Study On Saturated Carboxylic Acid By Indirect Photometric Chromatography With Phenylguanidine,Diphenylguanidine

With the technical innovation of reversed phase high liquid chromatographic columns and the discovery of new ion-pair probe reagents,it has established the methods for analysis of organic anion of none or terminal ultraviolet absorption by high performance liquid chromatography with photo-diode array detector,which is difficulty to analyze all the time in analysis field.By regulating the kind and concen-tration of carboxylic acid modifier,the saturated monocarboxylic and dicarboxylic ac-ids combine with phenylguanidine or diphenylguanidine—ion-pair probe reagents—forming the ion-pair compounds separated on RP8/18 chromatographic column bonded amide polar group,which is quantitatively and qualitatively analyzed by HPLC-UV.We explore a simple,rapid and efficient instrument of reversed-phase indi-rect photometric chromatography based on the optimized the theory and mechanism of indirect photometric chromatography in different phase.We make further research of the dynamic equilium model structured in the sur-face of amide polar group bonded on the stationary phase,while the mobile phase flows through the column.Meanwhile,we come up with three major mechanisms of balance,reaction and separation,and present the mechanism about reaction on the head of chromatographic column and separation after the head of the column on the base of the traditional theory of IPC.In the experiment process,the four-phase equili-brating process—enrichment,saturation,destabilization,re-equilibrium—of pro-tonated ion-pair probe reagent in the mobile phase combined with stationary phase is obtained.The dynamic equilium theory of hydrogen ion and protonated phenylgua-nidine or diphenylguanidine combine with-O-group,and the dissociated carboxyl an-ion link with(?)group in the amide group bonded on the stationary phase is devel-oped.The characteristic drift curve—4 characteristic peaks of two conditions-of indirect photometric chromatography on the base of phenylguanidine or diphenylgua-nidine as ion-pair probe reagent is grasped.We determine the content of diphenylgua-nidine in the stationary and mobile phase and calculate the distribution ratio,which confirms that the kind and concerntration of modifier affects diphenylguanidine amount accumulated on stationary phase and equilibrating time of chromatographic cording to the theory of acid-base balance and the dissociation constant,calculated distribution fraction,the key point for quickly optimizing analytical experiment condi-tion of acids and other samples by indirect photometric chromatography is gained.The method of re versed-phase high performance liquid chromatography for anal-ysis of saturated carboxylic acids with phenylguanidine and diphenylguanidine as the ion-pair probe reagent is established in this experiment.The saturated monocarboxylic acids are all separated with RP8 chromatographic column as stationary phase,and aqueous solution of 0.12 mmol·L-1 diphenylguanidine mingling with 1.0,0.5,0.5 mmol·1 L-1 butyric acid,1.0 mmol·1 L-1 pentanoic acid as mobile phase for respective analysis of formic acid,acetic acid,propionic acid,butyric acid,aqueous solution of 0.6 mmol·L-1 phenylguanidine with 0.4 mmol·L-1 hexanoic acid for pentanoic acid,aqueous solution of 0.6 mmol·L-1 phenylguanidine for hexanoic acid.The flow rate of mobile phase is 1.0 mL·min-1.Formic,acetic,propionic,butyric acid are detected at 232 nm wavelength,pentanoic and hexanoic acid are at 247 nm.The testing results show that the LOD of formic acid and acetic acid are 1 mg·L-1,propionic acid and butyric acid are 5 mg·L-1,pentanoic acid is 1 mg·L-1,hexanoic acid is 10 mg · L-1.Saturated monocarboxylic acids present clearly linear relationship in the certain con-cerntration,and the correlation coefficients are all above 0.997.The average recoveries of high and low fortification level are between 98.08%and 102.26%,the RSD of 8 parallel samples is among the range of 0.43-1.40%.The determination result indi-cated that the pure samples can be accurately quantified with the single standard,but for the mixing samples,standard addition method should be adopted to offset the in-fluence of matrix to ensure the results accuracy according to the true value.Camparing with titration method of national standard for determination of formic acid,acetic acid,propionic acid,the results of acetic acid and propionic acid are close determinated with two methods,but there is great deviation for formic acid of low content.Similarly,we explore the quantitative method for analysis of saturated dicarbox-ylic acid by reversed-phase indirect photometric chromatography using phenylguani-dine as ion-pair probe reagent.Oxalic acid and malonic acid are separated between sta-tionary phase of RP18 chromatographic column and mobile phase of aqueous solution of 0.6 mmol·L-1 benlguanidine mixed with 10.0,2.0 mmol·L-1 pentanoic acid re-spectively.Succinic acid and glutaric acid are distributed between stationary phase of RP8 chromatographic column and mobile phase of aqueous solution of 0.6 mmol ·L-1 benlguanidine mixed with 2.0,1.0 mmol·L-1 pentanoic acid respectively.These acids are detected at 247 nm wavelength.The LOD of oxalic acid is 10 mg·L-1,the others are 5 mg·L-1.Saturated dicarboxylic acids have clearly linear relationship in the concerntration range of 10-1400 mg·L-1,and r values are above 0.998.The average recoveries of high and low fortification level of four acids are between 97.75-103.83%,the RSD values of 8 parallel samples are in the range of 0.60-0.87%.The determination results of accuracy and precision can satisfy the requirement of macro analysis.The contents of samples determined by IPC match with the values marked on the labelThe reversed-phase indirect photometric chromatography is assembled with res-ervoir,high pressure pump,6-way valve sampler of the type of DIONEX DX-120 ion chromatography,a Waters SymmetryShield chromatographic column of 4.6 mm inter-nal diameter and 150 mm length packing with 3.5 ?m silica gel,a photodiode array detector of the type of Waters 2996,and Empower Pro Chinese version workstation.Camparing with results determined by suite of Waters HPLC-PDA,the absolute max-imum deviation of saturated monocarboxylic and dicarboxylic acids is 3.6%,which can meet the requirement of macro quantative analysis.It is feasible to explore a re-versed-phase indirect photometric chromatography for simply and efficiently analyz-ing non-conjugated organic anionic compound.The established method of indirect photometric chromatography for analyzing saturated monocarboxylic and dicarboxylic acids is simple,feasible,extensive and ef-ficient,which is the technical innovation shifting from chemical analysis to instru-mental analysis,and makes practical and instructive sense for the study of others non-conjugated organic anionic compound.