Differentiation of a pair of diastereomeric tertiarybutoxycarbonylprolylproline ethyl esters by collision-induced dissociation of sodium adduct ions in electrospray ionization mass spectrometry and evidence for chiral recognition by ab initio molecular orbital calculations

The fragmentation of the sodium adduct ions for tert-butoxycarbonyl-L-prolyl-L-proline ethyl ester (Boc-L-Pro-L-Pro-OEt) was compared with that for Boc-D-Pro-L-Pro-OEt in positive-ion electrospray ionization (ESI) mass spectrometry. In the collision-induced dissociation (CID) mass spectra of the [M + Na](+) ions, the abundance of the [M + Na - C(CH(3))(3) + H](+) ion, which is due to the loss of a tert-butyl group from the [M + Na](+) ion for Boc-D-Pro-L-Pro-OEt, was about eight times higher than that for Boc-L-Pro-L-Pro-OEt. In addition, in the CID spectra of the sodium adduct fragment ion ([M + Na - Boc + H](+)), the abundance of the [M + Na - Boc - prolylresidue + H](+) ion, which is due to the loss of prolyl residue from the [M + Na - Boc + H](+) ion for Boc-L-Pro-L-Pro-OEt, was about five times higher than that for Boc-D-Pro-L-Pro-OEt. These results indicate that Boc-L-Pro-L-Pro-OEt was distinguished from Boc-D-Pro-L-Pro-OEt by the CID mass spectra of the sodium adduct ions in ESI mass spectrometry. The optimized geometries of the [M + Na](+) and the [M + Na - Boc + H](+) ions calculated by ab initio molecular orbital calculations suggest that the chiral recognition of these diastereomers was due to the difference of the orientation of a sodium ion to the oxygen and nitrogen atoms in dipeptide derivatives, and to the difference of the total energies between them.     

Quantitative determination of ochratoxin A by liquid chromatography/electrospray tandem mass spectrometry

Mass spectrometry of ochratoxin A (OTA) and B (OTB) under electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) was studied. ESI offers higher sensitivities and less fragmentation than APCI. A sensitive LC/MS/MS method for the determination of ochratoxin A (OTA) in human plasma samples was developed. The absolute minimum detection limit was around 10-20 pg per injection, corresponding to 0.5 ppb in an injection equivalent to 20-40microg of human plasma. Ochratoxin B (OTB) was used as an internal standard and its absence in real-life samples was carefully checked before samples were spiked with the internal standard. It was found that these two ochratoxins are susceptible to sodium adduct formation. Fragment ions from the [M + H](+) and [M + Na](+) ions of both OTA and OTB were monitored in the multiple reaction monitoring mode. Three quantitative approaches, standard addition method, internal standard method (using ochratoxin B as an internal standard) and external standard method, were compared in the analysis of human blood plasma. Results from the mass spectrometric method were comparable to those from a conventional LC/fluorescence method. The LC/MS/MS method was also applied to the analysis of contaminated coffee samples.     

Post-source decay matrix-assisted laser desorption/ionization mass spectrometric study of tetracyclic 2,3-dihydro-1,5-benzothiazepines

The fragmentation behavior of six tetracyclic 2,3-dihydro-1,5-benzothiazepine derivatives cationized with protons and silver ions under post-source decay (PSD) matrix-assisted laser desorption/ionization (MALDI) conditions is reported. The protonated adduct ions decompose into several structurally important fragment ions, including substituted cyclopropane and benzohydrothiazole cations. Elimination of Ag and H and/or AgH from the silver-cationized adduct ions of these ([M+Ag](+)) compounds was observed. It was also found that [M+Ag](+) produced silver-depleted fragment ions exclusively. Based on the PSD results a fragmentation pathway is proposed for the [M+H](+) and [M+Ag](+) precursor ions.     

Cleavage reactions of the complex ions derived from self-complementary deoxydinucleotides and alkali-metal ions using positive ion electrospray ionization with tandem mass spectrometry

The dissociation reactions of the adduct ions derived from the four self-complementary deoxydinucleotides, d(ApT), d(TpA), d(CpG), d(GpC), and alkali-metal ions were studied in detail by positive ion electrospray ionization multiple-stage mass spectrometry (ESI-MS(n)). For the [M + H](+) ions of the four deoxydinucleotides, elimination of 5'-terminus base or loss of both of 5'-terminus base and a deoxyribose were the major dissociation pathway. The ESI-MS(n) spectra showed that Li(+), Na(+), and Cs(+) bind to deoxydinucleotides mainly by substituting the H(+) of phosphate group, and these alkali-metal ions preferred to bind to pyrimidine bases rather than purine bases. For a given deoxydinucleotide, the dissociation pathway of [M + K](+) ions differed clearly from that of [M + Li](+), [M + Na](+), and [M + Cs](+) ions. Some interesting and characteristic cleavage reactions were observed in the product-ion spectra of [M + K](+) ions, including direct elimination of deoxyribose and HPO(3) from molecular ions. The fragmentation behavior of the [M + K](+) and [M + W](+) (W = Li, Na, Cs) adduct ions depend upon the sequence of bases, the interaction between alkali-metal ions and nucleobases, and the steric hindrance caused by bases.     

Matrix-assisted laser desorption/ionization, fast atom bombardment and plasma desorption mass spectrometry of polyethylene glycol esters of (2-benzothiazolon-3-yl)acetic acid.

Fast atom bombardment (FAB), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and plasma desorption (PD) mass spectra of newly synthesized polyethylene glycols (PEGs), (M(w) 600-4000 Da) chemically modified with biologically active (2-benzothiazolon-3-yl)acetyl end-groups are described (products 1-6). The spectra were also used for the determination of the molecular mass characteristics (number average (M(n)) and weight average (M(w)) molecular masses) of the initial and modified PEGs. As expected, M(n) and M(w) of the modified samples are higher than those of the non-modified samples. However, it is shown that molecular mass dispersity (determined by the comparison of the polydispersity indices (PDI = M(w)/M(n)) of both types of PEGs) essentially do not change during this modification. The FAB mass spectra, together with molecular species, show the presence of abundant [M + Na](+) ions of product 1 and [M + Na + H](+) species of 2 and 3, and [M + Na + 2H](+) of product 4. Two main series of fragment ions, derived from the cleavage of the ether bonds, are observed. The number fractions of the molecular adduct ions and fragment adduct ions, determined from the FAB and PD mass spectra of the modified PEGs, are compared. The MALDI-TOF mass spectra of compounds 1-6 show the presence of two series of polymers. The most abundant peaks are due to [M + Na](+) and [M + K](+) ions originating from the polymers, in which the two terminal hydroxyl groups of PEGs are esterified with (2-benzothiazolon-3-yl)acetic acid. The less abundant peaks are due to the monosubstituted polymers.     

Probing the mechanisms of the self ion-molecule reactions of dopamine in an ion trap mass spectrometer

Our previous work was the first to report [M+CH](+) and [M+C(2)H(3)](+) ions in the self ion-molecule reactions (SIMR) of two aza-crown ethers in an ion trap mass spectrometer (ITMS). In this study, the CH and C(2)H(3) addition ions were also found in the SIMR of dopamine. The SIMR of dopamine lead to the formation of the protonated molecules ([M+H](+)), of adduct ions ([M+F](+), where F represents fragment ions), and of [M+CH](+), [M+C(2)H(3)](+) and [2M+H](+) ions. Based on the combination of the results of isolation experiments and semi-empirical calculations, the reactive site for the formation of the [M+H](+) and [M+CH](+) ions of dopamine is proposed to be the amino group.     

Ethylenediamine as a liquid chemical reagent to probe hydrogen bonding and host-guest interactions with crown ethers in an ion trap tandem mass spectrometer

Ethylenediamine (EDA) was used as a novel liquid chemical reagent to probe hydrogen bonding and host-guest interactions with crown ether derivatives in an ion trap mass spectrometer (ITMS). Selective ion/molecule reaction product ions were generated by reactions of EDA with oxygenated and aza-crown ethers. For the oxygenated crown ethers, glycols and dimethylglycols, ion/molecule reactions led to the formation of the protonated molecules ([M+H](+)) and adduct ions including [M+30](+), [M+44](+) and [M+61](+). The aza-crown ethers produced [M+H](+), [M+13](+) and [M+27](+) ions. Collisionally activated dissociation (CAD) experiments were applied to probe the binding strength of these ion/molecule reaction products. CAD results indicated that all these hydrogen-bonding complexes are weakly bound except for the [M+44](+) ion of 18-crown-6, since all the complexes dissociate to the protonated polyether and/or protonated EDA. Fragmentation of the [M+H](+) ions under CAD conditions indicates the extensive covalent bond cleavage of the protonated crown ether skeleton.     

Chemical ionization of substituted naphthalenes using tetrahydrofuran as a reagent in gas chromatography with ion trap mass spectrometry

The ion/molecule reactions of nine monosubstituted naphthalene compounds in chemical ionization mass spectrometry (CI-MS) were studied using tetrahydrofuran (THF) as CI reagent. Proton affinity factors, substituent effects and the preferred site of adduct ion attachment were examined. Good correlation was observed between proton affinity and the formation of [M](+*) and [M+H](+) ions. The influence of substituents on protonation and site-specific adduct [M+13](+) and [M+41](+) ion formation is also observed, with the cyano substituent showing the most stable [M+41](+) ion. Collision-activated dissociation experiments were used to characterize the variety of adducts formed under CI conditions, and provided insight into product ion structures and mechanisms of dissociation and condensation during CI-MS/MS.     

Gas-phase ion-molecule reactions in organophosphorus esters

Self-condensation ion-molecule reactions of trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, trimethyl phosphate and 2, 2-dichlorovinyl dimethyl phosphate (dichlorvos) were investigated by ion trap mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry. Reaction paths for the main processes observed were elucidated by parent ion selection and for reaction times up to 500 ms. In parallel, high-resolution measurements were performed in order to determine the composition of the principal ions. Among the compounds under examination, trimethyl phosphite and triethyl phosphite mainly give [M + H](+) and [M + (RO)(2)P](+) (R = CH(3), C(2)H(5)) adduct ions, whereas trimethyl phosphate and dimethyl phosphonate display [2M + H](+) ions, as the only abundant products, formed by reaction of [M + H](+) and M. 2,2-Dichlorovinyl dimethyl phosphate mostly shows fragmentation processes. The reaction patterns of the compounds examined were related to their different structural features. Gas-phase basicities of the phosphoryl compounds were also determined or re-examined. Copyright 1999 John Wiley & Sons, Ltd.     

Mass spectral studies of meso-dialkyl, alkyl aryl and cycloalkyl calix(4)pyrroles under positive and negative ion electrospray ionization conditions

A series of meso-dialkyl, alkyl aryl and cycloalkyl calix(4)pyrroles (1-15) are studied under positive and negative ion electrospray ionization (ESI) conditions. The positive ion spectra show abundant [M + H](+) and [M + Na](+) ions and the negative ion spectra show the [M + Cl](-) (the Cl(-) ions from the solvent) and [M - H](-) ions. The collision induced dissociation (CID) spectra of [M + H](+), [M + Na](+), [M + Cl](-) and [M - H](-) ions are studied to understand their dissociation pathway and compared to that reported for M(+) under electron ionization (EI) conditions. The beta-cleavage process that was diagnostic to M(+) is absent in all the CID spectra of the ions studied under ESI. Dissociation of all the studied ions resulted in the fragment ions formed by sequential elimination of pyrrole (A) and/or dialkyl/alkyl aryl/cycloalkyl (B) groups involving hydrogen migration to pyrrole ring at each cleavage of A--B bond, which clearly reveals the arrangement of A and B groups in the calix(4)pyrroles. The source of hydrogen that migrates to pyrrole ring during A--B bond cleavage is investigated by the experiments on deuterated compounds and [M + D](+) ions; and confirmed that the hydrogen attached to pyrrole nitrogen, hydrogen on alpha-carbon of alkyl group and the H(+)/Na(+) ion that added during ESI process to generate [M + H](+)/[M + Na](+) ions involve in the migration. The yields of [M + Na](+) ions are found to be different for the isomeric meso-cycloalkyl compounds (cycloheptyl, and 2-, 3- and 4-methyl cyclohexyl) and for normal and N-confused calix(4)pyrroles. The isomeric methyl and 3-hydroxy/4-hydroxy phenyl calix(4)pyrroles show specific fragmentation pattern during the dissociation of their [M - H](-) ions.     

Comparison of electrospray ionization,atmospheric pressure chemical ionization,and atmospheric pressure photoionization for the analysis of dinitropyrene and aminonitropyrene LC-MS/MS

The only relevant source for human exposure to dinitropyrenes is diesel engine emissions. Due to this specificity, dinitropyrenes may be used as biomarkers for monitoring human exposure to diesel engine emissions. Only few analytical methods have been described for the quantitation of dinitropyrenes and their metabolites, aminonitropyrenes, and diaminopyrenes. Therefore, for dinitropyrenes, aminonitropyrenes, and diaminopyrenes were selected as model compounds for the development of a sensitive HPLC-MS/MS method (high performance liquid chromatography coupled to triple quadrupole mass spectrometry) was to quantify polyaromatic amines and nitroarenes in biological matrices was developed optimal methods by comparing electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) sources. Dinitropyrene was not effectively ionized and diaminopyrene yielded mainly [M(.)](+) ions by electrospray ionization. With APCI and APPI, precursor ions of diaminopyrene and aminonitropyrene were [M + H](+) and [M(.)](-) for dinitropyrene. Precursor ions with [M - 30(.)](-) for dinitropyrene and [M - 30 + H](+) for aminonitropyrene were observed. Reversed and normal phase HPLC-MS/MS with ESI, APCI and APPI were optimized separately with respect to unequivocal analyte identification and sensitivity. Normal phase HPLC coupled to APPI-MS/MS gave the highest precision and sensitivity for aminonitropyrene (6%/0.2 pg on column) and dinitropyrene (9%/0.5 pg on column). The limit of detection in spiked rat plasma was 5 pg/100 microL for aminonitropyrene (accuracy 82%) and 10 pg/100 microL for dinitropyrene (accuracy 105%). In plasma of rats treated with dinitropyrene by oral administration, no detectable levels of dinitropyrene but higher aminonitropyrene levels compared with intratracheal instillation were observed. These findings clearly demonstrate that dinitropyrene was absorbed after oral and intratracheal application and that a reduction of nitro groups occurs to a high extent in the reductive environment of the intestine. To our knowledge, this is the first time that aminonitropyrene was observed in plasma after intratracheal or oral administration directly demonstrating the reductive metabolism of dinitropyrene in vivo.     

Fragmentation study of salinomycin and monensin A antibiotics using electrospray quadrupole time-of-flight mass spectrometry

The fragmentation pathways of two selected ionophore antibiotics, salinomycin and monensin A, were studied using electrospray (ES) orthogonal acceleration quadrupole time-of-flight mass spectrometry in positive-ion mode. The identity of fragment ions was determined by accurate-mass measurements. In ES mass spectra, ion signals of relatively high intensity were observed for [M+Na](+) and [M-H+2Na](+) for each antibiotic. Each of the ion species [M+Na](+) and [M-H+2Na](+) for salinomycin and [M-H+2Na](+) for monensin A were isolated in turn and subjected to fragmentation. In the fragmentation of [M+Na](+) and [M-H+2Na](+) from salinomycin, only Cbond;C single bond cleavage and dehydration were observed. Product ion mass spectra obtained from [M-H+2Na](+) of monensin A showed that ether ring opening, Cbond;C single bond cleavage and dehydration fragmentations had occurred. Fragment ions containing two sodium atoms were observed in the product ion mass spectrum of [M-H+2Na](+) from salinomycin, but not from monensin A. Both type A (containing the terminal carboxyl group) and type F (containing the terminal hydroxyl group) fragment ions were observed in the product ion mass spectra of sodium adduct ions of salinomycin and monensin A.     

Isomer differentiation by combining gas chromatography,selective self-ion/molecule reactions and tandem mass spectrometry in an ion trap mass spectrometer

This study presents a novel, simple and rapid procedure for isomer differentiation by combining gas chromatography (GC), a selective self-ion/molecule reaction (SSIMR) and tandem mass spectrometry (MS/MS) in an ion trap mass spectrometer (ITMS). SSIMR product ions were produced from four isomers. For aniline, SSIMR induces the formation of the molecular ion, [M+H](+), [M+CH](+), adduct ions of fragments ([M+F](+), where F represents fragment ions) and [2M-H](+). 2 and 3-Picoline produce [M+H](+), [2M-H](+) and [M+F](+), while 5-hexynenitrile produces [M+H](+), [M+F](+) and [2M+H](+) ions. The proposed method provides a relatively easy, rapid and efficient means of isomer differentiation via a SSIMR in the ITMS. Typically, isomer differentiation can be achieved within several minutes. The superiority of the SSIMR technique for isomer differentiation over electronic ionization (EI) is also demonstrated.     

Selective determination of pyridine alkaloids in tobacco by PFTBA ions/analyte molecule reaction ionization ion trap mass spectrometry

The application of perfluorotributylamine (PFTBA) ions/analyte molecule reaction ionization for the selective determination of tobacco pyridine alkaloids by ion trap mass spectrometry (IT-MS) is reported. The main three PFTBA ions (CF(3)(+), C(3)F(5)(+), and C(5)F(10)N(+)) are generated in the external source and then introduced into ion trap for reaction with analytes. Because the existence of the tertiary nitrogen atom in the pyridine makes it possible for PFTBA ions to react smoothly with pyridine and forms adduct ions, pyridine alkaloids in tobacco were selectively ionized and formed quasi-molecular ion [M + H](+)and adduct ions, including [M + 69](+), [M + 131](+), and [M + 264](+), in IT-MS. These ions had distinct abundances and were regarded as the diagnostic ions of each tobacco pyridine alkaloid for quantitative analysis in selected-ion monitoring mode. Results show that the limit of detection is 0.2 microg/mL, and the relative standard deviations for the seven alkaloids are in the range of 0.71% to 6.8%, and good recovery of 95.6% and 97.2%. The proposed method provides substantially greater selectivity and sensitivity compared with the conventional approach and offers an alternative approach for analysis of tobacco alkaloids.     

Tandem mass spectrometric approach for determining the structure of molecular species of ceramide in the marine sponge Haliclona cribricutis

Ceramides are important intracellular second messengers that play a role in the regulation of cell growth, differentiation and programmed cell death. Analysis of these second messengers requires sensitive and specific analytical method to detect individual ceramide species and to differentiate between them. Eight molecular species of ceramide were identified from the marine sponge Haliclona cribricutis using electrospray ionization tandem mass spectrometry (ESI-MS/MS). From this marine sponge N-hencicosanoyl (N21:0) to N-hexasanoyl (N26:0) Octadecasphing-4 (E)-enine have been reported for the first time. The ESI-MS spectra gave several strong protonated molecular ion [M+H](+) with the corresponding bis (2-ethyl hexyl) phthalate adduct [M+H+DHEP](+). The collision induced dissociation (CID) on ceramides at m/z 622.7337, 636.7645, 650.7789, 664.7925 and 678.8130 conducted at low-collision energy produced well characteristic product ions at m/z 252.31, 264.32, 278.33, 282.33 and 296 .35 for d18:1 sphingosine regardless of the length of the fatty chain. The MS/MS of the Phthalate adduct [M+H+DHEP](+) at m/z 1013.1820, 1027.1971, 1041.2176, 1055.2394 and 1069.2573 also yielded characterizing product ions for sphingosine and confirmed the molecular ion at m/z 391 for bis (2-ethyl hexyl) phthalate. The major ions in the [M+H](+) and [M+H+DHEP](+) were due to neutral loss of [M+H-H(2)O](+) and [M+H(H(2)O)(2)](+).     

Application of 1-alkylamines to a liquid chromatographic/turbo ionspray tandem mass spectrometric method for quantifying metabolites of a new bone anabolic agent,TAK-778, in human serum

We investigated the application of alkylamines, as additives to the mobile phase, to a quantification method for the metabolites, M-III and M-IV, of TAK-778, which is a new bone anabolic agent, in human serum using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Prior to setting up the analytical method, we found that 1-alkylamines co-existing with M-III and M-IV in the turbo ionsprayed solution formed 1-alkylammonium adduct molecules of these metabolites during the ionization process, and the abundance of the adduct ions was considerably higher than that of protonated molecules ([M + H](+)s) of these metabolites. Based on these findings, we investigated a variety of 1-alkylamines and their spiked concentrations in the mobile phase for LC/MS/MS analysis to obtain higher sensitivities for the quantification of these metabolites. After these examinations, we found that 1-hexylamine at a final concentration of 0.05 mmol l(-1) was the most suitable additive for the mobile phase, and set the selected reaction monitoring (SRM) ions for the 1-hexylammonium adduct molecule and [M + H](+), allowing about a fivefold gain in the SRM chromatographic peak compared with that without 1-hexylamine. The adduct ion was considered to be formed by interaction between the amino group of 1-hexylamine and the phosphoryl group of M-III and M-IV. The internal standard (I.S.) used was deuterated M-III for each metabolite. The analytes and I.S. were extracted with diethyl ether from serum samples at neutral pH and injected into the LC/MS/MS system with a turbo ionspray interface. The limit of quantification for both analytes was 0.5 ng ml(-1) when 0.1 ml of serum was used, and the calibration curves were linear in the range 0.5-100 ng ml(-1). The method was precise; the intra- and inter-day precisions of the method were not more than 5.6%. The accuracy of the method was good, with deviations between added and calculated concentrations of M-III and M-IV being typically within 16.6%. This method provided reliable pharmacokinetic data for M-III and M-IV after the intramuscular administration of TAK-778 sustained-release formulation in humans.     

Doping control analysis of insulin and its analogues in equine urine by liquid chromatography-tandem mass spectrometry

Insulin and its analogues have been banned in both human and equine sports owing to their potential for misuse. Insulin administration can increase muscle glycogen by utilising hyperinsulinaemic clamps prior to sports events or during the recovery phases, and increase muscle size by its chalonic action to inhibit protein breakdown. In order to control insulin abuse in equine sports, a method to effectively detect the use of insulins in horses is required. Besides the readily available human insulin and its synthetic analogues, structurally similar insulins from other species can also be used as doping agents. The author's laboratory has previously reported a method for the detection of bovine, porcine and human insulins, as well as the synthetic analogues Humalog (Lispro) and Novolog (Aspart) in equine plasma. This study describes a complementary method for the simultaneous detection of five exogenous insulins and their possible metabolites in equine urine. Insulins and their possible metabolites were isolated from equine urine by immunoaffinity purification, and analysed by nano liquid chromatography-tandem mass spectrometry (LC/MS/MS). Insulin and its analogues were detected and confirmed by comparing their retention times and major product ions. All five insulins (human insulin, Humalog, Novolog, bovine insulin and porcine insulin), which are exogenous in horse, could be detected and confirmed at 0.05ng/mL. This method was successfully applied to confirm the presence of human insulin in urine collected from horses up to 4h after having been administered a single low dose of recombinant human insulin (Humulin R, Eli Lilly). To our knowledge, this is the first identification of exogenous insulin in post-administration horse urine samples.     

Selective self-ion/molecule reactions in both external and internal source ion trap mass spectrometers

Novel results on the selective self-ion/molecule reactions (SSIMR) in both external and internal source ion trap mass spectrometers are demonstrated. Selective self-ion/molecule reaction product ions were produced between the oxygenated and nitrogenated crown ethers. For the oxygenated crown ethers, self-ion/molecule reactions lead to the formation of the protonated ions, adduct ions of fragments ([M + F](+)) and [M + H(3)O](+), while the nitrogenated crown ethers produce [M + H](+), [M + CH](+) and [M + C(2)H(3)](+) ions.     

Liquid chromatography tandem mass spectrometry method for the quantification of clonidine with LLOQ of 10 pg/mL in human plasma

A sensitive high-performance liquid chromatography-positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of clonidine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 230 to 44 for clonidine and m/z 254 to 44 for the internal standard. The assay exhibited a linear dynamic range of 10-2000 pg/mL for clonidine in human plasma. The lower limit of quantification was 10 pg/mL with a relative standard deviation of less than 6.8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 250 human plasma samples per day. The validated method was successfully used to analyze human plasma samples for application in pharmacokinetic studies. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Quantification of pramipexole in human plasma by liquid chromatography tandem mass spectrometry using tamsulosin as internal standard

A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of pramipexole in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 212/152 for pramipexole and m/z 409/228 for the IS. The method exhibited a linear dynamic range of 200-8000 pg/mL for pramipexole in human plasma. The lower limit of quantification was 200 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 3.5 min for each sample made it possible to analyze more than 200 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.