- #Chemlab 13 comparing rates of evaporation drivers
- #Chemlab 13 comparing rates of evaporation registration
In forensic casework, a request to re-analyse the blood specimen is not uncommon, such as if the accuracy of the result is challenged or if there is some doubt about integrity of the sample.
#Chemlab 13 comparing rates of evaporation registration
After registration the blood samples are placed in racks and kept in a refrigerator at 4 ☌ pending analysis a few days later. The specimens are shipped by express mail and usually arrive within 1–2 days.
#Chemlab 13 comparing rates of evaporation drivers
Venous blood samples from impaired drivers arrested throughout Sweden are sent for analysis of ethanol and other drugs to a central laboratory. Several years ago the manufacturer informed us that they intended to stop selling glass evacuated tubes, but were able to supply plastic tubes containing exactly the same chemical additives. These tubes were made of glass with a nominal volume of 10 mL and contained sodium fluoride (100 mg) and potassium oxalate (22.5 mg) as preservative and anticoagulant, respectively. This raises the question of the stability of blood-ethanol concentrations after various periods of storage in glass and plastic evacuated tubes.įor several decades the Swedish National Laboratory of Forensic Toxicology purchased fluoride-oxalate (grey stoppered) evacuated tubes from a Belgian company (Terumo Europe N.V.). The switch from glass to plastic tubes has also occurred in connection with forensic analysis of ethanol and other drugs in blood, such as in traffic-law when impaired drivers are arrested.
Tubes made of plastic are more robust and are less likely to break during transport, handling and storage of specimens or after cycles of freezing and thawing. These tubes were originally made of soda glass, although more recently plastic tubes have become available. The first evacuated tubes used to sample venous blood for clinical laboratory analysis appeared in the early 1950s.
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