(TDS) for Detection of Basic Drugs in Forensic Samples by GC-MS

Journal of Analytical Toxicology, Vol. 30, October 2006 

Performance Evaluation of Thermal Desorption System 

(TDS) for Detection of Basic Drugs in Forensic Samples 

by GC-MS 

Joseph A. Crifasi 1, Michael F. Bruder 1, Christopher W. Long 1, and Kimberly Janssen 2 

1Saint Louis University Forensic Toxicology Laboratory, St. Louis, Missouri and 2Saint Louis University Clinical Laboratory 

Science Program, St. Louis, Missouri 

Abstract I 

Stir bar sorptive extraction is an innovative sample extraction 

technique that can be used to process blood, urine, and tissue 

samples for routine drug screening in the forensic toxicology 

laboratory. The Gerstel Twister TM desorption unit (TDU) system is 

a multifunctional desorption unit capable of determining the 

presence of analytes from liquid samples after extraction using the 

Twister stir bar. The TDU desorption system was evaluated for use 

in combination with gas chromatography-mass spectrometry 

(GC-MS) for determining the presence of basic drugs in forensic 

samples. Human blood fortified with known quantities of drugs 

was used to evaluate sample diluents, extraction time, injection 

parameters and recovery. Case specimens containing drugs 

typically encountered in forensic samples were evaluated using the 

desorption method and compared with a liquid-liquid extraction 

method followed by GC-MS analysis. This evaluation 

demonstrated that the TDU desorptive method worked equally as 

well as the routine extraction method for the detection of basic 

drugs in screening forensic samples. In addition, the described 

technique avoids the use of extraction solvents and the subsequent 

centrifugation, transfer, and concentration steps required of 

liquid-liquid and solid-phase extraction methods. 

Introduction 

The gas chromatographic-mass spectrometric (GC-MS) 

analysis of basic drugs in biological samples is normally per- 

formed after isolation of the drug from the biological matrix. 

Most routine sample preparation methods are based on 

liquid-liquid extraction, solid-phase extraction, or protein pre- 

cipitation. These methods require the use of organic solvents, 

centrifuges, rotators, and concentrators. 

The stir bar sorptive extraction method (SBSE) was designed 

to extract organic compounds from any aqueous matrix. Com- 

mercially available from Gerstel, Twister is a small magnetic 

stirring rod encased in glass and coated with a layer of poly- 

dimethylsiloxane (PDMS). The Twister desorption unit (TDU) 

was specially designed and optimized for use with the Twister 

SBSE. The use of PDMS-coated stir bars in combination with 

state of the art thermal desorption instrumentation and 

GC-MS avoids the use of solvents for extraction, reduces 

sample preparation time, and minimizes equipment needed for 

sample preparation. 

Previous evaluations have included its performance in de- 

tecting specific drugs in urine, water, saliva, and bovine serum, 

along with analysis of pesticides in wine, contamination in 

lakes, and impurities and/or preservatives in food and bev- 

erage products (1-5). SBSE has also been used in combination 

with in-situ derivatization to enhance the recovery and chro- 

matographic analysis of polar solutes in biological fluids by 

GC-MS (6). The purpose of this evaluation was to examine 

the usefulness of Twister bar extraction and thermal desorption 

for basic drug screening of forensic samples by GC-MS in a 

forensic toxicology laboratory. The intent of this contribution 

was also to provide a platform for future investigations in- 

volving screening and/or specific target analysis by means of 

Twister bar extraction. 

This study was designed to investigate the necessary condi- 

tions for isolation of basic drugs using SBSE. The scope and 

feasibility of using this method were evaluated in the routine 

identification of these drugs in various biological samples. 

Experimental 

Chemicals and reagents 

All inorganic chemicals were of analytical grade and pur- 

chased from Sigma Chemical (St. Louis, MO). All organic sol- 

vents were high-performance liquid chromatography (HPLC) 

grade and purchased from Mallinckrodt Baker (Phillipsburg, 

N J). Stock drug standards, 1 g/L in methanol, were obtained 

from Sigma Chemical and Cerilliant (Round Rock, TX). SKF 

(Proadifen, #P1061) was obtained as the hydrochloric salt from 

Sigma Chemical. 

Reproduction (photocopying) of editorial content of this journal is prohibited without publisher's permission. 581

Preparation of buffer 

To prepare 1 L of carbonate/bicarbonate buffer, 100 g of 

sodium carbonate and 50 g of sodium bicarbonate were added 

to 1 L of deionized water. The pH was 9.6. 

Preparation of standards 

The methanolic stock standards were appropriately diluted 

with methanol to prepare working drug standards at a con- 

centration of 20 mg/L. The working standards were then used 

to spike blood samples to the desired concentrations. The in- 

ternal standard, SKF, was prepared by accurately weighing 

the salt and diluting with methanol to 1 mg/mL for the stock 

standard. The working internal standard solution was then 

prepared by dilution of the stock to a concentration of 100 

mg/L. 

Sample size and extraction time 

A 3-mL sample size was chosen for use in the Twister ex- 

traction because this was the sample amount routinely used in 

our laboratory's liquid-liquid basic extraction method followed 

by dual column GC-nitrogen-phosphorus detection (NPD) or 

GC-MS analysis. A 16-h (overnight) extraction time was chosen 

to insure complete equilibrium was 

reached for all drugs during the 

SBSE extraction. 

Diluent selection and instrument 

conditions 

The diluent was chosen after 

comparison of drug fortified blood 

samples that were extracted 

overnight using the Twister extrac- 

tion and various diluents. Deion- 

ized water, saline, 30% NaG, and 

pH 9.6 bicarbonate/carbonate buffer 

were all evaluated as diluents by 

combining them separately with a 

3-mL aliquot of blood spiked with 

25 different basic drugs each at a 

concentration of 1 mg/L. All 25 

drugs were detectable using the pH 

9.6 bicarbonate/carbonate buffer, 

and therefore this diluent was 

chosen for the evaluation. The in- 

strument conditions for the TDU 

and CIS were determined after re- 

view of recommended conditions 

in the Gerstel TDU Operations 

Manual. The conditions for cleaning 

and conditioning of used Twister 

bars were recommendations noted 

in the Twister bar package insert. 

Sample preparations for 

Twister extraction 

Three milliliters of blood, urine, 

bile, vitreous, gastric contents, or 

tissue homogenate was pipetted 

582 

[] New Twister 

8 3.~6 


into a 20-mL GC headspace vial. (A 1:3 dilution was used for 

urine and bile. Tissue homogenates were prepared at a 1:4 di- 

lution, and gastric contents were diluted 1:100 or 1:1000. 

All dilutions were made with deionized water.) Exactly 50 IJL 

of the 100 mg/L internal standard solution was added, and a 

10-mm stir bar (Twister, Gerstel) coated with 24 t~L PDMS 

was dropped into the vial. The remaining headspace vial 

volume was filled with the carbonate/bicarbonate buffer. The 

vial was sealed with a rubber stopper and crimp seal. The 

vial was set on top of a standard laboratory magnetic stir 

plate, positioned in the center, and allowed to stir at medium 

to high speed for approximately 16 h. The Twister bar was 

then removed with a pair of forceps, rinsed with deionized 

water, blotted dry with a Kimwipe TM, and inserted into a 

clean TDU liner. 

Sample preparations for liquid-liquid extraction 

A 3-mL aliquot of blood, urine, bile, or tissue homogenate 

was alkalized with 2 mL of the pH 9.6 carbonate/bicarbonate 

buffer in a 16 x 100-ram screw-capped tube. Exactly 50 taL of 

the 100 mg/L internal standard solution was added to each 

sample. The samples were vortex mixed briefly, and 7 mL of the 

,,. I .. J j 

9 "~ .~' 'e .~' '~ ,~S' '§ 

~ ~c, oooo 

"~ 4ooooo 

~ ~ . . . . t 

'~'.~6' '~.~b' ~ 6~b~ ~ ~'.~ ~ ~ '.~ ~ ~'.~ ~'.~ 

Time (min) 

~ e '~ 

~ooooo 

1OOOOOO4 [] 

.~ 5,83 

6.74 

Time (rain) 

Conditioned Twister 

=~176176176176 3~,32 I] 433 755 

9 ' 'A.&o''~.&b~" bo" " " 

,saoooo. Time (rain) 

4OOOOO : 

~00000' 

8 ~ooooo I 

400000 

~ooooo ' 

400000. 

~, ~ooooo : 

I ~.0017.001~.003 ~.00 20.0021.0022.00 2~.0024.00 2~.002~.00~7.00 2~,002~.00 


6,51 7.55 

Blank Twister Liner 

9 ' '4.g~" "&bb' '~bb' "-/.b6' "8.b6" '9.b6"-'~b'.dd :~ h '.dd "1 k'.6d "12~'.66 ~2a'.66 


~6W ~ ~.'id ~ a.'66 ~ ~!66 ~6 "66 ~-~ ~66 ==~66 ~M66 ~M66 ~dd ~&~66 ~9 ~6d =~66 ~;66 " ' 

Time (roW) 

Figure 1. Typical non-drug peaks of a new Twister bar, conditioned Twister bar, and the Twister liner used to 

transfer and hold the Twister bar in the TDU inlet.


extraction solvent, a 50:50 mixture of hexane and chlorobu- 

tane, was added to each of the samples. The extracts were 

rotated for approximately 15 min and then centrifuged at 3000 

rpm. The upper solvent layer was then transferred to 16 x 

100-mm culture tubes. One drop of 0.1% methanolic HC1 was 

oo 

< 

"0 

r., 

8 

8000. 

6000. 

4000. 

2000. 

J 101 

/ 

| 73!3 d 133 169 207 282 322 

0 .... t .... ; ,~, "'q II', .;~',,.,. ,: "' ,,,,I,l,, I,.., I,.,,I...,I,...I,,.,I L, 

20 40 60 80 100 120140 160 180 200 220 240 260 280 300 320 

m/z 

8000i 

6000! 

43 4-Hydroxy-4-methyl-2-pentanone 

(3.326 min) 

59 

Octamethylcyclotetrasiloxane 281 

(3.855 min) 

< 

400C 

200C 

40 59 73 8910311913314716317719.3207221 2~ 2}61 "` 

o: i,,.T.,.i....i ,,.:., ...;,;..,i",J;i,.., ir..:"r:.[.l.J;..i..., r...v...r.., r 

0 20 40 60 60 100 120 140 160 180200 220240260 280 

m/z 

9000 

8000 

Decamethylcyelopentasiloxane 355 

731 (4.828 rain) 

267 

8 

I= 

7000 

6000 

5000 

I _ I 

4000 

< 

I 

3000 

2000 

251 ;I 

1000 4559/88 1dt91331541791932072137] 1293 323339 

dJA .......... t...,~,~r~.La,.It i.30pt k 

0 

0 20 40 60 80 100120140160180200220240260280300320340360 

m/z 

8 

== 

"o 

== 

9000 

800C 

700C 

6000 

5000 

4000 

300~ 

2000 

100C 

Tetradecamethylcych ,heptasiloxane 

73 (6.737 min) 281 

147 

I29 

/ 191221 

44 / I00 / 171 I [ 251 

IdJ.,.,,,i I~iL ~, 

327 

3 3 399 503 

Figure 2. Mass spectra and identification of Twister bar peaks from Figure 1. 

added to each, and the solvent was evaporated at 40~ with a 

steady stream of nitrogen. Dried extracts were reconstituted 

with 150 laL of ethyl acetate and transferred to 2-mL ALS vials 

with 300-1aL inserts. The vials were crimp capped and stored at 

room temperature until time of injection. 

8 

8 

"o 

< 

g 

== 

< 

.J~ 

< 

9000 

8000 

7000 

6o00 

"~ 5000 

~ 9 4000 

3000 

2000 

1000 

0111111111 I Ill Ill lit ~-II II Ililll III III Ill Ill Ill Ill Ill I Ill Ill Ill I II II I' I I Illl 

20 

133 

Methoxyphenyloxime 

(3.442 rain) 

151 

4051r162 7- 89 105 121 

207 

0 .... 

Ill lu I fill lull ,I I '''I ,nil I'; ''11 lilt H| UlUl lll'l, 

40 60 80 100 120 140 160 180 200 220 240 260 280 

,oo] 

m/z 

57 2=Ethyl-lhexanol 


6o001 

70 83 

I I ~8112 207 281293 

40 60 80 100 120 140 160 180 200 220 240 260 280 

m/z 

73 Do decamethylcyclohexasiloxane 


341 

9OOO 

8000 

7000 

500O 

50OO 

4O00 

30OO 

200O 

147 

325 

I 

1000 91 1171331 17~931 ~37251267281311[ 

0 "l" ", '" i,.. . i k I k ". d, I I I ,11 

,IIH,I ,,, ,i ........ IINI ............ i, ,,,111111 ........ i,=, 

.............. 41.3,[.,. 

429 

40 60 80 100120140180180200220240260280300320340360380400420 

m/z 

73 [ 14-[l,2-bis [(trimethylsilyl)oxy]ethyl] 

12000 -l,2-phenylene]bis(oxy)]l ,is{trimethyl] 

11OO0 silane 355 

10000 

8OO0 

7oo4) 147 

60~0 221 281 

,5OOO 

I L Ol 

L Ik 4,~ 

2000 45 I 

1000 lO0 131 191 251~ . 384 / ,~.490 

e. !').. k.. :. HI =,....!,! l.. ,.~..t.,...~ ~ .... ~,,].l ?,~,;.. :. 

50 100 150 200 250 300 350 400 450 

m/z 

583

Materials and Methods 

Instrumentation 

Sample analysis was performed on two 

Agilent 6890 Gas Chromatographs both Deionized H20 

interfaced with an Agilent 5973 mass 

selective detector. For the analysis of 

Twister samples, the split/splitless inlet 

of a GC-MS was replaced with the Ger- 

stel cooled injection system (CIS) and 

the Gerstel manual thermal desorption 

system (TDS), which mounts directly 

onto the CIS. 

The GC was equipped with a Rtx| 

MS fused silica capillary column (25 m x 

0.20-mm i.d. x 0.33 lJm) with a 5-m in- 

tegrated guard column (Integra-Guard) 

from Restek Corporation. The initial 

oven temperature was held at 70~ for 

1.0 min and then increased to 310~ at 

25~ with a finat temperature hold 

of 19.4 min. Ultra pure helium at a flow 

rate of 1.3 mL/min was used as the car- 

rier gas. The CIS inlet was operated in 

the solvent vent mode. The TDU desorp- 

tion flow was 50.0 mL/min, and the vent 

pressure was set to 23.6 psi. The purge 

flow was set at 26.0 mL/min (20:1 split 

ratio), and the purge time was set at 0.01 

min. A single baffled general purpose 

liner packed with deactivated glass wool 

was used in the CIS inlet (Gerstel part# 

012742-010-00). Low pressure liquid nitrogen was used for 

cryo-cooling. The CIS and TDU parameters were set using the 

GersteI software installed on the GC-MS computer system, 

which consisted of a Hewlett-Packard computer with Windows 

NT and Agilent Chemstation software, The initial inlet tem- 

perature was set to -120~ with an initial time of 0.2 min. The 

CIS heating rate was set to 12.0~ to a final temperature of 

280~ for a final time of 5 min. The total run time was set to 

30 rain. The TDU was operated in splitless mode, and the 

sample mode was set to sample remove. The initial tempera- 

ture was set to 30~ with an initial time of 0.0 min and a delay 

time of 3.00 rain. The transfer temperature was set to 275~ 

The first rate was 60~ with a final temperature of 270~ 

and a final time of 5.0 min. Breathing quality air at an oper- 

ating pressure of 80 psi was used for the pneumatic closing 

mechanism of the TDU. The MS was operated in the EI mode 

with the electron voltage set at autotune value and full scan 

monitoring from 40 to 550 amu. For the analysis of 

liquid-liquid extractions, the second GC-MS was operated 

with the usual Agilent split/splitless injector and the 7673 ALS. 

The injection volume was 2 IJL. The inlet temperature was set 

at 250~ A splitless sample mode was used for sample injec- 

tions. The column used, parameters for oven temperature pro- 

gram, column flow, and MS conditions were the same as those 

described for the TDU application. The chemstation data anal- 

ysis software was used for peak integration and library searches. 

584 


Table I. The Detectability of Target Drugs at 1 mg/t using Twister and Various 

Extraction Diluents 

Carbonate/Bicarbonate 

Saline 30% NaCI Buffer (pH 9.6) 

Bupropion Bupropion Methamphetamine Methamphetamine 

Meperidine Meperidine Bupropion Bupropion 

Caffeine Fluoxetine Meperidine Meperidine 

Diphenhydramine Carisoprodal Fluoxetine Caffeine 

Lidocaine Diphenhydramine Carisoprodal Fluoxetine 

Methadone Lidocaine Diphenhydrarnine Carisoprodal 

Amitriptyline Methadone Lidocaine Diphenhydramine 

Mirtazapine Amitriptyline Doxylamine Lidocaine 

Sertraline Mirtazapine Methadone Propoxyphene 

Citalopram Sertraline Amitriptytine Doxylamine 

Diazepam Citalopram Mirtazapine Trarnadol 

Zolpidem Diazepam Sertraline Venlafaxine 

Chlorpromazine Citalopram Methadone 

Zolpidem Diazeparn Amitriptyline 

Verapamil Chlorpromazine Nortriptyline 

Zolpidem Mirtazapine 

Verapamil Sertraline 

Trazodone Citalopram 

Diazepam 

Chlorpromazine 

Paroxetine 

Olanzapine 

ZoIpidem 

Verapamit 

Trazodone 

Table II. Drug Recovery Determined for Several Analytes 

Spiked into Blood at 0.3 mg/L 

Drug % Recovery 

Fluoxetine 65.1 

Propoxyphene 48.5 

Chlorpheniramine 98.9 

Promethazine 88.8 

Sertraline 70.9 

Diazepam 22.7 

Methamphetamine 50.7 

Meperidine 78.5 

Diphenhydramine 86.5 

Methadone 84.2 

Amitriptyline 84.6 

Tramadol 38.0 

Lidocaine 59.0 

Doxylamine 83.0 

Venlafaxine 77.0 

Dextromethorphan 94.0 

Citalopram 82.0 

Mirtazepine 77.4 

Chlorpromazine 70.4 

Trazadone 38.7 

Verapamil 71.0


Table III. Drugs Extracted at 1 mg/L Concentration in Blood using Twister 

Relative Twister Partition Relative Twister Partition 

Retention Calc. Coefficient Retention Calc. Coefficient 

Compound Time (%) (Log Kow) Compound Time (%) (Log Kow) 

Acepromazine 1.185 61.5 2.3 Hydroxyamphetamine nd 13.8 1.3 

Alprazolam 1.350 51.3 2.12 Hydroxyzine 1.271 66.8 2.4 

Amantidine 0.547 68.8 -0.4 Ibuprofen 0.665 98.7 4.0 

Amitriptyline 0.968 99.8 4.94 Imipramine 0.979 99.8 2.5 

Amoxapine 1.154 nf* nf Ketamine 0.841 91.0 3.1 

Amphetamine 0.474 31.5 1.8 Lidocaine 0.841 68.8 2.4 

Atropine 0.971 35.1 1.8 Loxapine 1.124 97.0 3.6 

Baclofen nd 0.1 -1 Maprotaline 1.028 99.6 4.5 

Benztropine 1.012 0.4 0.4 MDA 0.663 25.9 1.64 

Brompheniramine 0.935 99.0 4.1 MDMA 0.689 nf nf 

Bupivicaine 0.996 95.4 3.4 Meclizine 1.401 100.0 5.9 

Bupropion 0.718 nf nf Meg X 0.813 nf nf 

Buspirone 1.729 77.3 nf Meperidine 0.790 80.8 2.7 

Caffeine 0.838 0.7 -0.07 Mepivacaine 0.921 41.6 1.9 

Captopril nd 1.7 0.34 Meprobamate nd 3.9 0.7 

Carbamazepine 0.893 69.3 2.45 Mescaline nd 4.6 0.8 

Carbinoxamine 0.923 76.1 2.6 Mesoridazine nd 100.0 5.6 

Carbofuran 0.566 nf nf Metaxalone 0.954 nf nf 

Carisoprodol 0.835 64.7 2.36 Methadone 0.943 98.6 3.93 

Chlordiazepoxide 1.092 68.8 2.44 Methamphetamine 0.385 48.5 2.1 

Chlorpheniramine 0.897 95.0 3.38 Methaqualone 0.962 99.4 4.3 

Chlorpromazine 1.09 100.0 3.4 Methylecgonine 0.668 nf nf 

Cimetidine nd 2.0 0.4 Methylphenidate 0.783 1.3 0.2 

Citalopram 1.042 97.8 3.74 Metoclopramide 1.019 76.9 2.6 

Clomipramine 1.046 99.9 5.2 Metoprolol 0.902 37.8 1.9 

Clonidine 0.931 23.7 1.59 Midazolam 1.125 99.4 4.3 

Clozapine 1.298 93.1 3.23 Mirtazapine 0.996 100.0 7.1 

Cocaethylene 0.988 nf nf 6-Monoacetylmorphine nd nf nf 

Cocaine 0.968 61.5 2.3 Morphine nd 5.8 -0.1 

Codeine 1.047 11.0 0.6 Nicotine 0.599 10.6 1.2 

Colchicine nd 13.8 1.3 Nifedipine nd 55.9 2.2 

Cotinine 0.770 nf nf Norcitalopram 1.051 nf nf 

Cyclizine 0.906 88.2 2.97 Nordiazepam 1.091 87.2 2.9 

Cyclobenzaprine 0.986 99.8 4.8 Noffluoxetine 0.822 nf nf 

Cyproheptadine 1.033 99.7 3.2 Nordoxepin 0.987 nf nf 

Desipramine 0.988 99.8 1.4 Normeperidine 0.806 nf nf 

Desmethyclomimpramine 1.058 nf nf Norpropoxyphene I 1.028 nf nf 

Dextromethorphan 0.986 nf nf Norpropoxyphene II 1.038 nf nf 

Diazepam 1.061 84.1 2.7 Norpropoxyphene III 1.043 nf nf 

Diltiazem 1.340 83.1 2.79 Norpmpoxyphene amide 1.099 nf nf 

Diphenhydramine 0.837 93.7 3.3 Nortriptyline 0.975 28.6 1.7 

Disopyramide 1.070 75.3 2.6 Norvenlafaxine 0.948 nf nf 

Doxepin 0.981 66.8 2.4 Norverapamil 1.576 nf nf 

Doxylamine 0.856 66.8 2.4 Noscapine nd 44.4 2.0 

EDDP nd nf nf Olanzapine I .I 99 nf nf 

Etomidate 0.852 90.0 3 Oxycodone I .I 08 3.9 0.7 

Flecainide 0.962 98.0 3.8 Papaverine 1.238 87.7 0.5 

Fluconazde nd 7.4 I Paroxetine 1.118 98.6 3.95 

Flunitrazepam 1.155 47.9 2.1 PCP 0.859 99.8 4.7 

Fluoxetine 0.830 98.9 4.05 Pentazocine 0.996 99.7 4.6 

Fluvoxamine nd 0.9 0.04 Phenmetrazine 0.651 20.2 1.5 

Guaifenesin 0.744 16.4 1.4 Phentermine 0.493 38.9 1.9 

Hydrocodone 1.073 55.9 2.2 Phenylephrine nd 0.4 -0.3 

Hydromorphone nd nf -4 Phenyltoloxamine 0.917 98.1 3.8 

* Abbreviations: nf, not found and nd, none detected. 

585

Table III. (continued)Drugs Extracted at I mg/L Concentration in Blood using Twister 


Relative Twister Partition Relative Twister Partition 

Retention Calc. Coefficient Retention Calc. Coefficient 

Compound Time (%) (Log Kow) Compound Time (%) (Log Kow) 

Pimozide nd 100.0 6.3 Sertraline 1.035 99.9 5.29 

PMA 0.611 nf nf SKF-525A 1.000 nf nf 

PMMA 0,638 nf nf Strychnine 1.876 40.5 1.9 

PPA nd 3.6 0.7 Temazepam nd 55.3 2.19 

Procainamide nd 5.7 0.9 Theophylline nd 0.8 0 

Promazine 1.036 99.6 2,5 Thioridazine 1.763 100.0 5.9 

Promethazine 1,001 86.4 2.9 Tiletamine 0.765 nf nf 

Propofol 0.505 98.0 3.79 Tramadol 0.876 89,1 3.01 

Propoxyphene 0.846 99,2 4.2 Tranylcypromine 0.530 24.2 1.6 

Propranolol 0.952 96.0 1.2 Trazodone 1.817 92.7 3.2 

Propylamphetamine 0.579 96.2 3,5 Trimethobenzamide 1.708 61.5 2,3 

Protriptyline 0.993 99.8 4.9 Trimethoprim nd 6.1 0.91 

Pseudoephedrine nd 5.8 0.9 Trimipramine 0.974 100,0 5.43 

Quinidine 1.243 95.7 3.4 Venlafaxine 0.923 2,1 0.43 

Quinine 1.240 95,7 3.4 Verapamil 1.503 98,0 3.8 

Quetiapine nd 1.6 nf Zaleplon 1.372 nf nf 

Ranitidine nd 1.5 0.3 Zolazepam 1.005 nf nf 

Salicylic acid nd 59.3 2.3 Zolpidem 1,323 98.3 3.85 

Scopolamine nd 7.1 1,2 

GC-MS analysis of Twister bars 

Twister bars from extracted samples were stored in labeled 16 

100-mm culture tubes until analysis. Just prior to analysis, 

each bar was inserted into a single baffle thermal desorption 

tube and sealed with a metal twister transportation adapter. All 

desorptions were done manually. A data file was created along 

with the appropriate sample information, and prep run was ini- 

tiated using the GC keypad when prompted. Cryo-cooling was 

initiated by using the computer's mouse to click on "To Ready" 

in the Gerstel operating software. The TDU desorption tube 

containing the Twister bar to be analyzed was then inserted 

into the TDU for analysis. The thermal desorption was initiated 

by the software once the initial temperatures reached set points 

and equilibration times. Data files were reviewed using the 

standard data analysis menu of the chemstation software. The 

auto integration function was used along with the library 

search routine to search for drugs in three libraries. The li- 

braries searched included a user drug library, Pfleger-Weber li- 

brary of drugs, poisons, and pesticides, and the NIST 98 library. 

Threshold values were lowered to detect peaks not initially in- 

tegrated with auto-integration. Ion searches consisting of a 

main ion and two common ions were done when necessary to 

find peaks of interest. 

Twister bar conditioning 

Twister bars were reused after thermal desorption. Condi- 

tioning of the Twister bars was necessary prior to them being 

re-used for analysis. Stir bars previously used were soaked 

overnight in a 50:50 mixture of dichloromethane and 

methanol. These bars were removed from the solvent and air 

dried for 1-2 h. To heat condition the Twister bars, a 1/8-in. 

copper gas line was plumbed into the oven of a 5890 Hewlett- 

Packard GC. A 88 swagelok tee fitting was attached using a 

586 

88 to 88 union. One side of the tee was plug capped, and the 

other was fitted with a 88 single taper inlet liner with no 

glass wool. This was installed using a graphite-vespel ferrule 

and a swagelok nut. Up to four Twister bars were conditioned 

inside the inlet liner at 300~ with a flow of standard purity 

helium gas of at least 50 mL/min. Twister bars were condi- 

tioned in this manner for a minimum of 1 h. Gas flows were 

checked prior to each conditioning using a soap film flow 

meter. 

Results and Discussion 

The purpose of this evaluation was to determine the useful- 

ness of the Twister bar and the TDU in the routine analysis of 

biological samples typically analyzed in a forensic toxicology 

laboratory 

The TDU allows for desorbing in the split or splitless mode 

into the CIS which acts as a cryotrap for focusing and con- 

centrating the analytes prior to their transfer to the capillary 

column. The analyte transfer from the CIS to the column can 

also be performed in the split or splitless mode. In this study, 

desorption was done in the splitless mode and operation using 

the TDU split mode was not evaluated. However, splits as well 

as splitless injection parameters were evaluated for the CIS. 

Initially, a splitless CIS injection mode was tried for sample ex- 

tractions. Grossly overloaded peaks were observed with sig- 

nificant carry over of some drugs in blank injections made 

subsequent to the splitless injections. A 4:1 split mode was 

next chosen for injections; however, though peak overload 

diminished, carryover in succeeding blank injections re- 

mained detectable. A 20:1 split ratio worked well and was


chosen for injection of standards and 

sample extracts. This split ratio gave 

excellent peak shape and good analyte 

responses without any notable carry 

over. Because the method developed 

was intended as a general drug screen, 

a cryo temperature of -120~ was 

adopted for use without evaluation of 

other temperatures. Routine CIS inlet 

maintenance included changing the 

liner every few weeks and solvent 

cleaning the inlet body as needed. This 

maintenance also contributed to elimi- 

nating carry over. Twister transporta- 

tion adaptors and glass desorption 

liners were also solvent cleaned occa- 

sionally to eliminate the possibility of 

contamination. Each day of analysis an 

autotune was done to check for readi- 

ness of the GC-MS. A blank run was 

performed by desorbing an empty 

Twister liner (no Twister bar inside) to 

determine system cleanliness prior to 

sample analysis. On a few occasions, the 

chromatogram of the blank run showed 

trace amounts of drugs from previous 

injections. The empty liner injection 

sometimes had to be repeated before a 

chromatogram free of any drugs would 

be obtained. Desorption of an empty 

Twister liner was also done after any 

inlet maintenance. Reconditioned 

Twister bars were randomly desorbed 

and compared to new Twister bars to 

monitor their extraction efficiency and 

check for cleanliness prior to reuse 

(Figure 1). Reconditioned Twister bars 

did not retain drugs from previous ex- 

tractions when reconditioned as de- 

scribed. New and reconditioned Twister 

bars showed typical siloxane peaks from 

the PDMS phase (Figure 2). These did 

not interfere with drug analysis or iden- 

tification. Vials containing stir bars 

were positioned in the center of the stir 

plate for optimal stirring conditions. 

Those placed away from the center of 

the plate "jumped" around in the vial 

rather than spinning, occasionally 

causing breakage to the ends of the 

glass insert encasing the magnetic bar. 

Because it was our goal to make as 

direct a comparison as possible, the 

sample size and the internal standard 

amount were matched to the 

liquid-liquid extraction method. There- 

fore, a 3-mL aliquot of blood was used to 

evaluate the Twister's capabilities be- 

Table IV. Comparison of Reported Case Findings and Liquid-Liquid Extraction 

versus Twister Extraction followed by GC-MS Analysis 

Sample Reported Results Liquid-Liquid Extraction Twister 

No. (mg/L) GC-MS Results GC-MS Results 

1 Phenobarbital (5.4) Negative Negative 

2 Negative Negative Negative 

(Caffeine < 0.1) 

3 Fluoxetine (1.1) Fluoxetine Fluoxetine 

Caffeine (2.6) Caffeine Caffeine 

Nicotine 

4 Methadone (0.75) Methadone Methadone 

Hydrocodone (< 0.05) Hydrocodone 

EDDP (< 0.1) Nicotine 

Acetaminophen (13) 


6 Carisoprodal (4.3) Carisoprodal Carisoprodal 

Hydrocodone (0.79) Hydrocodone Hydrocodone 

Diazepam (0.26) Diazepam Diazepam 


7 Venlafaxine (0.50) Venlafaxine Venlafaxine 

Diphenhydramine (0.17) Diphenhydramine Diphenhydramine 

8 Citaloprarn (0.11) Citalopram Citaloprarn 

9 Diazepam (1.9) Diazepam Diazepam 

Diphenhydramine (0.15) Diphenhydramine Diphenhydramine 

Chlorpheniramine (0.15) Chlorpheniramine Chlorpheniramine 

Hydrocodone (0.44) Hydrocodone Hydrocodone 

Dextromethorphan (< 0.10) Dextromethorphan Dextrornethorphan 


10 8upropion (0.26) Bupropion Bupropion 

Methadone (0.74) Methadone Methadone 


11 Caffeine (6.8) Caffeine Caffeine 

12 Lidocaine (2.2) Lidocaine Lidocaine 

Cocaine (0.2) Cocaine Cocaine 

Cocaethylene (< 0.05) Cocaethylene Cocaethylene 



Nordiazepam (0.66) 

Fentanyl (10 IJg/L) 

Temazepam (< 0.05) 

Cocaine (< 0.05) 

Nordiazepam Nordiazepam 

15 Clozapine (12.0) Clozapine Clozapine 

Fluoxetine (1.5) 

Fentanyl (3 pg/L) 

Fluoxetine Fluoxetine 

16 Amitriptyline (0.48) Amitriptyline Amitriptyline 

Alprazolam (56 pg/L) Nortriptyline 

17 Propofol (0.50) Propofol Propofol 

Diazeparn (0.08) Diazepam Diazeparn 

Promethazine (0.17) Promethazine Promethazine 

Nordiazepam (0.11) Nordiazeparn (tr)* 

Morphine (0.06) 

Hydrocodone (< 0.05) 

* (tr) = peak identified by ion search with poor chromatography but reasonable library match quality. 

587

Table IV. (continued) Comparison of Reported Case Findings and Liquid-Liquid 

Extraction versus Twister Extraction followed by GC-MS Analysis 

588 


No. (mg/L) GC-MS Results GC-MS Results 

18 Methadone (0.5) Methadone Methadone 



19 Diphenhydramine (0.14) Diphenhydramine 

Diphenhydramine 

Caffeine (2.6) 

Caffeine 

20 Venlafaxine (0.73) 

21 Flecainide (9.6) 

Trazodone (1.0) 

Venlafaxine Venlafaxine 


Flecainide Flecainide 

Flecainide Artifact Flecainide Artifact 

Trazodone Trazodone 

Nicotine (tr) Nicotine 

22 Chlorpheniramine (0.20) 


Chlorpheniramine Chlorpheniramine 

23 Citalopram (0.20) Citalopram Citalopram 

24 Citalopram (1.2) Citalopram Citalopram 

Nordiazepam (4.7) Nordiazepam Nordiazepam 

Carbamazepine (7.8) Carbamazepine Carbamazepine 

Alprazolam (211 pg/L) Nicotine 

25 Amphetamine (0.10) Methamphetamine Methamphetamine 

Methamphetamine (0.68) Methadone Methadone 

Diazepam (0.10) Diazepam Diazepam 


Methadone (0.44) 

EDDP (< 0.1) 

Benzoylecgonine (< 0.05) 

Nordiazepam Nordiazepam (tr) 

26 Alprazolam (27 pg/L) Diazepam Diazepam 

Methamphetamine (0.36) 

Diazepam (0.05) 


Amphetamine (< 0.05/ 

Methamphetamine Methamphetamine 

27 Diazepam (0.11) Promethazine Promethazine 

Metaxalone (0.45) Promethazine Metabolite Promethazine Metabolite 



Promethazine (0.98) 

Norpropoxyphene 

(I, II, III, amide) 

28 MDMA (0.62) MDMA MDMA 

MDA (< 0.10) Phencyclidine Phencyclidine 

Phencyclidine (< 25 pg/L) Nicotine 

Methylecgonine (< 0.05) 

Benzoylecgonine (0.12) 

29 Negative Atropine Negative 

30 Amantadine (3.6) Amantadine Amantadine 

Citalopram (0.13) Citalopram Citalopram 


Acetaminophen (31) Methamphetamine 

Oxycodone (0.20) 

Oxymorphone (0.12) 


Oxycodone (tr) 



cause subsequent testing would be com- 

pared to the liquid-liquid extraction 

method, which also used a 3-mL aliquot. 

Several different diluents, including 

water, saline (pH 5.5), 30% sodium chlo- 

ride (pH 8.25), and carbonate/bicar- 

bonate buffer (pH 9.6) were evaluated 

for sample preparation in the Twister 

method. Of these diluents, the car- 

bonate/bicarbonate buffer gave the best 

overall results in terms of number of 

drugs detected and the area response of 

the target compounds used to evaluate 

the diluents (Table I). For the other dilu- 

ents, Caffeine had the best recovery from 

deionized water, and Bupropion and 

Carisoprodal were recovered best from 

30% sodium chloride. 

Once the diluent was chosen, the ex- 

traction time was evaluated at 2, 4, and 

16 h (overnight). Again, a number of 

target drugs were extracted at these dif- 

ferent times at room temperature. 

Although the 2- and 4-h extraction 

times gave reasonable recovery for 

most drugs, several drugs, such as caf- 

feine, carisoprodal, olanzapine, and 

trazadone, had better recovery using 

the 16-h extraction time. With many 

drugs to be considered in the drug 

screen method, the 16-h extraction 

time was chosen to allow maximum 

drug absorption along with the conve- 

nience of an overnight extraction. The 

recovery of several drugs was deter- 

mined in blood which was spiked to a 

0.3 mg/L concentration, extracted 

overnight, and desorbed with the de- 

scribed Twister method. The area re- 

sponse of the extracted drug was com- 

pared to the area response of the same 

amount of drug dried directly onto a 

Twister bar in a TDU liner that was des- 

orbed in the same manner (Table II). 

To determine the scope of the Twister 

extraction method, blood was fortified 

with a number of different basic drugs 

and extracted with the described method. 

Each of the drugs was spiked into a 3-mL 

aliquot of blood at a 1 mg/L concentra- 

tion. An alphabetical listing of these drugs 

includes the measured relative retention 

time for the drug, the calculated Twister 

recovery, and partition coefficient (Table 

III). The Twister recovery was calculated 

using the Gerstel Twister Calc software. 

The software uses a database of partition 

coefficient (searchable by CAS number)


Table IV. Comparison of Reported Case Findings and Liquid-Liquid Extraction 

versus Twister Extraction followed by GC-MS Analysis (continued) 

Sample Reporled Results Liquid-Liquid Extraction Twister 

No. (rag/L) GC-MS Results GO-MS Results 

32 Negative 

33 Citalopram (0.65) 


VPA (40) 

Cocaine (< 0.05) 

34 Propoxyphene (0.88) 


Negative Negative 

Citalopram Citalopram 

Cocaine 

Propoxyphene Propoxyphene 

Norpropoxyphene Norpropoxyphene 

(I, II, III, amide) (I, II, III, amide) 

35 Dextromethorphan (0.19) Dextromethorphan Dextromethorphan 

Chlorpheniramine (0.46) Chlorpheniramine Chlorpheniramine 

Lorazepam (< 10 lag/L) Hydrocodone Hydrocodone 


Caffeine (4.5) 

Caffeine Caffeine 


Nordiazepam (0.30) Nordiazepam Nordiazepam 

Oxycodone (0.22) Caffeine Oxycodone fir) 

Oxymorphone (< 0.05) Nicotine 

37 Cocaine (0.14) Cocaine Cocaine 

Methylecgonine (0.24) 

Benzoylecgonine (I .7) 


38 Cocaine (0.05) Cocaine Cocaine 

Cocaethylene (0.08) Cocaethylene Cocaethylene 


Methylecgonine (0.09) 

N icotine 



40 Amphetamine (0.05) 

Methamphetamine (0.22) 

Methamphetamine fir) Methamphetamine 

41 Diphenhydramine (0.34) Diphenhydramine Diphenhydramine 

Methylecgonine (0.62) Methylecgonine Methylecgonine 

Cocaine (0.07) Cocaine Cocaine 

Cocaethylene (0.05) 



Cocaethylene Cocaethylene 

42 Amitriptyline (0.61) Amitriptyline Amitriptyline 

Nortriptyline (0.59) Nortriptyline Nortriptyline 

Citalopram (0.46) Citalopram Citalopram 

Cyclobenzaprine (0.10) Cyclobenzaprine Cyclobenzaprine 

Temazepam (0.06) 


Desmethylcyclobenzaprine 

43 Carisoprodal (21) Carisoprodal Carisoprodal 

Metoprolol (0.9) Metoprolol Metoprolol 

Hydrocodone (0.6) 


Quetiapine (< 0.5) 

Dihydrocodeine (0.05) 

Hydrocodone Hydrocodone 


Dextromethorphan 

45 Sertraline (0.14) Sertraline Sertraline 

Diphenhydramine (0.33) 

Acetaminophen (I 3) 

Diphenhydramine Diphenhydramine 

* (tr) = peak identified by ion seamh with poor chromatography but reasonable library match quality. 

and sample volume to predict the re- 

covery of an analyte at equilibrium. Pre- 

dicting a drug's recovery from its parti- 

tion coefficient can be a useful tool for 

method development because it would 

assist the analyst in choosing which ana- 

lytes would be likely candidates for 

Twister extraction. Drugs which exhibit a 

higher octanot/water (buffer) partition co- 

efficients are more likely to partition into 

the non-polar PDMS phase from an 

aqueous solution during the Twister ex- 

traction and will have the highest recov- 

eries. As seen in Table III, most drugs with 

low partition coefficients also had low cal- 

culated recoveries and were not detected 

after Twister extraction. However, several 

drugs with low calculated recoveries, 

such as venlafaxine, oxycodone, nicotine, 

and methylphenidate, were detected. Ven- 

lafaxine had a much higher measured re- 

covery (Table II) than the recovery pre- 

dicted by the partition coefficient. 

Postmortem blood samples from pre- 

viously tested case specimens were ex- 

tracted with the Twister method and 

compared to the described liquid-liquid 

extraction normally used prior to GC-MS 

analysis. Two GC-MS systems were used 

for the comparison as described. The 

total ion chromatograms of sample ex- 

tracts from both the methods were com- 

pared, and the mass spectra of peaks 

found were searched in the mass spectral 

database for identification. The qualita- 

tive results of each were noted and com- 

pared to the reported results for the case 

samples (Table IV). The reported results 

for case samples were recorded after rou- 

tine toxicological analysis by our labora- 

tory using the typical laboratory methods 

of GC-NPD, HPLC, FPIA, and GC-MS. 

Quantitative results for amphetamines 

(including MDMA and MDA), benzodi- 

azepines, cocaine and metabolites, fen- 

tanyl, fluoxetine, methadone (including 

EDDP), opiates, and PCP were deter- 

mined by GC-MS using selected ion 

monitoring. Barbiturates were quanti- 

tated by HPLC with UV detection. Ac- 

etaminophen was quantitated using flu- 

orescence polarization immunoassay. All 

other drugs were quantitated using 

GC-NPD after basic liquid-liquid extrac- 

tion using butyl chloride. It was con- 

cluded that case samples found to be pos- 

itive for a drug by the liquid-liquid 

extraction method followed by GC-MS 

589

analysis, but negative using the Twister method followed by 

GC-MS analysis were not readily extracted and/or desorbed by 

the described Twister method at the concentration found in the 

sample based on the reported results. Case specimens were 

chosen based on the availability of sample as well as type and 

concentration of drug present. A variety of drugs and concen- 

trations were selected when possible. Chromatograms of a case 

sample extracted by both methods (Figure 3) were typical for a 

blood extraction. Whereas a solvent delay time of 3.00 min was 

Table IV. (continued) Comparison of Reported Case Findings and Liquid-Liquid 

Extraction versus Twister Extraction followed by GC-MS Analysis 


No. (mg/t) GC-MS Results GC-MS Results 

46 Olanzapine (0.71) Olanzapine Negative 


47 Papaverine (not reported) 

48 Diphenhydramine (0.22) 

Chlorpheniramine (0.48) 

Amitriptyline (1.4) 

Nortriptyline (2.1) 



49 Methadone (0.47) 

Diazepam (0.24) 

Hydrocodone (0.09) 

Diltiazem (0.51) 

Zolpidem (0.13) 

Nordiazepam (< 0.05) 

EDDP (< 0.05) 

Hydrocodol (< 0.05) 

50 Fluoxetine (0.66) 

Venlafaxine (< 0.1) 

Trazodone (0.89) 

Papaverine Papaverine 

Diphenhydramine Diphenhydramine 

Chlorpheniramine Chlorpheniramine 

Amitriptyline Arnitriptyline 

Nortriptyline Nortriptyline 

Methadone Methadone 

Diazepam Diazepam 

Hydrocodone Hydrocodone 

Diltiazem 

Zolpidem 

Fluoxetine Fluoxetine 

Venlafaxine 


i ~ 

Rhmd drul~ ~r u~in~ 

1'~ ister extraction "" 

, ~ ., 1., ~; 

Tifr~ (rnlnl 


used for the desorption method (to match that used in the 

liquid-liquid acquisition method), a solvent peak was not seen 

with desorptions and a more practical solvent delay would be 0.5 

min. The liquid-liquid extraction did not include a back ex- 

traction, and a significant cholesterol peak was noted in blood 

and tissue samples extracted by this method. Little, if any, 

cholesterol was detected in the Twister extractions. Twister ex- 

tractions compared well with the liquid-liquid extractions fol- 

lowed by GC-MS analysis. Even though the Twister Calc pre- 

dicted low recovery for drugs such as 

e 

u - 

~o 

Z~r 

.i 

caffeine and venlafaxine, caffeine recov- 

ered well at concentrations of 1 mg/L and 

higher, and venlafaxine recovered well 

even at concentrations below 0.1 mg/L. 

Olanzapine did not recover well below 

concentrations of 1 rag/L; however, the 

detectability of olanzapine was greatly 

improved when a new CIS liner was used. 

Methamphetamine, nicotine, and bupro- 

pion recovered better with the Twister 

method than with the liquid-liquid ex- 

traction method. In addition to blood 

samples, other sample matrices, such as 

liver, kidney, brain, bile, urine, vitreous, 

and gastric contents, were successfully 

extracted and analyzed using the Twister 

method (Figures 4-7). 

Conclusions 

The Twister extraction method is a vi- 

able alternative to liquid-liquid or solid- 

phase extractions for the screening of 

basic drugs in biological samples. This 

method eliminates the need for many 

steps typical of the other extractions, 

such as transfer steps, sample rotation, 

centrifugation, and solvent evaporation. 

It also eliminates the need for the equip- 

HIm~ dru~ ~('r cl'n u,illg ~-~ 

liquid-liquid e~(tracti(m 

10==7 

619 11~5 

Time ~rnl~ 

Time (rr~n) Time (rnin; 

Figure 3. Comparison of the total ion chromatograms of Twister vs. liquid-liquid extraction of case sample. Whole blood sample was positive for propofol at 

0.5 mg/L and diazepam at 0.08 mg/L. 

590 

L


ment and the solvents usually needed for extractions. Twister 

bars are reusable after reconditioning and do not appear to car- 

ryover analytes from previous uses once desorbed and recon- 

ditioned. The use of the Twister method for forensic samples 

would require that each ~vister bar used and reconditioned for 

reuse be tested in the acquisition method for which it will be 

used in subsequent extracts to document that it is negative for 

the analytes being tested. Perhaps a disposable Twister bar 

could be developed to alleviate this issue9 It would also be 

useful in tracking the Twister bars if the magnetic stir bar 

were embossed with a unique identifier number to record 

along with the data documenting its use and reuse. Sample 

size, split ratios, and inlet maintenance will be important eval- 

uations in any method development in order to avoid carryover 

when using Twister for a particular application. Inlet mainte- 

nance will also be necessary to retain reasonable detectability 

of some analytes. 

Acknowledgments 

The authors would like to thank Ed Pfannkoch and Tim 

Pence of Gerstel for their technical assistance and helpful dis- 

cussions. 

i.*a?. 

Liver drug scr~n 

*-*~,~ Mcthamphetarnine 8.8 mg/L 

. . . . . . . i ) 

'ab6 ' ",.~:h6" "1l a" "6 6" " L~a ~a:oa " ~,[ob ~a'ab" ",'I'Oa" 

Time (m~n) 

Spleen drag screen 

~'~" Metaxalone 84 mg/L 

=..~. Sertraline 23 mg/L 

= =.~? 

al.o:, 

9 s~ 

ioooo~o 

~oc~oo 

aooc4ac~ 

Tim~ (rnln) 

Brain drug screen 

= I.~ 

a.~.--r Venlafaxine < 1 ms/l,, 

,, 

Time (min) 

Figure 4. Total ion chromatograms of homogenized tissues extracted with 

the Twister method. 

~ [ %'' 

7'o0 Sbo 

, 

J 

Bile drug screen 

900 lOJO 11.00 12.00 l&O0 14.~ 15.00 1600 17~ 


Tramadol 2 mg/L 

Cyclobenzaprine < 0 5mg/L 

i 

""~'t 

Blood drug screen Diphenhydramine 0.2 mg/L 

Chlorpheniramine 0.48 rag& 

Amitriptyline 14 mg/L 

i ...... ~ Nortriptyline 2.1 mg/L 

..Io~7 

l.I.~ 

a* ? 

9 9 ? 

. I .. .,... , .~ . . . . . . . . . . . . ,...~ . . . . . . . . . , . . . . , . . . . , 

$~O 8.80 900 g,~ 940 9~0 9.80 10.00 10;~ 1040 10.60 IOEO 1100 


Urine drug ~r Diphenhydraminc 

Orphenadrine 48 mg/L 

Venlafaxine 4.5 mB/L 

Amitriptyline 1 mg/L 

Nortriptyline 4.2 mg/L 

~, ~ Verapamil 2 mg/L 

o 

J '8.~ 10~00 II:00 12"(~ 13~00 1400 1500 160~ 171~ 1800 

TJrne(min) 

Figure 5. Total ion chromatograms of bile, blood, and urine after Twister ex- 

traction. Bile and urine were diluted 1:3 with deionized water. 

[ 

Z'-~E 

i'iiii" 

....... i 

"-'"--I 

.t.l. ~ "~ .I j 

Vilrcom drug scneen 

mM 

Cocaine 1.3 rag/L 

~.', .............................. -- .t~,L 

T~e (rain) 

..... ~ l,idocmne 23 mg/L 

..:--~_;~ 1063 Etomidate not qu~mtilaled 

".-:.=:-i 

. . . . . a ~ 

-_-.._---_: ~.~ ~ 


Figure 6. Total ion chromatograms of vitreous diluted 1:3 with deionized water 

and kidney homogenized 1:4 with deionized water. 

591

. . . . . i 

. . . . . . i 

...... i 

Gastric d~g~reen 

9.81 

10.62 

8.87 I 

, I 1 ,,.,1 , 

~me (rain) 

Diphcnhydr~m/nc 24 n~,/L 

Vcnl~ine 72 mg/L 

Figure 7. Total ion chromatogram of gastric diluted 1:100 and extracted 

with the Twister method. 

References 

1. P. Sandra, E. Baltusssen, F. David, and A. Hoffman, A novel 

592 


extraction technique for aqueous samples: stir bar sorptive 

extraction. Gerstel Application Note. Gerstel, Baltimore, MD, 

2000. 

2. A. Vendenin, V. Suvorkin, and E. Kachur. Stir bar sorptive ex- 

traction-thermal desorption-capillary GC-MS applied for analysis 

of amphetamine derivatives in biological fluids. Interlab, Moscow, 

Russia, 2004. 

3. S. Strano-Rossi, F. Molaioni, and F. Botr~. Application of solid- 

phase microextraction to antidoping analysis: determination of 

stimulants, narcotics, and other classes of substances excreted free 

in urine. J. Anal. Toxicol. 29:217-222 (2005). 

4. V. Kinton and J. Whitecavage. Preliminary screening of drugs in 

bovine serum and water utilizing Twister SBSE and thermal des- 

orption. Gerstel Application GUS-195-EP. Gerstel, Baltimore, 

MD. 

5. E. Pfannkoch, J. Whitecavage, and R. Bramlett. Feasibility of ex- 

traction and quantitation of delta-9-tetrahydrocannabinol in body 

fluids by stir bar sorptive extraction (SBSE) and GC-MS. Gerstel 

Application Note. Gerstel, Baltimore, MD, 2005. 

6. B. Tienpont, F. David, K. Desmet, and P. Sandra. Stir bar sorptive 

extraction-thermal desorption-capillary GC-MS applied to bio- 

logical fluids. Anal. Bioanal. Chem. 373:46-55 (2002).

(TDS) for Detection of Basic Drugs in Forensic Samples by GC-MS

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