Direct Determination of Sulfacetamide Sodium by Derivative UV Spectrophotometry

UV Derivative spectra were used for the direct quantitative determination of sulfacetamide sodium in distilled water. The quantification was accomplished using the integrated area under the peaks. The zero-order spectrum of sulfacetamide sodium shows an absorption band at λ = 258 nm, with an εmax = 14900 l. mol. cm, the determination limit was (0.55-25.4) μg/ml with R = 0.9999 and RSD =1.25 %. The determination limits were (0.25-50.80) μg/ml for both first and second-order derivatives with R = 0.9982, 0.9995 and RSD = 1.60 %, 2.40 % respectively. This indicates a more sensitive and accurate results as compared with the zero-order method. These methods were applied to the direct determination of the samacetamide eye drop. ــــــــــــــــــــــــــــــــــــــــــــــــــــ رشابملا ريدقتلا ل ةقتـشملا فيـط مادخـتساب مويدوصلا ديماتيـسافلس ةعشلأل ةيجـسفنبلا قوف صـخلـملا ةقيرط ثحبلا نمضتي فيـط مادخـتساب رطقملا ءاملا يف مويدوصلا ديماتيسافلس ريدقتل ةرشابم ةقتـشملا شلأل ةع ةيجـسفنبلا قوف . بملا يمكلا ريدقتلا دمتعي ةمزحلا تحت ةحاسملا سايق ىلع رشا . نإ فيطلا يدايتعلاا (zero-order spectra) لوطلا دنع صاصتما ةمزح رهظي يجوملأ 258 لماعمب و رتيمونان يرلاوم صاصتما 14900 رتل . لوم 1 . مس 1 . ريدقتلا ىدم ناكو ) 0.55 25.4 ( مارغوركيام / للم رت و 9 R=0.999 و RSD=1.25% . امأ دنع ةقتشملا فيط مادختساب رشابملا ريدقتلا ىلولأا و دقف ةيناثلا ترهظأ ريدقت ىدم ) 0.25 50.8 ( مارغوركيام / عم نيتقيرطلا اتلكل رتللم R = 0.9982, 0.9995 و RSD = 1.60% ,2.40% ع يلاوتلا ىل ، م يف ةدايز ىلع لدي امم ةقيقد و ةساسح ةقيرطلا ناو ريدقتلا ىد ، قئارطلا هذه تمدختسا دقو PDF created with pdfFactory Pro trial version www.pdffactory.com Isam J. Al-Nuri and Israa’ A. Al-Obaydi 18 ءاودل رشابملا ريدقتلا يف SAMACETAMIDE نيع ةرطقك مدختسملا و ترهظأ هذه حاجن جئاتنلا قئارطلا . ــــــــــــــــــــــــــــــــــــــــــــــــــــ INTRODUCTION The spectrum of any compound may be considered as a mathematical function relating the absorbance to the wavelength of a particular compound. Thus A = f (λ) The function f includes all parameters which affect the absorbance of the compound such as concentration, cell path length, etc., as well as, the molar absorptivity of the compound at all wavelengths in the spectrum. Most UV/Visible spectra may be considered to be made up of a series of overlapping Gaussian peaks. It is therefore, of interest to consider what happens to Gaussian function when it is differentiated. Figure 1 shows such a peak, with its first, second, third and fourth derivatives. Fig. 1: Idealised representation of 1st/4th derivative on Gaussian peak. One of the classic analytical problems for any researcher in the field of UV/Visible spectrophotometry is the resolution of a number of components in a mixture, particularly when the absorbance of those components is extremely variable and/or components with naturally narrow absorption bands are overlapped by components with wide absorption bands. The problem is to resolve small shoulders or peaks from the total spectrum. This is one of the applications of derivative spectroscopy beside the improved spectral resolution, precise λmax determination, elimination of background turbidity and improving detection limit (Himmadi, 2007). second first PDF created with pdfFactory Pro trial version www.pdffactory.com Direct Determination of Sulfacetamide Sodium.......... 19 N-acetylsulfonamide or sodium derivative of N-[(4-aminophenyl) sulphonyl] acetamide (Maffat et al.,2005) is called sulfacetamide. It is a medicine used to treat a variety of bacterial infections of the eye and skin. It has the following chemical structure: A number of methods were used for the quantitative determination of sulfacetamide. HPLC method with average recoveries 98.9% (n=5) and RSD = 0.64% (Xu et al.,1999), liquid chromatography the limit of detection was (0.002) mg kg (Pang et al.,2003),differential-pulse polarography with an experimental detection limit of (2.4×10 )M in aqueous solution (Sulaiman et al.,1989), specrophotometric methods: Beer's law is obeyed in the concentration range of (0.04-8.0) microg/ml at the wavelength of maximum absorption (Nagaraja et al.,2002). The Beer's law limits is (4-80) μg/ml (Amin and Zareh,1996), Beer's law is obeyed over the concentration range 10 to 70 mug/ml (Rao et al.,1988) and first-order derivative spectrophotometry (Abdellatef et al.,1989). In this work, the direct quantification of sulfacetamide was accomplished using the integrated area under the peaks within a range of wavelengths, the peak area measurements are often found to be more reliable than peak height measurements (Cottrell,1989). EXPERIMENTAL Chemicals and solutions: 1. Pure Sulfacetamide Sodium (SDI) : A stock solution of (10) M was prepared by dissolving (0.0118) g of pure sulfacetamide in 50 ml distilled water, then by proper dilution, other less concentrated solutions were prepared. 2. Pure Sodium Thiosulfate : A stock solution of (10) M was prepared by weighing (0.0076) g of sodium thiosulfate (Na2S2O3) and dissolving in 50 ml distilled water then by proper dilution, other more dilute concentrations were prepared. 3. Sulfacetamide Drug Solution : SAMACETAMIDE eye drops (SDI, Iraq, sulfacetamide sodium, 20%, sodium thiosulfate, 0.1% w/v): The molar concentration of the eye drop(SAMACETAMIDE 20%) was calculated (0.8467) M and then by proper dilution with distilled water, other more dilute solutions were prepared and their spectra were recorded. S N O O


INTRODUCTION
The spectrum of any compound may be considered as a mathematical function relating the absorbance to the wavelength of a particular compound.Thus A = f (λ) The function f includes all parameters which affect the absorbance of the compound such as concentration, cell path length, etc., as well as, the molar absorptivity of the compound at all wavelengths in the spectrum.
Most UV/Visible spectra may be considered to be made up of a series of overlapping Gaussian peaks.It is therefore, of interest to consider what happens to Gaussian function when it is differentiated.Figure 1 shows such a peak, with its first, second, third and fourth derivatives.One of the classic analytical problems for any researcher in the field of UV/Visible spectrophotometry is the resolution of a number of components in a mixture, particularly when the absorbance of those components is extremely variable and/or components with naturally narrow absorption bands are overlapped by components with wide absorption bands.The problem is to resolve small shoulders or peaks from the total spectrum.This is one of the applications of derivative spectroscopy beside the improved spectral resolution, precise λ max determination, elimination of background turbidity and improving detection limit (Himmadi, 2007).second first PDF created with pdfFactory Pro trial version www.pdffactory.comN-acetylsulfonamide or sodium derivative of N-[(4-aminophenyl) sulphonyl] acetamide (Maffat et al.,2005) is called sulfacetamide.It is a medicine used to treat a variety of bacterial infections of the eye and skin.It has the following chemical structure: A number of methods were used for the quantitative determination of sulfacetamide.HPLC method with average recoveries 98.9% (n=5) and RSD = 0.64% (Xu et al.,1999), liquid chromatography the limit of detection was (0.002) mg kg -1 (Pang et al.,2003),differential-pulse polarography with an experimental detection limit of (2.4×10 - 6 )M in aqueous solution (Sulaiman et al.,1989), specrophotometric methods: Beer's law is obeyed in the concentration range of (0.04-8.0) microg/ml at the wavelength of maximum absorption (Nagaraja et al.,2002).The Beer's law limits is (4-80) µg/ml (Amin and Zareh,1996), Beer's law is obeyed over the concentration range 10 to 70 mug/ml (Rao et al.,1988) and first-order derivative spectrophotometry (Abdellatef et al.,1989).
In this work, the direct quantification of sulfacetamide was accomplished using the integrated area under the peaks within a range of wavelengths, the peak area measurements are often found to be more reliable than peak height measurements (Cottrell,1989).

Chemicals and solutions:
1. Pure Sulfacetamide Sodium (SDI) : A stock solution of (10 -3 ) M was prepared by dissolving (0.0118) g of pure sulfacetamide in 50 ml distilled water, then by proper dilution, other less concentrated solutions were prepared.

Pure Sodium Thiosulfate :
A stock solution of (10 -3 ) M was prepared by weighing (0.0076) g of sodium thiosulfate (Na 2 S 2 O 3 ) and dissolving in 50 ml distilled water then by proper dilution, other more dilute concentrations were prepared.

Sulfacetamide Drug Solution :
SAMACETAMIDE eye drops (SDI, Iraq, sulfacetamide sodium, 20%, sodium thiosulfate, 0.1% w/v): The molar concentration of the eye drop(SAMACETAMIDE 20%) was calculated (0.8467) M and then by proper dilution with distilled water, other more dilute solutions were prepared and their spectra were recorded.A Shimadzu UV-Visible spectrophotometer model UV-1650 PC, connected to a computer with pentium 4 processor.The optimized conditions for spectrophotometic measurements were derivative modes 1 Dr (d 1 A/dλ 1 ), 2 Dr(d 2 A/dλ 2 ), scan speed fast, slit width 2nm, derivative UV spectra were recorded over a wavelength range of (200-400) nm, using (1×1×3) cm matched quartz cells.
PDF created with pdfFactory Pro trial version www.pdffactory.com1.702 1.176×10 -4 106.9 It is worth mentioning that the presence of 0.1% w/v sodium thiosulphate as additive in the solution of the sulfacetamide eye drop has no effect on the quantitative determination of the sulfacetamide, since the spectra of pure sodium thiosulfate and sulfacetamide eye drop at the different concentrations were recorded (Fig. 4).From the spectra, it is clear that there is negligible influence in changing the absorbance at λ = 258 nm at which sulfacetamide absorbs and is determined.
The first-order derivative spectrum of pure sulfacetamide shows a positive peak at λ = (232-258) nm, crossing the zero-axis at λ = 258 nm and a negative peak at λ = (258-326) nm.The quantitative determination of pure sulfacetamide was accomplished through plotting of a calibration curve between the integrated area under the positive peak against the molar concentration of pure sulfacetamide solutions.The result was a straight-line obeying the Beer-Lambert law with a determination limit of (0.25-50.80) µg\ml, R 2 = 0.9982 and RSD = 1.60 % (Fig. 5).
PDF created with pdfFactory Pro trial version www.pdffactory.comThe first-order derivative spectrum for SAMACETAMIDE drug solutions recorded at different concentrations and the area under the positive peak at λ = (230-258)nm was integrated and the recoveries were estimated (Table 3).The spectrum of the second-order derivative for different concentrations of pure sulfacetamide show a negative peak at λ = (242-274) nm (Fig. 1), their integrated area were plotted against the molar concentrations the result is a straight-line relationship obeying the Beer-Lambert law with a determination limit of (0.25-50.80) µg\ml, R 2 = 0.9995, and RSD = 2.40% (Fig. 6).PDF created with pdfFactory Pro trial version www.pdffactory.com The second-order derivative spectra of a series for SAMACETAMIDE drug solution show a negative peak at λ = (242-274) nm.The areas are integrated and the recoveries for them were estimated (Table 4).
Table 4: The integrated area under the negative peak of the second-order derivative spectra at λ = (242-274) nm for different concentration of SAMACETAMIDE eye drop solutions.

CONCLUSIONS
The second-order derivative method was the best method for the quantitative determination of pure sulfacetamide as compared with the zero and first-order methods.The same results proved fruitful for the determination of sulfacetamide in the eye drop SAMACETAMIDE (the best recovery percent and the minimum percent of error), even though that sulfacetamide was determined by first-order derivative according to peak height recording whereas in this work the integrated area under the peak was employed which more reliable for quantification.The determination limit of sulfacetamide was improved by using derivative spectrophotometry than the normal spectra.
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Fig. 5 :
Fig. 5: The calibration curve of the first-order derivative spectrum of pure sulfacetamide solutions

Fig. 4 :
Fig. 4: The zero-order overlay spectra for different concentration of pure sodium thiosulphate solutions in water

Fig. 6 :
Fig.6: The calibration curve of the second-order derivative spectra of pure sulfacetamide solutions.

Table 2 :
The absorbance of the zero-order spectrum at λ = 258 nm for different concentrations of sulfacetamide in SAMACETAMIDE eye drop solutions

Table 3 :
The integrated area under the positive peak of the first-order derivative spectra at λ = (230-258) nm for different molar concentration of SAMACETAMIDE eye drop solutions.
Thesis, College of Science, University of Mosul.
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