Chromatography Forum

Can I use UV spectrometer to detect concentration of nitrate and nitrite (inorganic compounds)? What is the different between uv spectrometer and HPLC since both of them using UV detector?

In a UV spectrophotometer, all analytes are in the cell at the same time. That means that they must have very different absorbance spectra.

In a UV detector, the analytes enter the cell at different times. That means that compounds with similar (or even identical) absorbance spectra can be quantitated.

There are colorimetric spectrophotometer methods for nitrite, commonly used in the processed meat industry, sensitive and specific. Reagents must be made fresh daily.

I never use colorimetric spectrophotometer before. May you brief more detail about this spectrophotometer? Is this can measure concentration of nitrate and nitrite? Is this need prepare mobile phase like HPLC?

Besides that, my sample has contains phophorus, acetate, bacteria. Will this affect the measurement by using this spectrophotometer?

This may help explain things:
http://en.wikipedia.org/wiki/Colorimetr ... _method%29

By comparing these three methods (HPLC, UV Spectrophotometer, calorimeter), which one is better to detect nitrate and nitrite since my samples contain other chemical compound?

Generally speaking, learn to ask questions. This question is "spheroic hourse in vacuum"

Can I use UV spectrometer to detect concentration of nitrate and nitrite (inorganic compounds)? What is the different between uv spectrometer and HPLC since both of them using UV detector?

Answer (correct, but useless)
"Yes of course. You can use UV spectrofotometr to detect concentration nitate & nitrite (theoretical)".
Right question.
"Can I use UV spectrometer to detect 1 mg/ml concentration of nitrate and nitrite (inorganic compounds) in water (centrifugate) culture of bacteria cells ?" you don't ask.
Answer (incorrect, but less)
You don,t use spectroscopy directly, but you can use a standard colorimetric test with diphenylamine if will get rid filtration and ion exchange chromatography from the cells and interfering compounds.
http://analusis.edpsciences.org/index.p ... 10998.html
HPLC- here's a sample of Jordanian on this topic. Google find it in moment.
http://jjc.yu.edu.jo/Issues/Vol3No1PDF/ ... ulture.pdf
But in practices microbiologists and technologists more often use ionselectivic nitrate electrode. Because they do not need the exact value, and the dynamics in the process. Up "plus - minus kilometer", but it quickly.

Bacteria and who knows what else is present? As a chemist for some 40+ years I would not be enthusiastic to tackle this. So I wonder what type of people asked you to do this. What for? To see what the bacteria do with the nitrates?

As a chemist for some 40+ years I would not be enthusiastic to tackle this.

Hello . 40 years, it's kruto! ( Crazy cool (best))

.... So I wonder what type of people asked you to do this. What for? To see what the bacteria do with the nitrates?

Do not be strict to the neophyte. Looks like veitze=> biologist, explores for example activity of nitrogen-fixing bacteria. Hence the problem with the correct formulation of the problem analysis.

You can measure nitrates in some cases in water samples directly without any reactions. But this would be more suitable for quick monitoring. APPHA has a standard method for this. Otherwise, Merck, Hach etc have reaction kits to perform nitrite and nitrate analysis on a UV-Vis instrument.

I guess that selective electrodes are the quickest way of all, but they are quite expensive and don't last very long.