“i grew up on antibiotics. every ailment - sore throats, earaches, flus - warranted a trip to the...

“I grew up on antibiotics. Every ailment - sore throats, earaches, flus - warranted a trip to the doctor and in most cases some kind of prescription”

“Am crescut cu antibiotice. Orice indispoziţie – dureri de gât, dureri de urechi, răceală – îmi garanta o vizită la doctor şi în cele mai multe cazuri

prescrierea unei reţete”

• Cephalosporins - one of the most important and probably the most frequently used antibiotics in the world - in terms of the number of compounds currently on the market as well as of their use for the treatment of infectious diseases.

Introduction

• Cephalosporins: β-lactam antibiotic

Capillary electrophoresis (CE)

N

S

R'

COOH

O

R-CO-NH

Aim of study• study of the electrophoretic behaviour of cephalosporins from different different generations having different structural characteristics using several background electrolytes at variuos pH.

• simultaneos separation of cephalosporins from complex mixtures.

• optimization of the electrophoretic parameters and analytical conditions of the separation – increased resolution and short analysis time.

Studied cephalosporins:

- 1st generation cephalosporins: cefalexin, cefadroxil, cefaclor, cefazolin;

- 2nd generation cephalosporins: cefuroxim, cefoxitin;

- 3rd generation cephalosporns: cefoperazone, cefotaxime, ceftazidim, ceftriaxon;

Studied cephalosporins

• Reagents: sodium tetraborate, disodium hydrogenophosphate, sodium dihydrogenophosphate, phosphoric acid, sodium hydroxide, methanol (Merck, Germany). Purified water - Milli-Q water purification system.

• Cephalosporins: cefalexin monohydrate, cefaclor monohydrate were obtained from Sandoz (Târgu-Mureş, România); cefadroxil monohydrate, ceftriaxon sodium, cefotaxime sodium, cefazolin sodium, cefoxitin sodium from Antibiotice (Iaşi, România); cefuroxim sodium from Medochemie (Cyprus); ceftazidim pentahydrate, cefoperazone sodium from Glaxo (Bucureşti, România).

• CE system: Agilent 6100 CE - DAD detection; software: Chemstation.• Capillary: polyimide-coated fused silica-capillaries of 48 cm (effective

length: 40 cm) x 50 μm I.D. (Agilent).• For the identification of the individual peaks, the UV spectrum of each

cephalosporin was recorded previously – detection at 210, 230, 250 nm.• “Standard” electrophoretic conditions: voltage + 25kV, temperature

25 0C, injection pressure/time: 50 mbar/3 sec., injection at the anodic end of the capillary.

• Stock solutions: 100 μg/ml in methanol – dilution.

Materials and methods

Electrophoretic behavior of cephalosporins at pH - 7

Electrophoretic parameters of cephalosporins at pH - 7

Cephalosporins separation at pH - 7

Electrophoretic behavior of cephalosporins at pH – 9.3

Electrophoretic parameters of cephalosporins at pH – 9.3

Cephalosporins separation at pH – 9.3

Electrophoretic behavior of cephalosporins at pH - 5

Cephalosporins separation by CZE

Optimum BGE: 25 mM disodium hydrogenophosphate – 25 mM sodium didydrogenophosphate mixture - pH – 7

Optimization of analytical conditions - Voltage

Optimization of analytical conditions - Temperature

Optimization of analytical conditions – Injection parameters

Analytical parameters

n = 6; c = 25 µg/ml

Analytical parameters

n = 6; c = 5 - 100 µg/ml

• Electrophoretic mobilities and behavior of cephalosporins – strongly related to structural characteristics.

• ECZ - can be used for the identification and determination of cephalosporins in formulated pharmaceutical products and for separations from complex mixtures.

• The use of an appropriate electrolyte at the right pH , or a combination of electrolytes enables the identification and separation of the studied substances from complex mixtures

• Optimum separation conditions: BGE - 25 mM NaH2PO4+ 25 mM Na2HPO4, pH=7, voltage: 25 kV, temperature: 25ºC, injection pressure/time: 50mbar/3sec, detection at 210 and 250 nm.

Conclusions

The first rule of antibiotics is try not to use them, and the second rule is try not to use too many of them.

Prima regulă a terapiei cu antibiotice este să încerci să nu le utilizezi, iar a doua regulă este să nu le utilizezi prea des