Determination of amoxicillin in pharmaceuticals using sequential ....pdf

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 DETERMINATION OF AMOXICILLIN IN PHARMACEUTICALS 
USING SEQUENTIAL INJECTION ANALYSIS (SIA) AND 
MULTIVARIATE CURVE RESOLUTION (MCR)
A.Pasamontes*, M.P. Callao
Chemometrics and Qualimetrics Group. Department of Analytical and Organic Chemistry. 
Rovira i Virgili University 
Plaça Imperial Tàrraco 1. 43005 Tarragona, Catalonia, Spain 
*apf@quimica.urv.es
http://www.quimica.urv.es/quimio
RROVIRA I OVIRA I VVIRGILIIRGILIUUNIVERSITATNIVERSITATWith SIA techniques, carrier, reagents and sample are stacked sequentially into the coil using a 
selector valve. 
 
In this study we report a method for quantifying amoxicillin in pharmaceuticals in presence of interferents using sequential injection analysis 
(SIA). The detection is done by using a diode-array spectrophotometric detector and later multivariate curve resolution with alternating least 
squares (MCR-ALS). We studied both the effect when we applied different mathematical constraints and the influence of the reference standard 
concentration in the calibration step.
Study of 
 constraints
 Study of reference 
 standard concentration
OBJECTIVE
INSTRUMENTAL
1. Smilde, A.K.; Tauler, R.; Saurina, J.; Bro, R.; Anal. 
Chim. Acta, 398 (1999) 237.
2. Ruzicka, J.; Marshall, G.D.; Christian, G. D.; Anal. 
Chem., 62 (1990),1861.
3. Izquierdo-Ridorsa, A.; Saurina, J.; Hernández-Cassou, 
S.; Tauler, R.; Chem. And Intll. Lab. Sys., 38 (1997), 183. 
4. Pasamontes, A.; Callao, M.P; Anal. Chim. Acta, 485 
(2003),195. 
REFERENCES
RESULTS
If the reactive introduced is NaOH, a pH gradient is 
generated in the interdiffusion process that carries the 
reactives through the channel to the detector. 
When the sample reaches the detector, all the 
spectra are recorded at regular intervals during the SIA 
peak evolution, so spectra at different pH are recorded. 
 Detector
NaOH
Amoxac
Amoxbas/Amoxac
 Reversed ForwardAmoxac + NaOH  Æ Amoxbas +  Amoxac
REACTION
CONCLUSIONS
 SIA with a diode-array spectrophotometric 
detection is an attractive technique for 
quantifying amoxicillin in pharmaceuticals in 
presence of interferents. In such cases the 
advantages of using this system is that the 
determination 
is 
fairly automatic, 
the 
frequency of analysis is high and the 
consumption of reactive is low.
 Sample
 Present (mg)
 a
 a indicated in the pharmaceutical
 Found (mg) ± s (n=6)
 Flubiotic
 500
 548 ± 36
 Augmentine
 500
 634 ± 35
 Clamoxyl 
 500
 550 ± 80
O
H
N
NH2 H
H
H
O
O
N
B
H
H
CH3
CH3
H
COOH
 Amoxicillin:
¾ A wide-spectrum bactericide that is present in 
many pharmaceuticals.
¾ It is a white or almost white crystalline powder.
¾ It is slightly soluble in both water and ethanol.
¾ Its first two pKa are 2.4 and 7.4 
AMOXICILLIN
 220
 240
 260
 280
 300
 320
 0
 0.1
 0.2
 0.3
 0.4
 0.5
 Wavelenght
 Absorbance Acid
 Basic
λ
t
R
4.2 Absorbance
Wavelength
  AbsorbanceAbsorbance  AbsorbanceAbsorbanceTime
Time
Time
 Concentration profile
 Time
 0
 50
 100
 50
 100
 0
 0.5
 1
 1.5
 2
 2.5
 0
  AbsorbanceAbsorbance Trilinear and synchronization for only some species
 200
 220
 240
 260
 280
 300
 320
 0
 0.1
 0.2
 0.3
 0.4
 0.5
 Pure spectra
  AbsorbanceAbsorbanceWavelength (nm)
 0
 50
 100
 50
 100
 0
 0.5
 1
 1.5
 2
 0
 Concentration profile
 Time
  AbsorbanceAbsorbance Trilinear without synchronization (all species)
 200
 220
 240
 260
 280
 300
 320
 0
 0.1
 0.2
 0.3
 0.4
 0.5
 Pure spectra
  AbsorbanceAbsorbanceWavelength (nm)
 0
 50
 100
 50
 100
 0
 0.5
 1
 1.5
 2
 0
 Concentration profile
  AbsorbanceAbsorbanceTrilinear, equal shape and synchronization (all species)
 200  220
 240
 260
 280
 300
 320
 0
 0.1
 0.2
 0.3
 0.4
 0.5
  AbsorbanceAbsorbanceWavelength (nm)
 Pure spectra
  AbsorbanceAbsorbance 0
 50
 100
50
 100
 0
 0.5
 1
 1.5
 2
  AbsorbanceAbsorbance Concentration profile
 200
 220
 240
 260
 280
 300
 320
 0
 0.1
 0.2
 0.3
 0.4
 0.5
 Pure spectra
Wavelength (nm)
No Trilinear
 Conc. Reference
 Range A
 p /A
 s
 Range C
 p /C
 s
 b
 1
 b
 0
 R
 2
 Detection limit (k=3)  Test T ( α=0.05)
 10 ppm
 1 - 5.03
 1 a 6
 0.824
 0.227
 0.9978
 0.473
 NO 
 20 ppm
 0.53 - 2.63
 0.5 - 3
 0.863
 0.127
 0.9978
 0.239
 NO 
 30 ppm
 0.36 - 1.83
 0.33 - 2
 0.889
 0.0906
 0.998
 0.154
 SI
 50 ppm
 0.22 - 1.12
 0.2 - 1.2
 0.9064
 0.0596
 0.9982
 0.087
 SI
 60 ppm
 0.2 - 0.99
 0.166 - 1
 0.972
 0.0496
 0.9972
 0.090
 SI
 The sequence of the analysis was:
¾ Carrier aspiration: 4.74 ml.
¾ Sample aspiration: 0.25 ml.
¾ NaOH aspiration: 0.01 ml.
¾ NaOH concentration: 0.025 mol/l.
¾ Flow rate: 1 ml/min for all steps.
¾ The spectrum is recorded every 2 nm in 
the range from 210 to 340 nm.
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 Sample
 Time (s)
 Absorbance Wavelength (nm)
 Standard
 Time (s)
 Absorbance Wavelength (nm)
 Concentration of amoxicillin
 in pharmaceuticals
 +
 Augmented  matrix