Page 16 - Application Notebook - Hand Sanitizer Analysis

Application Spectrophotometric Analysis

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Measurement of Impurities in Ethanol
No. A626 Using UV-Vis Spectrophotometer

At present, demand for ethanol for disinfection is increasing
sharply as preventive measure for an infectious disease.
When ethanol is to be used as a medical product,
identification testing and purity testing conforming to the
applicable Pharmacopoeias in each country are necessary.
Ultraviolet-visible (UV-Vis) spectrophotometry is used in
these tests as one technique for determining whether
impurities are present in ethanol.
In the experiment introduced here, measurement of “Other
impurities (absorbance)” in ethanols, which is described in
the Japanese Pharmacopoeia, European Pharmacopoeia, and
United States Pharmacopeia, was conducted using a
Shimadzu UV-1900i UV-Vis spectrophotometer, and
absorbance, which is specified as an acceptance standard in Fig. 1 UV-1900i UV-Vis Spectrophotometer
the Pharmacopoeias, was judged automatically by using the
evaluation function of LabSolutions™ UV-Vis.
Table 1 Measurement Conditions
H. Abo
Instrument : UV-1900i UV-Vis
Software
:
LabSolutions
„ Test Method for Ethanols Measurement wavelength range : 235 - 340 nm
The Japanese Pharmacopoeia (JP) describes the five items Scan speed : Medium
Sampling pitch : 0.5 nm
“Clarity and color of solution,” “Acidity or alkalinity,” “Volatile
Slit width : 1 nm (fixed)
impurities,” “Other impurities (absorbance),” and “Residue on

evaporation” under “Purity” testing of ethanol, anhydrous
ethanol and ethanol for disinfection. Among these, “Other
impurities (absorbance)” is measured in order to determine
the presence/absence of impurities contained in ethanol
based on absorption in the ultraviolet (UV) region.
The European Pharmacopoeia (EP) includes “Absorbance” as
one item in “TESTS” and describes similar testing using UV-Vis
spectrophotometry. Absorbance (Abs.)
The United States Pharmacopeia (USP) specifies
“ULTRAVIOLET ABSORPTION” in “SPECIFIC TESTS” and also
describes testing by UV-Vis spectrophotometry.
The measurement method for “Other impurities” is the same
in the three Pharmacopoeias. The absorption spectrum of the
sample is measured using a cell with an optical path length
of 5 cm and water as a blank, and judgment of acceptability Wavelength (nm)
is based on absorbance. Fig. 2 Result of Measurement of Anhydrous Ethanol
Specifically, the Pharmacopoeias provide that the absorbances
at 240 nm, between 250 and 260 nm, and between 270 and In Fig. 2, it can be confirmed that absorbance is not more than
340 nm are not more than 0.40, 0.30, and 0.10, respectively, 0.40 at 240 nm, not more than 0.30 between 250 and 260 nm,
when the absorption spectrum is measured in the 235 to and not more than 0.10 between 270 and 340 nm, and there
340 nm wavelength region. The provision also specify that the are no clear peaks or remarkable shoulders in the absorption
absorption spectrum should be smooth and “show a steadily spectrum curve.
descending curve with no observable peaks or shoulders.”

„ Measurement of Anhydrous Ethanol
Anhydrous ethanol was measured with the UV-1900i UV-Vis
spectrophotometer shown in Fig. 1, using a Shimadzu square
long-path absorption cell holder and a 50 mm square cell.
Table 1 shows the measurement conditions.
Fig. 2 shows the results of spectrum measurement.