Blood+Detection+by+Chemical+Methods+Outline+ACS

Blood Detection by Chemical Methods Crystal tests Blood forms crystals when it reacts with certain chemicals Rarely used anymore Reagents added to blood stain and crystal formation is viewed from under a microscope Should have a control when using this method Samples can be up to 0 years old and still form crystals Catalytic tests Blood breaks down hydrogen peroxide which reacts and causes other things to oxidize which changes the color of the blood The reaction with the chemicals form a luminescent color is another way to use catalytic tests Usually used for finding blood in urine, but is used to for finding dried up blood as well Extremely sensitive to surroundings Instrumental methods Chromatography- used to identify haemoglobin Can give an estimate of age for a blood stain Can identify origin of species that blood cam from Applications Confirmation of visible stains and making sure they are blood Sangur sticks Detecting reagent is in the stick Needs to be rubbed against stain and moistened Changes color immediately Kastle-Meyer reagent 95% ethanol and 10% hydrogen peroxide solution Stain is rubbed gently with a piece of filter paper and a drop of the reagent on it If only ethanol reacts with stain it is not blood Detection of non-visible bloodstains Luminol Used in areas such as vegetation or areas where blood has been attempted to be cleaned Can react with plant enzymes, oxidizing agents and metals Enhancement of blood stains Usually more fingerprint or footprint in blood then can be seen Sprayed with chemicals to allow the print to develop and can be photgraphed Subsequent reaction of stains treated with blood detecting reagent Uses a major part of stain to find out whose blood Problems if the whole stain has been treated with blood detecting reagents