Comparison of quadrupole and (quadrupole) ion-trap mass spectrometers for the analysis of benzodiazepines

On-Line Solid-Phase Extraction Coupled With High-Performance Liquid Chromatography and Tandem Mass Spectrometry (SPE-HPLC-MS-MS) for Quantification of Bromazepam in Human Plasma

A validated method for on-line solid-phase extraction coupled with high-performance liquid chromatography tandem mass spectrometry (SPE-HPLC-MS-MS) is described for the quantification of bromazepam in human plasma. The method involves a dilution of 300 muL of plasma with 100 muL of carbamazepine (2.5 ng/mL), used as internal standard, vortex-mixing, centrifugation, and injection of 100 muL of the supernate. The analytes were ionized using positive electrospray mass spectrometry then detected by multiple reaction monitoring (MRM). The m/z transitions 316-->182 (bromazepam) and 237-->194 (carbamazepine) were used for quantification. The calibration curve was linear from 1 ng/mL (limit of quantification) to 200 ng/mL. The retention times of bromazepam and carbamazepine were 2.6 and 3.2 minutes, respectively. The intraday and interday precisions were 3.43%-15.45% and 5.2%-17%, respectively. The intraday and interday accuracy was 94.00%-103.94%. This new automated method has been successfully applied in a bioequivalence study of 2 tablet formulations of 6 mg bromazepam: Lexotan(R) from Produtos Roche Químicos e Farmacêuticos SA, Rio de Janeiro, Brazil (reference) and test formulation from Laboratórios Biosintética Ltda, São Paulo, Brazil. Because the 90% CI of geometric mean ratios between reference and test were completely included in the 80%-125% interval, the 2 formulations were considered bioequivalent. The comparison of different experimental conditions for establishing a dissolution profile in vitro along with our bioavailability data further allowed us to propose rationally based experimental conditions for a dissolution test of bromazepam tablets, actually lacking a pharmacopeial monograph.

Adsorption–desorption effects in ion trap mass spectrometry using in situ ionization

Quadrupole mass spectrometers were compared for the GC-MS analysis of six molecules frequently encountered in analytical toxicology: diazepam, alprazolam, triazolam, LSD (lysergic acid diethylamide), trimethylsilylated LSD and trimethylsilylated buprenorphine. Experiments performed with ion trap detectors using in situ ionization led to important chromatographic peak tailing for the most polar compounds; it was assumed to result from adsorption-desorption of neutral molecules in the mass spectrometer. This study showed that the degree of peak tailing is correlated with analyte polarity, with materials coating ion trap surfaces and with analysis temperature and that this anomaly can be greatly reduced using passivated surfaces and a high temperature of analysis.

Sensitive method for the detection of 22 benzodiazepines by gas chromatography-ion trap tandem mass spectrometry

A gas chromatography-ion trap tandem mass spectrometry method for simultaneous detection of 22 benzodiazepines is presented. Four operating modes were first optimized: the electron impact ionization and chemical ionization modes were compared on both underivatized and trimethylsilylated drugs. Results were compared in terms of sensitivity in MS-MS experiments. The trimethylsilylation of benzodiazepines including a protic functional group allows decreasing their detection threshold by a factor of 10-100. In terms of sensitivity, the comparison between both ionization modes shows that the most efficient one depends on the benzodiazepine considered. The use of an ion trap analyzer allows switching from an ionization mode to another one during the chromatographic process. It also provides a great selectivity owing to the MS-MS and multiple reaction monitoring acquisition modes. The detection thresholds are in the range 10-500 pg/microl for all the studied benzodiazepines but the three "triazolo" ones: estazolam, alprazolam and triazolam, have a detection threshold of 1 ng/microl. The applicability of the method on whole blood and urine extracts was demonstrated on an example implying five benzodiazepines among the most frequently encountered in forensic toxicology: nordazepam, oxazepam, bromazepam, flunitrazepam and prazepam.

Sensitive gas chromatographic--mass spectrometric screening of acetylated benzodiazepines

GC-MS screening conditions were developed for 15 low-dosed benzodiazepines, covering alprazolam, flunitrazepam, flurazepam, ketazolam, lorazepam and triazolam, and the corresponding metabolites alpha-hydroxyalprazolam, 4-hydroxyalprazolam; 7-aminoflunitrazepam, desmethylflunitrazepam, 7-aminodesmethylflunitrazepam; hydroxyethylflurazepam, N-desalkylflurazepam; oxazepam and alpha-hydroxytriazolam, respectively. Benzodiazepines are analyzed on a polydimethylsiloxane column in both the scan and the multiple ion monitoring modes using on-column injection to attain maximal sensitivity. The reactive compounds are acetylated with pyridine and acetic anhydride for 20 min. The derivatives are stable for at least 4 days. The relative standard deviation observed with standard compounds at the low nanogram-level ranged from 1.13 to 4.87% within-day and from 1.12 to 4.94% between-day. Unequivocal identification potential, high chromatographic resolution and sensitivity are combined with minimal thermal degradation. The presented screening conditions provide the basis for a unique routine screening method for low-dosed benzodiazepines with a broad polarity range.

Factors determining the performance of triple quadrupole, quadrupole ion trap and sector field mass spectrometers in electrospray ionization tandem mass spectrometry of oligonucleotides. 1. Comparison of performance characteristics

The performance of triple-stage quadrupole (TSQ), quadrupole ion trap (QIT), and double focusing sector field (DFSF) mass spectrometers for the generation of fragment ions to obtain sequence information about oligonucleotides was compared. Upon electrospray ionization (ESI), the charge-state distribution of candidate precursor ions not only varied significantly with the type of mass spectrometer, but also with the size and sequence of the investigated oligonucleotides. While concentration limits of detection for an octanucleotide were in the 100 pmol/L range on the QIT and in the 5-10 nmol/L range on the TSQ and DFSF instruments, those of a 24-mer were in the 2-13 nmol/L range on all three instruments. Reproducibility of mass determination, an important prerequisite for reliable identification of fragment ions, was highest on the TSQ with 0.0037% relative standard deviation over three days. Finally, the tandem mass spectra of a dimethoxytritylated pentanucleotide recorded on the three instruments were compared. Relatively simple spectra dominated by complete series of fragment ions of the (a-B) and w type were obtained on the QIT. Complete series of (a-B) and w ions were also observed on the TSQ. However, additional fragments belonging to the b, c, d, x and z series were found in the spectrum. In the spectrum recorded after in-source fragmentation in the DFSF, only fragments corresponding to the loss of a nucleobase and a complete series of w ions were observed. All three mass spectrometers were suitable for the generation of fragment ions, from which the complete nucleotide sequence of the pentanucleotide could be deduced.

Validated method for the therapeutic drug monitoring of flunitrazepam in human serum using liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry with an ion trap detector

An HPLC-MS-MS method for the quantitative analysis of flunitrazepam in human serum was established. The method features a very simple liquid-liquid extraction, the use of a standard 4-mm HPLC column, isocratic elution using a buffer-free solvent, short retention times in connection with good peak resolution and the sensitivity and selectivity of an ion trap MS-MS detector. The procedure enables unambiguous identification of analytes by their product ion spectra, as well as sensitive quantitation (limit of quantitation for flunitrazepam=0.5 ng/ml). This feature was used for the confirmation of HPLC-UV results for nitrazepam.