Page 35 - Application Handbook - Liquid Chromatography

LAAN-A-LC-E254

Application High Performance Liquid Chromatography

News Analysis of Anionic Surfactants by Prominence-i and

RF-20Axs Fluorescence Detector
No.L477

According to the Ministerial Ordinance on Water Quality
1)
Standards , an HPLC method using a fluorescence N7
detector has been adopted as the test method for anionic n 1FBLT
2)
surfactants . (Please refer to Application News No. L303.) $
Since either the RF-20A or RF-20Axs fluorescence detector $
can be connected to the new Prominence-i integrated $
high-performance liquid chromatograph, the combination $
of integrated operability and high-sensitivity fluorescence $
detection is possible.
Here we present an example of the analysis of five anionic
surfactants using the Prominence-i integrated high-
performance liquid chromatograph with the RF-20Axs
high-sensitivity fluorescence detector.
n Analysis of Standard Anionic Surfactants
Fig. 1 shows the basic structural formula of the five anionic
surfactants which differ by the length of the hydrocarbon
chain. Quantitative analysis of anionic surfactants in water
samples is conducted by classifying the approximately
twenty peaks obtained from the analysis of a standard
solution containing the C10 – C14 branched- chain NJO
surfactants, and then summing the respective area values.
Depending on the type of column used for separation, there Fig. 2 Chromatogram of Standard Mixture of 5 Anionic Surfactants
is a type that can resolve branched chains for each carbon (Using Column 1) (10 mg/L each, total of 50 mg/L, 20 µL Inj.)
number and will produce multiple peaks, and there is a type
which cannot resolve branched chains, so only a single peak
appears for each carbon number.
Fig. 2 shows the chromatograms of a standard solution of
anionic surfactants in accordance with the water quality
inspection method (total of 50 mg/L for 5 substances, each N7
at 10 mg/L), and Table 1 shows the analytical conditions  1FBLT
used. This concentration is based on the standard $
concentration in accordance with the indicated pretreatment $
procedure (test water at 250-fold concentration). $
Fig. 3 shows an example of high speed analysis using a $
commercially available column (which cannot resolve $
branched chains).

CnH2n+1

SO3Na
n=10:Sodium Decylbenzenesulfonate
n=11:Sodium Undecylbenzenesulfonate
n=12:Sodium Dodecylbenzenesulfonate
n=13:Sodium Tridecylbenzenesulfonate
n=14:Sodium Tetradecylbenzenesulfonate

Fig. 1 Structure of Anionic Surfactants
NJO
Table 1 Analytical Conditions
Column (1) : Shim-pack VP-ODS (250 mm L × 4.6 mm I.D., 5 µm) Fig. 3 Chromatogram of a Standard Mixture of 5 Anionic Surfactants
Flowrate (1) : 1.0 mL/min (Using Column 2) (10 mg/L each, total of 50 mg/L, 20 µL Inj.)
Column (2) : Wakosil AS-Aqua (250 mm L × 4.6 mm I.D., 5 µm)
Flowrate (2) : 0.7 mL/min
Mobile Phase : A) Water
B) Acetonitrile
containing 0.1 M Sodium Perchlorate
B. Conc. 65 %
Column Temp. : 40 °C
Injection Volume : 20 µL
Detection : RF-20Axs, Ex at 221 nm, Em at 284 nm