Fundamental factors affecting evaporative light scattering detector ELSD

The Evaporative light Scattering Detector (ELSD) is increasingly used as a general-purpose detector in high performance liquid chromatography, supercritical chromatography (SFC), and countercurrent chromatography
.

The evaporative light scattering detector ELSD detects compounds without chromophores, such as carbohydrates, lipids, polymers, underived fatty acids and amino acids, surfactants, drugs, and detects unknown compounds without unknown standards and compound structural parameters
.

The basic factors affecting the evaporative light scattering detector ELSD 1, the choice of operating mode, the selection of the appropriate operating mode can improve the sensitivity of the method, the choice of operating mode depends on the volatility of the sample, the composition of the mobile phase and its flow rate
.

2, the composition of the mobile phase and the selection of flow rate, the better the volatility of the mobile phase, the higher
the sensitivity of the method.

The lower the flow rate of the mobile phase, the stronger
the corresponding signal.

3, the influence of drift tube temperature on baseline level and noise is not obvious
.

The preferred temperature should be a lower temperature that produces acceptable noise on the basis of the basic volatilization of the mobile phase
.

4, the carrier gas flow rate is a very important factor
affecting the detection performance.

The preferred carrier gas flow rate should be based on acceptable noise (e.
g.
0.
5mV), when the zui low flow rate
is generated when the zui large detection response value is generated.

The mathematical model commonly used in the data processing mode of the evaporative light scattering detector ELSD detection is lgy=algx+b (y is the response value, x is the injection amount or sample concentration, and a, b is the regression constant), and there are also quadratic curve models (y=ax2+bx+c).

Since the response value (y) and the injection amount (x) are not a linear relationship, the data processing is different from the ultraviolet detection method
.

When determining the content of a known substance, the accompanying standard curve method is generally used instead of the external standard method, because the intercept of the corrected linear equation is not zero
.

The establishment of new drug benchmarks, except that the control is another substance with known content and similar structure, the data processing method is similar
to the above.

When determining the purity of a substance, since the response value is not a linear relationship with the amount of injection, it is mostly corrected
by drawing the accompanying standard curve of one or more of the substances.

For the analysis of multi-component substances, the data processing is similar to the above, except that the linear range of the accompanying correction curve is different
.

Despite some shortcomings, ELSD as a new type of universal quality detector, with many unique advantages, such as its versatility, consistency of response factor, and compatibility with gradient elution, will play an increasingly important role
in the analysis of non-characteristic UV absorbent substances.