Determination of Vitamins A and E Exploiting Cloud Point Extraction and Micellar Liquid Chromatography

Cloud point extraction and micellar chromatographic methods were developed for determination of vitamins A and E. The stationary phase was C18 and the mobile phase was 3.00% (w/v) SDS, 15.0% (v/v) butyl alcohol and 0.02 mol L^?1 phosphate buffer solution at pH 7.0. The retention times for vitamins A and E were 9.6 and 13.0, respectively. The extraction solution was 100 mmol L^?1 Triton X-100, 650 mg NaCl and 1.0% ascorbic acid at 70°C for 30 min. The method is precise (r.s.d. < 7%), the linear range was from 5.0 up to 360.0 mg L^?1 for both vitamins. Recovery test showed recuperation between 90.2 and 99.2%, and LOD and LOQ of 0.234 and 0.108 mg L^?1, 0.780 and 0.360 mg L^?1 to vitamins A and E were found.     

Metal chelates of heterocyclic nitrogen containing ketones,Part IX. Magnetic and spectral studies of the dimeric copper(II) complex of 2-picolyl methyl ketone semicarbazone and its ligation by solvent molecules

Summary The preparation and characterization of [(PMKSC-H)Cu]₂Cl₂ by i.r. electronic and e.s.r. spectra as well as variable temperature magnetic susceptibility are described and a square planar geometry is assumed for the isolated complex. The magnetic susceptibility data indicates overall antiferromagnetic spin coupling. The variable temperature magnetic susceptibility in conjunction with the best fitting procedure yielded: 2J=–46cm^–1, g=2.15 and 6=–5 K. E.s.r. data confirm the existence of spin-spin coupling with D=0.0398 cm^–1. The g-values obtained from the e.s.r. studies were g₁₁=2.24, g=2.08 and g_av.=2.13. The results were used to estimate the Cu-Cu separation in the dimer. The problem of ligation of the dimeric copper(II) complex by various organic solvents was investigated. E.s.r., i.r. and electronic spectra together with the magnetic susceptibiliy studies indicate that [(PMKSC-H)Cu]₂Cl₂ dissociated in polar solvents to give the adducts [(PMKSC-H)CuL_s]Cl which were isolated and characterized.     

Cobalt- und Rhodiumphthalocyanine mit O-, S- und Se-Donorliganden

Phthalocyanines of Cobalt and Rhodium with O, S, and Se Donor Ligands Di(phenolato)-, -(benzenethiolato)- and -(benzeneselenonato)phthalocyaninatocobaltate(III) and -rhodate(III) are prepared by the reaction of di(hydroxo)phthalocyaninatometalate with phenol resp. benzenethiol or benzeneselenol and isolated as poorly soluble tetra(n-butyl)ammonium salts of the formula (ⁿBu₄N)[M(EPh)₂Pc^2?] (M = Co, Rh; E = O, S, Se). In the Uv-vis spectra π–π* transitions in the Pc^2?-typical B, Q, N and L regions are observed. For the Rh-complexes with E = S, Se there is a further band at 18.0 kK due to excitonic π(Ph)–π(Pc) interactions. The (E→Rh-charge-transfer(CT)) transition is observed for E = Se at 26.0 kK, being obscured by the Q, N region for E = O, S. The strong, broad (E → Co? CT) transition (E = O, S, Se) absorbs at ～20.5 kK. A second CT-transition is detected within the Q, N region for E = S, Se. Molecular vibrations (in cm^?1) are examined by m.i.r., f.i.r, FT-Raman and dispersive resonance-Raman(RR) spectra. The C? E stretching mode (v_7a) of the axial EPh ligands is observed for E = O at 1256/1262, 1269 (Co, m.i.r./RR), 1246/1265 (Rh), for E = S at 1085 (Co, Rh; RR) and for E = Se at 1069 (Co, Rh; RR). The C? C? E deformation mode (v_6a) is assigned for E = O at 554/557 (Co, RR), 568 (Rh, RR) and for E = S at 420 (Co, Rh; RR). The following vibrational modes of the trans-ME₂N₄ skeleton are assigned: v_s(ME) for Co: 381 (O)/271 (S)/139 (Se); for Rh: 408/297/156; v_as(ME) for Co: 352/277/235; for Rh: 391/278/225; v_as(MN) absorbs nearly independent of M and E at ～325 (f.i.r.) M? E? C deformation modes are observed between 246 and 200 (f.i.r.) resp. 217 and 186 (RR).     

The photo-induced decarbonylation of Cp′M(NO)(CO)2 (M = Cr,Mo, W) with diorgano dichalcogenides (R2E2; E = S,Se; R = Me,Ph)

The photo-induced decarbonylation of CpCr(NO)(CO)₂ (1a) in MeCN solution in the presence of R₂E₂ (E = S, Se; R = Me, Ph) leads to the formation of chalcogenolato-bridged binuclear complexes Cp₂Cr₂(NO)₂(-ER)₂ [E = S; R = Me (2a), Ph (3a); E = Se, R = Me (4a), Ph (5a)] while reactions between CpM(NO)(CO)₂ [M = Mo (1b), W (1c)] and Ph₂E₂ (E = S, Se) result in mononuclear complexes CpM(NO)(EPh)₂ [M = Mo; E = S (9b), Se (10b); M = W, E = S (11c), Se (12c)]. The corresponding reactions of (1b) with Me₂E₂ (E = S, Se) yielded both mono and binuclear complexes: CpMo(NO)(SeMe)₂ (8b), Cp₂Mo₂(NO)₂(-EMe)₂ [E = S (6b), Se (7b)]. The new complexes have been characterized by i.r., ¹H-, ¹³C-n.m.r. spectra and by electron-impact mass spectrometry.     

EPR- und optische Spektren von Nickel(III)-serinat

Zusammenfassung DieRacah Parameter des Ni(Ser)₃, (HSer=rac. Serin) wurden nach der vollständigen Energie-Matrix für d⁷-Elektronen in trigonalem Feld berechnet. Beim Grundzustand²E (starkes Ligandenfeld) und C4 B wurden die WerteDq=1778 cm^–1 undB=490 cm^–1 erhalten. Das EPR-Spektrum und der Wert desg-Faktors weisen auf einen kovalenten Charakter der O-Ni-Bindung hin.

---

EPR and optical spectra of nickel(III) serinate

TheRacah parameters of Ni(Ser)₃ (HSer=rac. serine) were calculated using the full energy matrix for d⁷-electrons in a trigonal field. The valuesD _q=1778 cm^–1 andB=490 cm^–1 were obtained at ground state²E and C4 B. The EPR-spectrum and the value of theg-factor show that the bonding O-Ni has a covalent character.

     

Electroconductivity of Potassium Orthophosphate Modified by Four-Charged Cations

Solid solutions based on K₃PO₄ in systems K_{3 – 4x} E" _x PO₄ (E" = Si, Ti, Ge, Zr, Sn, Hf, Ce) are synthesized. The crystal structure, thermal behavior, and electroconduction of the synthesized solutions is studied. The narrowest single-phase regions take place in the systems where E" = Si, Ge (x 0.025), and the widest, in the system with Zr (x 0.125, at 700°C). Introducing Ti or Sn additives (x 0.05) and minimum quantities of Zr, Hf, or Ce (x = 0.025) into potassium orthophosphate leads to stabilization of highly-conductive -modification of K₃PO₄ at room temperature. Maximum values of potassium-cation conduction in all the systems studied correspond to regions of single-phase solid solutions based on K₃PO₄. The maximum electroconductivity (0.005 S cm^–1 at 300°C, 0.1 S cm^–1 at 700°C) and the smallest activation energies (32–35 kJ mol^–1) take place in the systems with Zr and Hf.     

Benennungsprobleme in der Mikrochemie und ein Versuch,sie zu lösen

Zusammenfassung Die Einheit Emich, 1 E oder 1=0,001 pg=10^–15g, wird vorgeschlagen, da sie erlaubt, den Bereich zweckdienlicher Gewichtseinheiten in einfacher Weise bis zu 10^–30 g auszudehnen. Es ergibt sich damit auch die Möglichkeit, den Maßstab mikrochemischer Arbeit selbst unterhalb 10^–15 g kurz und objektiv anzugeben.Es wird weiters vorgeschlagen, Empfindlichkeit und Probevolumen chemischer Nachweisproben durch Anführung der negativen Logarithmen von Grenzkonzentration und Erfassungsgrenze festzulegen. Die Differenz (p ^C – p ^M ) gibt den positiven Logarithmus des Volumens der Probelösung. Die Anwendung des Vorschlages und die Angabe der Grenzverhältnisse wird an Beispielen besprochen.

---

Summary Use of the mass unit Emich, 1 E or 1=0.001 pg=10^–15 g, is suggested since it would permit extending the range of suitable units of mass and weight to reach 10^–30g. This would provide also the possibility of clearly indicating the scale of microchemical work in simple objective terms even when the magnitude of single molecules or atoms are being reached.In addition, it is suggested to state the sensitivity and the volume of test solution by listing the negative logarithms of limiting concentration and limit of identification. The difference (p ^C –p ^M ) represents the positive logarithm of the volume of the sample solution. Practical application of this notation and the extremely simple indication of limiting proportions are demonstrated with the use of examples.

---

Résumé On propose l'unité «Emieh», 1 E ou 1 =0,001 pg=10^–15 g, car elle permet d'élargir le domaine des unités de poids convenables d'une façon simple jusqu'à 10^–30 g. Elle permet aussi de préciser rapidement et objectivement l'échelle d'application microchimique même au-dessous de 10^–15 g.On propose, en outre, d'établir la sensibilité et le volume de la prise d'essai des échantillons chimiques par emploi de logarithmes négatifs pour les concentrations limites et les limites que l'on peut concevoir. La différence (p ^C –p ^M ) donne le logarithme positif du volume de la solution étudiée. On discute sur des exemples de l'application de la proposition et des données extrêmes d'utilisation.

---

---

Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich.     

REAKTIONEN VON THIOXOHETEROCYCLEN MIT N-CHLORAMIDEN 111.1 2- ODER 4-THIOPYRIDONE OHNE SUBSTITUENTEN AM STICKSTOFF UND NATRIUM-N-CHLORBENZOLSULFONAMIDE

Abstract

2- and 4-pyridinethiones (A) react with sodium N-chlorobenzenesulfonamides (1) in alcoholic solvents to N- (pyridy1thio)benzenesulfonamides (C), sodium N, N′-bis(phenylsulfonyl)-S-pyridylsulfodiimidates (D) and S-alkoxy-N-phenylsulfonyl-S-pyridylsulfimides (E). Constitution proofs for the new compounds D, E are reactions and ¹H-, ¹³C-, ¹⁵N-nmr data.

2- und 4-Thiopyridone (A) reagieren mit Natrium-N-chlorbenzolsulfonamiden (1) in alkoholhaltigen Lösungsmitteln zu N- (Pyridylthio)benzolsulfonamiden (C), Natrium-N, N′-bis(phenylsulfony1)-S-pyridylsulfodiimidaten (D) und S-Alkoxy-N-phenylsulfonyl-S-pyridylsulfimiden (E). Konstitutionsbeweise für die neuen Verbindungen D, E sind Reaktionen sowie ¹H-, ¹³C- und ¹⁵N-NMR-Daten.     

Novel bidentate ruthenium(III) Schiff base complexes: synthetic,spectral, electrochemical,catalytic and antimicrobial studies

Ru^III complexes of the type [RuX(L)₂(E)] (X = Cl or Br; L = novel bidentate Schiff base ligand; E = PPh₃ or AsPh₃) have been prepared by reacting [RuX₃(E)₃] or [RuBr₃(PPh₃)₂(MeOH)] with two novel bidentate Schiff base ligands derived from 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazole, in a 1:2 molar ratio in benzene, and characterised by analytical, spectral (i.r., electronic, ¹H-, ¹³C- n.m.r., and e.p.r.) and electrochemical data. An octahedral structure has been tentatively proposed for all the new complexes. The thermal properties of the ligands and their complexes have been studied by t.g.a. The new Ru^III complexes are effective catalysts for the oxidation of alcohols to carbonyl compounds but are unable to oxidise alkenes in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant. The antimicrobial activity of the ligands and complexes have also been tested against six microorganisms.     

Perfluormthyl-Element-Liganden. XVII. Adduktbildung von MenE(CF3)3−n-Liganden mit BX3-Verbindungen (Me = CH3; E = P,As, Sb; n = 0–3; X = H,CH3, Hal)

Perfluoromethyl-Element-Ligands. XVII. Formation of Adducts of Me_nE(CF₃)_3?n Ligands with BX₃ Compounds (Me = CH₃; E = P, As, Sb; n = 0–3; X = H, CH₃, Hal) The ligands Me_nE(CF₃)_3?n (Me = CH₃; E = P, As, Sb; n = 0–3) have been prepared (partly using new methods) and studied by n.m.r. spectroscopy (¹H, ¹⁹F, ³¹P, ¹³C). In order to deduce their relative donor strength their reactions with the Lewis acids “BH₃”, BMe₃, BMe₃, Me₂BBr, and BX₃ (X = F, Cl, Br) have been studied. Control of adduct formation occurs by n.m.r. spectroscopy (¹H, ¹⁹F). The following series of decreasing basicity or acidity are obtained:      

Quantitative 1h fourier transform nuclear magnetic resonance spectroscopic analysis of mixtures of pyrrolizidine alkaloids from senecio vulgaris

Summary An analytical method was developed in order to obtain qualitative and quantitative information on pyrrolizidine alkaloid mixtures from Senecio vulgaris L. (Compositae) by means of ¹H Fourier Transform Nuclear Magnetic Resonance spectroscopy. It was found that this plant contains not only seneciphylline, senecionine and retrorsine, but also the corresponding geometrical E-isomers spartioidine, integerrimine and usaramine. Some general instrumental conditions necessary for quantitative FT NMR were established, which enabled us to determine the total alkaloid level, the N-oxide level, the total Z/E ratio, and the amount of each Z/E isomer pair with good precision. The possibilities of using this method to analyze pyrrolizidine mixtures from other Senecio sp., and some advantages and limitations of quantitative analysis by means of ¹H FT NMR are discussed.

---

Quantitative Analyse von Gemischen von Pyrrolizidinalkaloiden aus Senecio vulgaris mit Hilfe der ¹H-Fourier-Transform-KMR-Spektroskopie

Zusammenfassung Mit Hilfe der entwickelten Methode konnte festgestellt werden, daß diese Pflanze nicht nur Seneciphyllin, Senecionin und Retrorsin enthält, sondern auch die entsprechenden geometrischen E-Isomeren Spartioidin, Integerrimin und Usaramin. Die notwendigen apparativen Bedingungen wurden festgelegt und erlaubten die Bestimmung des Gesamtalkaloidgehaltes, des N-oxidgehaltes, des Gesamtverhältnisses Z/E sowie des Gehaltes an jedem Z/EIsomerenpaar mit guter Genauigkeit. Die Möglichkeit zur Anwendung des Verfahrens auch für andere Senecio-Arten sowie die Vorteile und Grenzen der ¹H-FT-KMR-Analyse werden diskutiert.

---

---

Dedicated to Prof. Dr. E. Stahl on the occasion of his 60th birthday     

The predictive accuracy for estimating infinite dilution activity coefficients by γ∞-based UNIFAC

The predictive accuracy for estimating infinite dilution activity coefficients by a modification of the UNIFAC method wherein the group interaction parameters were based on only data (referred to as -based UNIFAC) has been studied. Estimates and measured values were compared for six prototypical solutes in a series of homologous n-alkanes, l-alcohols and alkanenitrile solvents. Despite the fact that the interaction parameters were derived using only data, this approach still gave serious errors due to several inherent problems in the original UNIFAC model. Its performance is sometimes even poorer than that of the original UNIFAC method. For example for nitromethane in alcohols and p-dioxane in nitriles values predicted by the -based UNIFAC are essentially zero. The large errors for these systems are most likely due to inaccurate interaction parameters in the -based UNIFAC method.     

Oxygenation of 4-tert-butylcatechol catalysed by a manganese(II) complex: implications for extradiol catechol dioxygenases

An N donor tetradentate manganese complex, [Mn^II(bispicen)Cl₂] (A) [bispicen = N,N-bis(2-pyridylmethyl)-1,2-ethanediamine)] catalyses the oxidative cleavage of 4-tert-butylcatechol (1) in the presence of O₂. The oxygenated products were isolated by t.l.c. and column chromatography and characterised by ¹H-, ¹³C-n.m.r., DEPT, i.r. and u.v.–vis. spectroscopy. The oxygenated products as well as other spectral evidence suggest that the oxygenation occurs via a 4-tert-butylsemiquinone bound complex, [Mn^II(bispicen)(4-sq)]⁺ (4-sq = 4-tert-butylsemiquinone). ¹H-n.m.r. spectroscopy suggests that the oxygenation follows multiple pathways. Isolation of the products suggests that the oxygenations proceed in an extradiol fashion and a probable mechanism is suggested. Some intradiol cleaved products have also been detected. E.s.r. spectroscopy suggests that manganese(II) is ultimately converted into the manganese(IV) species.     

E.p.r. studies on dichloromono(1-phenylamidino-o-alkylurea)copper(II) complexes. Evidence for field induced partial ordering in the solid state and some unusual features in solution

E.p.r. and optical absorption studies have been conducted on dichloromono(1-phenylamidino-o-alkylurea)copper(II) complexes (Alkyl = Me, Et, Pr, Bu or Pe). The e.p.r. spectra of solids, recorded at 300 K, confirmed the square-planar geometry with the unpaired electron in the dx ²–y ² orbital of copper. Magnetic field-induced partial molecular alignment has been observed in some of the polycrystalline samples when cooled in a magnetic field of 1 T at 77 K. E.p.r. spectra at 77 K in pyridine and DMF has shown axial ligation of solvent molecules (pyridine and DMF), whereas in MeOH and DMSO at least three structurally different Cu^II species have been identified. These features are consistent with differences in electronic absorption spectra in the powder and in solution.     

Optimizing the Triple‐Potential Waveform for the Pulsed Amperometric Detection of Streptomycin

Abstract

A triple‐potential waveform used for amperometric detection of streptomycin (STP) is investigated. The mobile phase is an aqueous solution of 75 mM phosphoric acid. Waveform parameters are optimized to maximize the signal‐to‐noise ratio (S/N). The potentials of the waveform are designated E1, E2, and E3, and potentials are maintained for time periods t1, t2, and t3. Unlike the normal triple‐potential waveform, the cleaning function is accomplished at negative potential instead of positive potential in our triple‐potential waveform. The detection limit of STP is <0.04 µg mL^?1 (S/N=3). The linearity of STP ranges from 0.1 to 5 µg mL^?1 (r=0.9986). RSD (n=30) of the peak area of STP is 5.8%. The triple‐potential waveform shows low detection limits and long‐term reproducibility.     

Einige spezielle Anwendungen eines polarographischen Me?ger?tes

Zusammenfassung Neben der Anwendung des Polarecord E 261 R für konventionelle Gleichspannungspolarographie sowie Rapid-Gleichspannungspolarographie ist das Gerät für einige spezielle elektrochemische Analysenverfahren geeignet. Mit Hilfe eines Zusatzgerätes können Wechselspannungs-polarogramme aufgenommen werden, wobei durch den Einsatz der kontrolliert schnelltropfenden Quecksilberelektrode bemerkenswerte Vorteile bezüglich der Kurvenform zu erzielen sind. Der schnelle Papier- und Spannungsvorschub des Gerätes ermöglicht polarographische Aufnahmen mit der Anodic stripping Technik, womit sich Metallionen-Konzentrationen bis zu 10^–9 molar erfassen lassen. In Verbindung mit einem Konstantstrom-Coulometer kann der Polarecord für chronopotentiometrische Analysen sowie auch für automatische coulometrische Titrationen mit potentiometrischer oder amperometrischer Endpunktsindikation verwendet werden.Vorgetragen von E. Greuter.     

New iron(III) complexes with thiosemicarbazones derived from 5-methyl-3-formylpyrazole

New iron(III) complexes of 5-methyl-3-formylpyrazole thiosemicarbazone (HMPzTS) and 5-methyl-3-formylpyrazole-4-phenylthiosemicarbazone (HMPzPTS), namely [Fe(MPzTS)₂]X and [Fe(MPzPTS)₂]X respectively, where X=Cl, NO₃, SCN and ClO₄, have been synthesised and physico-chemically characterised by magnetic measurements (polycrystalline state), electronic, i.r., e.s.r. and Mössbauer spectra. All are cationic complexes containing two monoprotonic tridentate ligands with NNS donor sites and an anionic counterpart; they behave as 1:1 electrolytes in MeOH/DMF. Coordination to central iron(III) via the pyrazolyl nitrogen (²N), the azomethine nitrogen and the thiolato sulphur atom is confirmed in the complexes from i.r. data. E.s.r. data (RT & LNT) reveal the presence of a spin-paired iron(III) cation with d² _xyd² _yzd¹ _xy configuration. The ⁵⁷Fe Mössbauer spectral data (RT) are commensurate with the presence of two iron(III) spin states, the percentage of each being dependent upon the counterion of the species.     

Infrarotspektroskopische untersuchungen an metallcupferronaten im bereich 4000-32 cm-1

The preparation and empirical interpretation of the m.i.r. and f.i.r. spectra of the cupferronates of Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Pb²⁺ und Bi³⁺ in the range 4000—32 cm^-1 is described. The bands in the range 1700—500 cm^-1 and the C—H valency vibrations can be assigned to vibrations of the pure ligand; differentiation of individual metal chelates in this range is therefore difficult. In contrast, the far i.r. region (below 500 cm^-1) contains many absorption bands (the metal chelate fingerprint region) which differ in position and intensity. The position of the bands with the highest v—M—O character, which can be recognised on the basis of the large metal-dependent frequency shifts, depends linearly on the second ionization potential of the metal atom, except for the Mn and Sn chelates. The relative absorptions, E_M—O/E, of the far i.r. bands of these cupferronates allow classification of the chelates into groups corresponding to the metal—ligand bonding involved (tetrahedral, octahedral and planar). The characteristic value used for this classification (the quotient of the absorption at the M—0 frequency and the absorbance of the strongest remaining band in the far i.r.) covers the range 0.92–2.17 for tetrahedral chelates, and 5.30–6.20 for planar chelates, with the octahedrally coordinated chelates having intermediate values.     

Comparative studies on conventional and microwave-assisted synthesis of a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a] pyrimidines and their antimicrobial activities

Comparative studies were performed on a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a]pyrimidines, which were synthesized with conventional and microwave heating methods. In microwave irradiation method, approximately, 95–97.5% of the reaction time was increased and 1–45% yield increase was obtained. All compounds were able to inhibit the growth of the screened microorganisms in vitro with MIC values between 3.9–250 μg mL⁻¹. The highest activity was expressed by compound IIId (2,4-diphenyl-benzo[4,5]imidazo[1,2-a] pyrimidine), which has the MIC value of 3.9 μg mL⁻¹ and 31.2 μg mL^-1 for Penicillium natatum ATCC 24791 and E. faecalis ATCC 29212, respectively.      

Nickel(II), palladium(II) and platinum(II) complexes of <Emphasis Type="Italic">N</Emphasis>-allyl-<Emphasis Type="Italic">N</Emphasis>′-pyrimidin-2-ylthiourea

Platinum(II), palladium(II) and nickel(II) complexes with N-allyl-N′-pyrimidin-2-ylthiourea were synthesized in 1:1 and 1:2 [metal:ligand] stoichiometric ratios and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and by i.r., u.v.-vis., ¹H- and ¹³C-n.m.r. and mass spectra. The ¹H- and ¹³C- n.m.r. chemical shifts reveal coordination of one pyrimidine-N and sulphur atoms to Pt^II and Pd^II. The i.r. spectra indicate that the ligand behaves as a neutral monodentate towards Ni^II; coordinates via a pyrimidine-N and as a bidendate towards Pd^II and Pt^II coordinates via thione-S and a pyrimidine-N. The magnetic moments and electronic spectral data suggest a square-planar geometry for Pt^II and Pd^II complexes, a mixture of square-planar and tetrahedral geometries for the tetracoordinate Ni^II complex and octahedral for the six-coordinate one. The E.I. mass spectra of the complexes showed some isotope ion peaks of [M]⁺ and fragments containing metals; assignments of fragments containing metal ions were supported by the appearance of their peaks among isotope clusters.