and lowered into u201c tube two u201d for washing in a wash solution eg modified buffered peptone water mbpw and are washed by moving the dipsticks up and down the arm is then raised and the dipsticks are lifted out of tube two and loaded into tube three which contains a growth medium eg in the case of salmonella this may be m broth the dipsticks remain in tube typically for three to four hours during which the temperature within the tube two is raised to an appropriate culture temperature by a heater unit eg a flexible heating mat.