Lower Limit Of Quantification Values Research Articles

Effect of saponins in Panax notoginseng (Burkill) F. H. Chen on the steroid hormone levels in the chronic unpredictable mild stress model of depression in rats

Recent research has indicated that Panax notoginseng saponins (PNS) extracted from the radix of Panax notoginseng (Burkill) F. H. Chen exert antidepressant effects. This study aimed to assess the antidepressive effects of ginsenoside Rg1 and PNS in a depression model induced by chronic unpredictable mild stress (CUMS). Over a period of three weeks, rats were administered ginsenoside Rg1 at a dose of 30 mg/kg and PNS at dosages ranging from 100 to 200 mg/kg body weight per day. To assess how ginsenoside Rg1 and PNS influence depression-like behaviours in rats, various assessments were conducted, including coat state evaluation, forced swim test, and elevated plus maze test. The levels of cortisol and testosterone in serum samples were analysed using the liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) method. LC-ESI-MS/MS method provides precise and accurate results. The lower limit of quantification values for cortisol and testosterone were determined as 100 and 2 pg/mL, respectively. Our data demonstrated that both ginsenoside Rg1 and PNS significantly reversed depression-like behaviour in rats by improving coat condition, reducing immobility time in the forced swim test, and increasing time spent in the open arms of the elevated plus maze test. Furthermore, ginsenoside Rg1 and PNS exhibited a regulatory effect on cortisol and testosterone levels in plasma. These findings suggest that ginsenoside Rg1 and PNS may be potential antidepressants in clinical treatment.

Does sildenafil citrate affect the pharmacokinetics of metformin in rats? Screening of mechanism through analytical and molecular docking approach.

In the present study, the effect of sildenafil on the pharmacokinetics of metformin was studied in experimental rats, and we also postulated the molecular mechanism by performing molecular docking studies. Analysis of metformin and sildenafil (SIL) from rat plasma was done by high performance liquid chromatography. Optimum chromatographic separation and quantification of MET, SIL and Cetirizine was achieved on Phenomenex EVO C18 column with triethyl amine (0.3%): Methanol: Acetonitrile (70:05:25 v/v) as mobile phase maintaining flow rate of 1 ml/min, the detector was tuned at 224 nm. The extraction of MET and sildenafil from rat plasma was achieved by solid-phase extraction using Strata-X cartridges. The method was validated as per the ICH guidelines. For docking studies, the crystal structure of organic cation transporter 1 (OCT1) protein and multidrug and toxin extrusion (MATE) protein (5XJJ) were downloaded from the PubChem database. The docking study was performed by PyRx virtual screening software, and the results were analyzed by BIOVIA Discovery Studio. The validation of HPLC method was done, intraday and interday precision study of HPLC method demonstrated %RSD values less than 5%, the extraction recovery for MET and SIL were near to 80 % for low, medium and high QC samples. The plasma stability of MET and SIL showed % RSD values <10% for low, medium, and high QC samples. A sensitivity study for MET and SIL in rat plasma suggested a lower limit of quantification values of 8 and 10 ng/mL, respectively. The pharmacokinetic parameters were recorded, Cmax of experimental and control rats was 611.2 and 913.2 ng/mL; t1/2 1.66 and 1.98, AUC (0-t) 1637.5 and 2727.24, AUC (0-∞) 1832.38 and 2995.24 for MET. The results suggested that the Cmax of MET in experimental rats (MET + SIL) was 33.07% lower than the control (MET only) and also the t1/2 was 0.32 h shorter. Docking analysis suggested a higher binding affinity of sildenafil with MATE protein (5XJJ) compared to OCT1, suggesting possible involvement of MATE family proteins for pharmacokinetic alterations of MET. The HPLC and solid-phase extraction method were developed and applied successfully for the pharmacokinetics of MET and SIL. Intake of SIL altered the pharmacokinetics of MET in rats. Molecular docking studies suggested the involvement of MATE family proteins for alterations of MET pharmacokinetics.

Volumetric Absorptive Microsampling as a New Biosampling Tool for Monitoring of Tamoxifen, Endoxifen, 4-OH Tamoxifen and N-Desmethyltamoxifen in Breast Cancer Patients.

IntroductionIn this research, we used a volumetric absorptive microsampling (VAMS) technique to collect blood samples from the patients. A rapid and simple sample preparation method and LC-MS.MS assay was then developed and validated for the simultaneous analysis of tamoxifen and its three active metabolites.MethodsVAMS extraction was performed in methanol by sonication-assisted extraction method for 25 min after 2 hof VAMS drying. Separation was carried out using Acquity UPLC BEH C18 column (2.1 x 100 mm; 1.7 µm), with a flow rate of 0.2 mL/min, and the mobile phase gradient of formic acid 0.1% and formic acid 0.1% in acetonitrile for 5 min. The multiple reaction monitoring (MRM) values were set at m/z 358.31>58.27 for N-desmethyltamoxifen, m/z 372.33>72.28 for tamoxifen, m/z 388.22>72.28 for 4-hydroxytamoxifen, m/z 374.25>58.25 for endoxifen, and m/z 260.26>116.12 for propranolol.Results and DiscussionThe lower limit of quantification value (LLOQ) was 2.50 ng/mL for tamoxifen, 2.50 ng/mL for endoxifen, 1.50 ng/mL for 4-hydroxitamoxifen, and 2.00 ng/mL for N-desmethyltamoxifen. Accuracy (%bias) and precision (%CV) were within 20% for LLOQ and 15% for other concentrations. There were no interference responses >20% of the LLOQ and 5% of the internal standard. The level of ion suppression in all analytes was less than 7%. The preparation system developed in this study successfully extracted more than 90% of analytes from the matrix with precision below 15%. Carryover was shown to be below 6% in all analytes. Stability of analytes in VAMS was demonstrated for up to 30 days, under room temperature storage in a sealed plastic bag with desiccant. This method was successfully applied to analyze tamoxifen and the metabolites level in 30 ER+ breast cancer patients.

Nurses' internal contamination by antineoplastic drugs in hospital centers: a cross-sectional descriptive study.

The aim of this study was to assess internal antineoplastic drugs (ADs) contamination in the nursing staff in French hospital centers, using highly sensitive analytical methods. This cross-sectional study included nurses practicing in care departments where at least one of the five ADs studied was handled (5-fluorouracil, cyclophosphamide, doxorubicin, ifosfamide, methotrexate). The nurses study participation lasted 24 h including collection of three urine samples and one self-questionnaire. All urine samples were assayed by ultra-high-performance liquid chromatography-tandem mass spectrometry methods with very low value of the lower limit of quantification (LLOQ). 74 nurses were included, 222 urine samples and 74 self-questionnaires were collected; 1092 urine assays were performed. The percentage of nurses with internal AD contamination was 60.8% and low levels of urinary concentrations were measured. Regarding nurses with internal contamination (n = 45), 42.2% presented internal contamination by methotrexate, 37.8% by cyclophosphamide, 33.3% by ifosfamide, 17.8% by 5-fluorouracil metabolite and 6.7% by doxorubicine. Among the positive assays, 17.9% (n = 26/145) were not explained by exposure data from the self-questionnaire but this could be due to the skin contact of nurses with contaminated work surfaces. This study reported high percentage of nurses with internal ADs contamination. The low LLOQ values of the used analytical methods, allowed the detection of ADs that would not have been detected with the current published methods: the percentage of contamination would have been 17.6% instead of the 60.8% reported here. Pending toxicological reference values, urine ADs concentrations should be reduced as low as reasonably achievable (ALARA principle).

Rapid Determination of Sufentanil in Human Plasma by UHPLC-QqQ-MS-MS.

This paper presents a rapid, sensitive and precise method developed and validated for the quantification of sufentanil in biological samples using ultra-performance liquid chromatography coupled with QqQ-MS-MS. Plasma samples were extracted with simple and fast liquid-liquid extraction (ethyl acetate, pH 9). Calibration curve showed linearity in the concentration range of 0.005-30 µg/L. The lower limit of quantification was 0.010 µg/L. The most important method features are low lower limit of quantification value, simple plasma extraction and small sample volume. This method is suitable not only for evaluation of the pharmacokinetics, toxicology, bioavailability and clinical pharmacology of sufentanil but also for the detection and identification of this compound in human plasma samples for forensic purposes.

VALIDATION OF A BIOANALYTICAL REVERSE-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC METHOD FOR THE QUANTITATION OF NYSTATIN IN AN ANIMAL MODEL AFTER INTRANASAL IN SITU GEL ADMINISTRATION

Objective: The aim of the study was to develop and validate a bioanalytical reverse-phase high-performance liquid chromatographic (HPLC) method for the estimation of nystatin in rat plasma after intranasal administration.&#x0D; Methods: The reversed-phase HPLC system was equipped with a Luna C18 column, the mobile system comprised of methanol, water, and dimethylformamide (55:30:15) and the flow rate was set at 0.9 ml/min.&#x0D; Results: The elution time for nystatin was 4.096±0.025 min. The calibration curves constructed in rat plasma were linear from 0.25 to 50 μg/ml. The lower limit of quantification (LOQ) was found to be 0.25 μg/ml. The standards for accuracy and precision of the intra- and inter-day variation studies were in the acceptable ranges as per the FDA guidelines.&#x0D; Conclusion: The LOQ value determined by the proposed method was noted to be satisfactory for inspecting the plasma pharmacokinetics of nystatin in rats’ post-administration of a nasal in situ gelling liquid crystalline precursor formulation in an in vivo study.

A highly sensitive UHPLC-MS/MS method for urine biological monitoring of occupational exposure to anthracycline antineoplastic drugs and routine application

Anthracycline antineoplastic drugs (doxorubicin, epirubicin, daunorubicin) are “hazardous drugs for handling” by healthcare professionals. To monitor their occupational exposure, a highly sensitive ESI-UHPLC-MS/MS method for the assay of anthracyclines in urine was developed. The urine extraction consisted of SPE extraction method. A good linearity (r > 0.996), precision (CV < 14.4%), and accuracy (bias < 13.6%) were achieved for the three drugs. The lower limit of quantification (LOQ) was 10 ng/L. This LOQ value is equal to the LOQ of published methods except for epirubicin, for which the LOQ value is better by a factor of 10 (best published LOQ value: 100 ng/L). Applying this method in routine, more than 77 healthcare professionals occupationally exposed to anthracyclines were monitored and 77 urines were analyzed. Two healthcare professionals (2.6%) were found to be contaminated to doxorubicin and/or epirubicin. The measured concentrations ranged from 17.7 to 218 ng/L. Such an efficient analytical tool, combining both high specificity and sensitivity is essential for reliable highlight of contamination during biological monitoring of healthcare professionals widely exposed to these drugs. This anthracycline antineoplastic drugs exposure monitoring allows healthcare professionals for assessing effectiveness individual and collective protective measures and for ensuring traceability of occupational exposure to these drugs.

Pharmacokinetics and metabolism of icaritin in rats by UPLC-MS/MS.

Icaritin (ICT) has distinct bioactivities, especially known for its beneficial effects on bone‐related degenerative disorders; however, its pharmacokinetic properties remain unknown. A novel developed UPLC‐MS/MS method for the determination of ICT and its main metabolite glucuronidated icaritin (GICT) was firstly applied to pharmacokinetic and metabolism studies of ICT in female rats, which were intraperitoneally given 40 mg/kg ICT. Following the protein precipitation of plasma samples with acetonitrile, ICT and GICT were separated on a C18 column using gradient elution mode and quantified in the multiple reaction monitoring mode. The linearities were acceptable for ICT (r = 0.9960) and GICT (r = 0.9968), and the lower limit of quantification values was 0.5 and 5 ng/ml, respectively. The accuracy fell in the range of 92.0%–103.1% and precisions were within 9.5%. Good linearity, accuracy, precision, and recovery were achieved for the UPLC‐MS/MS method. ICT was predominantly and rapidly biotransformed to GICT which was slowly eliminated in vivo with a terminal half‐life value of 4.51 hr. Pharmacokinetics of pure ICT eliminated biotransformation interference of Epimedium extract and disclosed genuine pharmacokinetic manner of ICT, as well as firstly elucidated low concentration and bioavailability of ICT in rat plasma.

Butyl Methacrylate-Co-Ethylene Glycol Dimethacrylate Monolith for Online in-Tube SPME-UHPLC-MS/MS to Determine Chlopromazine, Clozapine, Quetiapine, Olanzapine, and Their Metabolites in Plasma Samples.

This manuscript describes a sensitive, selective, and online in-tube solid-phase microextraction coupled with an ultrahigh performance liquid chromatography-tandem mass spectrometry (in-tube SPME-UHPLC-MS/MS) method to determine chlopromazine, clozapine, quetiapine, olanzapine, and their metabolites in plasma samples from schizophrenic patients. Organic poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith was synthesized on the internal surface of a fused silica capillary (covalent bonds) for in-tube SPME. Analyte extraction and analysis was conducted by connecting the monolithic capillary to an UHPLC-MS/MS system. The monolith was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The developed method presented adequate linearity for all the target antipsychotics: R2 was higher than 0.9975, lack-of-fit ranged from 0.115 to 0.955, precision had variation coefficients lower than 14.2%, and accuracy had relative standard error values ranging from −13.5% to 14.6%, with the exception of the lower limit of quantification (LLOQ). The LLOQ values in plasma samples were 10 ng mL−1 for all analytes. The developed method was successfully applied to determine antipsychotics and their metabolites in plasma samples from schizophrenic patients.

Pharmacokinetics of fentanyl citrate and norfentanyl in Holstein calves and effect of analytical performances on fentanyl parameter estimation.

This study describes the pharmacokinetics of intravenously administered (i.v.) fentanyl citrate, and its primary metabolite norfentanyl in Holstein calves. Eight calves (58.6±2.2kg), aged 3-4weeks, were administered fentanyl citrate at a single dose of 5.0μg/kg i.v. Blood samples were collected from 0 to 24hr. Plasma (nor)fentanyl concentrations were determined using liquid chromatography with mass spectrometry and a lower limit of quantification (LLOQ) of 0.03ng/ml. To explore the effect of analytical performance on fentanyl parameter estimation, the noncompartmental pharmacokinetic analysis was then repeated with a hypothetical LLOQ value of 0.05ng/ml. Terminal elimination half-life was estimated at 12.7 and 3.6hr for fentanyl and norfentanyl, respectively. For fentanyl, systemic clearance was estimated at 2.0Lhr-1 kg-1 , volume of distribution at steady-state was 24.8L/kg and extraction ratio was 0.42. At a hypothetical LLOQ of 0.05ng/ml fentanyl half-life, volume of distribution at steady-state and clearance were, respectively, of 3.0hr, 8.8L/kg and 3.4Lkg-1 hr-1 . Fentanyl citrate administered i.v. at 5.0μg/kg can reach levels associated with analgesia in other species. Pharmacokinetic parameters should be interpreted with respect to LLOQ, as lower limits can influence estimated parameters, such as elimination half-life or systemic clearance and have significant impact on dosage regimen selection in clinical practice.

Quantification of xanthine- and uric acid-related compounds in urine using a “dilute-and-shoot” technique coupling ultra-high-performance liquid chromatography and high-resolution Orbitrap mass spectrometry

Quantitative analysis of relevant metabolites in biofluids such as urine is often a tedious procedure, since it usually requires extraction, purification or preconcentration. For instance, in the analysis of methylxanthines in urine, a solid-phase extraction is often required. In the current work, a rapid and highly sensitive "dilute-and-shoot" method combining ultra-high-performance liquid chromatography and high-resolution mass spectrometry (UHPLC/HRMS) was validated for urinary determination of twelve analytes: uric acid, hypoxanthine, xanthine, 1-methyluric acid, 1,3-dimethyluric acid, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, theophylline, theobromine, paraxanthine and caffeine. These analytes are the major physiological metabolites of caffeine, theobromine or theophylline, or final products of purine catabolism. The separation was carried out on a core-shell Kinetek EVO C18 column coupled to a Q Exactive Orbitrap high-resolution mass spectrometer equipped with a heated electrospray ionization (HESI) probe, that operated both in positive and negative ionization modes. The twelve analytes eluted from between 1.5 and 10.5min. The lower limit of quantification (LLOQ) values ranged from 0.25 to 2.5ng/mL, and the calibration curves were linear from the LLOQ to 100ng/mL. The only pretreatment needed was to dilute each urine sample (typically to 1/500) with 0.1% formic acid solution, and then filter the diluted sample before injecting it into the UHPLC system. With this high dilution, there were no significant matrix effects, and the intra- and inter-day precision and accuracy values were acceptable (coefficients of variance and relative errors below 15%, except for the LLOQ, for which they were below 20%). Furthermore, the analysis of spiked urine samples with 25ng/mL of the target analytes showed excellent recoveries and precision levels for the twelve analytes. To our knowledge, there is no other published method that allows for the simultaneous determination of the concentrations of these twelve compounds, nor has a previously reported method been indicated to show such low LLOQ values as we have for the majority of the analytes. We expect our protocol to be useful for nutritional assessments, interventional studies, kidney stone research, and purine metabolism studies.

Highly sensitive LC-MS/MS methods for urinary biological monitoring of occupational exposure to cyclophosphamide, ifosfamide, and methotrexate antineoplastic drugs and routine application.

Highly sensitive ESI-LC-MS/MS methods were developed for urinary biological monitoring of occupational exposure to cyclophosphamide (CP), ifosfamide (IF), and methotrexate (MTX), which are hazardous antineoplastic drugs frequently handled by healthcare professionals. Extraction methods consisted of liquid/liquid extraction for simultaneous urinary CP and IF assays, and of solid phase extraction for the urinary MTX assay. A good linearity (r2>0.997), precision (CV<14.6%), and accuracy (bias<9.9%) were achieved for all compounds. The limit of detection (LOD) was 10pg/ml and the lower limit of quantification (LOQ) was 20pg/ml for all three drugs. Applying these methods in routine, more than 116 healthcare professionals occupationally exposed to antineoplastic drugs were monitored and 635 urines were analysed. Eleven healthcare professionals (9.5%) were found to be contaminated to at least one of the three antineoplastic drugs. Among analysed urines, 22 samples were found positives. The measured concentrations ranged from 20.1 to 1850pg/ml and, for six samples, concentrations were at CP trace level, between the LOD and LOQ values (10-20pg/ml). Such efficient analytical tools combining high specificity with high sensitivity are essential for reliable detection and routine biological monitoring of healthcare professionals occupationally exposed to these widely used antineoplastic drugs. These methods allow to monitor the healthcare professionals exposure to antineoplastic drugs in the aim to assess the effectiveness of collective and individual protective measures.

Dynamic Biodistribution of Icaritin and Its Phase-II Metabolite in Rat Tissues by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry.

Icaritin (ICT), a major component in herb Epimedium brevicornum Maxim., shows beneficial effects for the treatment of osteoporosis and various cancers, and is predominantly metabolized to glucuronidated icaritin (GICT). Although clinical trials of ICT have exhibited good safety and tolerance, the dynamic bioditributions of ICT and GICT have not been reported. In the present study, the chemical structure of GICT was firstly reported, and a reliable ultra-high performance liquid chromatography-tandem mass spectrometry method (UHPLC-MS/MS) was firstly established for the simultaneous quantifications of ICT and GICT in rat tissues. The dynamic distribution of ICT and GICT in rat tissues and their pharmacokinetic parameters have been reported for the first time. ICT, GICT and the internal standard coumestrol were separated on a C18 column with a gradient mobile phase of acetonitrile and water containing ammonium formate and formic acid at a flow rate of 0.3 mL min(-1). The analytes were quantified by a triple quadrupole tandem mass spectrometer in the negative ionization mode. The lower limit of quantification values for ICT and GICT were 0.2 and 2 ng mL(-1), respectively. Good selectivity, linearity, accuracy, precision and recovery were achieved, and no significant matrix effect was observed. The UHPLC-MS/MS was firstly applied to a dynamic biodistribution study of ICT and GICT in rats, following an intraperitoneal administration of ICT at a dose of 10 mg kg(-1).

Detection of Benzodiazepines and z-Drugs in Hair Using an UHPLC-MS/MS Validated Method: Application to Workplace Drug Testing.

A sensitive and reproducible Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry method has been developed for the simultaneous quantification of the 29 commonly prescribed benzodiazepines and z-drugs in hair. The method was validated according to international guidelines. After decontamination (with dichloromethane and water), compounds were extracted from 20 mg of pulverized hair samples using methanol at 45°C and sonication for 2 hours. The drugs were recovered by liquid-liquid extraction using 1-chlorobutane, evaporated to dryness, and reconstituted with 100 μL of methanol before injection in the UPLC-MS/MS. The applied gradient ensured the elution of all the compounds within 7 minutes using 0.1% formic acid in water and methanol as mobile phase. The lower limit of quantification values ranged from 0.5 to 5 pg/mg of hair. Calibration curves were linear for almost all the compounds and ranged from the limit of quantification to 620 pg/mg hair. The bias and relative standard deviation of the intraday and interday imprecision were lower than 15% in 3 fortified "in-house" quality control samples, 1 external quality control sample, and 1 authentic hair sample (from a diazepam user). No significant matrix effects were observed for most of the compounds, and the extraction efficiency of the sample cleanup procedure ranged from 19% to 82% with a relative standard deviation <15% [except for clobazam (16%), loprazolam (20%), brotizolam (18%), and 7-aminoclonazepam (20%)]. The method was then successfully applied to the analysis of 40 hair samples from the workplace drug testing, containing alprazolam, estazolam, clonazepam, diazepam, zolpidem, and desalkylflurazepam (and metabolites). The method was completely validated and can be of interest to clinical and forensic laboratories.

Quantitation of endogenous nucleoside triphosphates and nucleosides in human cells by liquid chromatography tandem mass spectrometry.

Nucleosides and nucleoside triphosphates are the building blocks of nucleic acids and important bioactive metabolites, existing in all living cells. In the present study, two liquid chromatography tandem mass spectrometry methods were developed to quantify both groups of compounds from the same sample with a shared extraction procedure. After a simple protein precipitation with methanol, the nucleosides were separated with reversed phase chromatography on an Atlantis T3 column while for the separation of the nucleoside triphosphates, an anion exchange column (BioBasic AX) was used. No addition of ion pair reagent was required. A 5500 QTrap was used as analyzer, operating as triple quadrupole. The analytical method for the nucleoside triphosphates has been validated according to the guidelines of the US Food and Drug Administration. The lower limit of quantification values were determined as 10pg on column (0.5ng/mL in the injection solution) for deoxyadenosine triphosphate and deoxyguanosine triphosphate, 20pg (1ng/mL) for deoxycytidine triphosphate and thymidine triphosphate, 100pg (5ng/mL) for cytidine triphosphate and guanosine triphosphate, and 500pg (25ng/mL) for adenosine triphosphate und uridine triphosphate respectively. This methodology has been applied to the quantitation of nucleosides and nucleoside triphosphates in primary human CD4 T lymphocytes and macrophages. As expected, the concentrations for ribonucleosides and ribonucleoside triphophates were considerably higher than those obtained for the deoxy derivatives. Upon T cell receptor activation, the levels of all analytes, with the notable exceptions of deoxyadenosine triphosphate and deoxyguanosine triphosphate, were found to be elevated in CD4 T cells.

Development and analytical comparison of microflow and nanoflow liquid chromatography/mass spectrometry procedures for quantification of cardiac troponin T in mouse hearts

Three procedures for the quantification of cardiac troponin T (cTnT) based on liquid chromatography/mass spectrometry (LC/MS) were developed, validated and compared. The procedures were applied to estimate the cTnT content in the hearts of wild type mice C57BL/6J (WT) and double knock-outs for apolipoprotein E and receptor for LDL (AL KO).Three variants of the procedure proposed include microflow, direct injection nanoflow and preconcentration nanoflow LC/MS. Troponin T tryptic peptide YEINVLR and its analog (internal standard) were monitored in a multiple reaction monitoring mode using triple quadrupole mass detector with electrospray (ESI) ion sources.The preconcentration nanoflow LC/MS method offered the best sensitivity with a lower limit of quantification (LLOQ) of 0.25fgµL−1 and a minimal matrix effect. The LLOQ value was 8 times better, compared with that in direct injection nanoflow LC/MS and 200 times better than in microflow LC/MS. The accuracy or precision for all three methods were not different. Separation time in the direct injection nanoflow (8min) was equivalent to the microflow method (6min). The cTnT contents in the mice hearts measured by the methods developed by the present authors were not different between the WT and AL KO.We conclude that nanoflow LC/MS based quantitative proteomics offers fundamentally better sensitivities while maintaining analytical quality and separation times equivalent to microflow procedures.

Determination of cocaine in postmortem human liver exposed to overdose. Application of an innovative and efficient extraction/clean up procedure and gas chromatography–mass spectrometry analysis

A simple and efficient method was developed for the determination of cocaine in post-mortem samples of human liver via solid–liquid extraction with low temperature partitioning (SLE–LTP) and analysis by gas chromatography coupled to mass spectrometry (GC–MS). The extraction procedure was optimized by evaluating the influence of the following variables: pH of the extract, volume and composition of the extractor solvent, addition of a sorbent material (PSA: primary–secondary amine) and NaCl to clean up and increase the ionic strength of the extract. A bovine liver sample that was free of cocaine was used as a blank for the optimization of the SLE–LTP extraction procedure. The highest recovery was obtained when crushed bovine liver (2g) was treated with 2mL of ultrapure water plus 8mL of acetonitrile at physiological pH (7.4). The results also indicated no need for using PSA and NaCl. The complete analytical procedure was validated for the following figures of merit: selectivity, lower limit of quantification (LLOQ), calibration curve, recovery, precision and accuracy (for within-run and between-run experiments), matrix effect, dilution integrity and stability. The within-run and between-run precision (at four levels) varied from 2.1% to 9.4% and from 4.0% to 17.0%, respectively. A maximum deviation of 11.62% for the within-run and between-run accuracies in relation to the nominal concentrations was observed. Moreover, the LLOQ value for cocaine was 50.0ngg−1 whereas no significant effects were noticed in the assays of dilution integrity and stability. To assess its overall performance, the optimized method was applied to the analysis of eight human liver samples collected from individuals who died due to the abusive consumption of cocaine. Due to the existence of a significant matrix effect, a blank human liver was used to construct a matrix-matched analytical curve. The concentrations of cocaine found in these samples ranged from 333.5 to 5969ngg−1.

Direct quantification of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine using liquid chromatography-tandem mass spectrometry

A liquid chromatography-electrospray ionization-tandem mass spectrometric method (LC-ESI-MS/MS) was developed and validated for the direct determination of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) and its glucuronide (THCCOOH-glu) in urine. The deuterium-labeled compounds were used as internal standards to quantify the analytes. After a simple liquid–liquid extraction with ethyl acetate at pH 4, the dried extracts were reconstituted in the mobile phase followed by injection onto the LC-ESI-MS/MS system. The mobile phase was composed of 0.2% formic acid and 2 mM ammonium formate in water and acetonitrile. A reversed phase column (C8, 150 mm × 2.1 mm i.d., 3.5 μm) was used as the analytical column. The limit of detection and lower limit of quantification values were 0.08 and 0.3 ng mL−1 for THCCOOH and 0.4 and 1.5 ng mL−1 for THCCOOH-glu, respectively. The calibration curve was linear over the concentration range of 0.3–100 ng mL−1 for THCCOOH and 1.5–100 ng mL−1 for THCCOOH-glu with the coefficients of determination (r2) above 0.9955. The intra- and inter-day precisions (% CV) were within 16.6% and 18.3%, respectively. The intra-day accuracies (% bias) ranged from −18.4 to 1.5% while inter-day accuracies were −5.9 to 1.8%. The validated method was successfully applied for the determination of THCCOOH and THCCOOH-glu in urine samples from marijuana users.

A sensitive and selective quantification of catecholamine neurotransmitters in rat microdialysates by pre-column dansyl chloride derivatization using liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography tandem mass spectrometry method for simultaneous quantification of catecholamine neurotransmitters in microdialysates was developed. The catecholamine neurotransmitters dopamine (DA) and norepinephrine (NE) were pre-column derivatized with dansyl chloride and analyzed. A gradient elution method was used to separate the analytes from the interferences on an Agilent Poroshell 120 EC-C18 outer porous micro particulate column. The method was robust and sensitive to determine with the lower limit of quantification value of 0.068pmol/mL and 0.059pmol/mL for DA and NE, respectively. It has acceptable precision and accuracy for concentrations over the standard curve range. The method was successfully applied for simultaneous quantitation of DA and NE in the prefrontal cortex (PFC) dialysates of rats obtained from a microdialysis study dosed with vehicle and atomoxetine through intra peritoneal (i.p.) route at a dose of 3mg/kg to monitor the change in extracellular concentrations. Thus, accomplishment of this method would facilitate the neurochemical monitoring for discovery of new chemical entities targeted for the treatment of attention deficit hyperactivity disorder (ADHD).

Determination of β-sitosterol and cholesterol in oils after reverse micelles with Triton X-100 coupled with ultrasound-assisted back-extraction by a water/chloroform binary system prior to gas chromatography with flame ionization detection

Ultrasonic back-extraction of Triton X-100 reverse micelles by a water/chloroform binary system and gas chromatography with flame ionization detection (GC-FID) was developed for extraction and determination of β-sitosterol and cholesterol in soybean and sunflower oil samples. After the homogenization of the oil samples with Triton X-100, an aliquot of 200 μL of methanol was added to the samples to form two phases. The clear Triton X-100 extract obtained by centrifugation was treated with a mixture of water (1000 μL) and chloroform (300 μL) for back-extraction of the analytes into the chloroform phase by ultrasonication. After centrifugation, the sedimented chloroform layer was withdrawn easily by a microsyringe and directly injected into the GC-FID system. The influence of several important parameters on the extraction efficiencies of the analytes was evaluated. Under optimized experimental conditions, the calibration graphs were linear in the range of 1.0–30.0 mg L −1 with coefficient of determination more than 0.994 for both analytes. The method detection limit values were in the range of 0.2–0.7 mg L −1. The lower limit of quantification values were in the range of 0.7–2.4 mg L −1. Intra-day relative standard deviations were in the range of 1.0–2.7%. This procedure was successfully applied with satisfactory results to the determination of β-sitosterol and cholesterol in spiked oil samples. The relative mean recoveries of oil samples ranged from 93.6% to 105.0%.