Restek Corporation • (800) 356-1688 • (814) 353-1300 •
sorbic acid) by reversed phaseHPLC using a Pinnacle II
™
Phenyl
column and acidified water:methanol as the mobile phase
(Figure 2). Bymonitoring theUV absorbance at 245nm, sensitive
detection of both benzoic and sorbic acids can be achieved. For
optimum sensitivity, benzoic acid canbemonitored at 228nm and
sorbic acid at 259nm.
Parabens, such as propyl paraben, can be used as antimicrobial
agents and as antioxidants. As antimicrobials, they act on yeasts
andmolds.Although they tend tobe somewhat higher incost, they
still are used in a range of applications. Themaximum allowable
concentration in most products is 0.1%. A series of parabens
analyzedusingaPinnacle II
™
C8column is shown inFigure3.The
separation was effected using an acidified mobile phase to sup-
press ionization of the analytes. Because these compounds are
strongUV absorbers, very sensitive detection can be achieved by
monitoring theUV at 254nm.
Antioxidants
Products containing fats and oils are prone to lipid oxidation,
which can promote off-flavors, off-odors, and color changes as
well as limiting shelf life. To inhibit lipid oxidation, antioxidants
LC_0199
0
2
4
6
8
10
12
14
16
18 min.
1
2
Column:
Pinnacle
II
™
Phenyl
Catalog #:
9215565
Dimensions: 150 x 4.6mm
Particle Size: 5µm
Pore Size:
110Å
Conditions:
Mobile Phase: 1% acetic acid:methanol
(80:20)
Flow:
1.0mL/min
Temp.:
25°C
Det.:
UV@230nm
PeakList:
1. sorbic acid
2.benzoic acid
Sample:
Inj.:
10µL
Conc.:
each 100ppm
Solvent: methanol
ThePinnacle II
™
phenyl column is an excellent choice to analyzemedium polarity compounds such as sorbic and benzoic acids.
Figure 2
LC_0176
PeakList:
conc. (µg/mL)
1. methyl paraben
10
2. ethyl paraben
20
3. propyl paraben
30
4. butyl paraben
40
Sample:
Inj.:
5µL
Solvent:
methanol:water (50:50 v/v)
Column:
Pinnacle
II
™
C8
Catalog #:
9213565
Dimensions: 150 x 4.6mm
Particle size: 5µm
Pore size:
110Å
Conditions:
Mobile Phase: 0.1% acetic acid inwater:
acetonitrile (50:50, v/v)
Flow:
1.0mL/min.
Temp.:
ambient
Det.:
UV@254nm
A series of parabens can be efficiently separated on aPinnacle II
™
C8 column, allowing for fast and accurate quantitation.
Figure 3
