Quasi-molecular Ions Research Articles

Molecular weight evaluation of poly-dimethylsiloxane on solid surfaces using silver deposition/TOF-SIMS

Molecular ions include information about end groups, functional groups and molecular weight. A method for directly detecting this in the high-mass region of the spectrum (>1000 amu) from poly-dimethylsiloxane (PDMS) on a solid surface was investigated. It was found that a TOF-SIMS analysis of silver-deposited surfaces (silver deposition/TOF-SIMS) is useful for this purpose. Two methods for silver deposition, the diode sputtering method and the vacuum evaporation coating method, were tried. The former required the sample to be cooled so as to prevent the damage of the sample surface due to thermal oxidation; the latter caused no damage to sample surfaces at room temperature. Using silver deposition/TOF-SIMS analysis, silver-cationized quasi-molecular ions were clearly detected from PDMS on solid surfaces and their images were observed without the interference of deposited silver. By applying to the analysis of paint defects, etc., it was confirmed that this technique is useful to analyze practical industrial materials. Silver-cationized ions were detected not only from PDMS, but also from other organic materials, such as some kinds of lubricant additives and fluorine oils on solid surfaces. Therefore, silver deposition/TOF-SIMS was proved to be useful for the analysis of thin substances on solid surfaces.

Isolation and identification of two isomeric forms of malonyl-coenzyme A in commercial malonyl-coenzyme A

Two isomers of malonyl-coenzyme A (malonyl-CoA) were detected in a commercial preparation of malonyl-CoA. These compounds were separated by preparative high-performance liquid chromatography (HPLC) and characterized by HPLC/ultraviolet (UV)/mass spectrometry. Both compounds had a UV absorbance maximum at 259–260 nm. Both compounds underwent negative electrospray ionization to produce a [M-H] −quasi-molecular ion at m/ z 852 and both compounds underwent collision-induced dissociation to produce a characteristic fragment at m/ z 808, all consistent with the structure of malonyl-CoA. Nuclear magnetic resonance spectrometry showed that the two chromatographically distinguishable malonyl-CoAs are structural isomers: the major component is the naturally occurring malonyl-CoA and the contaminant is 3 ′-dephospho-2 ′-phospho-coenzyme A.

Negative ion fab mass spectroscopy of some Ribose Alkylated 5′-ump derivatives

Characteristic fragment ions obtained in Fast atom bombardment (FAB) mass spectroscopy of ribose alkylated Uridine 5′-monophosphate (5′-UMP) derivatives in negative ion mode are described. All the compounds examined exhibited either [M]− or quasimolecular ion [M − H]− the fragmentations can be used to characterize these nucleotides.

Liquid chromatography coupled to negative electrospray/ion trap mass spectrometry for the identification of isomeric glutathione conjugates of catechol estrogens

Conjugation to glutathione (GSH) represents an important detoxification pathway for preventing DNA damage due to oxidation products of catechol estrogens. In order to identify isomeric GSH conjugates of catechol estrogens, liquid chromatography coupled to electrospray/ion trap mass spectrometry was used. For this purpose, both positive and negative ion modes were applied, generating protonated and deprotonated species, respectively. Energy-resolved fragmentation of each isomeric quasi-molecular ion was achieved in two regions of the mass spectrometer: (i) the mass analyzer (ion trap mass spectrometer) and (ii) the interface region of the electrospray ionization source. The resonance excitation of [M+H] + protonated ions carried out into the ion trap did not show any isomeric differentiation. Although ion source fragmentation of these same species allowed identification of each isomer, this method requires a good chromatographic separation, making it inefficient for the analysis of low sample amounts from in vitro or in vivo sources. Conversely, using resonance excitation of deprotonated ions, isomer distinction could be achieved. Thus, this technique should yield the best data for the direct characterization of isomers of catechol estrogen–GSH conjugates from biological samples.

Subcellular localisation of cholesterol and phosphocholine with pattern‐recognition‐imaging‐TOF‐SIMS

Molecular ions of cholesterol, and its fragments, and phosphocholine fragments of phospholipids, were localized in single cells with a resolution of <1 μm. This is the first example of subcellular localisation of membrane lipids with pattern‐recognition, imaging time‐of‐flight secondary ion mass spectrometry (PRITS) here utilized for identification and subcellular localisation of cholesterol and phosphocholine in PMN leukocytes. Cell imprints were produced by transferring the cell constituents of freeze‐dried cells to a silver foil, and the silver surface was analyzed by TOF‐SIMS. TOF‐SIMS spectra were recorded by scanning the primary ion beam over the analysis area and acquiring a positive mass spectrum of the ions leaving the surface. Data were collected at either high mass resolution m/Δm > 7000 or high lateral resolution. High mass resolution spectra were recorded on reference samples of pure cholesterol and phosphatidylcholine. Characteristic fragment peaks and the silver cationised quasimolecular ion [M+Ag]+ were selected as a pattern for the identification of the lipids in TOF‐SIMS images of surface‐adhering leukocytes. The localisation of membrane lipids showed lateral heterogeneity over the cell surface.

Determination of alkyltrimethylammonium surfactants in hair conditioners and fabric softeners by gas chromatography–mass spectrometry with electron-impact and chemical ionization

The commercial hair conditioners and fabric softeners were analyzed for the content of alkyltrimethylammonium compounds (ATMACs) by gas chromatography–mass spectrometry (GC–MS) with electron impact (EI) and low-pressure positive-ion chemical ionization (PICI) modes. The method involves mixed diluted samples (adjust pH to 10.0) with potassium iodide to enhance the extraction of iodide–ATMA + ion pairs by direct liquid–liquid extraction. The iodide–ATMA + pairs were then demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection-port. A high abundance of ADMAs was detected at the temperature above 300 °C in the GC injection-port. The enhanced selectivity of quasi-molecular ion chromatograms of C 12–C 18-ADMA, obtained using methanol PICI-MS enables ADMAs to be identified. The accuracy and precision of the method was validated and was successfully applied to determine contents of ATMAC in commercial hair conditioners and fabric softeners. The contents of total measured ATMAC ranged from 0.4 to 6.9% for hair conditioners, and from 3.3 to 4.6% for fabric softeners.

Simultaneous determination of fatty, dicarboxylic and amino acids based on derivatization with isobutyl chloroformate followed by gas chromatography—positive ion chemical ionization mass spectrometry

Gas chromatography–mass spectrometry (GC–MS) with positive ion chemical ionization (PICI) using isobutane as reagent gas was applied for analysis of isobutoxycarbonyl/isobutyl derivatives of 13 fatty, 6 dicarboxylic and 13 amino acids in a single run. For all investigated compounds (except several amino acids) the quasimolecular ions [MH] + were registered. Asparagine underwent fragmentation via decarboxylation followed by elimination of OC 4H 9 ([M−117] +), whereas serine and tyrosine produced the cluster ions [M+C 4H 9OCO] +. Estimated detection limits were 6–250 pg in the total ion current (TIC) mode and 3–10 times lower using the selected-ion monitoring (SIM) mode.

Surface-Ionization Mass Spectrometry of Opium Alkaloids

Surface ionization of the opium alkaloids morphine, codeine, thebaine, papaverine, and narcotine was investigated by mass spectrometry. It was shown that the alkaloid molecules were ionized with high efficiency through surface ionization. The mass spectra of morphine, codeine, and thebaine exhibited series of lines for quasimolecular ions with elimination of up to nine H atoms from the opiates that was accompanied by heterogeneous aromatization of the rings and their skeletal rearrangement. The results were compared with GC-MS data from electron ionization.

O-Phenylenediamine Electropolymerization by Cyclic Voltammetry Combined with Electrospray Ionization-Ion Trap Mass Spectrometry

The anodic oxidation of o-phenylenediamine at a platinum electrode in aqueous buffers at different pH (1−7), where growth of very thin (few nanometers thickness) and self-sealing polymeric films occurs, was investigated by cyclic voltammetry (CV) combined with off-line electrospray ionization-ion trap mass spectrometry (ESI-ITMS). Soluble oligomers (dimers, trimers, and tetramers in different oxidation states) formed in the course of the anodic oxidation were detected/identified by electrospray ionization-ion trap sequential mass spectrometry (ESI-ITMSn, n = 1−5) while their relative abundance could be estimated from full-scan ESI-MS spectra of the quasi-molecular ions. In particular, oligomer abundances and the abundance ratios between different n-mers of the same class (e.g., structures corresponding to the same value of n but having different m/z ratios) were considered, and their variation with pH and potential range adopted for polymerization was studied. A mechanistic pathway for the growth of poly(o-phenylenediamine) film (PPD), relying on the integration of CV and ESI-ITMS, could be formulated for the first time. Chain propagation seems to compete with two different intramolecular oxidation processes, leading to the formation of phenazine or 1,4-benzoquinonediimine units, whose relative importance is, in turn, dictated by polymerization conditions (pH and potential). The proposed mechanism can account for the different properties of PPD films prepared under different experimental conditions, as well as for the structural data obtained on the polymeric film itself by X-ray photoelectron spectroscopy.

Mexiletine carbonyloxy β-D-glucuronide: a novel metabolite in human urine

1. The study was performed to isolate and characterize a glucuronic acid conjugate of mexiletine that releases mexiletine on acid hydrolysis from urine samples obtained from healthy volunteers following a single oral dose of mexiletine. 2. The [M − H] − ion of the isolated metabolite was observed at m / z 398 in the negative electrospray ionization mass spectrum. This mass number was 44 higher than that of the product generated when mexiletine is subjected to direct glucuronidation. In positive-ion mode, collision-induced dissociation of the quasimolecular ion [M + NH 4] +, m / z 417, gave product ions at m / z 224, 180 and 58. These mass spectral data indicated that the metabolite contained a carbonyloxy moiety in its structure in addition to mexiletine and a glucuronic acid moiety. 3. The presence of this carbonyloxy moiety was further supported by the following chemical reactions. When the metabolite was hydrolysed with an aqueous solution of 1 M sodium hydroxide at room temperature, mexiletine was released, whereas the N -methoxycarbonyl derivative of mexiletine was obtained after treatment of the metabolite with methanolic sodium hydroxide solution. 4. The results indicated that the structure of the isolated metabolite was the N -carbonyloxy β -D-glucuronic acid conjugate of mexiletine.

Cationization of dendritic macromolecule adsorbates on metals studied by time‐of‐flight secondary ion mass spectrometry

AbstractTime‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was utilized to study dendritic macromolecules with various architectures, such as dendrons, dendrimers and hyperbranched polyesters prepared from bis‐(hydroxymethyl)propionic acid (Bis‐MPA) and a series of hyperbranched polyethers based on 3‐ethyl‐3(hydroxymethyl)oxetane. The measurements were performed on spin‐coated thin films of the branched molecules (D) onto silicon, chemically etched copper foil and silver‐coated wafers. They showed weak signatures of molecular ions by proton capture (D + H)+ in the high mass range of the spectra (m/z > 400). On the contrary, cationization of the intact molecules with alkali or transition metal ions such as Na+, Cu+ or Ag+ was observed. High‐intensity quasi‐molecular ions (D + M)+ (with M = Na+, Cu+ or Ag+) allowed the studied polymers to be identified. The whole molecular species were observed for Bis‐MPA dendrons and dendrimers up to 3000 Da for hydroxyl or acetonide‐terminated derivatives. The success of the so‐called cationization experiments with metal substrates compared with analysis of molecular adsorbates on silicon is highlighted. The ToF‐SIMS sensitivity appeared useful to provide information about the molecular end‐groups or to highlight incomplete reaction occurring during some deprotection step of the synthesis. Only uncationized fragments of low masses were detected for the hyperbranched polyesters. This result suggested the effect of molecular asymmetry and/or flattening of the molecules on the substrates, which hampered the molecule lift‐off efficiency. Nevertheless, the hyperbranched polyethers were characterized based on the peak distribution of intensities, which allowed estimation of their molecular weight average. This work was intended to illustrate the capabilities of ToF‐SIMS to analyse dendritic polymers on surfaces. Copyright © 2003 John Wiley & Sons, Ltd.

Photolysis of NSAIDs. I. photodegradation products of carprofen determined by LC-ESI-MS.

A solution of carprofen in methanol at a concentration of 2.74 x 10(-2) mg/mL is subjected to photoirradiation using a Hanovia 200-W high-pressure Hg lamp for 9 h. In total, seven photodegradation products are separated, and their quasimolecular ions are subsequently determined online using a liquid chromatography (LC)-electrospray ionization (ESI)-mass spectrometry (MS) method. The high-performance LC consists of an Inertsil 5 ODS-80A (2.1- x 150-mm) column. The mobile phase is initially CH(3)CN. NH(4)OAc (20mM in de-ionized H(2)O) is 43:57 (v/v), and after 14 min it is CH(3)CN. NH(4)OAc (20mM in de-ionized H2O) is 54: 46 (v/v). The UV detector was set at 260 nm. The parameters of LC-MS for mass determination involves an atmospheric pressure ionization electron spray interface with a negative mode of polarity (ESI(-)). The chemical structures of the degradants are elucidated based on the mass-to-charge ratio of the quasimolecular ions and the molecular weight changes by comparison with the parent drug (carprofen). The degradation proceeds via an initial dechlorination. A dechlorination or esterification reaction is competed with decarboxylation. This finding is in accordance with our previously reported result of first order photodecomposition kinetics for carprofen.

Investigation of the regio- and stereo-selectivity of deoxyguanosine linkage to deuterated 2-hydroxyestradiol by using liquid chromatography/ESI-ion trap mass spectrometry

From previous studies on the reactivity of estradiol 2,3-quinone towards deoxyribonucleosides, it was demonstrated that several isomeric adducts were formed. Although adduction on steroid ring A or B has been evidenced using sequential MS n experiments, in some cases attachment positions are difficult to identify unambiguously. In this work, 2-hydroxyestradiol labeled with deuterium at various positions [6β ( 1); 6α-7α ( 2); 6α-6β-7α ( 3)] have been used. Isomeric adduct differentiation could be achieved using LC-ESI-MS n. The m/ z shift of the quasi-molecular ions as well as the fragmentation pathways suggested that adduction could occur on both C6 and C9 sites of the steroid B ring: Nucleophilic attack of the base on the C6 position of the steroid led to major adducts and addition of the base on the activated C9 site gave minor adducts that were found to be unstable. LC-MS n experiments carried out under deuterated medium provided information about some fragmentation processes by studying the m/ z shift of fragment ions: (1) the loss of deoxyribose from the quasi-molecular ions took place according to a process involving a deuterium transfer from the deoxyribose alcohol function; (2) the cleavage of the steroid-base linkage involved a deuterium transfer from the hydroxy group of the catechol and likely occurred via the formation of an ion-dipole complex. The model studies conducted in this work provide new information on the fragmentation mechanisms of covalent adducts formed from estrogen quinones and deoxyguanosine, the most reactive DNA base. Besides, the first unequivocal characterization of adducts involving the steroid C9 position is shown by using deuterium labeled estrogen quinones.

Gas-phase synthesis of charged copper and silver Fischer carbenes from diazomalonates: mechanistic and conformational considerations in metal-mediated wolff rearrangements.

Copper(I) and silver(I) Fischer carbenes are synthesized in the gas phase. Various diazomalonate-based compounds with an attached metal ion are introduced into the gas phase by electrospray ionization and subjected to collisional activation. Loss of N(2) generates a metastable Fischer carbene, which subsequently undergoes Wolff rearrangement and loss of CO. Further excitation leads to the loss of another CO molecule and the generation of a stable Fischer carbene. Isotopically labeled compounds are utilized to confirm the assignment of the products resulting from this process. DFT calculations are used to evaluate various mechanistic possibilities and to quantitatively assess the energetics of reactants and products. Silver(I) is shown to be more effective in facilitating Wolff rearrangement than copper(I), although both are more effective when compared to spectator charges such as sodium or a fixed quaternary nitrogen. Carbenes are not produced when copper(II), nickel(II), or a proton is used to form a quasi-molecular ion from the diazomalonate carbene precursor. Finally, trapping of the Fischer carbene by various functional groups attached through the open coordination site of the metal is investigated.

Determination of alkyltrimethylammonium chlorides in river water by gas chromatography/ion trap mass spectrometry with electron impact and chemical ionization.

This work describes a modified method to analyze alkyltrimethylammonium chlorides (ATMACs) in river water samples. The proposed method involves adding solid potassium iodide to water sample (pH adjusted to 10.0) as a counterion to enhance the extraction of ATMAC residues by dichloromethane liquid-liquid extraction. The iodide-ATMA+ ion pairs were demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection port. The corresponding ADMAs were then identified and quantitated by gas chromatography/ion trap mass spectrometry (GC/MS) in electron impact and low-pressure positive ion chemical ionization (PICI) modes. A relatively high abundance of ADMAs was detected at a demethylation temperature above 300 degrees C in the injection port. Experimental results indicate that the proposed method is precise and sensitive in ATMACs analysis and allows quantitation at < or = 0.01 microg/L in 500 mL of the water samples. The enhanced selectivity of quasi-molecular ion chromatograms of C12-C18-ADMA, obtained using methanol PICI-MS, enables ATMAC residues to be identified at trace levels in environmental samples. Recovery of the ATMACs in various spiked water samples ranged from 70 to 94% while RSD ranged from 3 to 12%. The concentrations of total measured ATMAC residues in river water samples ranged from nondetectable to 1.24 microg/L.

Quantitative analysis of cytokinins in plants by liquid chromatography–single-quadrupole mass spectrometry

A sensitive method for the quantitative analysis of all natural isoprenoid cytokinins in plant material by electrospray single-quadrupole mass spectrometry is presented. A baseline chromatographic separation of 20 non-derivatised naturally occurring cytokinins has been developed. Precise analyses of O-glucoside and ribonucleotide fractions were also performed by the high-performance liquid chromatography–mass spectrometry (HPLC–MS) but run separately from the basic cytokinin metabolites. Using post-column splitting, the flux from narrow-bore (2.1 mm i.d.) reversed-phase liquid chromatography column was simultaneously introduced into the diode array and mass detector. Optimal conditions, including final flow rate, desolvation temperature, desolvation gas flow, capillary and cone voltage for effective ionisation in the electrospray ion source were found. When low cone voltage (20 V) was applied, all studied cytokinins were determined in aqueous methanol as dominant quasi-molecular ions of [ M+H] + with limits of detection ranging between 10 and 50 fmol. For routine analysis a linearity range between 25 (75) fmol and 100 pmol was obtained. Developed liquid chromatography–mass spectrometry (LC–MS) method in selective ion monitoring mode was employed to quantify cytokinin species in tobacco BY-2 suspension culture and poplar leaves ( Populus× canadensis Moench, cv Robusta). Purified plant cell (BY-2) and plant tissue (poplar leaves) extracts were obtained by using two different ion-exchange chromatography steps, in combination with immunoaffinity purification using a broad-spectrum monoclonal anti-cytokinin antibody. The antibody strongly recognises the presence of N 6-substituent on purine skeleton and thus does not bind adenine and related compounds. The presence of authentic cytokinins in the extracts quantified by LC–MS was further verified by enzyme-linked immunosorbent assays (ELISAs) with prior LC preparation. The combination of liquid chromatography–single-quadrupole mass spectrometry with immunoaffinity chromatography offers an efficient and elegant method for detection and quantification of cytokinin metabolites.

Atmospheric pressure ionization mass spectrometry of purine and pyrimidine markers of inherited metabolic disorders.

Purines and pyrimidines are of interest owing to their significance in processes in living organisms. Mass spectrometry is a promising analytical tool utilized in their analysis. Two atmospheric pressure ionization (API) methods (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)) in both negative and positive modes applied to selected purine and pyrimidine metabolites (markers of inherited metabolic disorders) were studied. APCI is less sensitive to alkali metal cations present in a sample and offers higher response than ESI for studied compounds. Both of the techniques afford quasi-molecular ions, but fragmentation also occurs to a certain extent. However, the application of collision-induced dissociation of quasi-molecular ions is essential to confirm a certain metabolite in a sample. Fragmentation of both positive and negative ions was evaluated using multi-stage mass spectrometric experiments. Typical neutral losses correspond to molecules NH(3), H(2)O, HCN, CO, H(2)NCN, HNCO and CO(2). The ion [NCO](-) arises in the negative mode. The cleavage of the glycosidic C-N bond is characteristic for relevant metabolites. Other neutral losses (CH(2)O, C(2)H(4)O(2) and C(3)H(6)O(3)) originate from fragmentation of the glycosidic part of the molecules. In addition to fragmentation, the formation of adducts of some ions with applied solvents (H(2)O, CH(3)OH) was observed. The composition of the solution infused into the ion source affects the appearance of the mass spectra. Tandem mass spectra allow one to distinguish compounds with the same molecular mass (uridine-pseudouridine and adenosine-2'-deoxyguanosine). Flow injection analysis APCI-MS/MS was tested on model samples of human urines corresponding to adenosine deaminase deficiency and xanthine oxidase deficiency. In both cases, the results showed potential diagnostic usefulness.

Capillary electrophoresis/mass spectrometry: a promising tool for the control of some physiologically hazardous compounds. I-derivatives of 3-quinuclidinol.

A method based on the coupling of capillary electrophoresis with mass spectrometry (CE/MS) was developed for the monitoring of 3-quinuclidinol and its four N-alkyl derivatives (methyl, ethyl, propyl and isopropyl derivatives). A fragmentation study (collision-induced dissociation of ions in an ion trap) and optimization of the ion optics set-up for CE/MS experiments using direct infusion of a methanolic solution of the standards into the mass spectrometer were carried out in advance. Molecular ions of all quaternary compounds and the quasi-molecular ion [M + H]+ of free 3-quinuclidinol prevail in the mass spectra. In the MS/MS of propyl and isopropyl derivatives, the elimination of the alkyl chain dominates, leading to the ion at m/z 128. The fragmentation of the other compounds is more complex. Previous CE separation of the mixture of isobaric propyl and isopropyl derivatives is necessary for their unambiguous identification. A 10 mM ammonium acetate buffer (pH 4.0) is the optimum running electrolyte, allowing the CE separation of methyl, ethyl, propyl and isopropyl derivatives. A 0.5% (v/v) solution of acetic acid in methanol provides sufficient detection sensitivity when used as the sheath liquid. Limits of detection of 0.1 ppm for 3-quinuclidinol and 0.05 ppm for quaternary derivatives were achieved under the optimum conditions. The optimized method was applied to the determination of 3-quinuclidinol and related quaternary derivatives spiked into a sample of pond water. The experimental set-up for CE/MS/MS was investigated, which strongly increases the identification capability of the technique.

An unusual rearrangement of Zofenopril, a new ACE inhibitor drug: mass spectrometric and conformational studies.

Zofenopril (1) is a new ACE inhibitor, used in therapy for hypertension and post-myocardial infarction. The protonated quasi-molecular ion (m/z 430) of 1, obtained under positive electrospray ionization conditions, loses a benzoic acid molecule (m/z 308), which in turn decomposes via loss of CO (m/z 280) when low-energy collisional-induced dissociation (CID) and in-source experiments are performed. This rearrangement is the main fragmentation process and can be observed both in-source and in the product ion tandem mass spectra, using either an ion trap or a triple quadrupole instrument. Other known diastereoisomers of 1, an impurity with an acetyl in the place of the benzoyl group (2) and an impurity with two propanoyl chains in series (3), give the same rearrangement. On the other hand, the mass spectra of the methyl ester (4) and an impurity with two proline moieties (5) do not show this unusual fragmentation. Time-resolved CID spectra of 1 show that the rearrangement occurs after about 2 ms, a time scale comparable to those of the other non-rearrangement cleavages. These experiments suggest a conformation in the gas phase for 1 in which the benzoyl group is close to the hydroxyl of the carboxylic acid group, from which the rearrangement could readily occur. Since compounds 4 and 5 do not show the same behaviour, the presence of a carboxylic acid in the proline ring seems to play a crucial role in the rearrangement, probably due to an intramolecular hydrogen bond. To confirm this hypothesis, deuterium exchanges in mass spectrometric experiments and a conformational analysis via computational methods were performed.

A quasi-classical description of the stochastic dynamics of a Rydberg electron in a diatomic quasi-molecular complex

We investigate the stochastic migration of a Rydberg electron (RE) along its Coulomb energy spectrum in the variable electric field of a quasi-molecular ion produced in a symmetric collision between two alkali metal atoms. We give a kinetic description of the RE time evolution in the quasi-classical approximation using Fokker-Planck-type equations. The corresponding diffusion coefficient is derived in analytic form by taking into account the quantum defect for energy levels. We calculate the rate constants for diffusion ionization in Na**(nP)+Na(3S) collisions. Good agreement with experimental data is shown.