Isotopic analogs as internal standards for quantitative analyses by GC/MS--evaluation of cross-contribution to ions designated for the analyte and the isotopic internal standard

Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative analyses of drugs and their metabolites in biological matrices by GC/MS procedures. Contributions of the analyte and the IS to the intensities of ions designated for the IS and the analyte, respectively--an undesirable phenomenon termed "cross-contribution"--greatly weakens the effectiveness of this approach. The cross-contribution phenomenon has been, in the past, evaluated by a "direct measurement" approach, in which intensities of interested ions were measured in two separate experiments using equal quantities of the analyte and the IS. Alternate procedures that may generate improved results are hereby studied. For the "improved direct measurement" approach, ion intensity data derived from the previously reported direct measurement procedure are first normalized before being used to calculate the extent of cross-contribution. An "internal standard" approach is also developed, in which a set amount of a third compound is incorporated into these two separate experiments, thus allowing corrections of ion intensity data that are imbedded with variations inherent to separate experiments. Finally, a "standard addition" approach, involving a series "addition" of "standards", generates multiple data points; thus, providing a mechanism to validate the resulting cross-contribution data. Secobarbital/(2)H(5)-secobarbital and secobarbital/(13)C(4)-secobarbital pairs are adapted as the exemplar systems for this study.     

Isotopic analogs as internal standards for quantitative GC/MS analysis--molecular abundance and retention time difference as interference factors

The following analyte/isotope-labeled internal standard (IS) systems are adapted to further study the interference phenomenon previously reported from our laboratory--the intensity ratio of the ion-pair designated for a specific analyte/2H-analog system increases as the solvent used to reconstitute the extraction/derivatization residue is increased: (a) Three analyte/2H-analog pairs with 2H-atoms positioned at allylic sites (butalbital, secobarbital, methohexital); (b) Two analyte/2H-analog pairs without these structural features (pentobarbital, phenobarbital); and (c) Two analyte/13C-analog pairs (butalbital, secobarbital). Major experimental parameters adapted in this study include: (a) Varying reconstitution solvent volume while keeping a constant analyte/IS concentration ratio; (b) Varying analyte/IS concentration ratio; (c) Varying gas chromatograph (GC) injection port temperature; and (d) Varying GC column temperature programming conditions, rendering difference in the degree of overlap of the peaks derived from the analyte and the 2H-analog. This study results in the following observations: (a) Changes in the intensity ratio of the ion-pair designated for a specific analyte/2H-analog system depend on molecular abundance, regardless of whether the 2H-atoms are positioned at active allylic positions or not--thus, ruling out hydrogen/deuterium exchange as the cause of the observed interference phenomenon; (b) Variations in GC injection port temperature do not alter the observed interference phenomenon-thus, ruling out chemical reactions at the injection port as the underlying cause; (c) Variations in peak-overlapping between the analyte and the 2H-analog, facilitated by changing GC column programming conditions, alter the observed interference phenomenon. Abundance of the analyte and the 2H-analog and their overlapping characteristic in the mass spectrometer ion source are believed to be the underlying cause of the observed interference phenomenon. The interference phenomenon observed for a specific analyte/2H-analog system has significant consequences on the linearity of the thereby generated calibration curves. Nonlinear approaches can better describe the calibration data and are needed more in comparison to systems in which 13C-analogs are used as the ISs.     

Positive identification of the principal component of a white powder as scopolamine by quantitative one-dimensional and two-dimensional NMR techniques

An unidentified white powder collected as evidence in an intelligence investigation was characterized exclusively by nuclear magnetic resonance (NMR) analysis. A small fraction of the powder dissolved in D2O was subjected to a series of one- and two-dimensional techniques which were used to elucidate the molecular structure of the powder's major component and positively identify it as the scopolamine biotoxin. Quantitative one-dimensional experiments identified individual proton and carbon atom sites, and conventional 14N spectroscopy detected a single nitrogen atom site. Heteronuclear single quantum coherence data correlated all protons to their directly bonded carbon atom, and together with the quantitative spectra, were used to determine the number of protons directly bonded to each carbon atom. The presence of a methyl, carboxyl, and a benzyl group was also identified from these data. Correlation spectroscopy detected a three proton and a nine proton JH,H network, representing a CH2CH moiety and seven carbon atom ring, respectively. These five elements were assembled into an almost complete molecular structure by using long-range, J-coupled, 1H-13C pairs detected by heteronuclear multiple bond correlation (HMBC) spectroscopy and 1H-1H dipolar-coupled pairs found from nuclear Overhauser effect spectroscopy (NOESY) data. Additional oxygen atom sites were inferred from 1H-13C correlation intensities in the HMBC spectra along with 1H and 13C chemical shift values, or directly from NOESY correlations. Only a single oxygen atom site could not be inferred from NMR data, but its presence was inferred from comparisons to target analyte structures to complete the structure of the scopolamine molecule. To confirm these results, an ethanol/H2O solution of the powder was analyzed by direct infusion into an ion trap mass spectrometer. A prominent base signal was observed at m/z 304.1 amu, corresponding to the protonated molecular ion of scopolamine. Subsequently, the ion was selected and subjected to collision-induced dissociation, producing characteristic major MS/MS fragments at m/z 138.1 and 156.1. Comparisons of 1H and 13C chemical shift values and JH,H values measured from our NMR data were found to agree very favorably with previously reported values for scopolamine in D2O.     

Mass spectrometric data characteristics of commonly abused amphetamines with sequential derivatization at two active sites

There have been reports on improved chromatographic parameters derived from the incorporation of sequential derivatization in preparing biological specimens for the analysis of opiates. This current study was designed to characterize the mass spectrometric data resulting from sequential derivatizations of commonly abused amphetamines (along with all commercially available deuterated analogs) containing two active sites, i.e., amphetamine, methylenedioxyamphetamine, phenylpropanolamine. The first derivatization groups included in this study were trifluoroacetyl, pentafluoropropionyl, and heptafluorobutyryl, while t-butyldimethylsilyl was used as the second derivatization group. Products resulting from the first step and the two-step derivatization processes were analyzed by GC-MS. Full-scan mass spectrometric data were used to select ions with potential for designating the analytes and their respective isotopically labeled analogs in quantitative analysis protocols. Selected ion monitoring data were then collected and assessed to determine the quality of these ions when one or two different derivatization groups were incorporated in the sample preparation processes. A total of 77 full-scan mass spectra and 8 ion intensity cross-contribution tables, representing various forms of derivatization and isotopic analogs of the three amphetamines, are systematically presented for reference. Evaluations of these data concluded that many, but not all, products derived from "double derivatization" (sequential derivatization with two derivatization groups), generate ions of higher quality than those derived from "single derivatization".     

Positive and negative ion mass spectrometry of tricyclic antidepressants

Positive electron impact (EI), positive chemical ionization (CI), and negative CI mass spectra of eight tricyclic antidepressants are presented. In the positive EI mode, peak(s) at m/z 193 and/or 195, which corresponded to the tricyclic nucleus, appeared for five compounds; a peak at m/z 58 was common to compounds having a gamma-dimethylaminopropyl group as their side chain. Molecular ions appeared for all compounds though they were very small in some compounds in the positive EI mode. In the positive CI mode, [M + H]+ quasi-molecular peaks appeared together with [M + C2H5]+ peaks in five compounds; the ion at m/z 196, which corresponded to the tricyclic nucleus also appeared in five compounds. In the negative CI mode with 1 Torr chamber pressure, [M - 1]- quasi-molecular ions were observed for all compounds except for lofepramine; [M + 43]- anions, which probably corresponded to [M + C3H4]-, appeared in five compounds; strong [M + Cl]- ions appeared in carpipramine and clocapramine. The anions due to the tricyclic nucleus also appeared in this mode. In the negative CI mode at low pressure (0.01 Torr), the spectra were generally similar to those in the 1 Torr negative CI mode. However, the cluster anions never appeared at the low pressure. Some data on extraction for some antidepressants from human urine and plasma, and their separation by gas chromatography, are also presented.     

芬氟拉明和苯丙胺类兴奋剂的固相微萃取

用固相微萃取技术从血中提取芬氟拉明、苯丙胺和甲基苯丙胺。在 70℃条件下用 10 0 μm聚二甲基硅氧烷萃取头吸附 15min。重氢甲基苯丙胺作内标 ,采用柱前衍生化的进样方式 ,气质联用仪测定。选择离子m /z2 6 8(芬氟拉明 )、m/z2 40 (苯丙胺 )、m /z2 5 4(甲基苯丙胺 )和m/z2 5 8(重氢甲基苯丙胺 ,内标 )的峰面积比定量。血中检测浓度可达 0 0 1～ 0 0 3μg/g。通过解剖例中芬氟拉明的实际测定 ,证明这是一个从血液中提取分析苯丙胺类衍生物的快速准确的方法     

Postmortem determination of the biological distribution of sufentanil and midazolam after an acute intoxication

A case is presented of a death caused by self-injection of sufentanil and midazolam. Biological fluids and tissues were analyzed for midazolam by high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS) and for sufentanil by GC/MS. Midazolam was extracted from basified fluids or tissues homogenated with n-butyl chloride and analyzed by HPLC by using a phosphate buffer: acetonitrile (60:40) mobile phase on a mu-Bondapak C18 column at 240 nm. Sufentanil was extracted from basified fluids and tissue homogenates with hexane:ethanol (19:1). GC/MS methodology for both compounds consisted of chromatographic separation on a 15-m by 0.25-mm inside diameter (ID) DB-5 (1.0-micron-thick film) bonded phase fused silica capillary column with helium carrier (29 cm/s) splitless injection at 260 degrees C; column 200 degrees C (0.8 min) 10 degrees C/min to 270 degrees C; and electron ionization and multiple ion detection for midazolam (m/z 310), methaqualone (IS, m/z 235), sufentanil (m/z 289), and fentanyl (IS, m/z 245). Sufentanil concentrations were: blood 1.1 ng/mL, urine 1.3 ng/mL, vitreous humor 1.2 ng/mL, liver 1.75 ng/g, and kidney 5.5 ng/g. Midazolam concentrations were: blood 50 ng/mL, urine 300 ng/mL, liver 930 ng/g, and kidney 290 ng/g. Cause of death was attributed to an acute sufentanil/midazolam intoxication and manner of death a suicide.     

LC-MS/MS分析人全血中五氟利多

目的建立人体全血中五氟利多浓度的液相色谱-质谱联用法（LC-MS/MS）分析方法。方法全血中五氟利多和利培酮（内标）经正己烷液-液提取后,采用Capcell Pak C18色谱柱（250mm×2.0mm5,μm）进行分离,流动相为乙腈：20mmol/L乙酸胺和0.1%甲酸溶液（75∶25,V/V）,流速为0.2mL/min,然后以MS/MS电喷雾正电离的多反应监测扫描方式（MRM）测定。用于定量分析的离子为m/z 524→109（五氟利多）和m/z 411→191（内标）。结果五氟利多的最低检测限为0.2ng/mL,在0.4～400ng/mL浓度范围内线性良好（r=0.9994）,低、中、高浓度（1ng/mL、10ng/mL、100ng/mL）准确度分别为97%,108%和95%,日内和日间RSD均小于15%。结论该方法简便、快速、灵敏,适用于全血中五氟利多浓度的测定。     

Determination of bromadiolone in whole blood by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A rapid, sensitive and selective high-performance liquid chromatography tandem mass spectrometric method (HPLC/MS-MS) has been developed and validated for the determination of bromadiolone in whole blood using warfarin as an internal standard (IS). Bromadiolone was extracted from the whole blood samples by liquid-liquid extraction with ethyl acetate. Multiple-reaction monitoring (MRM) was used to detect bromadiolone and IS, using precursor --> product ion combinations at m/z 527 --> 465 and 307 --> 161, respectively. The calibration curve was linear (r2=0.998) in the concentration range of 0.5-100.0 ng/mL with a lower limit of quantification of 0.5 ng/mL in whole blood. Intra- and inter-day relative standard deviations (R.S.D.s) were less than 7.5 and 11.9%, respectively. Recoveries of bromadiolone ranged from 82.1 to 85.2%. This method is found to be determined trace bromadiolone in whole blood and can be used in the diagnosis of the poisoned human beings.     

Spectroscopic characterization of 3,4-methylenedioxypyrrolidinobutyrophenone: a new designer drug with α-pyrrolidinophenone structure

This study presents and discusses the infrared spectroscopic, the nuclear magnetic resonance spectroscopic and mass spectrometric data of the designer drug 3,4 methylenedioxypyrrolidinobutyrophenone (MDPBP), a homolog of 3,4 methylenedioxypyrovalerone (MDPV). MDPBP was first seized in Germany in the year 2009. The structure elucidation of the aliphatic part of MDPBP was carried out by product ion spectrometry of the immonium ion with m/z=112 formed after electron ionization, and by one- and two-dimensional (1)H- and (13)C NMR spectroscopy.     

Characterization of the explosive triacetone triperoxide and detection by ion mobility spectrometry

The improvised explosive triacetone triperoxide (TATP) was synthesized and characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Raman and infrared (IR) spectroscopy. Triacetone triperoxide was subsequently analyzed by ion mobility spectrometry (IMS) in positive ion mode, and detected as a cluster of three peaks with a drift time of the most intense peak at 13.06 ms. Triacetone triperoxide was then analyzed after dissolution in toluene, where a dramatic increase in peak intensity was observed, at a flight time of 12.56 ms (K0=2.71 cm2V(-1)s(-1)). Triacetone triperoxide was subsequently analyzed by coupling the ion mobility spectrometer to a triple quadrupole mass spectrometer, where a single peak at m/z of 223 atomic mass units identified the species present in the ion mobility spectra as being triacetone triperoxide.     

Positive and negative ion mass spectrometry and rapid isolation with Sep-Pak C18 cartridges of ten local anaesthetics.

The positive ion electron impact (PIEI), positive ion chemical ionization (PICI) and negative ion chemical ionization (NICI) mass spectra and a rapid isolation procedure using Sep-Pak C18 cartridges are presented for ten local anaesthetics. In the PIEI mode, molecular peaks were very small or missing for most compounds. Peaks at m/z 86 due to the diethylaminoethyl or propylaminoethyl group constituted base peaks in six compounds. In the PICI mode, peaks due to M + H and M + C2H5 appeared. The cation at m/z 86 was also observed for the six compounds. This ion seems useful for the screening of local anaesthetics. In the NICI mode, anions at m/z M - H constituted base peaks for all compounds, peaks at m/z M + 12 appeared in many compounds. The total ion current in the PIEI and PICI modes generally gave higher sensitivity than in the NICI mode. Local anaesthetics present in whole blood or cerebrospinal fluid (CSF) could be rapidly isolated by use of Sep-Pak C18 cartridges with chloroform/methanol as an elution solvent. Their detection was possible using wide-bore capillary gas chromatography with SPB-1 and HP-17 wide-bore capillary columns with satisfactory separation from impurities.     

Hair analysis for diphenhydramine after surreptitious administration to a child

Diphenhydramine is one of the first effective antihistamine agents to have been discovered. The compound is also used for its sedative and antiemetic effects. The first case involving repetitive sedation linked to the use of diphenhydramine as a drug-facilitated crime and subsequent impairment of a 9-year-old female victim is reported. Due to the long delay between the alleged crime and clinical examination, collection of blood or urine was of little value. Hence, the laboratory developed an original approach based on hair testing by LC-MS/MS. A single strand of hair from the victim was sampled about 7 weeks after the last suspected administration and was cut into small segments. After cutting into small pieces, about 20 mg of hair per segment was incubated overnight in a phosphate buffer (pH 8.4). The aqueous phase was extracted with 5 ml of a mixture of methylene chloride/diethyl ether (80/20), in presence of diazepam-d5, used as internal standard (IS). The hair extract was separated on an XTerra MS C18 column using a gradient of acetonitrile and formate buffer. Detection was based on two daughter ions: transitions m/z 256.2-152.1 and 167.1 and m/z 289.9-154.0 for diphenhydramine and the IS, respectively. In the hair of the child, diphenhydramine was detected at concentrations in the range 33-39 pg/mg, depending on the segment.     

Detection of amitriptyline, nortriptyline and bromazepam in liver, CSF and hair in the homicidal poisoning of a one-month-old girl autopsied 8 months after death

We reported on the death by poisoning of a one-month-old baby that had followed the death of one of her sister (due to cyamemazine overdose). Exhumation of the corpse was done 8 months after burial and revealed the presence of amitriptyline. Parent drug and its metabolite were analysed by HPLC-MS/MS in positive ionisation mode on a C(18) analytical column using a gradient of acetonitrile and 2mM formate buffer at pH=3. Quantification is based on the main ion m/z=233, the common product ion of nortriptyline (MH(+), m/z 264), amitriptyline (MH(+), m/z 278) and nortriptyline D3 used as internal standard (MH(+), m/z 267). Amitriptyline and nortriptyline in the liver were measured at a concentration of 29.8 and 3.6 μg/g, respectively. Hair analyses revealed the presence of amitriptyline and nortriptyline at concentrations of 1811 and 43 pg/mg, respectively, while complementary analyses showed the presence of bromazepam in the hair at a concentration of 740 pg/mg, thus documenting previous administrations. The mother confessed later having used the drinkable form of the pharmaceutical LAROXYL(?) by pouring the content of a 20 ml bottle (at 40 mg/ml) into the feeding-bottle of her child. The milk was sweet but still bitter and following the testimony of a close relative, the whole family helped to feed the crying baby.     

Instability of pancuronium in postmortem blood and liver taken after a fatal intramuscular Pavulon injection

The present study was designed to determine the stability of pancuronium in postmortem blood and liver during storage. Results were obtained using the method by Kerskes et al. [C.H.M. Kerskes, K.J. Lusthof, P.G.M. Zweipfenning, J.P. Franke, The detection and identification of quaternary nitrogen muscle relaxants in biological fluids and tissues by ion-trap LC-ESI-MS, J. Anal. Toxicol. 26 (2002) 29-34.], modified and validated in our laboratory. Target analytes were isolated after enzymatic hydrolysis followed by solid phase extraction (BondElut C18 column). Internal standardisation was carried out using laudanosine and the target ions were monitored by LC-ESI-MS (monitoring ions m/z 358 for IS and 286 for pancuronium). Materials were taken from a 46-year-old woman, who had been found dead. A syringe (2 ml) and an empty ampoule of Pavulon (4 mg/2 mL) were found in her hand. The residual volume of fluid in the syringe was 0.7 ml. An autopsy was performed six days after death. It revealed a needle mark on the left thigh. Postmortem materials (muscle from the injection site, blood and liver) and the syringe with fluid were stored for four months in a freezer at -20 degrees C. The initial pancuronium concentrations were 81 ng/mL in blood and 532 ng/g in liver. The analyte was stable when stored at -20 degrees C in blood even up to seven months. In liver samples its concentrations were variable. Pancuronium in blood stored at 20 degrees C underwent degradation very rapidly. After three months of storage these blood samples had concentrations not greater about 10% of the initial value. The degradation patterns of pancuronium depended on temperature and the biological matrix.     

Evaluation of nicotine and cotinine in human hair.

To validate data on tobacco use, the authors investigated the use of hair samples for quantifying nicotine and cotinine by gas chromatography/mass spectrometry. Hair was taken from 22 nonsmokers and 42 smokers, cut close to the scalp at the back of the head. The hair (about 100 mg from each subject) was incubated in 3 mL of 1N NaOH at 100 degrees C for 1 h. After this, the samples were extracted by diethyl ether. The drugs were separated on a 12-m BP-5 capillary column and detected using selected ion monitoring (nicotine, m/z 84; cotinine, m/z 98). Hair from nonsmokers and smokers contains nicotine and cotinine. Although it is difficult to determine an absolute cutoff level, an amount greater than 2 ng of nicotine per milligram of hair can be used to differentiate smokers from nonsmokers. In the population of nonsmokers, the influence of environmental smoke exposure was noted.     

GC-MS检测新型策划毒品K3

目的基于气相色谱-质谱（GC-MS）检测结合特殊质谱库信息检索建立新型策划毒品的鉴定方法。方法未知样品用甲醇超声溶解,吸取上清液采用气相色谱-质谱（GC-MS）联用仪检测。结果测得A组分（t R=19.47min）的质谱特征碎片峰（m/z）信息为215.1（基峰）、144.9、294.1、337.1和365.1,B组分（tR=23.29min）的质谱特征碎片峰（m/z）信息为359.1（基峰）、127.1、144.0、155.0、232.1、284.1和342.0。经美国缉毒署毒品分析谱库检索获得的信息资料,鉴定为新型策划毒品＂K3＂,其主要组分为＂AKB48＂和＂AM2201＂,此类化合物具有大麻类似精神活性,归属合成大麻素。结论本方法可用于新型策划毒品组分的鉴定。     

A fatality involving secobarbital, nitrazepam, and codeine

A fatal case involving the suicidal ingestion of secobarbital, nitrazepam, and codeine is presented. The drugs were quantified using gas chromatography for codeine and high-performance liquid chromatography for the two other drugs. The blood concentrations of secobarbital, nitrazepam, and codeine were found to be 11.48, 1.72, and 0.036 microgram/ml, respectively. Results are discussed in the light of the existing literature.     

Screening and quantification of antipsychotic drugs in human brain tissue by liquid chromatography-tandem mass spectrometry: application to postmortem diagnostics of forensic interest

A quantitative LC-MS/MS method has been developed for the simultaneous determination of 17 antipsychotic drugs in human postmortem brain tissue. Sample preparation was performed using Hybrid Solid Phase Extraction-Precipitation technology for the removal of endogenous protein and phospholipid interferences. The chromatographic separation was performed for 16 min on a C8 column, which used a gradient elution of formate ammonium and acetonitrile, and a flow rate gradient. Triple quadrupole mass spectrometry was employed to generate tandem mass spectrometric (MS/MS) data of the target analytes to select the ion m/z signals. Quantitation of the analytes was performed by operating in the dynamic multiple reaction monitoring (dMRM) mode using an electrospray ionization interface. Calibration curves prepared in the spiked brain tissue were linear in the range 20-8000 ng/g (r(2)>0.993) for all drugs (except olanzapine). Within- and between-day coefficients of variation were lower than 25% for all drugs at the LOQ. The LOQ in the matrix ranged between 2 ng/g and 80 ng/g. The method was successfully applied to the unequivocal identification and accurate quantification of antipsychotic drugs in human postmortem brain tissues: therefore, this method can be used in forensic investigations.     

Mass, NMR and IR spectroscopic characterization of pentedrone and pentylone and identification of their isocathinone by-products

This study presents and discusses the mass spectrometric, nuclear magnetic resonance spectroscopic and infrared spectroscopic data of the designer drugs pentedrone (2-methylamino-1-phenylpentan-1-one) and its methylenedioxy analog pentylone (2-methylamino-1-(3,4-methylenedioxyphenyl)pentan-1-one). The structure elucidation of the aliphatic parts was carried out by product ion spectroscopy of the immonium ion with m/z=86 formed after electron ionization, and by one- and two-dimensional (1)H- and (13)C-NMR spectroscopy on the hydrochloride salts to verify the structure of the alkyl side chain and to determine the methylenedioxy position in the aromatic ring of pentylone. Furthermore, two typical cathinone synthesis by-products were detected besides the main compounds. Their mass spectra are discussed and for one of them (1-methylamino-1-phenylpentan-2-one (isopentedrone)) a NMR assignment was possible in the existing mixture.