Quadrupole Mass Spectrometric Method Research Articles

Development of an analytical method for indoor polycyclic aromatic hydrocarbons and their halogenated derivatives by using thermal separation probe coupled to gas chromatography-tandem mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) have been a concern because of their high toxicity. Monitoring indoor PAHs and XPAHs concentrations is important for risk assessment because humans typically spend >90 % of their time indoors. However, the background levels of indoor PAHs and XPAHs concentrations are unknown because of the low sensitivity of conventional analytical methods. In this study, we developed a highly sensitive analytical method using a thermal separation probe (TSP) coupled to a gas chromatograph with a triple quadrupole mass spectrometer method for 26 PAHs and 40 XPAHs. The method quantification limit (MQL) values of the TSP method were 1.1 (3,8-dichlorofluoranthene)–906 (dibenzo[a,e]pyrene) times lower than those of the conventional method. The regression line comparing the TSP and conventional methods was y = (0.944 ± 0.0401)x, which was in good agreement. These results demonstrate that the TSP method can be applied to indoor air analysis. The total concentrations of PAHs and XPAHs were 944 and 73.5 pg m−3 for the house and 735 and 0.924 pg m−3 in the office, respectively. Among the detected compounds, 13 PAHs and XPAHs could not be detected using conventional methods because of their high MQL values. The composition of total toxicity equivalency values in the house was dominated by dibenzo[a,i]pyrene (DBaiP: 43.2 %) and dibenzo[a,h]pyrene (DBahP: 27.1 %), which could not be detected using the conventional method. Therefore, the TSP method can improve the risk assessment of indoor PAHs and XPAHs.

Development of liquid chromatography-triple quadrupole mass spectrometric method for the quantitative determination of a novel adjuvant, Imidazoquinoline gallamide in aluminum hydroxide gel-Imidazoquinoline gallamide and COVAXIN.

Imidazoquinoline gallamide is a toll-like receptor 7/8 agonist, belongs to the imidazoquinoline class, has the potential to activate antigen-presenting cells, and enhances immune response, primarily Th1 response. The COVAXIN is a whole virion inactivated Coronavirus disease 2019 vaccine formulated with this novel adjuvant called, aluminum hydroxide gel Imidazoquinoline gallamide, wherein, Imidazoquinoline gallamide is chemisorbed onto aluminum hydroxide gel. Herein, an analytical method based on liquid chromatography-tandem mass spectrometry was developed to identify and quantify Imidazoquinoline gallamide in aluminum hydroxide gel Imidazoquinoline gallamide and COVAXIN. The multiple reaction monitoring transitions were optimized for Imidazoquinoline gallamide quantification are [M+H]+ ions with 512.24→343.19 m/z (quantifier ion) and 512.24→360.22 m/z (qualifier ion). The developed method was validated as per the international conference on harmonization quality2 revison1 guidelines. The method was linear in the range of 0.025-10µg/mL with a coefficient of determination of 0.9985 and the limit of quantification is 0.025µg/mL. The accuracy was in the range of 82-121 % and intra- and inter-day precision was less than 7.1% and 5.39%, respectively. The expanded uncertainty results are 9.2% for Imidazoquinoline gallamide in the sample. The validated method was successfully applied to evaluate Imidazoquinoline gallamide concentration in every batch of COVAXIN.

Ultra-Performance Liquid Chromatography Coupled with a Triple Quadrupole Mass Spectrometric Method for the Quantification of Antiepileptic Drugs Methsuximide and Normesuximide in Human Plasma and its Application in a Pharmacokinetic Study

Background: Extensive therapeutic drug monitoring needs an analytical method for efficient and sensitive quantification of analytes of interest in clinical pharmacology. Objective: A rapid, robust, sensitive and simple UPLC-MS/MS method to quantify Methsuximide (Ms) and N-desmethyl methsuximide/Normesuximide (MsMET) in human plasma was optimized, developed, and validated for application in a pharmacokinetic study. Method: Reverse phased chromatography was performed using Zorbax SB-C18, 4.6 x 75 mm., 3.5 μm as stationary phase, methanol and 0.1% formic acid (60:40 v/v) as mobile phase which was delivered isocratically at a flow rate of 0.9 mL/min. The sample injection volume was 5 μL. Mass spectrometric quantification of the analytes was performed using positive electrospray ionization as mass interface along with multiple reaction monitoring (MRM) as acquisition mode. Results: The selected mass transition ions for analyte, metabolite and its respective internal standards are as follows, precursor ion (m/z) and product ion (m/z): Ms (204.06 and 119.02), MsMET (190.05 and 119.82), Ms internal standard (MsIS) (209.17 and 124.02), and MsMET internal standard (MsMETIS) (195.09 and 124.16), respectively. The current method was found to be linear for Ms (60.720-6043.800 ng/mL) and MsMET (60.389 - 6010.800 ng/mL) with r2 values not less than 0.999. The mean recoveries of all analytes ranged between 71.37 and 86.38 percentage. Conclusion: This method was validated in accordance with USFDA’s bioanalytical guidelines. Conclusion: This method was validated in accordance with USFDA’s bioanalytical guidelines. This method could be applied for a routine analysis of Ms and MsMET in clinical pharmacological practice.

Polar Reversed-Phase Liquid Chromatography Coupled with Triple Quadrupole Mass Spectrometer Method for Simple and Rapid Determination of Maleic Hydrazide Residues in some Fruits and Vegetables

Maleic hydrazide (MH) is used as a plant growth regulator, herbicide, and sprouting inhibitor for some crops to improve the growth and the quality of some fruits and vegetables so that MH residues should be analyzed in food. Most of the chromatographic analysis methods for MH residues were operated by using ion chromatographic (IC) columns which need complicated with extra washing and conditioning steps. The developed method has overcome this problem by using Synergi polar reversed-phase (RP) column and non-scheduled multiple-reactions monitoring (MRM) scanning modes. Liquid chromatography coupled with negative electrospray ionization triple quadrupole mass spectrometer LC-ESI (-) MS/MS method was developed and validated according to SANTE/12682/2019 at four fortification levels in four food matrices. The method optimization was carried out by using different extracting solvents, LC columns, and mobile phase ratios. The extraction was developed and operated by using 1% formic acid in methanol. The limits of quantification (LOQ) for MH were in the range 0.05–0.1 μg/g that was below the EU maximum residue limit (MRL), set for the studied food matrices such as onion, potatoes, citrus, and grape (15, 50, 0.2, and 0.2 μg/g) respectively. Good method linearity was obtained in the concentration range 0.01–2 μg/ml with correlation coefficients (r2) ≥ 0.99. The average recoveries ranged from 84 to 110% with relative standard deviations RSDs ≤ 17%. The matrix effects on the MH signals were studied and compensated by using the standard addition technique. This polar-RP-LC-ESI (-) MS/MS method was developed to help laboratories which determine the MH residues in food.

Methyl-4-Hydroxybutyrate and Ethyl-4-Hydroxybutyrate as Potential Markers for Simultaneous Consumption of GHB/GBL and Alcohol: Preliminary Investigations.

γ-Hydroxybutyric acid (GHB) and its corresponding lactone γ-butyrolactone (GBL) are misused as knock out (k.o.) drugs. The short detection window and the major inter- and intra-individual variations of endogenous GHB concentrations in commonly used matrices such as blood and urine complicate the analytical proof of an exogenous GHB/GBL administration. We searched for an alternative way to prove an exogenous GHB/GBL administration via detection of methyl- and ethyl-4-hydroxybutyrate, which could arise in alcoholic solutions after spiking with GHB/GBL. A liquid chromatographic-triple quadrupole mass spectrometric method was developed and validated to quantitatively determine methyl- and ethyl-4-hydroxybutyrate in alcoholic beverages (limit of detection [LoD]: 5.8 and 3.4 ng/mL, respectively). A sample collective of alcoholic beverages (n = 47) revealed natural occurring amounts of ethyl-4-hydroxybutyrate (<LoD-approx. 3980 ng/mL) with higher concentrations particularly found in wine samples. Nearly no ethyl-4-hydroxybutyrate was observable in spirits/liqueurs and no methyl-4-hydroxybutyrate was detectable at all. A moderate correlation was shown between the ethyl-4-hydroxybutyrate concentration and the pH-value in wine samples (pH 2.9-3.7, n = 29) as well as between the ethyl-4-hydroxybutyrate concentration and the GHB concentration in all measured beverages (GHB: < limit of quantification [LoQ]-11.4 µg/mL, n = 47). A dependency on alcohol content could not be observed. A voluntary intake (n = 1) of 750-mL wine naturally containing high amounts of ethyl-4-hydroxybutyrate (approx. 2010 ng/mL) revealed no observable GHB-ester concentrations in blood and urine. Furthermore, an experiment simulating a beverage that could potentially be used in a drug-facilitated crime (DFC) case showed ethyl-4-hydroxybutyrate concentrations exceeding the concentrations naturally observed in beverage samples. However, in order to evaluate whether ethyl-4-hydroxybutyrate could be useful as marker for the co-consumption of GHB/GBL and alcohol and to prolong the detection window of unintended GHB/GBL intake, further experiments have to be performed.

A Validated Ultra-Performance Liquid Chromatography Tandem Triple Quadrupole Mass Spectrometric Method for Fast Determination of Losartan in Rabbit Plasma.

A rapid UPLC-MS-MS method was developed and validated for determination of losartan in rabbit plasma. Protonated adducts of losartan and eprosartan (IS) were monitored in multiple reaction monitoring mode. Molecular masses of daughter species of losartan were m/z 423.19 > 207 and m/z 423.19 > 180; and of eprosartan were m/z 425.11 > 135 and m/z 425.11 > 107. Losartan from plasma samples was extracted by protein precipitation method. The mobile phase comprising water (0.1% formic acid) (A) and acetonitrile (0.1% formic acid) (B) was used in gradient mode. Analytes were eluted on Acquity UPLC®BEH C18 1.7 μm, 2.1 × 50 mm column. Sample run time was 3.0 min. The validation parameters: accuracy, precision and recovery were within recommended limits. Losartan as well as internal standard remains stable in benchtop stability study as well as in post-preparative stability study. Pharmacokinetic parameters such as Cmax (182.79 ± 23.80 ng/mL), Tmax (1.16 ± 0.28 h), AUC0-t (1188.57 ± 404.60 ng h/mL) and Kel (0.0954 ± 0.0140 h-1) of losartan were measured. Method was successfully applied for pharmacokinetic investigation in rabbits and can be used for losartan determination in plasma sample obtained from other animals.

Determination and pharmacokinetic study of AZD-3759 in rat plasma by ultra performance liquid chromatography with triple quadrupole mass spectrometer.

BackgroundAZD‐3759 is a new, potent, oral, active central nervous system‐penetrant EGFR inhibitor. Despite promising clinical activity among patients pretreated and never treated with EGFR‐tyrosine kinase inhibitors, no time saving pharmacokinetic study method has been reported in an animal model.MethodsProtein was precipitated with acetonitrile and then used for sample pre‐processing. A CORTECS BEH C18 column was used to separate the analytes at 40°C. Acetonitrile and water (containing 0.1% formic acid) were chosen as the mobile phase at a flow rate of 0.4 mL/min. The analytes were quantified by multiple reaction monitoring mode with positive electrospray ionization.ResultsThe target fragment ions were m/z 460.38→141 for AZD‐3759 and m/z 285.1→193.1 for internal standard diazepam. The calibration curve exhibited good linearity for AZD‐3759 at a range of 1–500 ng/mL. The intra‐run and inter‐run precision variations were both < 8.22%. The recovery rate of AZD‐3759 from plasma was > 76.4%.ConclusionAn accurate, simple ultra performance liquid chromatography with triple quadrupole mass spectrometer method was developed and validated to determine AZD‐3759 in rat plasma. Our validated method can be applied to the pharmacokinetic study of AZD‐3759 at an oral dosage of 10 mg/kg.

Development and Validation of Gas Chromatography-Triple Quadrupole Mass Spectrometric Method for Quantitative Determination of Regulated Plasticizers in Medical Infusion Sets.

A method for the quantitative determination of dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), bis(2-ethylhexyl) adipate (DEHA), bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), dioctyl terephthalate (DOTP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) in medical infusion sets was developed and validated using gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS) in the multiple reaction monitoring (MRM) mode. Solvent extraction with polymer dissolution for sample preparation was employed prior to GC-MS/MS analysis. Average recoveries of the eight target analytes are typically in the range of 91.8–122% with the relative standard deviations of 1.8–17.8%. The limits of quantification (LOQs) of the analytical method were in the ranges of 54.1 to 76.3 ng/g. Analysis using GC-MS/MS provided reliable performance, as well as higher sensitivity and selectivity than GC-MS analysis, especially for the presence of minority plasticizers at different concentrations.

Development of a high-speed MALDI-triple quadrupole mass spectrometric method for the determination of 3,4-methylenedioxymethamphetamine (MDMA) in oral fluid.

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is still a widely used illicit designer drug and its detection in different matrices is of major importance for forensic purposes (e.g. driving under the influence) as well as for workplace drug testing or abstinence control. Established analytical methods for the determination of MDMA are mainly employing high performance liquid chromatography (HPLC) or gas chromatography (GC) coupled to mass spectrometric detection. Matrix assisted laser desorption/ionization-triple quadrupole-tandem mass spectrometry (MALDI-QqQ-MS/MS) is so far rarely used in forensics and offers an ultrafast high-throughput platform. The Quantisal™ Oral Fluid Collection Device was used for sample collection. After addition of the deuterated internal standard and a carbonate buffer (0.75 M Na2 CO3 ), oral fluid samples were liquid-liquid extracted (ButOAc/EtOAc, 1:1). As little as 1 microlitre of a mixture of this extract and the MALDI matrix (alpha-cyano-4-hydroxycinnamic acid) was spotted onto the MALDI plate and could directly be analyzed. With MALDI omitting chromatographic separation, very short analysis times of about 10 s per sample were possible. The method was developed and validated according to international guidelines including specificity, recovery, matrix effects, accuracy and precision, stabilities and limit of quantification. All validation criteria were fulfilled except for ion suppression/enhancement. Comparison with a routine liquid chromatography-tandem mass spectrometry (LC-MS/MS) method showed good agreement of the results. Applicability of the method was shown by analyzing about 250 oral fluid samples collected after controlled administration of 125 mg MDMA in a pharmacokinetic study. The whole lot of samples could be analyzed in less than 1 h, proving the ultra-high-speed of the method.

Enantiospecific determination of naftopidil by RRLC–MS/MS reveals stereoselective pharmacokinetics and tissue distributions in rats

Naftopidil (NAF) is used as a racemate to treat benign prostatic hyperplasia (BPH) and to prevent prostate cancer. However, racemic NAF has low bioavailability; therefore, it is commonly administered at higher clinical dosages compared to other therapeutic BPH drugs. Differences in interactions between individual enantiomers and biological macromolecules may result in variations in pharmacokinetics and dispositions. This study aimed to investigate the pharmacokinetics, bioavailability and tissue distributions of NAF enantiomers in rats after intragastric administration of the individual enantiomers. A rapid and sensitive liquid chromatography coupled with triple–quadrupole mass spectrometric method (RRLC–MS/MS) was developed and validated for determination of NAF enantiomers in rat plasma, tissues, urine and feces. After intragastric administration, S(−)-NAF in plasma [maximum concentration (Cmax)=186.4ng/mL, area under the curve from 0h to 24h (AUC0–24h)=877.9ngh/mL] was significantly higher than that of R(+)-NAF (Cmax=133.2ng/mL, AUC0–24h=602.1ngh/mL). Moreover, S(−)-NAF bioavailability was twice that of R(+)-NAF. R(+)-NAF distributions in the prostate, liver, and kidney were significantly higher than S(−)-NAF distributions (R/S ratios of 3.16, 1.33, and 2.90, respectively). These data reveal the stereoselective pharmacokinetic profiles of the two enantiomers in rats.

A validated quantitative liquid chromatography–tandem quadrupole mass spectrometry method for monitoring isotopologues to evaluate global modified cytosine ratios in genomic DNA

5-Hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC) represent important epigenetic modifications to DNA, and a sensitive analytical method is required to determine the levels of 5hmC in the genomic DNA of tumor cells or cultured cell lines because 5hmC is present at particular low levels in these cells. We have developed a sensitive liquid chromatography-tandem quadrupole mass spectrometric method for quantifying 5-hydroxymethyldeoxycytidine (5hmdC), 5-methyldeoxycytidine (5mdC), and deoxyguanosine (dG) levels using stable isotope labeled internal standards, and used this method to estimate the global level of 2 modified cytosines in genomic DNA prepared from small number of cells. The quantification limits for 5hmdC, 5mdC and dG were 20pM, 2nM and 10nM, respectively. MRM transitions for isotopologue (isotopologue-MRM) were used to quantify the 5mdC and dG levels because of the abundance of these nucleosides relative to 5hmdC. The use of isotopologue-MRM for the abundant nucleosides could also avoid the saturation of the detector, and allow for all three nucleosides to be analyzed simultaneously without the need for the dilution and re-injection of samples into the instrument. The global ratios of modified cytosine nucleosides to dG were estimated following the quantification of each nucleoside in the hydrolysate of genomic DNA. The limit of estimation for the global 5hmC level was less than 0.001% using 200ng of DNA. Using this method, we found that MLL-TET1, which a fusion protein in acute myelogenous leukemia, did not produce 5hmC, but interfered with TET1 activity to produce 5hmC in cells. Our analytical method is therefore a valuable tool for further studies aiming at a deeper understanding of the role of modified cytosine in the epigenetic regulation of cells.

Development and validation of a microfluidic chip-based nano-liquid chromatography–triple quadrupole tandem mass spectrometry method for a sensitive and reliable quantification of 7-ethyl-10-hydroxycamptothecin (SN38) in mouse plasma

There is an increasing need for more sensitive analytical methods in pharmacokinetic studies, for example, for phase 0 clinical trials. A novel HPLC Chip-triple quadrupole mass spectrometer method (HPLC Chip-MS/MS method) for the quantification of 7-ethyl-10-hydroxycamptothecin (SN38) was developed, validated, and employed to the pharmacokinetic analysis of SN38 in ICR mice. Protein precipitation with a ratio of plasma/acetonitrile of 1:10 was chosen as the sample processing method. The nano-electrospray inserted in the microfluidic chip operated in positive mode, and selected reaction monitoring was used for quantification. Our bioanalytical method met all essential validation parameters-selectivity, accuracy, precision, dilution integrity, calibration curve, matrix effect, recovery, and different stability tests (benchtop, freeze-thaw, autosampler stability). The calibration curves (weight 1/x (2)) were linear for the range 50-10,000 pg/mL. Clogging was not observed until the end of the lifetime of the microfluidic chip (350-400 injections), and carryover was practically eliminated through the introduction of a step gradient elution program. After intraperitoneal injection of 0.1 mg/kg irinotecan, SN38 concentration could be measured up to 6 h with accuracy and precision. Thus, we developed a new, very sensitive HPLC Chip-MS/MS method for the determination of plasma SN38 that has been validated in compliance with guidelines from different regulation authorities.

Increased Levels of Inosine in a Mouse Model of Inflammation

One possible mechanism linking inflammation with cancer involves the generation of reactive oxygen, nitrogen, and halogen species by activated macrophages and neutrophils infiltrating sites of infection or tissue damage, with these chemical mediators causing damage that ultimately leads to cell death and mutation. To determine the most biologically deleterious chemistries of inflammation, we previously assessed products across the spectrum of DNA damage arising in inflamed tissues in the SJL mouse model nitric oxide overproduction ( Pang et al. ( 2007 ) Carcinogenesis 28 , 1807 - 1813 ). Among the anticipated DNA damage chemistries, we observed significant changes only in lipid peroxidation-derived etheno adducts. We have now developed an isotope-dilution, liquid chromatography-coupled, tandem quadrupole mass spectrometric method to quantify representative species across the spectrum of RNA damage products predicted to arise at sites of inflammation, including nucleobase deamination (xanthosine and inosine), oxidation (8-oxoguanosine), and alkylation (1,N(6)-ethenoadenosine). Application of the method to the liver, spleen, and kidney from the SJL mouse model revealed generally higher levels of oxidative background RNA damage than was observed in DNA in control mice. However, compared to control mice, RcsX treatment to induce nitric oxide overproduction resulted in significant increases only in inosine and only in the spleen. Further, the nitric oxide synthase inhibitor, N-methylarginine, did not significantly affect the levels of inosine in control and RcsX-treated mice. The differences between DNA and RNA damage in the same animal model of inflammation point to possible influences from DNA repair, RcsX-induced alterations in adenosine deaminase activity, and differential accessibility of DNA and RNA to reactive oxygen and nitrogen species as determinants of nucleic acid damage during inflammation.

Rapid determination of pesticide residues in herbs using selective pressurized liquid extraction and fast gas chromatography coupled with mass spectrometry

A selective pressurized liquid extraction and gas chromatography coupled with triple quadrupole mass spectrometer method was developed for simultaneous determination of 52 pesticide residues in medicine and food dual-purpose herbs. The developed extraction method integrated extraction and cleanup processes for sample preparation. The sorbents, 5 g Florisil and 100 mg graphitized carbon black, were placed inside the extraction cell to remove matrix interferences. Optimized conditions of selective pressurized liquid extraction were ethyl acetate as extraction solvent, 120°C of extraction temperature, 6 min of static extraction time, 50% of flush volume extracted for two cycles. An ultra inert capillary GC-MS HP-5 UI column (20 m × 0.18 mm id, 0.18 μm) and column backflush system were used for the analysis. Multiple-reaction monitoring was employed for the quantitative analysis with electron ionization mode. All calibration curves showed good linearity (r(2) > 0.995) within the test ranges. The average recoveries of most pesticides were from 81 to 118%. The validated method was successfully applied for the determination of pesticide residues in four herbs. The results indicate that selective pressurized liquid extraction and GC-MS/MS is a sensitive and reliable analytical method for the simultaneous determination of multiple pesticide residues in herbs.

Fast gas chromatography‐full scan quadrupole mass spectrometry for the determination of allergens in fragrances

The Scientific Committee for Cosmetics and NonFood Products in the 7th Amendment to the European Cosmetics Directive established 26 fragrance components, widely used in cosmetic products, as being responsible for a series of contact allergies (Directive 2003/15/EC, Official Journal of the European Union, L66/26, 11.3.2003). The regulation foresees that any allergen, present in excess of 100 mg/kg in rinse-off and of 10 mg/kg in leave-on formulations, must be reported on the label of the product. The present research reports a fast GC-full scan quadrupole mass spectrometric method (under 5 min) for the qualitative/quantitative analysis of allergens in perfumes. Reliable peak identification was achieved through a twin-filtered MS library matching procedure, considering a minimum degree of spectral similarity (90%) and retention data (a linear retention index window was applied). Peak quantification was carried out by using a specific extracted ion. In case a suspected allergen fell within its retention time window but presented a low degree of spectral purity (< 90%), analyte determination was achieved by using three extracted ions (one quantifier and two qualifiers). The fast GC-MS method was validated in terms of intraday retention time and peak area precision, LODs and LOQs, and method linearity. Finally, peak skewing was also evaluated and was within more than acceptable limits.

Ultra-performance liquid chromatography for the determination of pesticide residues in foods by tandem quadrupole mass spectrometry with polarity switching

An ultra-performance liquid chromatographic (UPLC) electrospray ionisation tandem quadrupole mass spectrometric method has been developed for the determination of 52 pesticides in cereal-based baby foods, oranges and potatoes. The fast polarity switching capability of the mass spectrometer used enabled the determination of 44 of the compounds in the positive ionisation mode and 8 of the compounds in the negative ionisation mode in a single run. Prior to analysis, co-extractives were removed from acetonitrile extracts using dispersive solid-phase extraction with primary secondary amine (50 mg). The UPLC method separates all of the pesticides, resolves structural isomers (e.g. butocarboxim sulfoxide and aldicarb sulfoxide) and has a short (7 min) cycle time. Extracts spiked with pesticides at 0.10 and 0.01 mg kg −1 yielded average recoveries in the range of 66–124% with relative standard deviations less than 19% for the majority of the analytes.

Deposition of Polyethylene Thin Films Using Synchrotron Radiation Ablation

Crystalline polyethylene thin films were deposited on Si substrates using the synchrotron radiation(SR) ablation method. The deposited films were characterized by X-ray diffraction and Fourier-transform infrared spectroscopy. In order to understand the mechanism for the decomposition that occurs due to SR ablation, analysis of gases resulting from the decomposition was performed using the quadrupole mass spectrometric method. The mechanism involved in the carbonization was clarified.

Mass and velocity distributions of laser ablated species ejected from a colossal magnetoresistant Pr 0.67Sr 0.33MnO 3 target

Pulsed laser ablation of the colossal magnetoresistant (CMR) material, Pr 0.67Sr 0.33MnO 3, has been investigated using a time-resolved quadrupole mass spectrometric method under both 355 nm and 532 nm laser irradiation. Mass and velocity distributions of the ionic and neutral ablated species are measured. The major ablated species include metal atoms and ions as well as binary metal oxides. The time-of-flight (TOF) spectra of ablated species are well fitted by a Maxwell–Boltzmann distribution with a center-of-mass velocity. The kinetic energies of ablated metal ions are found to be up to 8 eV while those of neutral species are estimated to be less than 1.0 eV. The ablation yields of ablated species increase with increasing of laser fluence while the kinetic energies of ionic species are nearly independent of laser fluence. Possible mechanism of laser ablation of a Pr 0.67Sr 0.33MnO 3 target is discussed.

An angle-resolved time-of-flight mass spectrometric study of pulsed laser ablated Ta2O5

Pulsed laser ablation of a Ta2O5 target at 532 nm has been investigated using an angle-resolved time-of-flight quadrupole mass spectrometric method. Mass and velocity distributions of the ionic and neutral ablated species were measured. The major ablated species, O (m/e=16), O2 (m/e=32), Ta (m/e=181), TaO (m/e=197), and TaO2 (m/e=213) were observed at a laser fluence of 0.7 J cm−2, and the intensities of neutral species were found to be higher than those of the ionic species. The time-of-flight spectra of ablated species were fitted by a Maxwell–Boltzmann distribution with a center-of-mass velocity. The angular distributions of the ionic and neutral ablated species can be fitted with cosn θ (n=15) and 0.25 cos θ+0.75 cosn θ (n=15), respectively. The laser fluence had no obvious influence on the translational energies of the ablated species. In addition, a continuous wave oxygen molecular beam was introduced into the ablated plume, and the enhancement of the intensities of the TaO and TaO2 signals was observed. This result implies that the reactions of ablated Ta-containing species with ambient oxygen molecules in the gas phase play an important role in the pulsed laser deposition process.