Mr. Alwakwak,

You can try solvent mixture with CH3CN and DMF.

Thank you Dr.Lvanova,

Keep in mind that I used DMF as solvent of my starting material, so can I use it as mobile phase. On the other hand, my expected product is benzoic acid so should I use buffer solution or no?

Thank you again

Dear Sir. Concerning your issue about the determination of carboxylic acid in Bromobenzene using the solvent is DMF by HPLC . A simple and sensitive high-performance liquid chromatographic (HPLC) method involving UV detection was developed for the determination of 9,10-anthraquinone-2-carboxylic acid (AQCA) in rabbit serum. A reverse-phase column (Lichrosher R 100RP-18) was eluted with a mobile phase of 0.4% phosphoric acid: acetonitrile (7:3) / methanol = 45 : 55 at a flow rate of 1.2 mL/min. The UV absorbance was monitored at 256 nm. After a simple clean-up procedure, the limit of quantitation achieved was 0.6 μg/mL and the standard curve was found to be linear over the serum concentration of 0.6 ~ 18μg/mL. The intra-assay and inter-assay coefficient of variance in serum was less than 2%, and the recovery was 96.98%. Also a new labeling reagent for carboxylic acids, 2-(2-(anthracen-10-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)ethyl 4-methylbenzenesulfonate (APIETS) has been designed and synthesized. It was used to label eight fatty acids (lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid and linolenic acid) and four hydroxy pentacyclic triterpene acids (oleanolic acid, ursolic acid, betulinic acid and maslinic acid), successfully. APIETS could easily and quickly label carboxylic acids in the presence of K(2)CO(3) catalyst at 85°C for 35 min in N,N-dimethylformamide solvent. The carboxylic acids derivatives were separated on a C(8) reversed-phase column with gradient elution and fluorescence detection at λ(ex)/λ(em)=315/435 nm. Identification of these derivatives was carried out by online mass spectrometry with atmospheric pressure chemical ionization in positive ion mode. The detection limits obtained were 13.37-30.26fmol (signal-to-noise ratio of 3). The proposed method has been applied to the quantification of carboxylic acids in sultana raisin (Thompson seedless), hawthorn flake (Crataegus pinnatifida Bge.), Lycium barbarum seed oil and Microula sikkimensis seed oil with recoveries over 95.3%. It has been demonstrated that APIETS is a prominent labeling reagent for determining carboxylic acids with high performance liquid chromatography. I think the following below links and the attached file may help you in your analysis:

https://www.ncbi.nlm.nih.gov/pubmed/21726743

http://www.rsc.org/suppdata/gc/c2/c2gc36900a/c2gc36900a.pdf

Thanks

Many thanks all of you for your help.