《精细化工专业英语第二册》由会员分享，可在线阅读，更多相关《精细化工专业英语第二册（24页珍藏版）》请在金锄头文库上搜索。
1、7 DETERMINATION OF BLOOD ALCOHOL WITH GAS CHROMATOGRAPHYThe effect of alcohol have both medical and medicolegal implications. The estimation of alcohol in the blood or urine is relevant when the physician needs to know whether it is responsible for the condition of the patient. From the medicolegal
2、standpoint the alcohol level is relevant in cases of sudden death, accidents while driving, and in cases when drunkenness is the defense plea. The various factors in determining the time after ingestion showing maximum concentration and the quality of the alcohol are the weight of the subject, the a
3、mount and concentration of the alcohol, how the alcohol was ingested, the presence or absence of food, and the physical state of the subject concerned1.The effects of alcohol vary among individuals and for the same individuals at different times. The action depends mostly on the environment and the
4、temperament of the individual and on the degree of dilution of the alcohol consumed. The habitual drinker usually shows relatively less effect than would be seen with an occasional drinker from the same amount of alcohol. Drugs potentiate the effect of alcohol.Many cases document the synergistic eff
5、ect of alcohol and barbiturates as a cause of death in cases appearing to be suicide. Alcohol itself is probably the most frequent cause of death due to poisoning. A gas-solid chromatographic technique using flame ionization detection and a Porapak Q column has been used for the identification and d
6、etermination of ethanol, isopropanol, and acetone in pharmaceutical preparations. The technique involves direct injection of an aqueous dilution of the product and thus is simple and direct. Sample Preparation. Two 0.5-ml volumes of an isobutanol internal standard (10 mg/ml water; pipette 12.4 ml of
7、 isobutanol and dilute to 1 liter with water) are pipetted into two different 2-dram (7.4-ml) shell vials, one market “known.” and the other “unknown.” A 0.5-ml portion of the ethanol working standard (50 mg/100ml of blood; pipette 5ml of ethanol stock solution; dilute 12.7 ml of absolute ethanol to
8、 1 liter with water, and dilute with 100 ml of blood from blood bank) is transferred to the vial marked “known.” The pipette is washed three times with the internal standard solution. With a 10-m l Hamilton syringe, 0.5 m l of “known” and “unknown” are injected in duplicate, and the alcohol and isob
9、utanol peak heights are measured for each.Gas Chromatographic Parameters. A gas chromagraph equipped with a hydrogen flame detector is used. Flame-ionization detection allows the use of samples containing water. The column is stainless steel (6ft 0.25in.o.d.) packed with 30% Carbowax 20M on acid-was
10、hed 60/80-mesh Chromosorb W. The column was conditioned overnight at 180oC with a flow of nitrogen carrier gas. Operating conditions were: Oven temperature 100 or 130oC Injection temperature 160oCNitrogen flow 35ml/min Hydrogen 28ml/minOxygen 100mL/minCalculations. Peak heights of both the alcohol a
11、nd the internal standard are used in the calculations. The following formula can be employed for determinations:Where, W1 = mg ethanolW2 = 100 ml of unknownCs = Concentration of standard ethanol solution (here it is 50mg/100ml)hx = peak height of ethanol from knownhs = peak height of internal standa
12、rd (isobutanol) in unknownRx = peak height of ethanol from knownRs = peak height of internal standard (isobutanol) in known sampleDiscussion. Fig.1 shows a typical chromatogram obtained by injecting 0.5m l of blood-isobutanol internal standard mixture. The peaks are clearly separated and sharp. Tabl
13、e 1 gives the retention and relative retention times of some common volatile compounds associated with alcohol ingestion, diabetes, and glue sniffing. The operating parameters such as column temperature or gas flow are not critical. They may vary with the type of compound under investigation, as wel
14、l as the nature of the gas chromatograph in use. Other packings may also be used in this determination, including Hallcomid M 180L on Chromosorb W 80/100 mesh, or Porapak Q 80/100 mesh. Porapak has different characteristics but has the advantage that it represents a packing without a coating. Table
15、1 Retention Data for Some CompoundsOven Temperature 100oC Oven Temperature 130oC Retention Time (min) Retention time Relative to EtOH Retention Time (min) Retention time Relative to EtOH Acetaldehyde 2.56 0.73 1.25 0.60 Acetone 2.38 0.68 1.62 0.76 Chloroform 5.62 1.61 3.25 1.53 Ethanol 3.50 1.00 2.12 1.00 Isobutanol 7.25 2.10 3.94 1.86 Isopropanol 3.19 0.91 2.06 0.97 Propyl acetate 4.50 1.29 2.75 1.30 The blood that is injected into the system enters the injection port and is trapped there, while the volatiles are carried by gas flow into the column. On colu
