In the application, the change in the magnetic state of the haemoglobin caused by the
malarial infection is exploited by detecting suitable properties of haemozoin which are dependent on the application of a
magnetic field. FIG. 1 shows apparatus, shown generally at (10), for performing
magneto-optical detection using photo-acoustic techniques. The apparatus (10) comprises a
light source (12), producing a beam of
optical radiation (14) which passes through a
polarizer (16), a variable LC
retarder (0 or 180° retardance) (18), and a (
chopper 20), before impinging on a sample (22) held in a sample holder (24). The sample is in direct contact with an acoustic
detector (26). The apparatus (10) further comprises an
electromagnet (28), and a Gauss meter (30) can be utilized to measure the applied
magnetic field strength. Advantages associated with this approach are the—possibility of making
in vivo measurements, and the avoidance of problems of optical scattering associated with conventional
optical measurements on turbid liquids such as
whole blood.