Question

please answer both questions typed not hand writing.

(6) 8. Which of the following is generally not used as the basis of a detector for high performance liquid chromatography? HPLC (a ) uv-visible (b) refractive index (c) Thermal conductivity (d) electrochemical (e) fluorescence (9) 9. Explain the differences in the techniques and the advantages of split, splitless, and on- column injections in GC.

Answer 1

ANSWER:

1)- the correct answer is Refractive index detector

RI detector has lower sensitivity compared to all other detector, and that's the main reason why RI is not as commonly used.

2)- split/splitless injector work with the same requirements as packed column injectors carrier gas inlet ,a septum, septum purge,injector insert,heater block and column connection. but the heart of this technological performance is another set of gas lines out of the injector-another path that the vaporized sample can take.this is called the split line or vent.

the main advantage of split/splitless injection is analysis of sample components over a vast concentration range without the need for time-consuming sample dilutions or pre-concentrations.

on-column injector is that mode of injection which avoid the hot injection linear all together is useful for labile GC samples with large analyte-boiling point differences that suffer discrimination in flash vaporization.

the main advantage of on-column injector is that a liquid sample is introduced directly into the column with a thin injection needle. During the course of the temperature program the vapour pressure of the solutes increases and the chromatographic process begins.