PVC which expand its applications in biomedical and clinical
field. Exploiting these complexes by their interaction with PVC
should lead to the increased utility of the inorganic complexes
with a glance at future trends and challenges in biotechnology
and industrial field.
of the metal chlorides for Co(II), Ni(II) (25 ml, 0.1 mmol) to a hot
ethanolic solution of HL1 (25 ml, 0.2 mmol in case of binary or
0.1 mmol in case of ternary complexes) and DL-alanine (H2L2) (0.1
mmol). The resulting mixture was stirred under reflux for 2 h and
left to cool, whereby the complexes precipitated as fine powders.
The solid complexes were filtered, washed with ethanol, then with
diethyl ether, and dried in a vacuum desiccator over anhydrous
calcium chloride where the solid complexes were obtained as a
solid powder; several trials are in process in order to obtain suitable
crystals. The formed complexes showed similar melting points
(~260 ◦C, 263, 267 and 269 ◦C) for (1), (2), (3) and (4), respectively.
Experimental
General procedures and materials
All chemicals used were of the analytical reagent grade (AR) and
of highest purity available. They included enrofloxacin, DL-alanine,
sparfloxacin (Sigma), CoCl2·6H2O and NiCl2·6H2O (BDH), were
used. Absolute ethyl alcohol, diethyl ether (Adwic), Yeast extract
and agar (Sigma) were also used. De-ionized water collected from
all glass equipment was used in all preparations. The commercial
PVC (suspension) used in this study was additive free, with a
K-value 70 (Hu¨ls) dibasic lead carbonate (DBLC) (Rolite lead)
(National Lead, West Germany), Ca–Zn soap (Lagor-S.P.A.,
Italy).
Preparation of PVC samples
Samples of PVC for heat degradation were prepared by thoroughly
mixing 1 g of PVC powder with 2 wt.% of the stabilizer (or a mixed
stabilizer) in a mortar and 0.2 g of the resulting fine powder was
used in the investigation.
Evaluation of stabilizing efficiency
FTIR spectra were obtained from dispersions in KBr using
a Perkin-Elmer FT-IR type 1650 spectrophotometer. The spectra
were collected in the range from 200 to 4000 cm-1 with a resolution
of 2 cm-1. UV-Vis spectrophotometric measurements were carried
out using automated spectrophotometer UV-Vis Thermo Fischer
Scientific Model Evolution 60 ranged from 200 to 900 nm. Molar
conductivity was measured on a ELICO(CM82T) conductivity
bridge. The molar magnetic susceptibility was measured on
powdered samples using the Faraday method. The diamagnetic
corrections were made by Pascal’s constant and Hg[Co(SCN)4]
was used as a calibrant. The solid reflectance spectra were
performed on a Shimadzu 3101pc spectrophotometer. Thermal
analyses of the complexes were carried out using a Shimadzu
TGA-50H and DTA-50H thermogravimetric analyzer in a dy-
namic nitrogen atmosphere (flow rate 20 ml min-1) with a heating
rate of 10 ◦C min-1. The percentage weight loss was measured from
ambient temperature to 1000 ◦C, highly sintered a-Al2O3 was used
as reference.
Evaluation of the stabilizing efficiency of the investigated thermal
stabilizers was carried out by using Congo Red dye paper to
measure the thermal stability values (Ts), i.e., the time elapsed
for the detection of HCl gas evolved at 180 ◦C, in air.51
Notes and references
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Antimicrobial activity
Antimicrobial activity of the tested samples was determined using
a modified Kirby–Bauer disc diffusion method.47,48 100 ml of the
test bacteria/fungi were grown in 10 ml of fresh media until they
reached a count of approximately 108 cells ml-1 for bacteria or 105
cells ml-1 for fungi.49 100 ml of microbial suspension was spread
onto agar plates. Plates inoculated with filamentous fungi as
Aspergillus flavus, Candida albicans at 25 ◦C for 48 h; Gram-positive
bacteria as Staphylococcus aureus and Gram-negative bacteria as
Escherichia coli; were incubated at 35–37 ◦C for 24–48 h and
yeast as Candida albicans incubated at 30 ◦C for 24–48 h and the
diameters of the inhibition zones were measured in millimetres.50
Standard discs of tetracycline (antibacterial agent), Amphotericin
B (antifungal agent) served as positive controls, while filter discs
impregnated with 10 ml of solvent (distilled water, chloroform,
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Synthesis of (1)–(4)
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The reported complexes were prepared according to the following
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◦
procedure by addition of a hot water-ethanolic solution (60 C)
1830 | Dalton Trans., 2012, 41, 1824–1831
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