Study On The Decomposition Kinetics Of Lidocaine, Procaine And Bupivacaine In Biological Specimens

Objective:1 To develop a qualitative and a quantitative method for the simultaneous determination of lidocaine,procaine,bupivacaine and its main metabolite in biological specimens by a GC and a GC/MS.2 To develop the decomposition kinetics model and method for lidocaine,procaine and bupivacaine in biological specimens.3 To investigate the decomposition regularity of idocaine,procaine and bupivacaine in biological specimens,and to guide the choice of best storage conditions for biological specimens,then to provide a scientific evidence for the forensic identification of the anesthesia accident caused by lidocaine, procaine or bupivacaine.Methods:1 Gas Chromatography/Gas Chromatography-Mass Spectrometry (GC/MS):1.1 extraction:After having been added Internal Standard to,the brain,blood and urine samples were acidized,lkalized and extracted with ether.1.2 GC:NPD,capillary column of DB-5(30m×0.25mm×0.25μm),COL 150 degrees C(1min)→10 degrees C·min^-1→280 degrees C(2min);DET 300 degrees C,air 60 KPa,hydrogen 1.3 KPa;carrier gas:N₂ 1.5 ml/min.1.3 GC/MS:capillary column of DB-5(30m×0.25mm×0.25μm),ion source 70ev, mass range:50-650,COL:150 degrees C(lmin)→10 degrees C·min^-1→280 degrees C (2min);ion source:200 degrees C,temperature of transmission lion:250 degrees C,carrier gas:He 1.5 ml/min.1.4 qualitative and quantitative analysis:Analysis was performed by a GC equipped with a NPD or a GC-MS.The qualitative analysis was based on retention time in the chromatographic system coupled with the ion fragmentation spectrum in the mass spectrometer. The quantitative analysis was on an internal standard method.2 studies on the decomposition kinetics:2.1 groups:Each group of 4 dogs was given a cavities subarachnoidealis anesthesia with an even speed in five minutes with 30mg·kg^-1, 60mg·kg^-1and 10mg·kg^-1weight of lidocaine hydrochloride,procaine hydrochloride and bupivacaine hydrochloride.2.2 Study on the decomposition kinetics:After being given drugs, the brain,blood and urine were collected and divided equally to three group in 20,4 and -20 degrees C.The concentrations of drugs at different days were determined by the GC.The equation and sparameters of decomposition kinetics were imitated and calculated with winolin program.2.3 The data were compared with SAS9.0.Results:1Gas Chromatography/Gas Chromatography-Mass Spectrometry(GC/MS): The retention times of lidocaine,procaine,bupivacaine,SKF_525Aand resolvent were 8.20,9.70, 12.00,12.10 and 7.80,8.62,11.58min;Ion fragment characteristic were 86,58,30;86,99,120; 140,84,98;86,91,99 and 68,121,165;120,137,92;98,70,42.The linear range for lidocaine, procaine and bupivacaine in brain,blood and urine by GC/MS were covered respectively the ranges of 0.5～20μg·ml^-1,0.5～25μg·ml^-1and 0.5～20μg·ml^-1.The limit of detection was 0.05μg·ml^-1.The recoveries were from91±2.1%to114±4.2%;The inter-and intra-day precisions were less than 10.0%.2Study on the decomposition kinetics of lidocaine,procaine and bupivacaine in biological specimens:2.1 Decomposition kinetics:The decomposition kinetics of lidocaine, procaine,bupivacaine in brain,blood and urine were fit to the first order kinetics.The common equation was lgC=lgCo-kt/2.303 and k was the decomposition constant of first order reaction. The decomposition half-life(unit:day)of lidocaine in brain,blood and urine at 20,4 and -20 degrees C were 17,30 34;27,35,35 and 13,14,47;The decomposition half-life(unit:day)of procaine in brain,blood and urine at 20,4and -20 degrees C were 2,2,2;2,7,15 and 35,42, 49;The decomposition half-life(unit:day)of lidocaine in brain,blood and urine at 20,4 and -20 degrees C were 33,64,72;51,71,80 and 17,60,81.2.2 The tendency of content change at different preserve temperature:At 20,4and -20 degrees C,lidocaine concentrations in brain, blood and urine were found to be significant decrease at the eighth,forty-eighth and eighth day (P＜0.05).The concentrations of lidocaine in brain were 0μg/g up to 80 days at 20 degrees C and 120 days at 4 degrees C,and were 4.2%of the initial analyses up to 120 days at -20 degrees C.Concentrations in blood were 0μg/ml up to 96 days at 20 degrees C and were 5.0% and 7.6%of the initial analyses up to 120 days at 4 and -20 degrees C.Concentrations in urine were 1.1%,4.5%,13.0%of the initial analyses up to 120 days at 20,4 and -20 degrees C.At 20,4and -20 degrees C,procaine concentrations in brain,blood and urine were found to be decreased significantly at the second,the second,the second;the second,fourth,eighth and the thirty- second,forty-eighty,sixty-fourth(P＜0.05).Concentrations in brain,blood and urine were 1.0%,1.9%and 35.6%of the initial analyses up to 120 days in -20 degrees C.At 20,4and -20 degrees C,bupivacaine concentrations in brain,blood and urine were found to be significant decreased at the eighth,sixteenth,sixty-fourth;the fourth,fourth,eighth and the second,fourth,sixteenth(P＜0.05).Concentrations in brain,blood and urine were 54.5%, 35.5%and 33.2%of the initial analyses up to 120 days in -20 degrees C.Conclusions:1 A GC and GC/MS method for the determination of lidocaine,procaine, bupivacaine and its metabolite in biological specimens was established.The method proved to be simpler,more sensitive and more reproducible,and could be applied to forensic identification of anesthetic accident.2 The decomposition kinetics models for lidocaine,procaine and bupivacaine in biological specimens was develope,which could be applied to the study of forensic toxicology.3 Lidocaine,procaine and bupivacaine in specimens were found to be decomposed at various kinds preserved environment.Their decomposition was quick at 20 degrees C,then 4 degrees C,and slowly at-20 degrees C.Biological specimens used for the forensic identification of the anesthesia accident caused by lidocaine,procaine or bupivacaine should be stored at refrigerated(4 degrees C)or freezed(-20 degrees C)and be analyzed as soon as possible.4 Decomposition kinetics of lidocaine,procaine and bupivacaine in biological specimens were found to fit the first order reaction kinetics model.The common equation was lgC=lgCo-kt/2.303 and the decomposition kinetics equations were estimated,which could used to conclude the initial concentrations of lidocaine,procaine and bupivacaine in corpse and to provide a scientific evidence for the forensic identification of the anesthesia accident caused by lidocaine,procaine and bupivacaine.