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Structural characterization of calcium glycinate, magnesium glycinate and zinc glycinate

Journal of Innovative Optical Health Sciences

October 2016
10(03)

DOI:10.1142/S1793545816500528

License
CC BY 4.0

Authors:

Lihui Yin

National Institutes for Food and Drug Control, China

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Metal glycinate chelates are formed by glycine and metal compounds through chemical reactions. Calcium glycinate, magnesium glycinate and zinc glycinate are kinds of new-type and ideal nutrient supplements, which have satisfactory physico-chemical properties and bioactivities. They are important for prophylaxis and treat metal deficiency. The structural characterization shows that the metal ion is bonded to the amino and carboxyl group to form two five-membered rings. This paper mainly studies the structure characterization of the metal chelated glycinates by their solubility, infrared spectrum, thermal analysis, mass spectrometry, polycrystal diffraction, the metal contents and glycine contents of calcium glycinate, magnesium glycinate and zinc glycinate.

The structure of chelated metal glycinate.

…

. Results of thermal analysis.

…

The infrared spectrum of glycinate (a), calcium glycinate (b), magnesium glycinate (c), and zinc glycinate (d).

…

. The contents of calcium ion in calcium glycinate.

…

. Summary of the comprehensive analysis results.

…

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Structural characterization of calcium glycinate,

magnesium glycinate and zinc glycinate

Li-Hui Yin

, Xu-Ping Liu

†

‡

, Lu-Yao Yi

†

, Jin Wang

, Ya-Jun Zhang

and Yu-Fei Feng

National Institutes for Food and Drug Control

Beijing 100050, P. R. China

†

JiangXi Provincial Institute for Drug Control

Nanchang 330029, P. R. China

‡

sanyezao@yeah.net.

Received 20 March 2016

Accepted 31 August 2016

Published 14 October 2016

Metal glycinate chelates are formed by glycine and metal compounds through chemical reactions.

Calcium glycinate, magnesium glycinate and zinc glycinate are kinds of new-type and ideal

nutrient supplements, which have satisfactory physico-chemical properties and bioactivities.

They are important for prophylaxis and treat metal de¯ciency. The structural characterization

shows that the metal ion is bonded to the amino and carboxyl group to form two ¯ve-membered

rings. This paper mainly studies the structure characterization of the metal chelated glycinates

by their solubility, infrared spectrum, thermal analysis, mass spectrometry, polycrystal di®rac-

tion, the metal contents and glycine contents of calcium glycinate, magnesium glycinate and zinc

glycinate.

Keywords: Calcium glycinate; magnesium glycinate; zinc glycinate; structure characterization.

1. Introduction

Metal glycinate chelates are formed by glycine and

metal compounds through chemical reactions, and

are kinds of new-type and ideal nutrient supple-

ments, which have satisfactory physico-chemical

properties and bioactivities. They are the raw

materials of great quantity of health care products

having large market in China. But they are re-

stricted because their structures not detected. Cal-

cium glycinate, magnesium glycinate and zinc

glycinate are formed by 2 to 1 chelate, and the

metal ion is bonded to the amino and carboxyl

group to form two ¯ve-membered rings (Fig. 1).

Understanding the structures of these species

require a couple of analytical tools for their

‡

Corresponding author.

This is an Open Access article published by World Scienti¯c Publishing Company. It is distributed under the terms of the Creative

Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly

cited.

Journal of Innovative Optical Health Sciences

Vol. 10, No. 3 (2017) 1650052 (10 pages)

cThe Author(s)

DOI: 10.1142/S1793545816500528

1650052-1

determination. Infrared spectroscopy and X-ray

powder was applied to prove the reaction of iron

and amino acid carboxyl group with one or more

coordinate covalent bonds.

If iron ion reacts with

more than one carboxyl functional groups, it can

generate to a 1:2 or 1:3 metal amino acid chelate

molecules. 1:2 zinc glycinate was studied by X-ray

di®raction to show the two chelating ¯ve-membered

rings.

2,3

The thermodynamic parameters for the

formation of glycine complexes were detected.

The

di®erence between the 13C NMR spectra of mag-

nesium glycinate and glycine was reported.

And a

study was undertaken for the structures and frag-

mentation modes of the gasphase complexes of zinc

attached to deprotonated amino acids in the gas

phase by electrospray ionization.

But the above

detections cannot readily assess the structures of

the chelated metal glycinate. Here, we present the

structural characterization of calcium glycinate,

magnesium glycinate and zinc glycinate by their

solubility, infrared spectrum, thermal analysis,

mass spectrometry, polycrystal di®raction, the

metal content and glycine content of them.

2. Materials and Methods

2.1. Samples

Calcium glycinate (Fan mei (Beijing) Biological

Products Co., Ltd., batch: 20071103C, 20071105C),

magnesium glycinate glycine chelated magnesium

(Fan mei (Beijing) Biological Products Co., Ltd.,

batch: 20071111M, 20071113M), zinc glycinate

(Fan mei (Beijing) Biological Products Co., Ltd.,

batch: 20071107Z, 20071109Z).

2.2. Solubility

Metal oxide and glycine were the two raw materials

which were used in the making of chelated metal

glycinate. The solubilities of metal oxides and

chelated metal glycinate were investigated at 25C.

200 mg of metal oxides (calcium oxide, zinc oxide,

magnesium oxide) and the batches of chelated

metal glycinates respectively, were dissolved in

20 mL water, and then added 1 mol/L hydrochloric

acid in drops.

2.3. Infrared spectrum

All infrared spectrum of calcium glycinate, magne-

sium glycinate, and zinc glycinate were collected

using a NEX us FT-IR spectrometer (Thermo

Nicolet).

The mid Fourier transform infrared

spectrum recorded at 300 K in the range of 400–

4000 cm1following the KBr pellet technique. The

functional groups were identi¯ed by the infrared

spectrum.

2.4. Mass spectrum

High resolution mass spectrometry was used to

determine the exact molecular weight of the com-

pounds,

which was an important parameter for

chelate determination. The experimental setup with

micro Q-TOF mass spectrometer (BRUKER),

which includes a sample manipulator and a time-

of-°ight mass spectrometer (TOF-MS), which are

housed in an ultra-high vacuum chamber (UHV)

with a base pressure of about 109Torr.

2.5. Thermal analysis

The thermal stabilities of GZC were studied by

gravitation thermal analysis (GTA) using TGA-

Q500 TGA (U.S. TA company) between the tem-

peratures 30C and 1000 C at a heating rate of 15 C/

min in nitrogen atmosphere, and di®erential thermal

analysis (DTA) using DSC-Q200 (U.S. TA company)

between the temperatures 40C and 200Cata

heating rate of 10C/min in nitrogen atmosphere.

2.6. Polycrystal di®raction

X-ray absorption spectra were recorded at the in-

stitute of Materia Medica,

Chinese Academy of

Medical Sciences with the storage ring SPEAR op-

erating at 3 GeV and ring currents of 50 100 mA.

Selenium K-edge spectra were recorded on beamline

7-3 using a Si (220) double crystal monochromator

with an upstream vertical aperture of 1 mm.

Fig. 1. The structure of chelated metal glycinate.

L.-H. Yin et al.

1650052-2

Selenium K-edge X-ray absorption spectra were

measured as the Ka °uorescence excitation spectra

using a Canberra 13-element germanium detector.

The spectrum of hexagonal Se was collected simul-

taneously with each data set for energy calibration,

with the ¯rst in°ection of its absorption edge

taken to be 12,658.0 eV. Sulfur K-edge spectra

were recorded on beamline 6-2 with a Si (111)

double crystal monochromator. Sulfur °uorescence

was collected using a Stern–Heald–Lytle detector.

Spectra were calibrated with reference to a solid

sodium thiosulfate standard measured periodically

during the run, the lowest energy K-edge absorption

peak of which was 2469.2 eV. Samples were at

room temperature for the sulfur measurements.

Background subtraction and normalization were

carried out according to established procedures.

2.7. The contents analysis of metal ions

Ion chromatography method was a high sensitivity,

good accuracy method for the content analysis of

metal ions. We used ion chromatographic methods to

determine the metal ion contents of calcium glycinate

and magnesium glycinate.

But we could not de-

termine zinc ion by the ion chromatography, so we

used the inductively coupled plasma mass spec-

trometry (ICP-MS) to simultaneously determine the

calcium, magnesium and zinc ion contents.

The concentration of calcium and magnesium

cations (Ca2þ,Mg

2þ) was determined with a Dio-

nex ICS-3000 dual system consisting of a dual pump

(DP) module, an eluent generator (EG) module, a

detector chromatography (DC) module (single

temperature zone con¯guration), and an auto-

sampler (AS). The eluent contained 60 mmol/L

sodium hydroxide (NaOH), and the °ow rate was

0.25 mL/min. Detection was the conductivity de-

tector (CD) with integrated cell held at 35C. The

conductivity suppressor was CSRS ULTRA II

(4 mm), the guard column was Ionpac CG12A

(cations) (4 50 mm), and the column was Ionpac

CS12A (cations) (4 250 mm).

The concentrations of zinc cations (Zn2þ) was

carried out on an ICP-MS (ICP-MS X-7, Thermo

Scienti¯c), which was operated with the plasma

screen plus sensitivity enhancement option ¯tted,

Xt interface cones, and with Peltier cooling of the

spray chamber. A standard quartz nebulizer was

used, together with a standard quartz impact bead

spray chamber and standard single piece,1.5 mm ID

injector quartz torch. The instrument was operated

using standard instrument operation. Plasma Lab

software was applied to instrument control, data

acquisition, and analysis. The instrumental and

operating condition were optimized with the com-

mentated tune solution. The operating parameters

of ICP-MS instrument were as follows: RF power

1830 W, coolant gas °ow 14.3 L/min, auxiliary gas

°ow 0.95 L/min, nebulizer gas °ow 0.87 L/min,

pump rate 1.0 mL/min, and peak jumping data

acquisition mode: dwell time 10 s, duration time

60 s, and three replicates per sample. The isotope of

SC (IS) was monitored at m/z 45, full validation

according to the FDA guidelines was, as far as

applicable for ICP-MS, performed for the assay.

2.8. The contents analysis of glycine

Ion exchange chromatography was the common

method for determination of amino acid. The

methods were applied to analyze the glycinate

contents of calcium glycinate, magnesium glycinate

and zinc glycinate.

The concentration of glycine was determined

with a Dionex ICS-3000 dual system consisting of a

DP module, an EG module, a DC module (single

temperature zone con¯guration), and an AS. The

eluent contained 25% 250 mmol/L sodium hydrox-

ide (NaOH), and the °ow rate was 0.25 mL/min.

Detection was the amperometric detector, the

guard column was Aminopac PA-10 Dionex

(anions) (4 50 mm), and the column was Amino-

pac PA-10 Dionex (anions) (4 250 mm).

The ionic species was identi¯ed and quanti¯ed by

interpolation on a proper calibration curve. All

experiments were performed at room temperature

and lasted approximately 10 min for each injected

sample.

3. Results

3.1. Results of solubility

The chelated metal glycinate after oral administra-

tion was absorbed in the small intestine. We studied

the solubility in the di®erent pH solutions (pH 2–12).

The solubilities of chelated metal glycinates were

better than the corresponding metal oxides (calcium

oxide, zinc oxide, magnesium oxide). The calcium

Structural characterization of calcium glycinate, magnesium glycinate and zinc glycinate

1650052-3

glycinate, magnesium glycinate and zinc glycinate

were also clear in the acidic solution.

3.2. Results of infrared spectrum

We studied the infrared spectrum of chelated metal

glycinate and glycine. The formation of NH

–M

bond and COO–M bond and the disappearance of

-glycine bond and COO- bond were the indi-

cations of the formation of ¯ve-membered ring

structure of chelated metal glycinates.

There were NH

and COO- groups in the

molecules. In the infrared spectrum of chelated

metal glycinate, NH

peaks (1111 cm1, 1131 cm 1,

2120 cm1Þand COO-characteristic peaks

(502 cm1, 607 cm 1, 697 cm1) all disappeared

(Note COO- and other base groups combined).

The NH2peaks (3342 cm1, 3450 cm1Þalso

inferred that the three chelated metal glycinates have

generated M–NH

group and COO–M groups

(Fig. 2).

3.3. Results of mass spectrum

Calcium glycinate, magnesium glycinate and zinc

glycinate were analyzed by high-resolution mass

spectrometries. The results showed that all the

three had the molecular ion peaks ([MþGly2þ

H1þ, M: metal ions, Gly: glycine) in the mass

spectrum, which proved that molar ratio is 1:2 of M

and glycines (Fig. 3).

(a)

(b)

Fig. 2. The infrared spectrum of glycinate (a), calcium glycinate (b), magnesium glycinate (c), and zinc glycinate (d).

L.-H. Yin et al.

1650052-4

(c)

(d)

Fig. 2. (Continued )

(a)

Fig. 3. The mass–mass spectra of calcium glycinate (a), the mass–mass spectra of magnesium glycinate (b), the mass–mass spectra

of zinc glycinate (c).

Structural characterization of calcium glycinate, magnesium glycinate and zinc glycinate

1650052-5

(b)

(c)

Fig. 3. (Continued )

(a)

Fig. 4. The GTA of calcium glycinate (a), the DTA of calcium glycinate (b), the GTA of magnesium glycinate (c), the DTA of

magnesium glycinate (d), the GTA of zinc glycinate (e), the DTA of zinc glycinate (f).

L.-H. Yin et al.

1650052-6

(b)

(c)

(d)

Fig. 4. (Continued )

Structural characterization of calcium glycinate, magnesium glycinate and zinc glycinate

1650052-7

Mass spectrometry proved that M–O ionic bond

and M...N coordinate covalent bond exists in

molecules. They con¯rmed the structures of calcium

glycinate, magnesium glycinate and zinc glycinate,

the structures were shown in Fig. 1.

3.4. Results of thermal analysis

We studied calcium glycinate, magnesium glycinate

and zinc glycinate for the GTA and di®erential

scanning analysis. The scanning prints showed the

Table 1. Results of thermal analysis.

Calcium glycinate Magnesium glycinate Zinc glycinate

The temperature range 90–180C 130–180 C60–180C

The weight loss range 15.02C–16.69% 16.58 C–18.45% 7.02 C–9.01%

The supposed molecular formula Gly2Ca.2H2O Gly2Mg.2H2O Gly2Zn.H2O

The theoretical value of water content 16.06% 17.27% 7.78%

Conclusion Contained two molecular

crystal water

Contained two molecular

crystal water

Contained one molecular

crystal water

(e)

(f)

Fig. 4. (Continued )

L.-H. Yin et al.

1650052-8

GTA and DTA in Fig. 4. The results were sum-

marized in Table 1.

3.5. Results of polycrystal di®raction

Polycrystal di®raction methods were used to

study glycine and three chelated metal glycinates.

The results showed that: the powders of glycine

and three chelated metal glycinates were quite

di®erent. It proved that chemical reaction

happened during the formation of chelated

compounds.

3.6. Results of metal ion contents

analysis

The results were shown in Tables 2–4.

3.7. Results of the contents analysis

of glycine

Ion exchange chromatography was commonly

used for the determination of amino acid, in

which we utilized it to analyze the glycine content

of the three chelated metal glycinates. It could

be used for almost any kind of charged molecule

including large proteins, small nucleotides and

amino acids.

The method was used to determine

the glycine contents of the three metal chelated

glycinates, the glycine contents were shown in

Table 5.

4. Discussion

The summary of the results of solubility, infrared

spectroscopy, thermal analysis, mass spectrometry,

polycrystal di®raction, metal content and glycine

content are shown in Table 6.

With this result, we can determine that all the

three chelated metal glycinates have ¯ve-membered

ring structure (Fig. 1). Calcium glycinate and

magnesium glycinate contained two crystalline

water molecules and zinc glycinate contained one

crystalline water molecule.

Table 2. The contents of calcium ion

in calcium glycinate.

Batch Calcium glycinate (%)

20071103C 14.2

20071105C 14.9

Table 3. The contents of magnesium

ion in magnesium glycinate.

Batch Magnesium glycinate (%)

20071111M 9.8

20071113M 10.1

Table 4. The contents of zinc

ion in zinc glycinate.

Batch Zinc glycinate (%)

20071107Z 32.7

20071109Z 28.3

Table 5. The glycine contents of the three metal chelated

glycinates.

Sample Batch The glycine content (%)

Calcium glycinate 20071103C 67.0

20071105C 65.2

Zinc glycinate 20071107Z 66.9

20071109Z 66.6

Magnesium glycinate 20071111M 71.0

20071113M 71.6

Table 6. Summary of the comprehensive analysis results.

Molecular formula Mol.wt.

The theoretical

value of water

content (%)

The actual

value of

water

content (%)

The theoretical

value of glycine

content (%)

The actual

value of

glycine

content (%)

The theoretical

value of metal

ion content (%)

The actual

value of metal

ion content (%)

(NH2CH2COO)2ZnH2O 231.51 7.78 8.28 63.98 69.4 28.25 30.50

(NH2CH2COO)2Mg2H2O 208.43 17.27 16.95 71.06 71.1 11.66 10.00

(NH2CH2COO)2Ca2H2O 224.20 16.06 17.46 66.07 63.0 17.88 14.60

Structural characterization of calcium glycinate, magnesium glycinate and zinc glycinate

1650052-9

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Jan 2022
ANIM FEED SCI TECH

The objective is to investigate the effects of dietary zinc form and concentration in broiler chickens. Day-old broiler chicks (n = 6) were allotted to treatments in a 2 ×3 factorial arrangement to examine supplemental zinc from sulfate (ZS) and glycinate (ZG) and concentration (40, 80, and 120 mg/kg). In healthy conditions, no difference in poultry performances is to be expected between organic and inorganic zinc sources, supplemented at the same zinc dose to the diets. We found that on day 21, zinc supplemented at 80 mg/kg increased body weight gain (BWG) by 113 g compared to zinc supplemented at 40 mg/kg (P < 0.01). Similarly, on day 35, zinc supplemented at 120 mg/kg increased BWG by 155 g compared to zinc supplemented at 40 mg/kg (P < 0.05). On day 35, zinc supplemented at 120 mg/kg increased feed intake by 239 g compared to zinc supplemented at 40 mg/kg (P < 0.05). The villi length on day 21 was increased by 63 µm in birds supplemented at 120 mg/kg compared to 40 mg/kg (P < 0.05). On day 21, cecal tonsil gene expression of interleukin 1 beta (IL-1β) was higher by 2.5 and 2.4-fold in the ZG-80 mg/kg group than the ZG-40 mg/kg and ZS-120 mg/kg groups (P < 0.01), and interleukin 10 (IL-10) was lower by 2-fold in the ZS-120 mg/kg group than ZS-40 mg/kg, while IL-10 was lower in the ZG-40 mg/kg than ZS-40 mg/kg group (P < 0.01). On day 35, cecal tonsil gene expression of IL-1β was overall higher by 1.3-fold in the ZG group compared to ZS (P < 0.05). On day 21, spleen gene expression of transforming growth factor-beta (TGF-β) was higher by 1.4-fold in the ZG-80 mg/kg group compared to ZG-40 mg/kg (P < 0.05). On day 35 spleen gene expression of lipopolysaccharide-induced TNF factor (LITAF) was lower in the ZG-80 mg/kg group compared to ZS-80 mg/kg (P < 0.05). On day 35 jejunum gene expression of claudin-2 was higher by 2.1-fold in the ZG-80 mg/kg group than ZS-80 mg/kg (P < 0.05). This study supports that zinc supplementation at 120 mg/kg improves the growth performance of broiler chickens. This is accompanied by improvements in intestinal morphology and modulation in immunity through an altered cytokine production profile.

Y2O3-MgO highly-sinterable nanopowders for transparent composite ceramics

Article

Full-text available

Nov 2019

Composite nanopowders Y2O3-MgO (1: 1 by volume) were synthesized by the method of self-propagating glycine-nitrate synthesis with an excess of glycine and nitric acid. It was shown that freshly prepared powder (precursor) contains about 19% of unreacted components and intermediate reaction products, which are removed by subsequent calcining. Crystallization of the precursor starts at calcination temperature above 600°C and leads to nucleation of the crystalline phases MgO and Y2O3. It was shown that calcining at temperatures from 800 to 1000°C leads to the formation of nanocrystals with sizes from 20 to 90 nm, respectively. The specific surface area (BET) of composite nanopowders decreases from 48 to 16 m2/g with increasing calcination temperature in the range T = 700-1000°С. It was shown that during Y2O3-MgO calcination in the air, intense chemisorption of CO2 occurs on the surface of nanopowders. According to calculations, about 5% of MgO is converted to magnesium carbonate. Finally, Y2O3-MgO composite ceramics with average grain size of 255 nm and transmittance of 71 % at λ=6000 nm have been obtained by spark plasma sintering of synthesized nanopowders.

Binding of Iron Ions with Soybean Protein

Article

Jan 1982

Bonding between iron ions and soybean protein (produced by the hydrolysis of soybean meal) in an iron-protein compound, which was prepared by mixing the soybean protein and iron (II) sulfate solution, was studied by infrared spectroscopy and an X-ray powder diffraction method. The oxidation state of the predominant iron ions within the compound was +3, but some Fe (II) ions were also present. In the infrared spectrum of the iron-protein compound, the band ascribable to stretching of the COO-group was shifted to the higher frequency side by 40 cm-1 in comparison with that of the free protein. No evidence was found for the formation of any crystalline iron compounds such as Fe2O3, Fe3O4 and FeO in the X-ray powder patterns. The possibility of the formation of gel-like compounds of iron (II) and iron (III) such as Fe(OH)2 and Fe(OH)3, respectively, was excluded, because the hydrolyzed product of iron (II) is easily oxidized to iron (III) and Fe(OH)3 transforms, at least partly to Fe2O3 or Fe3O4 after aging or storing the product in air. Thus, we concluded that the iron ion is bound to the soybean protein molecule through one or more carboxyl groups. Although other coordination sites within the protein molecule could also combine with the iron ions, we could not find evidence for other bondings.

A novel chelating organosilicone resin bearing long chain imidazolyl ligands: Preparation, characterization, and adsorption properties

Article

Mar 2013
J ORGANOMET CHEM

The imidazole ring is an important chemical component in nature that plays various critical roles. In this study, the imidazole used as a metal-chelating ligand was combined with a silicone resin structure by a long chain. The preparation, surface properties, thermal stability, complexation and adsorption properties with respect to Cu2+ ions, and multiple use cycles of the synthesized organosilicone resin bearing long chain imidazolyl ligands (ImSR) were studied using Fourier transform infrared spectroscopy (FTIR), 1H, 13C and 29Si nuclear magnetic resonance (NMR), a contact angle goniometer, thermogravimetric analysis (TGA) and UV–visible spectrophotometry methods. ImSR is a hydrophilic material with a water contact angle of 56° on a flat surface. It possesses good thermal stability and exhibits rapid weight loss above 230 °C. ImSR was evaluated as a promising adsorbing material for Cu2+ ions. It exhibited a high affinity for Cu2+ ions, with a maximum adsorption ability of 66.1 mg/g. Langmuir, Freundlich and Dubinin–Radushkevich isotherm models were used to analyze the experimental data. The results showed that the ImSR absorbent exhibited chemisorption and monolayer distribution on homogeneous active sites. The equilibrium adsorption capacity remained relatively constant after 5 use cycles.

Structure of bis(glycinato)zinc(II) monohydrate, a five-coordinate zinc(II) complex

Article

Jan 1990

Structural studies in solution and in the solid state on the zinc chelate of 2-hydroxy-(4-methylthio)butanoic acid, an effective mineral supplement in animal feeding

Article

Mar 2009
INORG CHIM ACTA

The bis-chelate complex of Zn2+ with 2-hydroxy-(4-methylthio)butanoate (MHA-H the anion derived from the so-called methionine hydroxy-analogue, MHA) is an effective, bioavailable mineral supplement for animal feeding. It can be obtained in two solid forms: the anhydrous [Zn(OC(O)CH2CH(OH)CH2CH2SCH3)2] and the corresponding dihydrate species, both well distinguishable by IR spectroscopy and powder X-ray diffraction. The crystal and molecular structure of the dihydrate form has been solved by single-crystal X-ray diffraction. It consists of dinuclear bis-chelate species with a bridging carboxylate group, both zinc atoms displaying hexacoordination involving all the hydroxyl and carboxyl groups from the four MHA-H anions and three oxygens from different water molecules. The fourth water molecule does not participate in coordination. Therefore, the dihydrate complex must be formulated as [Zn2(OC(O)CH2CH(OH)CH2CH2SCH3)4(H2O)3]·H2O (1). A molecular computational analysis has been carried out by density functional theory (DFT) on three possible MHA-H zinc chelates, i.e. the dinuclear bis-chelate observed in the solid state, the mononuclear bis-chelate diaquo-complex, and the monochelate tetraaquo-complex. Calculations have suggested that between the dinuclear and mononuclear bis-chelates, the preferred form in aqueous solution may be the second one. Moreover, both 1H (chemical shifts and relaxation rates) and 13C NMR data provide further evidence for the formation of Zn/MHA-H chelates in solution.

Cyclometalated rhodium(III) and iridium(III) complexes containing amino acids as N,O-chelates

Article

May 2011
INORG CHIM ACTA

The synthesis of bis-cyclometalated aminocarboxylato complexes [M(α-aminocarboxylato)(ptpy)2] (M=Rh, 3, 4, 5; M=Ir, 6, 7, 8), ptpy=2-(p-tolyl)pyridinato; aminocarboxylato=glycinato, l-alaninato, l-prolinato) from [{M(μ-Cl)(ptpy)2}2] (M=Rh, 1; M=Ir, 2) is described. The molecular structure of [Ir(l-alaninato)(ptpy)2] (7) was confirmed by a single-crystal X-ray diffraction study. Compound 7 crystallized from methanol-iso-hexane in the space group P21. For 7 the two diastereoisomers ΔIr, SC and ΛIr, SC were found crystallizing twice per unit. Absorption and emission spectra were recorded. The rhodium compounds are weak yellow-green and the iridium species strong green emitters.

Structures and fragmentations of zinc(II) complexes of amino acids in the gas phase. III. Rearrangement versus desolvation in the electrospray formation of the glycine-zinc complex

Article

Feb 2001
INT J MASS SPECTROM

The zinc complex of deprotonated glycine (Gly), denoted [Gly−H+Zn]+, is readily formed in the gas phase by electrospray ionization. Low energy collisional activation of [Gly−H+Zn]+ leads to three primary fragments, resulting from the losses of CO2, H2O+CO, and CO. Previous work has shown that the first two reactions require isomerization of the glycinate to nonclassical structures before the last desolvation step, and that loss of CO can only occur from a N-deprotonated glycine complex. It is shown herein, using accurate ab initio calculations, that such a structure does not pre-exist in solution, and that it is also formed in the electrospray process, during one of the last desolvation steps. Solvent molecules participate in this mechanism as proton relays between the two functional groups of Gly. These results provide a complete picture of the fragmentation of gaseous [Gly−H+Zn]+: each of the primary fragmentations arises from a specific precursor, none of which is the parent structure formed in solution.

Thermodynamic parameters for the formation of glycine complexes with magnesium(II), calcium(II), lead(II), manganese(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) at different temperatures and ionic strengths, with particular reference to natural fluid conditions

Article

May 1995
THERMOCHIM ACTA

Protonation constants and Mg2+, Ca2+, Pb2+, Mn2+-, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+glycine complex formation constants have been determined in different aqueous media at different temperatures. Salt effects are explained by a complex formation model which takes into account the formation of weak species. From the temperature dependence of the formation constants, thermodynamic parameters ΔHθ (and in some cases ΔCθp) have been obtained. A rigorous analysis of literature data, together with experimental findings, allows recommended formation parameters, in the ranges 0 ≤ Ie ≤ 1 mol l−1 (Ie is the effective ionic strength) and 5°C ≤ T ≤ 45°C, to be obtained. Because the proposed model can be used in any electrolyte mixture in the above I and T ranges, the speciation in seawater, and other natural fluids, can be simulated by appropriate computer programs. The validity of the present approach which takes into account the ionic strength dependence of formation constants, together with the concepts of effective ionic strength and complex formation model, is discussed.

Insight in the transport behavior of copper glycinate complexes through the porcine gastrointestinal membrane using an Ussing chamber assisted by mass spectrometry analysis

Article

Apr 2010

An Ussing chamber study was conducted in order to investigate the transport behavior of copper glycinate complexes through a porcine gastrointestinal membrane. Organic copper complexes such as copper tri- and tetraglycinates (GGG-Cu(II) and GGGG-Cu(II)) were used as model system. In a novel analytical approach the Ussing chamber was combined with mass spectrometry. Therefore, relevant analytical methods based on MALDI-MS and a coupling of capillary electrophoresis to ICP-MS and ESI-MS were developed for the determination of copper complexes in the mucosal and serosal half-chambers. It was found that 86.1+/-8.5% of copper triglycinate but only 20.8+/-9.9% of copper tetraglycinate penetrated the digestive membrane without modification. Furthermore, inorganic copper species were not detected but a new copper complex (m/z 442) was found to be formed in both compartments of the Ussing chamber.

Validation of the determination of copper and zinc in blood plasma and urine by ICP MS with cross-flow and direct injection nebulization

Article

Sep 1997
TALANTA

The simultaneous determination of copper and zinc in human plasma and urine by inductively coupled plasma mass spectrometry (ICP MS) is discussed. The performances of a cross-flow nebulizer and a direct-injection nebulizer (DIN) were compared. Flow-injection-DIN-ICP MS analysis of clinical samples using 1-2 mul samples was optimized. Isobaric interferences were discussed and were demonstrated to be eliminated for the (65)Cu and most of the Zn nuclides. The need for standard addition to compensate for signal suppression in the case of some serum samples was indicated. Results obtained by ICP MS using calibration with aqueous standard solutions were found to be in good agreement with those obtained by flame AAS for a batch of real blood plasma and urine samples. The methods developed were validated by analysis of several standard reference materials.

Recent developments in ion chromatography

Article

Jun 2002
J CHROMATOGR A

Corrado Sarzanini

This paper summarizes how ion chromatography is now a multimode technique suitable for solving analytical problems in all areas of interest. Current and more recent applications will be overviewed within the new trends.