Page 87 - Application Notebook - Solution for Food Safety

Application Food Additives / Nexera X2

News
Fast and High Sensitivity Analysis of Six
Preservatives in Beverages by UHPLC with

No. AD-0095 Photodiode Array Detection

 Introduction Instrumental and Analytical Conditions
Food preservatives are additives to inhibit, retard or A Nexera X2 UHPLC system (Shimadzu Corporation,
prevent mould, acidification or other deterioration of Japan) was used in this work. The system is consisted of
foodstuffs caused by microbial contamination. The most a high pressure binary gradient solvent delivery unit (LC-
commonly used preservatives in beverages are benzoic 30AD pumps) and an UHPLC autosampler (SIL-30AC)
acid, sorbic acid and four parahydroxybenzoic acid coupled to a photodiode array detector (SPD-M30A)
esters (parabens). However, excess amounts of these with a high sensitivity capillary flow cell (85 mm optical
additives can be harmful to consumer health. In this path length) featured as total reflection and low
regard, the minimum permissible concentrations of dispersion. A YMC Triart C18 column of 1.9 μm particle
preservatives are regulated in most countries to ensure size (150 mmL. × 2.0 mm l.D.) was used for the separation
1
safety for consumer * . Therefore, quantitative analysis of preservatives (benzoic acid, sorbic acid and methyl,
of these preservatives in food is not only required for ethyl, propyl, butyl parabens) with an optimized linear
food quality assurance but also important for consumer gradient program developed. The details of the LC
interest and protection. High performance liquid conditions are shown in Table 2.
chromatography (HPLC) has been used for analysis of the
2,
4
3,
preservatives in beverage * * * . In this Application
News, a new rapid and high sensitivity UHPLC method Table 2 Analytical Conditions of Preservatives
in Beverages on Nexera X2 UHPLC
for simultaneous determination of the six preservatives
in beverages is described. A gradient elution was Column : YMC Triart C18 1.9 μm 150 × 2.0 mm l.D.
Flow Rate
: 0.45 mL/min
optimized for separation and quantitation of the six Mobile Phase : A: 1.5 % acetic acid + 1.5 % ammonium
preservatives with a photodiode array detector. acetate in H2O
B: 1.5 % ammonium acetate in MeOH
A capillary flow cell with extra long optical path of Elution Mode : Gradient elution: 40 % B (0.01 to 4.0 min) →
85 mm was employed to achieve high sensitivity for a 80 % B (4.01 to 5.5 min) → 40 % B (5.51 to 8.5 min)
very small injection amount of sample (1 μL) which was Oven Temp. : 45 °C
not cleaned up except filtration. Injection Volume : 1 μL
Detection (PDA) : Wavelength 240 to 600 nm; Ref: 720 nm
Quant, 240 nm for benzoic acid, 260 nm for
other compounds
 Experimental
Preparation of Standards and Samples
Benzoic acid, sorbic acid and parabens were obtained
from chemicals suppliers. A mixed stock solution of
1.0 g/L of benzoic acid, sorbic acid and methyl, ethyl,
propyl, butyl parabens were prepared with ethanol/water
(70/30) solvent as the diluent. A set of nine working
standards was prepared from the stock solution using
the same diluent at the concentrations shown in Table 1.
Soft drink, mango juice and cocoa drink were purchased
at the local supermarket. The soft drink and mango
juice were diluted 20 times and 2 times with diluent
respectively while cocoa drink was not diluted. All the
samples were filtered through a 0.45 μm syringe filter
prior to injection to UHPLC.

Table 1 Concentrations of Working Standards of Six
Preservatives for Setting Calibration Curves
Working Benzoic acid Sorbic acid Parabens
No.
Standard (mg/L) (mg/L) (mg/L)
1 S1 0.2 0.008 0.01
2 S2 2.0 0.08 0.1
3 S3 4.0 0.16 0.2
4 S4 20.0 0.8 1.0
5 S5 60.0 2.4 3.0
6 S6 80.0 3.2 4.0
7 S7 100.0 4.0 5.0
8 S8 150.0 6.0 7.5
9 S9 200.0 8.0 10.0