Comparison of two methods for ginsenosides quantitation

The present study provides a comparison of two liquid chromatography–tandem mass spectrometry methods for ginsenosides analysis. The two methods have the same liquid chromatography separation procedure, and both use tandem mass spectrometry detection. However, one method uses multiple reaction monitoring transitions commonly recommended in the literature starting with [M + Na]⁺ as the molecular ions and with detection of specific fragment ions from the molecules M, while the other is an original method using [M + Cs]⁺ as molecular ions and Cs⁺ as fragment ion. The method using [M + Cs]⁺ as molecular ion has a very high sensitivity allowing the measurement of concentrations in the injecting solutions as low as 4 ng/ml with peaks at this concentration showing signal to noise ratio of 20 or higher. The procedures were utilized for the measurement of eight ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf (S), Rg1, and Rg2), although the method using [M + Cs]⁺ has the potential for measuring other ginsenosides. As an application, the ginsenosides were measured in several types of ginseng root, several dietary supplements containing ginseng extracts, four energy drinks, and a sample of ashwagandha.     

Über Alkali-hexachlorochromate(III): Na3CrCl6

Alkali-hexachlorochromates(III): Na₃CrCl₆ X-ray investigations on single crystals yielded for Na₃CrCl₆ a trigonal structure: space group P3 1c; a = 682.0(3) pm; c = 1203.4(5) pm; Z = 2. In a hexagonal-close arrangement of Cl^? ions, 2/3 of the octahedral holes are occupied orderly by Na⁺ and Cr³⁺ ions. The Na compounds of V³⁺ and Mo³⁺ are isotypic. The chlorochromates with K and Rb are crystallizing with the K₃MoCl₆ structure according to X-ray photos of powders. The alkali metal ions habe the C.N. 8 or 11 related to the chloride ions. These compounds and elpasolithes A₂BCrCl₆ (A = Cs? K; B = Rb? Na) can be treated in the same way with the concept of tolerance factors as it is known for the chloro-perovskites AMCl₃. For all compounds the temperatures of phase transitions were determined by DTA. Some structures could be solved from high-temperature-Guinier-patterns, by comparing them with patterns of substances with known structures.     

Collision-induced dissociation of glycoside–alkali metal adduct ions in fast atom bombardment mass spectrometry

The collision-induced dissociation (CID) spectra of glycoside–alkali metal adduct ions [M + C]⁺ (C = Li, Na, K and Rb) produced under fast atom bombardment (FAB) conditions are reported. The results obtained suggested that the CID spectra of the [M + C]⁺ ions of some flavonoid glycosides reflect the coordination structures because the CID patterns generally changed with the metal cation size. In diglycosides, the CID spectra showed that the relatively small cations Li⁺ and Na⁺ rather bind to the sugar moiety, whereas the large cations K⁺ and Rb⁺ rather bind to the aglycone moiety. In monoglycosides, the cations C⁺ rather bind to the aglycone moiety. It was concluded that the CID technique combined with FAB is useful for the structural elucidation of [M + C]⁺ ions and, in principle, the CID spectra reflect the coordination structures in the gas phase.     

Structural Study of Alkaline 1-Phenyl-1H-1, 2, 3, 4-tetrazole-5-thiolate Salts: An Example of Periodicity in Alkaline Cations

The alkaline 1-phenyl-1H-1, 2, 3, 4-tetrazole-5-thiolate salts, M[C₆H₅N₄CS] (M = Li ( 1 ), Na ( 2 ), K ( 3 ), Rb ( 4 ) and Cs ( 5 )) were obtained and characterized by means of mass spectrometry (FAB⁺) and NMR (¹H; ¹³C) spectroscopy. The structures of Na ( 2 ), K ( 3 ), Rb ( 4 ) and Cs ( 5 ) compounds were determined by X-ray diffraction methods. The ligand shows a rich variety of coordination patterns with the alkaline cations. The formation of a four-membered ring MSCN in the compounds with heavier alkali cations (K, Rb and Cs) is shown. In all the cations the coordination number around it increases with the ionic radius. Compounds with Cs⁺ and Rb⁺ exhibited the formation of Cs-C and Rb-C interactions with the phenyl group.     

The vanadium monophosphates AVOPO4: Synthesis of a second form β-KVOPO4 and structural relationships in the series

A new form of potassium vanadophosphate β-KVOPO₄ has been synthesized using hydrothermal technique which showed the role of the extra adduct, here W or WO₃. The structure of this phase, isotypic to Rb and Cs monophosphates, has been determined from a single crystal X-ray study. Structural relationships between the different monophosphates of the AVOPO₄ series with A = Li, Na, K, Rb, Cs, NH₄ are presented in which K⁺ appears as a boundary cation: with cations smaller than K⁺ the vanadium(IV) is octahedral and pyramidal with larger ones, both coordinations existing with K⁺.     

Features of Cation Hydration in Concentrated Aqueous Solutions of MeCl (Me = Li, Na, K, Rb): A Study by the Method of Integral Equations

The structural features of concentrated aqueous solutions of MeCl (Me = Li, Na, K, Rb; molar ratio [salt] : [water] = 1 : 15) at 293 K and 0.1 MPa were studied by the method of integral equations. The calculation results show that the disordering effect of the cation on the solvent structure grows in the order NaCl < KCl < RbCl (the number of free water molecules grows, and the content of tetrahedrally ordered molecules decreases). With LiCl, the changes in these parameters are maximal. In the systems containing Li⁺ and Na⁺ ions, the association parameter is lower than in pure water, whereas in the solutions with the K⁺ and Rb⁺ ions it is higher, in agreement with the concept of positive and negative hydration. It was suggested that, with increasing cationic radius, formation of hydrogen bonds between bulk water molecules becomes more preferential, and interactions between the anion and solvent molecules are weakened. On the contrary, the coordination number of the cation increases with its radius. In the examined series of solutions, the probability of formation of contact ion pairs grows considerably, and that of formation of hydration-separated ion pairs decreases.     

Electron impact mass spectra of some salts of carboxylic acids with alkali (group Ia) metals

Thirteen of the salts of the alkali metals (Li, Na, K, Rb, Cs) with acetic, 2,2-dimethylpropionic, trifluoroacetic and heptafluorobutyric acid have been found to be sufficiently volatile to give mass spectra under normal electron impact conditions. The metal containing ions observed include (M=metal): [M]⁺, [MO]⁺, [MCO₂]⁺, [M₂]^+·, [M₂O]^+·, [M₂CO₂]^+· and the cluster ions [M_n (carboxylate)_n-1]⁺ for n = 2–8.     

Investigation of the relative stability of positive alkali halide cluster ions generated by fast atom bombardment

The stabilities of alkali halide cluster ions [M(MX)_n]⁺ (M ? Li, Na, K, Rb, Cs; X ? F, Cl, Br, I) have been studied by measuring the fragment ion yields following dissociation of the ions in the second field free region of a ZAB-2F mass spectrometer. Extractable cluster ions were observed for certain values of n. It was found that the stabilities of the neutral fragment species formed are also of importance in determining the fragmentation rates. Possible configurations of M and X in the stable ions are discussed.     

Phosphanides of the Heavier Alkali Metals

A variety of structures are shown in the solid state by the phosphanides MPHR of alkali metals. Whereas oligomeric and polymeric ladder or helical structures based on M–P bonds predominate for compounds of the lighter homologues (M=Li, Na, K), the 2,6-dimesitylphenylphosphanides of Rb and Cs are present as a Rb₄P₄ cubane and a Cs⁺{Cs₂(PHR)₃}⁻ contact ion pair, respectively (the partial structures are shown above). These unexpected new structures show interactions between the metal center and π electrons of the ligand.     

Ozone-Induced Dissociation of Conjugated Lipids Reveals Significant Reaction Rate Enhancements and Characteristic Odd-Electron Product Ions

Ozone-induced dissociation (OzID) is an alternative ion activation method that relies on the gas phase ion-molecule reaction between a mass-selected target ion and ozone in an ion trap mass spectrometer. Herein, we evaluated the performance of OzID for both the structural elucidation and selective detection of conjugated carbon-carbon double bond motifs within lipids. The relative reactivity trends for [M + X]⁺ ions (where X = Li, Na, K) formed via electrospray ionization (ESI) of conjugated versus nonconjugated fatty acid methyl esters (FAMEs) were examined using two different OzID-enabled linear ion-trap mass spectrometers. Compared with nonconjugated analogues, FAMEs derived from conjugated linoleic acids were found to react up to 200 times faster and to yield characteristic radical cations. The significantly enhanced reactivity of conjugated isomers means that OzID product ions can be observed without invoking a reaction delay in the experimental sequence (i.e., trapping of ions in the presence of ozone is not required). This possibility has been exploited to undertake neutral-loss scans on a triple quadrupole mass spectrometer targeting characteristic OzID transitions. Such analyses reveal the presence of conjugated double bonds in lipids extracted from selected foodstuffs. Finally, by benchmarking of the absolute ozone concentration inside the ion trap, second order rate constants for the gas phase reactions between unsaturated organic ions and ozone were obtained. These results demonstrate a significant influence of the adducting metal on reaction rate constants in the fashion Li > Na > K.      

Free energies of transfer of alkali metal halides in isodielectric acetonitrile and ethylene glycol mixtures at 25°C

Standard free energies of transfer (G _t ^o ) of alkali metal chlorides MCl (M=Li, Na, K, Rb, Cs) and of potassium bromide and iodide from ethylene glycol to its isodielectric mixtures containing 20, 40, and 60 wt. % acetonitrile have been determined from emf measurements at 25°C. The standard potentials of the M/M⁺, the Ag–AgBr, and the Ag–AgI electrodes have been calculated using auxiliary emf measurements. All electrolytes were found to be increasingly destabilized in mixed solvents of increasing acetonitrile content; the relative order of cation destabilization is Li⁺>Na⁺>K⁺>Rb⁺>Cs⁺ and that of anion destabilization is Cl^–>Br^–>I^–, both following (a) the order of increasing softness of ions and increasing interaction with the soft base, acetonitrile,and (b) the order of decreasing hydrogen-bonding propensity of ions and decreasing interactions with the hard base, ethylene glycol.     

Absorption and photoluminescence spectra of Tm3+-doped fluorophosphate glasses

We have carried out absorption and photoluminescence spectra of six newly prepared TmF₃ (2 M%) doped fluorophosphate glasses of composition: (NaPO₃)6BaF₂ZnF₂RF where R = Li, Na, K, (LiNa), (NaK) and (KLi). By evaluating the Judd—Ofelt intensity parameters for the measured absorption levels, the recorded photoluminescence spectra have been analysed to estimate the fluorescent radiative properties (A, A_T, β_R) and the stimulated emission cross-sections (σ^E_P) of the following luminescence transitions:¹G₄→³H₆ (λ=451 nm)¹D₂→³H₄ (λ=468 nm)³P₀→³F₂ (λ=482 nm)¹D₂→³H₅ (λ=492 nm)These have been determined in order to understand the alkali effects on the Tm³⁺-optical glasses studied.     

Effect of alkali metal cationization on the collision-induced decomposition of alkyl per-O-acetyl-2-deoxy-2-halo-α-O-mannopyranosides

The effect of alkali metal cationization on the collision-induced decomposition of alkyl per-O-acetyl-2-deoxy-2-bromo-and-iodo-α-O-mannopyranosides was studied. The bromo sugars gave fairly abundant MH⁺, whereas for the iodo sugars the MH⁺ ions were insignificant. However, both the bromo and the iodo derivatives gave abundant M + alkali metal ion complexes. In contrast to the behaviour of the MH⁺ ion, the [M + Li]⁺, [M + Na]⁺ and [M + K]⁺ ions of these compounds do not decompose by loss of the C(1) substituent. Elimination of AcOH is the preferred fragmentation pathway of [M + Cat]⁺. Elimination of HX occurs only after loss of AcOH and CH₂CO from MH⁺, whereas [M + Cat]⁺ directly loses HX. The elimination of HX is more pronounced from [M + Na]⁺ and [M + K]⁺ than from [M + Li]⁺. Loss of AcOLi is an additional fragmentation route observed in the case of the decomposition of [M + Li]⁺ ion.     

Determination of alkali metals in high-temperature Bi-containing superconductors by ICP-AES

Lowering of the detection limits of the alkali elements in Bi-containing superconductors was achieved by optimization of the carrier gas flow rate in ICP-AES. The contents of the alkali metals in the final superconducting products, obtained on the basis of the Li, Na, K, Rb and Cs doped Bi-containing materials, were investigated. A significant decrease of their concentrations after the synthesis was found. The limits of detection with respect to the dissolved solid were as follows: 1.0×10^–4% Li, 1.0×10^–3% Na, 7.7×10^–4% K and 9.7×10^–4% Rb. The relative standard deviation was not more than 0.6 % for Li, 1% for Na and 2% for K and Rb.     

Collisional activation spectra of [M + Li]+, [M + Na]+ and [M + K]+ ions formed by field desorption of some monosaccharides

The collisional activation spectra of monosaccharide ions formed by [Li]⁺, [Na]⁺ and [K]⁺ ion attachment under field desorption conditions are reported. It is shown that the elimination of the alkali ions is determined by the alkali ion affinities of the molecules (M) and competes with a fragmentation of M which is almost independent of the alkali ion attached. Correspondingly the alkali ion is predominantly retained in the fragment ions. The usefulness of this method for the differentiation of underivatized isomers is demonstrated.     

M2Ga6Te10 (M: Li,Na): Two New Non‐metallic Filled β‐Manganese Phases – X‐ray and NMR Studies

Two new non‐metallic filled β‐manganese phases M₂Ga₆Te₁₀ (M: Li, Na) are obtained as black, homogeneous, microcristalline samples as well as single crystals by direct reaction of the elements. According to the single crystal structure determinations both compounds crystallize in space group R32 (No. 155, Z = 2) with the lattice constants: a = 1436.9(2), c = 1759.0(4) pm (T = 180 K, Li₂Ga₆Te₁₀) and a = 1458(1) pm, c = 1776.1(4) pm (T = 290 K, Na₂Ga₆Te₁₀). Their structures are characterized by tetrahedral close packings of Te^2–, corresponding to the arrangement of Mn atoms in β‐Mn. While Ga³⁺ ions are distributed in an ordered way over 12% of the tetrahedral holes, the M⁺ ions occupy all distorted octahedral (“metaprismatic”) holes. As the Li⁺ ions are too small they occupy off‐center positions inside the metaprisms. Positions with the strongest off‐centering can only be refined on the basis of a split model. MAS‐NMR measurements, including multiple quantum NMR, allowed the two different crystallographic M⁺ sites to be distinguished unambigously by separate ⁷Li and ²³Na signals, respectively. The assignment of the NMR signals was supported by measurements of samples in which Li⁺ was partly substituted by larger cations (Sn²⁺, Pb²⁺).     

Volumetric properties of water–poly(acrylic acid) salt systems from the pure solid to highly concentrated solutions

Volumetric properties of poly(acrylic acid) alkali-metal salts (Li, Na, K, Rb, and Cs) with different degrees of neutralization and water contents were studied in the range from pure solid to highly concentrated solutions. The apparent partial molar volume ?₂ of the polymer and the partial molar volume V₁ of water were calculated from density data. The value of ?₂ decreased with decreasing polymer concentration and eventually leveled off. Values of V₁, which at low water contents were much smaller than that of free water, increased with increasing water content and eventually reached a constant value equivalent to that of free water, thus indicating the appearance of free water. Water contents corresponding to the appearance of free water increased in the order of Li < Na < K < Rb < Cs, differing from the usual trend of hydration numbers observed in dilute solutions. The change of the slope of the plots of V₁ versus composition suggested a change in the hydration mechanism. For Li, Na, and K salts, the limiting values of V₁ at very low water content is considerably smaller than the 18 cm³/mol of free water. In contrast, for Rb and Cs salts, these values were relatively large, indicating the relatively weak electrostriction effects of these ions.     

EMK-Messungen in binären ladungsunsymmetrischen Salzschmelzen aus Bariumchlorid und Alkalimetallchloriden

EMF Measurements in Binary Chargeunsymmetrical Salt Melts of Barium- and Alkali Chlorides The EMF is measured of cells with transference of the type Cl₂[C]/MCl//MCl? BaCl₂(x)/[C]Cl₂ in the molten mixtures BaCl₂? MCl (M ? Li, Na, K, Rb, Cs). From the EMF values and values of activities from another independent methods the transference numbers of the cations Ba²⁺ and M⁺ relative to the chloride ion in the molten mixtures BaCl₂? (Li, Na, K) Cl are calculated. The values of activities for the system BaCl₂? LiCl are calculated from cryoscopic analysis of the phase diagram.     

Tandem mass spectrometry of lithium-attachment ions from polyglycols

A detailed study has been carried out of the fast atom bombardment tandem mass spectrometry (MS/MS) behavior of lithium-attachment ions from three glycol polymers: linear poly(ethylene glycol), linear poly(propylene glycol), and an ethoxylated fatty alcohol. Collisional activation was carried out in the “collision octapole” of a BEoQ hybrid mass spectrometer at a translational energy of 50 eV, with collision gas air. It was found that [M + Li]⁺ ions provide a number of advantages as precursors for practical MS/MS analysis as compared to the use of [M + H]⁺ or [M + Na]⁺ ions. First, [M + Li]⁺ ions are much more intense than the corresponding [M + H]⁺ ions. Second, [M + Li]⁺ ions dissociate to lithiated organic fragments with reasonable efficiency, which is not the case with [M + Na]⁺ precursors. Third, product ions are generally formed over the entire mass range for low molecular weight polyglycols. The most intense product ions are lithiated, linear polyglycol oligomers. These ions are formed via internal hydrogen transfer reactions which are facilitated by lithium (charge-induced). Two series of less intense product ions are formed via charge-remote fragmentations involving l,4-hydrogen elimination. A fourth product ion series consists of lithiated radical cations; these form via homolytic bond cleavages near chain ends. Overall, MS/MS analysis of [M + Li]⁺ polyglycol ions proved to be quite useful for chemical structure elucidation.     

Oligomerization of vinyl monomers 20. Carbon-13 NMR of oligomers of 2-vinylpyridine. Studies of labelled end groups

Oligomers of 2-vinylpyridine initiated with Li, Na, K, and Rb salts of ¹³C-labeled or-unlabeled 2-ethylpyridine and terminated with ¹³C-labeled or -unlabeled methyl iodide were separated by liquid chromatography and analyzed by ¹³C-NMR of the initial or terminal CH₃ group. The stereochemistry of the three dyads which flank the initial or terminal methyl group could be determined and this allowed us to evaluate the stereochemistry of both methylation and vinyl addition. The methylation of the Li and Na salts of the oligomer anions is highly (> 95%) stereoselective and independent of chain length, whereas the stereoselectivity of the K and Rb salts is substantially less. These data indicate that the Li and Na oligomer and polymer anions exist in a chelated form in which the metal ion is complexed with the penultimate 2-pyridine group, the other counterions being chelated to a lesser extent. The stereochemistry of monomer addition was found to be less stereoselective than that of methylation for the Li and Na salts. In addition, the apparent meso-stereoselectivity of monomer addition of the Na, K, and Rb systems was greater than that of the Li ion. For the latter system, in particular, the mechanism appeared to be Markoff-like and consistent with different reactivities of anions flanked by a distinct dyad or triad stereochemistry. These data appear to be consistent with the intramolecular coordination that tends to hold the third asymmetric center close to the propagating carbanion.