Method and apparatus for automatic analysis

A method for estimating the concentration of a reduced or oxidised form of a redox species in a liquid comprising the steps of:

• (1) contacting an area of a first electrode with a sample of predetermined volume of the liquid,
• (2) contacting the sample with an area of a second electrode spaced apart from the first,
• (3) applying a potential between the electrodes while the electrodes are sufficiently closely spaced that reaction products formed at each electrode diffuse to the other electrode while the potential is applied,
• (4) measuring or estimating a value indicative of the change in current as a function of time and a value indicative of the steady state current, and
• (5) determining from said volume, said current as a function of time, and said steady state current the concentration of reduced or oxidised form of the species in the liquid sample,
• the method characterized in that at least one of the electrodes is in the form of a continuous strip.

A method for estimating the concentration of a reduced or oxidised form of a redox species in a liquid comprising the steps of:

• (1) contacting an area of a first electrode with a sample of predetermined volume of the liquid,
• (2) contacting the sample with an area of a second electrode spaced apart from the first,
• (3) applying a potential between the electrodes while the electrodes are sufficiently closely spaced that reaction products formed at each electrode diffuse to the other electrode while the potential is applied,
• (4) measuring or estimating a value indicative of the change in current as a function of time and a value indicative of the steady state current, and
• (5) determining from said volume, said current as a function of time, and said steady state current the concentration of reduced or oxidised form of the species in the liquid sample,
• the method characterized in that at least one electrode is covered with a layer which serves to define wells on the electrode surface.

An automatic analysing apparatus comprising:

• a first electrode,
• means for placing a predetermined volume of a liquid sample in contact with the first electrode, wherein the volume is a drop and wherein the drop is bounded by a gas/liquid interface intermediate the electrodes when the current is measured,
• means for contacting the sample with a second electrode spaced from the first,
• means for applying a potential between the electrodes, and
• means for measuring the current as a function of time while the electrodes are in sufficiently close proximity that reaction products formed at one electrode diffuse to the other and achieve a steady state distribution.

An automatic analysing apparatus comprising:

• a first electrode,
• means for placing a predetermined volume of a liquid sample in contact with the first electrode,
• means for contacting the sample with a second electrode spaced from the first,
• means for applying a potential between the electrodes, and
• means for measuring the current as a function of time while the electrodes are in sufficiently close proximity that reaction products formed at one electrode diffuse to the other and achieve a steady state distribution,
• the apparatus characterized in that at least one electrode is in the form of a continuous strip.

An automatic analysing apparatus comprising:

• a first electrode,
• means for placing a predetermined volume of a liquid sample in contact with the first electrode,
• means for contacting the sample with a second electrode spaced from the first,
• means for applying a potential between the electrodes, and
• means for measuring the current as a function of time while the electrodes are in sufficiently close proximity that reaction products formed at one electrode diffuse to the other and achieve a steady state distribution,
• the apparatus characterized in that at least one electrode is on a flexible backing.