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Questions related from Fuad Al-Rimawi
Colistin has weak chromopheres, therefore it is usually analyzed by microbilolgy methods and not by HPLC. is it possible to analyze it by HPLC with PDA detector.
01 January 2018 804 0 View
In an HPLC method of analysis, Copper (II) sulfate is used in the mobile phase which makes the mobile phase blue. However this affects adversely the PDA detector where its intensity is...
09 September 2017 399 2 View
In some monographs of pharmacopoeias, TLC method is used for analysis/quantification of impurities. Does this method have adequate accuracy, precision, LOD, LOQ for such trace analysis of...
07 July 2017 2,409 0 View
In a method of analysis of chlorhexidine hydrochloride by HPLC, chlorhexidine acetate is used in system suitability. should be there a difference in retention time between chlorhexidine...
04 April 2017 1,525 5 View
Valproic acid and sodium valproate when dissolved in the mobile phase and injected into HPLC, they coelute and can not be separated as they become identical in solution. Is there a method for...
03 March 2017 3,924 5 View
In analysis of cefixime isomer, tetrabutylammonium hydroxide is used in the mobile phase at a concentration of 2.5%. why is it used? can we use tetramethylammonium hydroxide instead of it.?
03 March 2017 4,233 5 View
In an analysis of impurity in pharmaceutical drug, sodium-1decanesulfonate is used as ion pairing agent at a concentration of 1 g per liter which is higher than the solubility of it in water. Is...
03 March 2017 3,420 3 View
During an HPLC analysis of an analyte (reversed-phase) using a mixture of 1% trifluoroacetic acid/acetonitrile mixture, bubbles arises in the mobile phase and the baseline is not stable at...
02 February 2017 940 9 View
In a separation of a basic drug analyte from its impurity using strong cation exchange chromatography (HPLC), using 150 mM of ammonium dihydrogen phosphate at pH 3 and flow of 1.4 ml/min, the...
01 January 2017 8,112 6 View
In preparation of standard and sample solutions in HPLC, diluent is used (usually mobile phase), but I have noticed sometimes it is not working to use the same mobile phase (with same pH) as...
10 October 2016 7,861 3 View
In RP-LC there is a type of C18 column called Inertsil. Is there any difference between it and the conventional C18 columns in terms of separation, selectivity, resolution..etc.
09 September 2016 9,631 9 View
Many stationary phases and columns in NP-LC can be used in HILIC analysis. So what is the difference between the stationary phases of NP-LC and HILIC.
07 July 2016 8,691 7 View
In a trace analysis by HPLC with photodiode array detector (impurity/degradation product), using two instruments (HPLC from the same company), a very dilute analyte solution appears in one...
06 June 2016 1,913 11 View
In an HPLC analysis of different analytes (salicylic acid, salicylamide, and other analytes), a mixture of phosphate buffer pH 4.5 and acetonitrile (gradient) using a C18 column, results in...
06 June 2016 9,832 5 View
Strong cation exchange HPLC columns are used for separation of positively charged compounds. What is the optimum parameters (washing solvent and time) for washing the column after daily use of it...
09 September 2015 7,440 3 View
Some researchers reported that the separation efficiency and ruggedness of a UPLC depends highly on the UPLC type e.g. WATERS or JASCO UPLC. So, anyone have experience with UPLC systems regarding...
08 August 2015 4,399 2 View
Antioxidants protect active ingredients from oxidation/degradation, and the antioxidants themselves will be oxidized and so their concentration will decrease. But in some regulations, they require...
06 June 2015 7,912 4 View
In analysis of a weak acid with pKa of 4.6, using mobile phase of phosphate buffer pH 7.7 and methanol (63:37, v/v) and hypersil C18 column, the retention time of this analyte is not stable (it is...
05 May 2015 306 14 View
Antioxiadant activities of plant extracts are measured using FRAP and ABTS assays, and usually vitamin C is used as positive control. The question is what is the antioxidant activity of Vitamin C?
02 February 2015 8,307 9 View
Is there a difference between Caretonoids and carotenes? and what is the best method for their determination in olive oil?.
12 December 2014 1,506 2 View
I am testing the potential of olive leaves extracts as natural antioxidants in food applications (meat products) by inclusion of different concentrations of olive leaves extracts in the meat...
08 August 2014 2,942 3 View
I am doing analyses of natural products using NMR andC13 NMR for fractions from plant extracts collected from preparative HPLC, but no signals appears in either proton NMR or C13 NMR.
08 August 2014 7,099 16 View
Quercetin and morin have the same molecular formula (C15H10O7) and molar mass (302.2 g/mol). Quercetin is 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one while morin is...
07 July 2014 8,382 12 View
What is the best column (stationary phase) for separation of polar vitamins in pharmaceutical preparations? Is it HILIC or silica?
03 March 2014 4,491 12 View
In method validation (ICH and USP) they use specificity of an HPLC method. Can we say that a validated HPLC method is specific for a particular analyte (e.g. pharmaceutical or impurity)? What I...
03 March 2014 5,838 10 View
Does it need filtration through 0.4 or 0.2 micrometer filters?
03 March 2014 8,506 13 View
