Simultaneous screening and quantitation of 18 antihistamine drugs in blood by liquid chromatography ionspray tandem mass spectrometry

Bioavailability assessment of a brompheniramine taste-masked pediatric formulation in a juvenile porcine model

A brompheniramine taste-masked pediatric formulation was developed as part of the National Institutes of Health Pediatric Formulation Initiative to help address low patient compliance caused by the bitter taste of many adult formulations. To confirm that the taste-masked formulation can provide a similar pharmacological effect to the previous marketed adult formulations, a juvenile porcine model was used to screen the model pediatric formulation to compare the bioavailability between the marketed brompheniramine maleate and the taste-masked maleate/tannate formulation. Pigs were dosed orally with both formulations and blood samples were obtained from 0 to 48 h. Plasma samples were prepared and extracted using solid-phase extraction. The mass spectrometer was operated under selected ion monitoring mode. The selected ion monitoring channels were set to m/z 319.1 for brompheniramine and m/z 275.2 for the internal standard chlorpheniramine. Calibration curves were linear over the analytical range 0.2-20 ng/ml (r2 > 0.995) for brompheniramine in plasma. The intra- and inter-day accuracies were between 98.0 and 105% with 5.73% RSD precision. The bioanalytical method was successfully applied to a preclinical bioavailability study. The bioavailability profiles were not significantly different between the two formulations, which demonstrates that taste-masking with tannic acid is a promising approach for formulation modification for pediatric patients.

Microliquid/Liquid Interfacial Sensors: Biomimetic Investigation of Transmembrane Mechanisms and Real-Time Determinations of Clemastine, Cyproheptadine, Epinastine, Cetirizine, and Desloratadine

Antihistamines relieve allergic symptoms by inhibiting the action of histamine. Further understanding of antihistamine transmembrane mechanisms and optimizing the selectivity and real-time monitoring capabilities of drug sensors is necessary. In this study, a micrometer liquid/liquid (L/L) interfacial sensor has served as a biomimetic membrane to investigate the mechanism of interfacial transfer of five antihistamines, i.e., clemastine (CLE), cyproheptadine (CYP), epinastine (EPI), desloratadine (DSL), and cetirizine (CET), and realize the real-time determinations. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques have been used to uncover the electrochemical transfer behavior of the five antihistamines at the L/L interface. Additionally, finite element simulations (FEMs) have been employed to reveal the thermodynamics and kinetics of the process. Visualization of antihistamine partitioning in two phases at different pH values can be realized by ion partition diagrams (IPDs). The IPDs also reveal the transfer mechanism at the L/L interface and provide effective lipophilicity at different pH values. Real-time determinations of these antihistamines have been achieved through potentiostatic chronoamperometry (I-t), exhibiting good selectivity with the addition of nine common organic or inorganic compounds in living organisms and revealing the potential for in vivo pharmacokinetics. Besides providing a satisfactory surrogate for studying the transmembrane mechanism of antihistamines, this work also sheds light on micro- and nano L/L interfacial sensors for in vivo analysis of pharmacokinetics at a single-cell or single-organelle level.

Magnetic Solid-Phase Extraction of Drugs and Pesticides from Human Plasma Using COOH-mMWCNTs

Carbon nanotubes (CNTs) are useful for extracting chemical compounds due to their properties, such as surface area and the potential for chemical modification. Especially the formation of CNTs with carboxylic acid functional group makes them disperse in water-based samples and have strong interaction forces with cationizable analytes. Based on these features, carboxylic acid functionalized multi-walled CNTs (COOH-MWCNTs) have been used as extraction sorbents. CNT can also be gathered using an external magnet by forming complex with iron oxide (Fe3O4) magnetic nanoparticles (MNPs). In this study, COOH-MWCNTs with MNPs were subjected to magnetic solid-phase extraction (mSPE) in order to extract the targeted substances such as diphenhydramine, doxylamine, tramadol, escitalopram, zolpidem, diphenamid, paclobutrazol, hexaconazole, cyproconazole and mepronil from human plasma samples. The following five factors were optimized: (i) the ratio of COOH-MWCNTs to MNPs as a sorbent from 1:1 to 1:4; (ii) sorbent amount starting from 12.5 to 75%; (iii) sample pH tested pH 2 to pH 10 with 1 N hydrochloride and 1 N sodium hydroxide; (iv) agitating time from 0 to 4 min and (v) elution solvent. Limit of detection of 10 targeted substances in human plasma were in the range of 0.1-0.4 mg/L. The recovery of targeted substances (except diphenamid) in human plasma was 73.06-110.28% for intra-day and 83.00-107.70% for inter-day and the precision (relative standard deviation, %) in human plasma was 0.3-13.3% for intra-day and 2.9-15.6% for inter-day. The method was applied to nine authentic biological samples from overdose patients in the emergency room of Chungnam National University Hospital. The performance of mSPE was compared with the liquid-liquid extraction method using ethyl acetate. The results showed that the newly developed method in this study can be used for screening analysis in forensic and clinical toxicology.

Collision-induced dissociation pathways of H1-antihistamines by electrospray ionization quadrupole time-of-flight mass spectrometry

Over the past decades, mass spectrometry technologies have been developed to obtain mass accuracies of one ppm or less. Of the newly developed technologies, quadrupole time-of-flight mass spectrometry (Q-TOF-MS) has emerged as being well suited to routine and high-throughput analyses of pharmaceuticals. Dietary supplements and functional foods have frequently been found to be contaminated with pharmaceuticals. In our continuous efforts to develop methodologies to protect public health against adulterated dietary supplements, we have constructed a mass spectral database for 21 H₁-antihistamines encountered as adulterants by using liquid chromatography-electrospray ionization (LC-ESI)/Q-TOF-MS, and have proposed their possible collision-induced dissociation pathways. This database will be very useful for the rapid and accurate detection of H₁-antihistamines (known) and their analogues (unknown) illegally added to dietary supplements as well as in other sample matrices.

Development and validation of an ultra-performance liquid chromatography method for simultaneous analysis of 20 antihistaminics in dietary supplements

The purpose of this study was to develop and validate an ultra-performance liquid chromatography method for simultaneous analysis of 20 antihistamines (illegal additives) in dietary supplements. The limits of detection and quantitation of the method ranged from 1.5 to 2.5 µg/mL and from 20.0 to 50.0 µg/mL, respectively. The determination coefficient was >0.999, precisions were 0.2-5.1% (intra-day) and 0.1-8.8% (inter-day), and accuracies were 84.5-111.2% (intra-day) and 91.9-112.0% (inter-day). The mean recoveries of 20 targeted compounds from dietary supplements ranged from 75.4 to 119.3%. The relative standard deviations were <6.6% and complied with established international guidelines. The relative standard deviation of stability was <0.8%. Fifty-two commercially available dietary supplements were evaluated using this method, and were found to have none of the 20 antihistamines in significant abundance.

Second-generation antihistamines exhibit a protective effect on drivers in traffic-a preliminary population-based case-control study

INTRODUCTION

Although there have been experimental studies concerning driving and drugs, studies on the risk of antihistamines are not numerous. This is the first population-based epidemiological study concerning the association of sedating/nonsedating antihistamines and fatal traffic accidents.

METHODS

Car drivers (n = 428) who died in accidents before reaching the hospital and controls (n = 688) matched for accident area and driving season were studied for antihistamines in blood. At the time of the fatal road traffic accident, 6 drivers had a detectable amount of sedating antihistamines in blood, and the corresponding number for controls was 4; nonsedating antihistamines in blood were detected in 12 accident cases and 28 controls. The fatal accidents occurred between 1998 and 2002 and the information on the controls was collected between 2000 and 2002 in Finland.

RESULTS

Regarding fatal traffic accident causality, the nonsedating antihistamines proved to have a protective effect after adjusting for age and gender (relative risk = 0.40, 95% confidence interval [CI], 0.20 to 0.82; P =.01). The risk of fatal traffic accident of those driving under the influence of sedating antihistamines was 1.61 (0.38 to 6.77, P =.51) times the risk of those without medication.

DISCUSSION

This preliminary study supports the protective effect of second-generation antihistamines with respect to fatal traffic accidents. Due to the small sample size the results are not conclusive.

Qualitative confirmation of 9 synthetic cannabinoids and 20 metabolites in human urine using LC-MS/MS and library search

INTRODUCTION

Synthetic cannabinoids are an emerging illicit drug class. The variety of available substances is large and ever-changing, making it difficult for laboratories to remain current. We present a qualitative LC-MS/MS method identifying urinary metabolites of JWH-018, JWH-073, JWH-081, JWH-122, JWH-200, JWH-210, JWH-250, RCS-4, and AM2201 and the parent compounds JWH-018, JWH-073, JWH-081, JWH-122, JWH-210, JWH-250, RCS-4, AM2201, and MAM2201.

METHODS

After enzymatic hydrolysis, urinary proteins were precipitated with acetonitrile. Chromatography utilized a 10 min gradient on a Kinetex XB-C18 column with 0.1% formic acid in water and acetonitrile. Scheduled multiple reaction monitoring "survey scans" were followed by information-dependent acquisition-enhanced product ion scan experiments on an ABSciex 5500 QTRAP mass spectrometer. Analytes were identified by software-assisted library searching against reference spectra.

RESULTS

The method was fully validated, including proof of selectivity (no exogenous or endogenous interferences were observed), assessment of matrix effects (95-122%) and recovery (53-95%), determination of limits of detection (0.5-10 ng/mL), carry-over studies (thresholds between 100 and 1000 ng/mL), and determination of autosampler stability (samples were stable for at least 3 days). Hydrolysis efficiency was thoroughly investigated for a wide range of glucuronides and for the reference standard, JWH-018 5-hydroxypentyl glucuronide.

Development and validation of a methodology to qualitatively screening veterinary drugs in porcine muscle via an innovative extraction/clean-up procedure and LC-MS/MS analysis

A qualitative multiresidue method that facilitates rapid monitoring of veterinary drugs in porcine muscle is described. The method comprises the application of an innovative extraction/clean-up procedure, namely liquid-liquid extraction with partition at very low temperature (LLE-FPVLT), and analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Besides the high selectivity, sensitivity and specificity, this high-throughput method proved to be quite general as 34 veterinary drugs (from six distinct classes: tetracyclines, sulfonamides, penicillins, quinolones, macrolides and benzimidazoles) could be successfully detected. The whole screening procedure was validated according to the directives from European Commission Decision 2002/657/EC and guidelines for the validation of screening methods. Acceptable values for the evaluation parameters were achieved for all analytes (except for ampicillin, clindamycin and erythromycin). Finally, these very promising results have strengthened the possibility of inclusion of such a methodology as an integral part of the National Residue Control Plan scope of the Ministry of Agriculture, Livestock and Food Supply of Brazil.

Fragmentation of toxicologically relevant drugs in positive-ion liquid chromatography-tandem mass spectrometry

The identification of drugs and related compounds by LC-MS-MS is an important analytical challenge in several application areas, including clinical and forensic toxicology, doping control analysis, and environmental analysis. Although target-compound based analytical strategies are most frequently applied, at some point the information content of the MS-MS spectra becomes relevant. In this article, the positive-ion MS-MS spectra of a wide variety of drugs and related substances are discussed. Starting point was an MS-MS mass spectral library of toxicologically relevant compounds, available on the internet. The positive-ion MS-MS spectra of ∼570 compounds were interpreted by chemical and therapeutic class, thus involving a wide variety of drug compound classes, such benzodiazepines, beta-blockers, angiotensin-converting enzyme inhibitors, phenothiazines, dihydropyridine calcium channel blockers, diuretics, local anesthetics, vasodilators, as well as various subclasses of anti-diabetic, antidepressant, analgesic, and antihistaminic drugs. In addition, the scientific literature was searched for available MS-MS data of these compound classes and the interpretation thereof. The results of this elaborate study are presented in this article. For each individual compound class, the emphasis is on class-specific fragmentation, as discussing fragmentation of all individual compounds would take far too much space. The recognition of class-specific fragmentation may be quite informative in determining the compound class of a specific unknown, which may further help in the identification. In addition, knowledge on (class-specific) fragmentation may further help in the optimization of the selectivity in targeted analytical approaches of compounds of one particular class.

A multi-target screening analysis in human plasma using fast liquid chromatography-hybrid tandem mass spectrometry (Part I)

OBJECTIVES

Evaluate a new LC-MS/MS screening method for drugs and drugs of abuse as an alternative to the existing methods used in clinical toxicology laboratories.

DESIGN AND METHODS

The work was divided in two parts. The first part was dedicated to the technical development and evaluation of the method for which a set of 97 drugs and relevant metabolites was used to perform a complete investigation of matrix effects and lower limit of identification (LOI). The second part was a comparison of identified drugs between LC-MS/MS and Remedi® instrument on clinical serum samples.

RESULTS

The method offers good performance allowing an automatic peak detection and compound identification. The limit of identification is equivalent to 50 μg/L for the majority of the studied compounds. The process efficiency (PE) is higher than 70% for 65% of the evaluated compounds. Thus, a sufficient detection capability in terms of limit of detection for identification and PE satisfied the expected performance.

CONCLUSION

The described methodology allows the identification of the main drugs incriminated in intoxications within a quite short analysis time. The separation of most of the analytes is performed in 15 min. The procedure is sufficiently sensitive and selective.

Simple analytical method for determination of pesticide residues in human serum by liquid chromatography tandem mass spectrometry

The aim of this study was to develop an analytical method for the determination of residues of organophosphorus and carbamate pesticides which are widely used in Tunisia. This method involves a liquid-liquid extraction procedure followed by liquid chromatography tandem mass spectrometry (LC/MS/MS) for the identification and quantification of compounds. Ionization of molecules was performed by the electrospray mode. Multiple reactions monitoring (MRM) was the acquisition mode used for the monitoring of two MS/MS transitions for each compound. The average recoveries obtained, at three different fortification levels, ranged between 65% and 106% for most of the pesticides studied, except for methamidophos (lower than 25%).The linearity of the method was in the range of 5 to 50 micro g/L with a correlation coefficient from 0.995 to 0.999, depending on the analyte. The estimated limit of detection and limit of quantification were 2 micro g/L and 5 micro g/L, respectively. The precision of the analytical procedure was satisfactory and the coefficients of variation, evaluated at three concentration levels were lower than 15% for most pesticides studied. The application of the method was investigated in a population of agricultural workers chronically exposed to various pesticides some of which, such as carbofuran, carbendazim, methomyl and pirimicarb, were detected in some serum samples.

Forensic chemistry

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

Alternative and improved method for the simultaneous determination of fexofenadine and pseudoephedrine in their combined tablet formulation

An alternative method for the determination of fexofenadine (FEX) and pseudoephedrine (PSE) in their combined tablet formulation has been developed, employing the partial least squares (PLS) analysis of spectral data of the analytes in their pharmaceutical association. A full-factorially designed set of 16 synthetic samples was employed for calibration purposes. The calibration models were constructed with wavelengths selection, in the ultraviolet region, according to their predictive ability. These were validated internally by the leave-one-out procedure and externally, employing appropriate sets of validation samples. The described method was linear for both analytes, over the range 160.6-301.2 mg L(-1) for FEX (R(2)=0.9993) and between 325.6 and 610.5 mg L(-1) for PSE (R(2)=0.9992). It was accurate, exhibiting 99.8% and 99.9% drug recoveries for FEX and PSE, respectively (N=9), while in the intermediate precision experiment relative standard deviations were 1.4% for FEX and 1.2% for PSE. The contents of both analytes were assayed in commercial tablets employing this method and the results were compared with those furnished by HPLC, being in good statistical agreement. The method represents an improvement over the first derivative of spectral ratio (DSR) technique and allows high sample throughput with minimum reagent consumption and waste generation. The obtained results confirm that the method is highly suitable for its intended purpose.

Utility of NBD-Cl for the spectrophotometric determination of some skeletal muscle relaxant and antihistaminic drugs

A simple, accurate, precise and sensitive colorimetric method for the determination of some skeletal muscle relaxant drugs, namely orphenadrine citrate (I), baclofen (II), antihistaminic drugs as acrivastine (III) and fexofenadine hydrochloride (IV) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in non-aqueous medium. The orange color products were measured at 472, 465, 475 and 469 nm for drugs I, II, III and IV, respectively. The optimization of various experimental conditions was described. Beer's Law was obeyed in the range (2.5-17.5), (5-70), (2.5-25) and (10-50)microg/ml for drugs I, II, III and IV, respectively. The molar absorptivity (epsilon), sandell sensitivity, detection((LOD)) and quantitation limits((LOQ)) are calculated. The procedure was favorably applied for determination of certain pharmaceutical dosage forms containing the studied drugs. The obtained results were compared with the official and reported methods. There were no significant differences between proposed, reported and the official methods.

High throughput screening of sub-ppb levels of basic drugs in equine plasma by liquid chromatography–tandem mass spectrometry

This paper describes a high throughput LC-MS-MS method for the screening of 75 basic drugs in equine plasma at sub-ppb levels. The test scope covers diversified classes of drugs including some alpha- and beta-blockers, alpha- and beta-agonists, antihypotensives, antihypertensives, analgesics, antiarrhythmics, antidepressants, antidiabetics, antipsychotics, antiulcers, anxiolytics, bronchodilators, CNS stimulants, decongestants, sedatives, tranquilizers and vasodilators. A plasma sample was first deproteinated by addition of trichloroacetic acid. Basic drugs were then extracted by solid-phase extraction (SPE) using a Bond Elut Certify cartridge, and analysed by LC-MS-MS in positive electrospray ionization (+ESI) and multiple reaction monitoring (MRM) mode. Liquid chromatography was performed using a short C(8) column (3.3 cm L x 2.1mm ID with 3 microm particles) to provide fast analysis time. The overall instrument turnaround time was 8 min, inclusive of post-run and equilibration time. No interference from the matrices at the expected retention times of the targeted masses was observed. Over 60% of the drugs studied gave limits of detection (LoD) at or below 25 pg/mL, with some LoDs reaching down to 0.5 pg/mL. The inter-day precision for the relative retention times ranged from 0.01 to 0.54%, and that for the relative peak area ratios (relative to the internal standard) ranged from 4 to 37%. The results indicated that the method has acceptable precision to be used on a day-to-day basis for qualitative identification.

Development and full validation of a sensitive quantitative assay for the determination of clemastine in human plasma by liquid chromatography-tandem mass spectrometry

A sensitive high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was developed and validated for the determination of clemastine in human plasma. After having been extracted from plasma samples by ethyl acetate, clemastine and internal standard, diphenhydramine, were separated on a C(18) column. Detection was performed on Thermo Finnigan TSQ Quantum triple quadrupole mass spectrometer by selected reaction monitoring (SRM) mode via electrospray ionization (ESI) source. The method was linear in the concentration range of 5.0-1000.0 pg/ml for clemastine. The intra- and inter-day precisions were within 13.4% and the deviations were between -1.1% and 5.6%. The fully validated LC/ESI-MS/MS method has been successfully applied to the preliminary pharmacokinetic study in healthy male Chinese volunteers.

Requirements for bioanalytical procedures in postmortem toxicology

The application of analytical techniques in postmortem toxicology is often more difficult than in other forms of forensic toxicology owing to the variable and often degraded nature of the specimens and the diverse range of specimens available for analysis. Consequently, analysts must ensure that all methods are fully validated for the particular postmortem specimen(s) used. Collection of specimens must be standardized to minimize site-to-site variability and should if available include a peripheral blood sample and at least one other specimen. Urine and vitreous humor are good specimens to complement blood. In some circumstances solid tissues such as liver are recommended as well as gastric contents. Substance-screening techniques are the most important element since they will determine the range of substances that were targeted in the investigation and provide initial indication of the possible role of substances in the death. While immunoassay techniques are still commonly used for the most common drugs-of-abuse, chromatographic screening methods are required for general unknown testing. These are still predominately gas chromatography (GC) based using nitrogen/phosphorous detection and/or mass spectrometry (MS) detection, although some laboratories are now using time-of-flight MS or liquid chromatography (LC)-MS(MS) to cover a sometimes more limited range of substances. It is recommended that laboratories include a second chromatographic method to provide coverage of acidic and other substances not readily covered by a GC-based screen when extracts do not include all physiochemical types. This may include a gradient high-performance liquid chromatography (HPLC) photodiode array method, or better LC-MS(MS). Substance-specific techniques (e.g., benzodiazepines, opiates) providing a second form of identification (confirmation) are now divided between GC-MS(MS) and LC-MS(MS) procedures. LC-MS(MS) has taken over from many methods for the more polar compounds previously used in HPLC or in GC methods requiring derivatization. Analysts using LC-MS will need to obtain clean extracts to avoid poor and variable sensitivity caused by background suppression of the signal. Isolation techniques in postmortem toxicology tend to favor liquid extraction; however solid-phase extraction and solid-phase microextraction methods are available for many analytes.

Blood levels of 3-methylfentanyl in 3 fatal poisoning cases

Three fatal poisoning cases due to 3-methylfentanyl are described. In each case, the death was accidental and occurred after injection of the opioid combined with amphetamine, heroin, or other drugs. The victims' ages, ranging from 30 to 41 years, were higher than those typically found in heroin poisonings in Finland. The blood concentrations of cis-3-methylfentanyl, measured here for the first time by a specific tandem mass spectrometric method, ranged from 0.3 to 0.9 microg/L (mean 0.5 microg/L). These values are significantly lower than the levels reported for alpha-methylfentanyl and fentanyl in fatal poisonings. Repeated seizures of fentanyl and its analogs have been reported in Europe close to the Russian border.

Precolumn fluorescence labeling method for simultaneous determination of hydroxyzine and cetirizine in human serum

A highly selective and sensitive method was developed for simultaneous determination of the antihistaminic drug hydroxyzine (HZ) and its pharmacologically active metabolite cetirizine (CZ) in human serum using haloperidol as internal standard. The method was based on fluorescence labeling of both drugs with a fluorescent arylboronic acid 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl boronic acid followed by separation on silica column using a mobile phase consisting of acetonitrile and water (90:10, v/v%) containing triethylamine and acetic acid. The labeling reaction conditions were optimized and the liquid-liquid extraction method was successfully applied to extract the both drugs from serum. The linearity range was 0.025-2.00 microg/mL for HZ and CZ. The limit of detection (S/N = 3) was 10 and 5 ng/mL for HZ and CZ, respectively.

Comparison of HPLC and CE methods for the determination of cetirizine dihydrochloride in human plasma samples

Two methods, capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC), for analysis of cetirizine dihydrochloride in small sample volumes of human plasma were compared. The CE and HPLC assays were developed and validated by analyzing a series of plasma samples containing cetirizine dihydrochloride in different concentrations using these two methods. The extraction procedure is simple and no complicated purification steps or derivatization are required. The analysis time in the HPLC method was shorter than that in the CE method, but solvent consumption was considerably lower in the CE method. The calibration curve was linear to at least 10-1000 ng/mL both for CE and HPLC with r(2) = 0.9993 and r(2) = 0.9994, respectively. The detection limits for cetirizine dihydrochloride were 3 and 5 ng/mL with CE and HPLC (a UV detector was applied in the both cases), respectively. Both methods were selective, robust and specific, allowing reliable quantification of cetirizine dihydrochloride, and could be useful for clinical and biomedical investigations.

Chiral separation of cetirizine by capillary electrophoresis

Chiral separation of cetirizine, a second-generation H(1)-antagonist, was studied by CD-mediated CE. Several parameters, including pH, CD type, buffer concentration, type of co-ion, applied voltage and temperature, were investigated. The best conditions for chiral separation were obtained using a 75 mM triethanolamine-phosphate buffer (pH 2.5) containing 0.4 mg/mL heptakis(2,3-diacetyl-6-sulfato)-beta-CD and 10% ACN. Online UV detection was performed at 214 nm, a voltage of 20 kV was applied and the capillary was temperature controlled at 25 degrees C by liquid cooling. Hydrodynamic injection was performed for 1 s. The method was validated for the quantification of levocetirizine in tablets and for enantiomeric purity testing of the drug substance. Selectivity, linearity, LOD and LOQ, precision and accuracy were evaluated for both methods. The amount of levocetirizine dihydrochloride in the commercially available tablets was quantified and was found to be within the specification limits of the claimed amount (5 mg). The amount of distomer in levocetirizine drug substance was found to be 0.87 +/- 0.09% w/w, which is in agreement with the certificate of analysis supplied by the company.

Optimization by factorial design of a capillary zone electrophoresis method for the simultaneous separation of antihistamines

A 3(2) full factorial design was used to optimize the experimental conditions of a capillary zone electrophoresis method aimed at achieving simultaneous separation and quantification of the antihistamines brompheniramine, chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, hydroxyzine, and loratadine according to their therapeutic group. A statistical program, SPSS, was used to calculate the mathematical model with which to obtain the response surface. Critical parameters such as pH and applied voltage were studied to evaluate their effect on resolution and on efficiency. Optimum separation conditions were phosphate buffer pH 2.0, 5kV, and 2psis(-1) at 214nm. The analysis time was below 9min and the theoretical plates were between 6000 and 63,000N. Calibration curves were prepared for the antihistamines. The limits of detection were 4-14ngmL(-1), which allow their quantification in pharmaceuticals. The RSD% of each antihistamine was fairly good. Up to seven antihistamines belonging to the antihistaminic H(1)-receptor group were separated in the same electropherogram. The proposed method was then applied to the determination of antihistamines in pharmaceutical, urine, and serum samples with recoveries in agreement with the stated contents.

Simultaneous determination of ten antihistamine drugs in human plasma using pipette tip solid-phase extraction and gas chromatography/mass spectrometry

Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18- bonded monolithic silica gel was fixed. Human plasma (0.1 mL) containing the ten antihistamines was mixed with 0.4 mL of distilled water and 25 microL of a 1 M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30 m x 0.32 mm i.d., film thickness 0.25 microm). The recoveries of the ten antihistamines spiked into plasma were 73.8-105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02-5.0 ng/0.1 mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented.

Capillary electrochromatography with a neutral monolithic column for classification of analytes and determination of basic drugs in human serum

Capillary electrochromatography (CEC) using a neutral hydrophobic polymer-based monolithic column has been developed for classification of analytes based on their acidity and charges of group. The monolithic columns were prepared by in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate without any charged monomers in the reaction mixture. The ionic analytes will only be driven by their electrophoretic mobilities and were separated on the basis of their differences in electrophoretic mobility and in hydrophobic interaction with the stationary phase. Only negatively or positively charged analyte (acid or basic) migrated toward detection window in a single run by applying negative or positive voltage. The CEC system was also applied for the analysis of basic drugs in human serum by internal standard method using acidic running buffer. The sample of human serum spiked with basic drugs was directly injected after a simple sample pretreatment. The calibration curves with regression coefficients (0.9995-0.9997) in the range of 0.318-80 microg/mL were obtained with the limits of detection being below 0.15 microg/mL. The intra- and inter-day precisions, determined as relative standard deviations, were less than 4.21%.

Multi-analyte procedures for screening for and quantification of drugs in blood, plasma, or serum by liquid chromatography-single stage or tandem mass spectrometry (LC-MS or LC-MS/MS) relevant to clinical and forensic toxicology

This paper reviews multi-analyte procedures for screening and quantification of drugs in blood, plasma, or serum using liquid chromatography coupled with a single stage or tandem mass spectrometer (LC-MS, LC-MS/MS). These procedures are relevant tools in clinical and forensic toxicology, and cover analysis of amphetamines, cocaine, hallucinogens, opioids, anesthetics, hypnotics, benzodiazepines, antidepressants, neuroleptics, antihistamines, sulfonylurea-type antidiabetics, beta-blockers, and other cardiac drugs. Basic information on the procedures is given in two tables and multi-analyte screening, identification, and quantification are illustrated in three figures. A critical discussion on the pros and cons of such LC-MS procedures is also included.

High-performance liquid chromatographic-tandem mass spectrometric method for the determination of clemastine in human plasma

A highly sensitive high-performance liquid chromatographic-tandem mass spectrometric method (HPLC-MS-MS) has been developed to quantitate clemastine in human plasma for the purpose of pharmacokinetic studies. Sample preparation was carried out by liquid-liquid extraction using deuterated clemastine as an internal standard. Chromatographic separation used a C18 reversed phase polymer column giving an extremely fast total run time of 2 min. The method was validated and used for the bioequivalence study of clemastine tablets in healthy male volunteers (n=28). The lower limit of detection proved to be 0.01 ng/ml for clemastine.

Development of a multi-target screening analysis for 301 drugs using a QTrap liquid chromatography/tandem mass spectrometry system and automated library searching

A new multi-target screening (MTS) procedure for drugs in blood and urine for toxicological analysis has been developed using a hybrid triple-quadrupole linear ion trap mass spectrometer (QTrap) for the fast detection and identification of 301 forensically important drugs, e.g. tranquilizers (benzodiazepines), hypnotics, drugs of abuse (opiates, cocaine, amphetamines, cannabinoids), antidepressants, neuroleptics, and some cardiac drugs, in one single liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. Samples were extracted either with liquid-liquid extraction or solid-phase extraction. A multiple reaction monitoring (MRM) as survey scan and an enhanced product ion (EPI) scan as dependent scan were performed in an information-dependent acquisition (IDA) experiment. Finally, drug identification was carried out by library search with a newly developed MS/MS library based on EPI spectra at three different collision energies in positive mode. The advantage of this newly developed method is the possibility to detect and identify 301 drugs in one single LC/MS/MS run.

Automated 96-well solid phase extraction and hydrophilic interaction liquid chromatography–tandem mass spectrometric method for the analysis of cetirizine (ZYRTEC®) in human plasma—with emphasis on method ruggedness

A high-throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) analysis, has been developed for the determination of cetirizine, a selective H(1)-receptor antagonist. Deuterated cetirizine (cetirizine-d(8)) was synthesized as described and was used as the internal standard. Samples were transferred into 96-well plates using an automated sample handling system. Automated solid phase extraction was carried out using a 96-channel programmable liquid-handling workstation. Solid phase extraction 96-well plate on polymer sorbent (Strata X) was used to extract the analyte. The extracted samples were injected onto a Betasil silica column (50 x 3, 5 microm) using a mobile phase of acetonitrile-water-acetic acid-trifluroacetic acid (93:7:1:0.025, v/v/v/v) at a flow rate of 0.5 ml/min. The chromatographic run time is 2.0 min per injection, with retention time of cetirizine and cetirizine-d(8) both at 1.1 min. The system consisted of a Shimadzu HPLC system and a PE Sciex API 3000 or API 4000 tandem mass spectrometer with (+) ESI. The method has been validated over the concentration range of 1.00-1000 ng/ml cetirizine in human plasma, based on a 0.10-ml sample size. The inter-day precision and accuracy of the quality control (QC) samples demonstrated <3.0% relative standard deviation (R.S.D.) and <6.0% relative error (RE). Stability of cetirizine in stock solution, in plasma, and in reconstitution solution was established. The absolute extraction recovery was 85.8%, 84.5%, and 88.0% at 3, 40, and 800 ng/ml, respectively. The recovery for the internal standard was 84.1%. No adverse matrix effects were noticed for this assay. The automation of the sample preparation steps not only increased the analysis throughput, but also increased method ruggedness. The use of a stable isotope-labeled internal standard further improved the method ruggedness. Practical issues of analyzing incurred samples were discussed. This HILIC-MS/MS method for analysis of citirizine in human plasma was successfully used to support clinical studies.

Advances in analytical toxicology: the current role of liquid chromatography?mass spectrometry in drug quantification in blood and oral fluid

This paper reviews procedures for quantification of drugs in the biosamples blood, plasma, serum, or oral fluid (saliva, etc.) using liquid chromatography coupled with single-stage or tandem mass spectrometry (LC-MS, LC-MS-MS). Such procedures are important prerequisites for competent toxicological judgment and consultation in clinical and forensic toxicology. They cover blood (plasma, serum) analysis of amphetamines and related designer drugs, anesthetics, anticonvulsants, benzodiazepines, opioids, serotonergic drugs, tricyclic antidepressants, neuroleptics, antihistamines, beta-blockers, muscle relaxants, and sulfonylurea-type antidiabetics, and oral fluid analysis of amphetamines and related designer drugs, cocaine, benzoylecgonine, codeine, morphine, enantiomers of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), the nicotine metabolites cotinine and hydroxycotinine, and finally risperidone and its metabolite 9-hydroxyrisperidone. Basic information on the procedures is given in two tables and an example of quantification is illustrated in two figures. The pros and cons of such LC-MS procedures including sample work-up and ion suppression effects are critically discussed.

Screening for central nervous system-stimulating drugs in human plasma by liquid chromatography with mass spectrometric detection

Liquid chromatography and electrospray mass spectrometry was evaluated for screening of more than 70 central nervous system-stimulating drugs in human plasma. Protein precipitation was utilized as a simple sample preparation procedure, and the subsequent screening procedure involved two injections in a liquid chromatography-mass spectrometry system for each sample; a first screening without source induced dissociation to maximize sensitivity where potential positive identifications were based on retention time and molecular ion masses, and secondly a source induced dissociation confirmation based on retention time, molecular ions, and one or two fragment ions for each target generated by a 25 V fragmentation energy. The majority of central nerve system stimulating drugs were possible to identify within the actual therapeutic ranges. Experiences with 175 real samples supported this and strongly indicated that information reported by patients on their consumption of central nerve system stimulating drugs is highly unreliable. Thus, protein precipitation and liquid chromatography-mass spectrometry may be a valuable tool for broad drug screening in human plasma in the future.

Position of chromatographic techniques in screening for detection of drugs or poisons in clinical and forensic toxicology and/or doping control

This paper reviews chromatographic screening procedures for simultaneous detection of several drug classes relevant to clinical and forensic toxicology or doping control in urine or blood using gas chromatography-mass spectrometry (GC-MS), liquid chromatography coupled with a diode-array detector (LC-DAD) or a mass spectrometer (LC-MS). The pros and cons of the different techniques and procedures are discussed leading to the following conclusions and perspectives. GC-MS, especially in the electron ionization full-scan mode, is still the method of choice for comprehensive screening providing best separation power, specificity and universality, although requiring derivatization. LC-DAD is also often used for screening, but its separation power and its specificity are still inferior to those of GC-MS. Finally, LC-MS has shown to be an ideal supplement, especially for the detection of more polar, thermolabile and/or low-dose drugs, especially in blood plasma. It may become the gold standard in clinical and forensic toxicology and doping control if, at a later date, the costs of the apparatus will be markedly reduced, the current disadvantages like irreproducibility of fragmentation, reduction of ionization by matrix, etc. will be overcome, and finally if one of the increasing number of quite different techniques will become the apparatus standard.

Simultaneous screening for 238 drugs in blood by liquid chromatography-ion spray tandem mass spectrometry with multiple-reaction monitoring

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method is presented for the qualitative screening for 238 drugs in blood samples, which is considerably more than in previous methods. After a two-step liquid-liquid extraction and C(18) chromatography, the compounds were introduced into a triple quadrupole mass spectrometer equipped with a turbo ion spray ion source operating in the positive ionization mode. Identification was based on the compound's absolute retention time, protonated molecular ion, and one representative fragment ion obtained by multiple reaction monitoring (MRM) at an individually selected collision energy of 20, 35, or 50 eV. The limit of detection (LOD) for the majority of the compounds (80%) was < or = 0.05 mg/l, ranging from 0.002 mg/l (e.g., antihistamines) to 5 mg/l (acidic compounds), and for malathion it was 10 mg/l. The LOD values were sufficiently low to allow the majority of compounds to be detected at therapeutic concentrations in the blood.