Blood is a fluid substance that circulates in the arteries and veins of the body. Blood is bright red or scarlet when it has been oxygenated in the lungs and passes into the arteries; it becomes bluish red when it has given up its oxygen to nourish the tissues of the body and is returning to the lungs through the veins and the tiny vessels called capillaries. In the lungs, the blood gives up the carbon dioxide wastes it has taken from the tissues, receives a new supply of oxygen, and begins a new cycle. This movement of blood is brought about by the coordinate activity of the heart, lungs, and blood vessels.
Blood is composed of a yellowish fluid, called plasma, in which are suspended the millions of cells that constitute about 45 percent by volume of whole blood. It has a characteristic odor and a specific gravity between 1.056 and 1.066. In an average healthy adult, the volume of blood is one-eleventh of the body weight, or between 4.5 and 6 liters (5 and 6 qt). A great portion of the plasma is composed of water, a medium that facilitates the circulation of the many indispensable factors of which blood is composed. A cubic millimeter of human blood contains about 5 million red corpuscles called erythrocytes; 5000 to 10,000 white corpuscles called leukocytes; and 200,000 to 300,000 platelets called thrombocytes. The blood also carries many salts and organic substances in solution.
Blood type, in medicine, classification of red blood cells by the presence of specific substances on their surface. Typing of red blood cells is a prerequisite for blood transfusion. In the early part of the 20th century, physicians discovered that blood transfusions often failed because the blood type of the recipient was not compatible with that of the donor. In 1901 the Austrian pathologist Karl Landsteiner classified blood types and discovered that they were transmitted by Mendelian heredity .
The four blood types are known as A, B, AB, and O. Blood type A contains red blood cells that have a substance A on their surface. This type of blood also contains an antibody directed against substance B, found on the red cells of persons with blood type B. Type B blood contains the reverse combination. Serum of blood type AB contains neither antibody, but red cells in this type of blood contain both A and B substances. In type O blood, neither substance is present on the red cells, but the individual is capable of forming antibodies directed against red cells containing substance A or B. If blood type A is transfused into a person with B type blood, anti-A antibodies in the recipient will destroy the transfused A red cells. Because O type blood has neither substance on its red cells, it can be given successfully to almost any person. Persons with blood type AB have no antibodies and can receive any of the four types of blood; thus blood types O and AB are called universal donors and universal recipients, respectively.
Other hereditary blood-group systems have subsequently been discovered. The hereditary blood constituent called Rh factor is of great importance in obstetrics and blood transfusions because it creates reactions that can threaten the life of newborn infants. Blood types M and N have importance in legal cases involving proof of paternity.
A chemist uses liquid chromatography to analyze a complex mixture of substances. The chromatograph utilizes an adsorbtive medium, which when placed in contact with a sample, adsorbs the various constituents of the sample at different rates. In this manner, the components of a mixture are separated. Chromatography has many valuable applications, such as determining the level of pollutants in air, analyzing drugs, and testing blood and urine samples.
Gas chromatography separates the volatile constituents of a sample, and liquid/liquid chromatography separates small, neutral molecules in solution. The goal in conducting a separation is to produce a purified or partly purified form of the desired constituent for analytical measurement, or to eliminate other constituents that would interfere with the measurement, or both. Separation is often unnecessary when the method is highly specific, or selective, and responds to the desired constituent while ignoring others. Measuring the pH, or hydrogen ion content, of blood with a glass electrode is an example of a measurement that does not require a separation step.
QHP 7694 Head Space Sampler is a machine that equilibrates the sample vials at the desired temperature for the specified time period. A needle then punctures the teflon coated septum at the top of the vial and draws a measured sample of the vapor which it sends to the Gas Chromatograph.
HP 5890 Gas Chromatograph. This machine takes the vapor from the Head Space Sampler and passes it through a packed column designed specifically for alcohol in blood. As the vapor passes through this column, different compounds will travel at different rates thus exiting at different times. As the separated compounds exit, they pass through a Flame Ionizing Device (FID) which consists of a hydrogen-oxygen flame and ionizing detectors. The intensity of the ionization is measured and sent to the computer for processing. Helium Carrier Gas carries the vapors through the Gas Chromatograph. A Power Macintosh 7600 is used for report generation, correspondence and on line communication. Reports are printed using a variety of laser printers to insure optimum print quality. Blood samples are quantitatively added to an aqueous solution into which an internal standard has been added in order to compensate for sampling fluctuations within the Gas Chromatograph. Static head space methodology is employed in which an aliquot of equilibrated vapor is injected and analyzed by a Flame Ionization Detector in the Gas Chromatograph,which consists of a hydrogen-oxygen flame and ionizing detectors. The intensity of the ionization is measured and sent to the computer for processing. Helium Carrier Gas carries the vapors through the Gas Chromatograph.
Blood analysis is very important in many different situations. For example, in forensics, if a bloodstain pattern is obtained, analysis is vital. BPA (Bloodstain Pattern Analysis) may on many occasions, clearly define the location of the victim or the assailant by establishing the actions of either or both. Possible and impossible scenarios may be established to determine if the victim, witness, orassailant is accurately describing what took place.
Some questions that may be answered are:
What type of weapon or impact occurred to cause the bloodstains present?
How many times was the victim struck ?
Where was the victim at the time the injuries were inflicted?
Where was the assailant during and following the assault?
Is the bloodstain evidence consistent with the medical examiner findings?
Is the bloodstain evidence on the suspect and his clothing consistent with the crime scene?
Numerous courts throughout the country have upheld the value and scientific reliability of BPA. Court case information is available upon request. BPA is a valuable asset during and after the initial investigation. BPA has been extremely valuable during the establishment of the courtroom trial strategy.
Blood analysis can be very important in testing for drugs. If drugs are in your system, your blood can be tested using more sophisticated means than static head space gas chromatography. You can also use urine tests and breath tests. Urine, however is the least reliable, while blood is the most.
DNA Detection is a very important part of blood analysis. Thanks to a powerful biochemical tool called polymerase chain reaction (PCR), it is possible to detect incredibly tiny amounts of particular DNA molecules. Even one single molecule can be enough!
DNA (deoxyribonucleic acid) is the central molecule of life. It contains sequences of information coded along its length. The information tells cells how to build protein molecules. PCR uses proteins called enzymes, combined with small pieces of DNA called primers. The primers match the sequence of the target molecule (the one being looked for) and the enzymes make lots more of any matching molecules. The result is that one matching molecule is multiplied into billions! DNA is very important because nobody has the same DNA pattern. Every single person’s is different. DNA also lasts forever, it never disappears.
“Blood” – Encarta Encyclopedia
“Blood Type” – Encarta Encyclopedia
“Forensics”- Encarta Encyclopedia