A Sensitive LC–ESI–MS Method for Pharmacokinetic Studies of Picroside II in Dog Plasma

A high-performance liquid chromatography-electrospray ionization-mass spectromentry (LC–ESI–MS) method has been developed for the determination of picroside II in dog plasma. Plasma samples were deproteinated with acetonitrile and a Hypersil ODS2 column was used with a mobile phase consisted of methanol-water. The determination was validated in the concentration range of 0.10–50 μg mL^?1 using 50 μL of plasma. The method was successfully applied to a pharmacokinetic study of picroside II.     

A Pretreatment Method for GC–MS Determination of Endocrine Disrupting Chemicals in Mollusk Tissues

Automatic soxhlet extraction followed by silica gel cartridge cleanup process was developed as a pretreatment method for GC–MS determination of seven endocrine disrupting chemicals in mollusk tissues. Operation parameters including extraction time, adsorption flow rate and elution flow rate were optimized as 140 min, 2 mL min^?1 and 2 mL min^?1, respectively. Thirty percent dichloromethane in n-hexane and 70% dichloromethane in n-hexane were used as elution solvents in turn. Recovery rates were 93.7, 91.7, 84.5, 83.3, 88.4, 81.2, and 79.7% for nonylphenols (NPs), bisphenol A (BPA), 17α-ethynylestradiol (EE2), estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (E2), and estriol (E3), respectively. Acceptable relative standard derivations ranged from 8.5 to 12.1%. Method detection limits ranged from 0.27 to 0.68 ng g^?1 dry weight (dw), and quantitative detection limits ranged from 0.62 to 1.26 ng g^?1 dw. The method was successfully applied to five mollusk species in Dapeng Bay of China to verify its practicability, and NPs, BPA, EE2, E1 and 17α-E2 were detected in the range from 1.6 to 131.5 ng g^?1 dw.     

A Novel Derivatization Method Coupled with GC–MS for the Simultaneous Determination of Chloropropanols

A sensitive and rapid derivatization method for the simultaneous determination of chloropropanols [1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP) and 3-chloropropane-1,2-diol (3-MCPD)] has been developed. The three chloropropanols were silylated with 1-trimethylsilylimidazole and then determined by GC–MS. n-Undecane was used as the internal standard. The limits of detection (LOD) were 0.20, 0.10, 0.14 μg kg^?1 for 1,3-DCP, 2,3-DCP and 3-MCPD, respectively. The three compounds behaved >0.999 of linearity and satisfactory precision with the relative standard deviation (RSD) <10%. The excellent validation data suggested that this method was more effective than heptafluorobutyrylimidazole derivatization, and 1-trimethylsilylimidazole was considered as a promising silylating reagent to be widely applied to measurements of chloropropanols in real samples.     

LC–MS/MS Method for the Simultaneous Determination of Free Urinary Steroids

Cortisol homeostasis is implicated in hypertension and metabolic syndrome. Two enzymes modulate cortisol availability; 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) preferentially converts inactive cortisone to cortisol, whereas 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) converts cortisol to cortisone. In contrast, 5α and 5β reductases inactivate cortisol by conversion to its tetrahydrometabolites: tetrahydrocortisol, allo-tetrahydrocortisol and tetrahydrocortisone. A subtle local increase in cortisol can be detected by measuring 24-h urine metabolites, LC–MS/MS being the reference method. The 11β-HSD2 activity is assessed based on the cortisol/cortisone ratio, and the 11β-HSD1 activity on the (tetrahydrocortisol + allo-tetrahydrocortisol)/tetrahydrocortisone ratio. To better understand hypertension and/or metabolic syndrome pathogenesis a method for simultaneous determination of cortisol, cortisone, tetrahydrocortisol, allo-tetrahydrocortisol and tetrahydrocortisone was developed and validated in an LC coupled with the new detector AB Sciex QTrap^® 4500 tandem mass spectrometer. The steroids were extracted from 1 mL urine, using cortisol-D4 as internal standard. The quantification range was 0.1–120 ng/mL for cortisol and cortisone, and 1–120 ng/mL for tetrahydrometabolites, with >89 % recovery for all analytes. The coefficient of variation and accuracy was <10 %, and 85–105 %, respectively. Our LC–MS/MS method is accurate and reproducible in accordance with Food and Drug Administration guidelines, showing good sensitivity and recovery. This method allows the assessment of 11β-HSD2 and 11β-HSD1 activities in a single analytical run providing an innovative tool to explain etiology of misclassified essential hypertension and/or metabolic syndrome.     

A New LC–MS–MS Method for Quantitative Analysis of Adefovir,and Its Use for Pharmacokinetic Studies in Healthy Chinese Volunteers

A rapid and sensitive liquid chromatographic–tandem mass spectrometric method for analysis of adefovir in human plasma has been developed and validated. After protein precipitation and evaporation, 10 μL supernatant was injected for reversed-phase LC separation. Adefovir and the internal standard (acyclovir) were monitored in selected reaction monitoring (SRM) mode at m/z 274.10 → 256.00 and 226.10 → 152.00, respectively. The calibration plot was linear over the concentration range 0.5–100 ng mL^?1, and correlation coefficients were >0.999. Mean intra-day and inter-day accuracy ranged from 89.43 to 93.20% and from 91.40 to 95.57%, respectively, and mean intra-day and inter-day precision was between 2.40 and 7.66% and between 5.60 and 10.47%, respectively. The method was successfully applied to a Phase I pharmacokinetic study of adefovir after oral administration of adefovir dipivoxil capsules at doses of 5, 10, and 20 mg to twenty-four healthy Chinese volunteers.     

UPLC–MS–MS法测定塑料包装材料中四溴双酚A

建立超高效液相色谱–串联质谱法(UPLC–MS–MS)测定塑料包装材料中四溴双酚A的含量。塑料包装材料样品经研磨粉碎后,采用纯甲醇进行超声萃取,萃取液经氮吹浓缩后用UPLC–MS–MS测定。四溴双酚A的质量浓度在2.5~50 ng/g范围内与色谱峰面积呈良好的线性关系,线性相关系数为0.999 8,检出限为0.6μg/kg,定量限为2.0μg/kg。加标平均回收率为93.2%~97.3%,测定结果的相对标准偏差为1.0%~2.6%(n=6)。该方法简便、快速、准确度高,可为塑料包装材料产品质量监测提供检测方法。     

An LC–MS–MS Method for the Simultaneous Quantitation of Acyclovir and Valacyclovir in Human Plasma

A simple, sensitive and selective LC–MS–MS method has been developed for the simultaneous determination of acyclovir and valacyclovir in human plasma. Acyclovir and valacyclovir in plasma were concentrated by solid phase extraction and chromatographed on a C18 column using a mobile phase of 0.1% formic acid: methanol (30:70% v/v). The method was validated over a linear range of 47–10,255 and 5–1,075 ng mL^?1 for acyclovir and valacyclovir respectively. The LOQs were 47.6 and 5.0 ng mL^?1. The validated method was applied for the quantitation of acyclovir and valacyclovir from plasma samples in a pharmacokinetic study.     

Method optimization for the determination of carbonyl compounds in disinfected water by DNPH derivatization and LC–ESI–MS–MS

A method has been developed for quantitative determination of carbonyl disinfection by-products (DBP) from aqueous samples by derivatization with 2,4-dinitrophenylhydrazine combined with high-performance liquid chromatography (HPLC) and electrospray ionization (ESI) tandem mass spectrometry (MS-MS). The effect of excess of derivatization reagent and derivatization time, the effect of buffer and dry-gas temperature in the ESI process, and the effect of focus potential and collision energy in MS measurement are shown. Major fragment ions for compound identification on the basis of collision-induced dissociation (CID) mass spectra (MS) are given, as are common fragments for screening analyses by MS experiments such as the use of precursor ion scans. Detection limits in the microg x L(-1) range could be achieved by selected ion monitoring measurements without sample preconcentration. Solid-phase extraction improved the sensitivity by a factor of 25 to 250. The applicability of the method is illustrated by DBP analyses of samples from outdoor swimming pools after chlorination. Several carbonyl compounds, e.g. aldehydes, ketones, hydroxybenzaldehyde, and dicarbonyl compounds were identified.     

Rapid and Sensitive LC–MS–MS Method for the Simultaneous Estimation of Alfuzosin and Dutasteride in Human Plasma

A simple, rapid, specific and sensitive liquid chromatography–tandem mass spectrometric method has been developed and validated for the simultaneous estimation of alfuzosin and dutasteride in human plasma. Both alfuzosin and dutasteride were extracted from human plasma by solid-phase extraction using terazosin and finasteride as the internal standards for alfuzosin and dutasteride, respectively. Chromatographic separation of analytes and their respective internal standards was carried out using a Hypurity C18 (50 × 4.6 mm i.d., 5 μm particle size) column followed by detection using an applied biosystems API 5000 mass spectrometer with a UPLC as the front end. The method involves a rapid solid phase extraction from plasma, simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using multiple reactions monitoring that enables detection down to low nanogram levels with a total run time of 2.5 min only. The method was validated over a range of 0.25–20.0 ng mL^?1 for alfuzosin and 0.1–10.0 ng mL^?1 for dutasteride. The absolute recoveries for alfuzosin (65.57%), dutasteride (103.82%), terazosin (69.38%) and finasteride (102.25%) achieved from spiked plasma samples were consistent and reproducible. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Due to the short run time of 2.5 min it was possible to analyze a throughput of more than 180 human plasma samples per day. The validated method can be successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailabilty or bioequivalence studies. As an example the application of this validated method to a bioequivalence study is also illustrated.     

LC–MS Method for the Quantification of Clonazepam in Rat Plasma

A sensitive and specific high-performance liquid chromatography–tandem mass spectrometry method has been developed and validated for the determination of clonazepam in rat plasma. Clonazepam and internal standard diazepam were extracted from plasma samples by a single-step protein precipitation. The chromatographic separation was performed on a Dikma ODS-C18 reversed-phase column at 40 °C. The mobile phase composed of a premix of solvent A (0.1% formic acid–4 mM ammonium acetate–water)–solvent B (acetonitrile) (13:87, v/v) at a flow-rate of 0.7 mL min^?1. Positive electrospray ionization was utilized as the ionization source. Clonazepam and the internal standard were determined using multiple reaction monitoring of precursor → product ion transitions at m/z 316.0 → 270.0 and m/z 285.1 → 193.2, respectively. The lower limit of quantification was 0.25 ng mL^?1 using 50 μL plasma samples and the linear calibration range was from 0.25 to 128 ng mL^?1. The within- and between-batch RSDs were lower than 15% and the relative recoveries of clonazepam ranged from 97.4 to 104.7%. The mean extraction recoveries of clonazepam and IS were 79.7 and 77.6%, respectively. The method has been successfully applied to the pharmacokinetic studies in rat after oral administration of clonazepam.     

LC–MS–MS Method to Simultaneously Determine Six Probe Drugs for CYP450 Isozymes in Human Liver Microsomes

Here, we report a rapid and specific method based on high-performance liquid chromatography coupled with tandem mass spectrometry (LC–MS–MS) capable of quantifying six CYP450-specific probe substrates in human liver microsomal incubation mixtures simultaneously. These analytes were prepared by single-step extraction and detected in one run by switching polarity of electrospray ionization mode three times. Following optimization of the chromatographic conditions, the peaks were well separated, and retention times ranged between 2.0 and 8.4 min. The total run time for a single injection was within 9 min. This method was fully validated over linear range of 18.8–3,000.0 ng mL^?1 for diclofenac, 0.8–3,000.0 ng mL^?1 for dapson, 1.5–3,000.0 ng mL^?1 for dextromethorphan, 2.0–4,000.0 ng mL^?1 for omeprazole, 75.0–3,000.0 ng mL^?1 for chlorzoxazone and 0.8–3,000.0 ng mL^?1 for phenacetin using diazepam as internal standard. Samples were prepared by protein precipitation and analyzed on the LC–MS–MS equipped with ESI interface. For each analyte, inter- and intra-day precision (RSD%) were <15 % and accuracy was within 85–115 %. The specificity, precision, accuracy, stabilities and matrix effect were evaluated.     

A Novel Derivatization Method for Separation of Sarcosine from Isobaric l-Alanine in Human Urine by GC–MS

Sarcosine, an isomer of l-alanine, has been recently proposed as a potential biomarker for prostate cancer risk and aggressiveness, while some studies debated its importance. As both sarcosine and l-alanine are present in human urine, it is a great challenge to separate and accurately quantify these isobaric (i.e., same m/z) compounds by chromatographic separation and mass spectrometric detection. In this study, we developed a novel 1,3-dipolar cycloaddition derivatization method that resolves sarcosine from l-alanine and allows accurate quantification of sarcosine in human urine by gas chromatography–mass spectrometry (GC–MS). This novel derivatization approach was specific to sarcosine only, while the common silylanization method resulted in overlapped derivates of both sarcosine and l-alanine. The derivatization conditions, including reagent amount, reaction temperature and time, were optimized. The method developed here has excellent precision (relative standard deviation <4.7 %, n = 5), good linearity (slope = 0.2408; r ² = 0.9996, 0.1–100 μg mL^?1), and a low limit of detection in human urine (0.15 ng mL^?1). Application of this analytical method to urine samples spiked with standard sarcosine indicates that it is a robust and powerful alternative for resolving and quantifying sarcosine from l-alanine isomer in human urine by GC–MS.     

A Simple and Sensitive LC–MS/MS Method for Simultaneous Determination of Temsirolimus and Its Major Metabolite in Human Whole Blood

A simple, fast and sensitive LC?CMS/MS method was developed and validated for the simultaneous determination of the concentrations of temsirolimus and its major metabolite, sirolimus, in human whole blood. The blood sample (100???L) after adding temsirolimus-d7 and sirolimus-d3 internal standards was precipitated with 0.200?mL of methanol/0.300?M zinc sulfate (70/30, v/v), then analyzed by a Shimatzu LC system coupled to a Sciex API-5000 mass spectrometer. The chromatographic separation was carried out on a BDS Hypersil C8 column (50?×?3.0?mm, 5???m) at 50?°C with a mobile phase composed of methanol/water/formic acid (72/28/0.1) (v/v/v) containing 2.50?mM ammonium acetate. Mass spectrometric detection was performed using electrospray positive ionization with multiple reaction monitoring mode. This method was validated from 0.250 to 100?ng?mL^?1 for temsirolimus and 0.100 to 40.0?ng?mL^?1 for sirolimus. The lower limits of quantitation were 0.25?ng?mL^?1 for temsirolimus and 0.1?ng?mL^?1 for sirolimus. The intra-day and inter-day precisions (CV?%) of spiked quality control (QC) samples were less than 10.4 and 9.6?%, respectively. The accuracies as determined by the relative error for QC samples were less than 12.1?% for intra-day and 7.3?% for inter-day. No significant matrix effect was observed. This method has been successfully applied to analyze clinical pharmacokinetic study samples. The assay reproducibility was also demonstrated by using incurred samples.     

LC–MS/MS Method for Simultaneous Determination of Monoethanol- and Dimethylnitramine in Aqueous Soil Extracts

Monoethanol (MEA)- and dimethyl (DMA)-nitramines are by-products of amine-based post-combustion CO₂ capture (PCCC) processing, and are potentially carcinogenic. The compounds are challenging to measure, also with LC–tandem mass spectrometry (MS/MS), attributed to their high polarity and extreme proneness to matrix effects. In contrast to related methods, the MEA- and DMA-nitramines were simultaneously determined in aqueous soil extracts in less than 10 min using a 1 mm × 150 mm Atlantis^® T3 (3 µm) C18 column. A mobile phase of water/methanol (90/10, v/v) and 2 mM acetic acid allowed for electrospray ionization (ESI) of both analytes [in contrast to the need for both ESI and atmospheric pressure chemical ionization (APCI) in related methods]. Polarity switching electrospray was required for the simultaneous detection of the analytes, and concentration limits of detection (LODs) in the aqueous soil extracts were ≤5.0 µg L^?1 using an injection volume of 20 μL and no prior enrichment step. Matrix effects were compensated for using isotope-labelled internal standards, and satisfactory precision and linearity were obtained (within- and between-day precisions ≤19%, r ² ≥ 0.995 for concentrations up to 500.0 µg L^?1). To avoid signal decrease over time when measuring DMA-nitramine alone, the use of polarity switching was beneficial, in addition to frequent cleaning of the ion transfer capillary. The validated method can be used to determine nitramines in aqueous soil extracts, which is of importance as soil sorption is a determinant of the compounds’ environmental fate.     

Rapid and Sensitive LC−MS–MS Method for the Determination of Sarpogrelate in Human Plasma

A rapid and sensitive liquid chromatographic–tandem mass spectrometric method has been developed and validated for the estimation of sarpogrelate in human plasma. Sarpogrelate was extracted from human plasma by solid-phase extraction. Temocapril was used as the internal standard. Heated electron spray ionization mass spectrometry was performed on a TSQ Quantum Ultra MS system. The LC column was a Hypurity C₁₈ and the mobile phase was 2 mM ammonium formate (pH 3.00 ± 0.05):acetonitrile (30:70 v/v). A flow rate of 0.250 mL min^?1 was used. The quantitative analyses were carried out in the positive ion and full scan mode over the mass range m/z 60–500. The capillary, vaporiser temperatures were 325 and 200 °C respectively. The sheath gas pressure, spray voltage, collision energy and tube lense were 40, 3,500 V, 19 V, 198 V, respectively, and the mass spectra of the drugs were recorded by total ion monitoring. Retention times and characteristic mass fragments were recorded and the chosen diagnostic mass fragments were monitored in the mass chromatography mode. Signal intensities of each of the mass fragments: m/z 477 [M + H]⁺ for temocapril, m/z 430 [M + H]⁺ for sarpogrelate, were used for quantification. The calibration curves (the ratio between the peak areas as signal intensities of the drug analyzed and that of the internal standard (temocapril: m/z 477 [M + H]⁺) vs. the concentration of drug) exhibited linearity over the concentration range 5.00–2,500.00 ng mL^?1 human plasma. The recovery and the accuracy were calculated by comparing the peak areas as the signal intensities of each mass fragment for the drug in spiked samples after solid-phase extraction from human plasma to the peak area as the signal intensity of the mass fragment of internal standard sample. The method involves a rapid solid phase extraction from plasma, simple isocratic chromatography conditions and mass spectrometric detection that enables detection up to picogram levels with a total run time of 3.0 min only. The method was validated over the range of 5.0–2,500.0 ng mL^?1. The absolute recoveries for sarpogrelate (93.72%) and IS (91.42%) achieved from spiked plasma samples were consistent and reproducible.     

LC–MS–MS Analysis of Strictosamide in Rat Plasma, and Application of the Method to a Pharmacokinetic Study

A rapid and simple high-performance liquid chromatographic tandem mass spectrometric method has been developed and validated for analysis of strictosamide in rat plasma. Chromatographic separation was achieved on a C₁₈ column by gradient elution with mixtures of methanol, water, and acetonitrile containing 0.05% acetic acid. Digoxin was used as internal standard. Selected reaction monitoring (SRM) was used for MS quantitation. Linearity was good in the range 0.05–20 ng mL^?1 in rat plasma. The lower limit of quantitation was 0.04 ng mL^?1. The method is precise and reliable and can be applied to pharmacokinetic studies.     

Validated LC–MS–MS Method for Quantitative Determination of Batifiban in Human Plasma and Its Application to a Pharmacokinetic Study

Batifiban is a new platelet GPIIb/IIIa receptor antagonist. In this work, an analytical method based on liquid chromatography and electrospray ionization tandem mass spectrometry has been firstly developed and validated for the quantitative measurement of batifiban in human plasma to support the investigation of this compound. Separation of analyte and the internal standard eptifibatide was performed on a Thermo HyPURITY C18 column (150 × 2.1 mm, 5 μm) with a mobile phase consisting of formic acid 0.1% (v/v)–acetonitrile (40:60, v/v) at a flow rate of 0.25 mL min^?1. The Waters QuattroMicro API triple quadrupole mass spectrometer was operated in multiple reaction monitoring mode via positive electrospray ionization interface using the transition m/z 819.2 → m/z (623.9 + 159.4) for batifiban and m/z 833.4 → m/z (645.7 + 159.3) for IS. The method was linear over the concentration range of 2.45–5,000 μg L^?1. The intra- and inter- day precisions were less than 15% in terms of relative standard deviation, and the accuracy was within 8.5% in terms of relative error (RE). The lower limit of quantification (LLOQ) was identifiable and reproducible at 2.45 μg L^?1 with acceptable precision and accuracy. The validated method offered sensitivity and wide linear concentration range. This method was successfully applied for the evaluation of pharmacokinetics of batifiban afer single oral doses of 55, 110 and 220 μg kg^?1 batifiban to 36 Chinese healthy volunteers.     

Fast Determination of Fumonisin B1 and B2 in Corn Using a Modified QuEChERS Method and LC–MS–MS

A fast analytical method for the simultaneous determination of fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂) in corn using a novel QuEChERS method and LC–MS–MS was developed and validated. Samples were extracted with methanol–water (3:1 v/v) by means of ultrasonic extraction. The extract was purified with a novel modified QuEChERS method. Firstly, FB₁ and FB₂ in the extract were retained with primary secondary amine (PSA). Then, FB₁ and FB₂ were released from PSA with 1.0 % formic acid in methanol. The final eluate was diluted with water, and analyzed by LC–MS–MS on a Waters Acquity BEH C₁₈ column with 0.1 % formic acid in water/methanol as mobile phase with gradient elution. Mean recoveries of 83.5–102.4 % with CVs of 3.6–10.5 % were obtained at fortification levels of 2, 50 and 1,000 μg kg⁻¹. The limit of quantification was 2.0 μg kg⁻¹.