ABSTRACT
A highly sensitive and selective DNA biosensor is described based on the fluorescence quenching ability of MoS2 nanosheet and exonucleaseⅢ( ExoⅢ) assisted dual-signal amplification. In this sensor, the fluorescence probes ( HP1 and HP2 ) cannot be degraded by Exo Ⅲdue to the 3 '-termini protrusion and thus are adsorbed on the surface of MoS2 nanosheets, which will result in the quenching of MoS2 nanosheets toward the probes and induce a low fluorescent signal. The presence of the target DNA leads to the desorption of probes on the surface of MoS2 nanosheets due to the hybridization toward probes, generating many fluorescent fragments by Exo Ⅲdigestion and inducing dual-signal amplification. This method can improve the sensitivity and detection limit compared with single amplification method, and shows excellent selectivity in the discrimination of single base mismatched targets. On the basis of the significantly high sensitivity, the developed biosensor can be potentially extended to detect various DNA targets with excellent sequence selectivity.
ABSTRACT
OBJECTIVE:To establish a HPLC method for simultaneous determination of paracetamol and dioxopromethazine hydrochloride in compound paracetamol and zinc gluconat tablets. METHODS: The determination was performed on Sinochrom ODS-BP column with the mobile phase consisting of 0.04 mol?L-1 KH2PO4 (pH=2.60,0.40% triethylamine)-acetonitril (75∶25) at a flow rate of 1.0 mL?min-1;the detection wavelength was set at 264 nm;the column was maintained at room temperature and the sample size was 20 ?L. RESULTS: The calibration curve was linear over the range of 2.818? 10-3～3.605?10-1 mmol?L-1 for paracetamol and 1.118?10-4～1.431?10-2 mmol?L-1 for dioxopromethazine hydrochloride. The recovery rates of both were greater than 99.2%. The intra-day RSDs of both were less than 1.82% and the between-day RSDs of both were less than 1.90%. CONCLUSION: The method is rapid,simple and accurate,and it is applicable for the quality control of the tablets.
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OBJECTIVE: To establish spectrophotometry and HPLC methods for the determination of ferrous succinate tablet and to compare the results of above two methods with that of cerium sulphate method.METHODS: Ferrous reacted with 1,10-phenanthroline to form colored complex and spectrophotometry was applied to measure its absorbance.The detection wavelength was set at 510 nm.HPLC method was performed on C18 column with mobile phase consisted of 0.05 mol?L-1 KH2PO4 (pH=2.5) at detection wavelength of 215 nm.The method was quantified by an external standard mode.RESULTS: The linear range of ferrous in spectrophotometry was 0.042 44～2.546 4 mg?L-1 (r=0.999 8) with an average recovery of 99.5% (RSD
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OBJECTIVE:To establish HPLC method for the simultaneous determination of calcium lactate and calcium gluconate in compound calcium gluconate oral solution.METHODS:The test was performed on C 18 column with column tem?perature at25℃;the mobile phase was composed of0.025mol/L NaH 2 PO 4 (pH=2.50)with a flow rate of1.0ml/min and sam ple size of20?l;the detection wavelength was210nm.RESULTS:The calibration curves were linear over the range of0.719～46.040mmol/L(r=0.9999)for lactic acid and0.315～20.160mmol/L(r=0.9999)for gluconic acid.The average recovery rates of which were99.0%(RSD=1.65%)and100.5%(RSD=1.36%),respectively.CONCLUSION:This method is fast,simple,accurate,and it can be employed directly without isolation to determine the content of calcium lactate and calcium glu?conate simultaneously and to control the quality of compound calcium gluconate oral solution as well.
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OBJECTIVE:To establish a method for the determination of the dissolution rates of azithromycin tablets and to compare the dissolution rates among azithromycin tablets that from different manufacturers so as to provide references for clinical medication.METHODS:The concentrations and drug cumulative dissolution rates of a total of 5 batch numbers' azithromycin tablets that from 5 pharmaceutical factories were determined based on the related standard procedure indexed in China Pharmacopoeia(2005 edition),then the dissolution parameters were calculated with Weibull formula.RESULTS:The dissolution rates at 45 min were above 75%,which was up to the standard.The analysis of variance showed that there were significant differences among samples in dissolution parameters(P
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OBJECTIVE: To studies on the stability of glucosamine-?-aminoacids-nickel(Ⅱ) ternary complexes(GANTC). METHODS: The formation constant of GANTC were determined at (25?0.1) ℃,I=0.1 mol?L-1 KNO3 by pH method. RESULTS: The formation constant of GANTC were Gly 13.73(7.33),Pro 13.97(7.12),Ser 13.15(7.07),Val 13.46(6.84),iLe 13.55(6.88),Phe 13.13(6.93) and Met 13.17(7.18). CONCLUSIONS: The two biologically active ligand,?-aminoacid and glucosamine accommodate each other when coordinated to nickel(Ⅱ) ion. The formation constant of the ternary complexes linearly increase with the increase of protonation constant of aminoacid. Linear free energy relationship does exist in the presence of ternary system.