After the sample was extracted with ethanol,the extract was injected to the capillary for capillary electrophoresis (CE) separation by electric sampling for 10 s with the injection voltage of 10 kV.The running buffer solution for CE was 10 mmol · L-1 PBS (pH 5.13) and the separation voltage was 15 kV.The dendrobine after CE separation reacted with 5 mmol · L-1 Ru(bpy)32+ solution (in 70 mmol· L-1 PBS with pH 8.10) in electrochemiluminescence (ECL) detection cell,resulting the ECL intensity of Ru(bpy) 3 2+ increaced at the detection potential of 1.17 V (vs.Ag/AgC1).Linear relationship was found between the peak area of ECL signal with the mass concentration of dendrobine in the range of 1.0-100 mg · L 1,with detection limit (3S/N)of 0.045 mg · L-1.The proposed method was applied to the determination of dendrobine in Dendrobium nobile Lindl,giving recovery rates obtained by standard addition method in the range of 92.0％-105％ and RSDs (n=5) were in the range of 2.5 ％-5.1％.
HPLC was applied to the simultaneous determination of 8 kinds of salicylic acid ester UV absorbers,including ethylhexyl salicylate,homosalate,octyl salicylate,phenyl salicylate,salicylic acid,salicylic acid hexyl ester with sixteen salicylic acid,ethylene glycol and benzyl salicylate,in sunscreen cosmetics.1.000 0 g of sample was extracted by ultrasonic with 5 mL of ethyl acetate at 20 ℃ for 10 min,and the extract was separated on an Agilent ZORBAX Eclipse XDB-C18 chromatographic column with a mixture of methanol,tetrahydrofuran,and 0.1％ (w) formic acid solution as mobile phase for gradient elution.UV detection was made at the wavelength of 340 nm.Linear relationships were found between peak areas and mass concentrations of the 8 kinds of salicylic acid ester UV absorbers in the range of 5.0-100.0 mg · L1,with detection limits (3S/N) in the range of 0.5-2.5 mg · kg-1.Recovery rates obtained by standard addition method were in the range of 90.6％-98.8％,and RSDs (n=6) were in the range of 1.4％-3.6％.
UHPLC-MS/MS was used for the determination of sibutramine in health products for weight-loss.The sample was extracted with methanol by ultrasonic,then separated on a Phenomenex Kinetex C18 column with the mixture of acetonitrile and 10mmol·L-1 ammonium acetate solution containing 0.1%(φ)formic acid solution as mobile phase for gradient elution.MRM was adopted in MS detection.D6-Sibutramine was used as internal standard for quantification.The linear range for the mass concentration of sibutramine was 5.00-400μg·L-1,and the lower limit of determination(10S/N)was 10ng·g-1.The recovery rates measured by standard addition method were in the range of 97.0%-104%,with RSD(n=9)in the range of 1.1%-3.0%.
Through macroscopic examination,several kinds of non-destructive testing,on-site hardness testing and metallurgical coating examination,SA335-P22 steel main steam pipe which had accumulatively run for more than 113 000 hwas studied.And combined Larson-Miller formula predicting method and creep damage level taxonomy method,remaining life of the main steam pipe was evaluated.The results show that the remaining life of the pipe was not more than 105 937 h,which could provide a reference for the power plant operator.
Taking non-conductive mesoporous SiO2(SBA-15)with nano pore structure as the research material,the effects of three kinds of common electrical conductive coatings(Au,Pt and Cr coatings)on the field emission scanning electron microscopy(FE-SEM)images were studied.The results show that the charging phenomenon of the FE-SEM images could be reduced by all these three kinds of coatings.However,the morphology of the nano-size pores totally disappeared after coating Au film.When the Pt film was deposited on the sample surface,SBA-15 still kept the mesoporous structure but the pore size became smaller.Meanwhile,the pore and wall sizes of SBA-15 were close to the original morphology even though the Cr film was deposited on the sample.The grain sizes of the conducting coatings were the key factor of affecting the morphologies.The sizes of most of Au particles were over 5nm,and sizes of most of Pt particles were about 2nm.So the 4nm pores of SBA-15 would be obscured by them.The sizes of Cr particles were only 1nm and most of Cr particles were amorphous.Therefore,the real structure of SBA-15 could be shown even after the Cr film with several nano thickness was deposited.
A method of GC-MS for the determination of 15 fragrance allergens in plastics with accelerated solvent extraction was proposed.The plastic sample was mixed with kieselguhr,then extracted for 20 min with acetone twice at 80℃ under pressure of 1 500 MPa.The extracts were separated on DB-17 quartz capillary chromatographic column,then determined under the full-scanning mode and the selected ion monitoring mode in MS.Deep color extract was cleaned up with a silica gel solid phase extraction column before analysis.The analytes were quantified by internal standard method.Linearity ranges of the 15 compounds were found between 0.005mg·L-1 and 60mg·L-1 with detection limit(3S/N)in the range of 0.005-0.03mg·L-1.The proposed method was applied to the analysis of plastic samples of polypropylene,polyethylene and acrylonitrile butadiene styrene copolymers,giving values of recovery and RSD′s(n=5)in the ranges of 83.3%-118% and 3.0%-9.9%,respectively.
HPLC was applied to determine food orange 8( canthaxanthin) in cosmetics. The sample was extracted with methonal from water based cosmetics and cream cosmetics,or with a mixture of tetrahydrofuran and methonal from the oily cosmetics,powder cosmetics and lipsticks. The supernatant was separated by isocratic elution with XDB-C18 column as stationary phase,methanol and 0. 05%( φ) trifluoroacetic acid( 97 + 3) as mobile phase,then quantified by measuring absorbance at 470 nm. The detection limit( 3S / N) was 0. 5 mg·kg- 1and the quantization limit was 1. 0 mg·kg- 1. The recovery rates and RSDu0027s( n = 6) were found in the range of 96. 4%- 105% and 0. 49%- 4. 8% respectively.
A method of Headspace-GC-MS was proposed for the determination of acrylonitrile in acrylonitrilebutadiene-styrene(ABS)toys.The sample was dissolved in N,N-dimethyl formamide,then injected isothermally with the headspace sampler,and separated on a HP-INNO Wax polar column.The target ion with m/z 53 was selected in MS detection.External standard method was used for quantification.The linearity range of the mass of acrylonitrile was 1.00-40.0μg with detection limits of 0.4mg· kg-1.The method was used for analysis of ABS toys samples,giving recovery rates measured by standard addition method of 78.0%-116%,with RSD′s(n=6)in the range of 2.6%-7.9%.
The head of engine exhaust valve cracked in radial direction during the durability test.The cracking causes of exhaust valve were analyzed by chemical compositions analysis,macroscopic inspection and metallographic inspection.The results show that the weld overlaying technology of cone area of exhaust valve was not optimum, and the stress relief treatment was not in-time and complete.As a result of that,high residual stress remained in weld overlaying cladding.Under the combined action of mechanical stress and thermal stress,cracks were formed in weld overlaying cladding near the cone area and then propagated on radial direction.
TC4 titanium alloy welded by electron beam was chosens as the specimen to research.The elastic constants of welding seam,heat affected zone and base metal were calibrated through X-ray diffractometer and four-point bending machine,to discuss the difference of elastic constant among these areas.The results show that the testing data of elastic constant of heat affected zone and welding seam were relatively dispersive because of the coarse microstructure.The testing data of elastic constant of base metal were relatively consonant.The calibrated value of elastic constant of TC4 titanium was 12.827×10-6 MPa-1 when tested on diffracted crystallographic plane (213).
The deterioration level of the magnetic properties of motor iron core due to its size reduction after punching was quantified.The internal causes for the magnetic property deterioration,including the changes of shearing surface and internal texture,were researched.The results show that during the manufacture of the iron cores,stress relief annealing should be done when the width of core tooth is less than 1 5 mm.
Macrocracks were found in bearing roller of one railway axle box during the overhaul work.The crack formation cause of the bearing rolling was analyzed by macrographic inspection, chemical compositions analysis,hardness test and micrographic inspection.The results show that grinding burn exsited in the crack area of bearing roller,which led to the stress concentration in this area.Due to the combined action of mechanical stress and residual stress,cracks generated and extended in the grinding burn area,and finally propagated into macrocracks.
The 0Cr13Ni4 Mo stainless steel shaft of a steam feed pump of a 300 MW thermal power unit fractured during service.The investigation for the failure including chemical compositions analysis,mechanical properties test,microstructure observation and fracture pattern examination of the shaft was taken to find out the fracture reasons.The results show that there were many micro cracks vertical to base body in the surface chromium coating of the shaft because of chromizing treatment,which not only reduced the fatigue strength of the shaft,but also provided many cracking sources.Under the action of cycled torsion loading,micro cracks in the chromium coating extended continuously to base body of the shaft until fracture.
One piece of Q345R steel plate (thickness 95 mm)fractured during coiling process in one chemical machinery plant.The fracture reason was analyzed through macroscopic inspection,chemical compositions analysis, mechanical properties test and metallographic inspection.The results show that burrs on surface layer produced in the process of gas cutting groove were not clear away before coiling,and over burning,carburizing and quenching cracking layer were remained.The crack expanded quickly under the action of external force in coiling process,and eventually led to the fracture of the Q345R steel plate.
A fasten bolt of the stabilizer of a nuclear power plant was found fractured during the onsite inspection after installation.The fracture failure analysis was performed according to the examination of the material and mechanical properties of the bolt.The microstructure,chemical compositions,mechanical properties and fracture surface were examined to investigate the root causes of the failure.Abnormal microstructure was found near the outer side at the fracture initiation position with lower micro hardness and strength which resulted in the initiation of cracks,and the bolt fractured for the cracks propagation.The abnormal microstructure was caused by the local high temperature during the heat treatment process.
The isothermal spheroidizing annealing effect with different temperatures and cooling rates was investigated by SEM analysis and hardness test,and the morphology and distribution of the carbide under different process parameters were analyzed by quantitative metallography methods.The results show that the hardness distribution was most uniform and the spheroidizing annealing effect was best when the GCr15 bearing steel was austenitized at 790 ℃ and cooling at 20 ℃.h-1 .In this case,the standard deviation about average particle diameter of carbide was the minimum,the ratio of the major axis and minor axis was not greater than 2.1,the particle roundness was not less than 0.17,and percentage of 0.5~1.1 μm carbide was about 50%.This method can provide some references to accurately and quantitatively evaluate the spheroidizing annealing effect of GCr15 bearing steel,and it is significant for practical production.
HPLC was applied for the determination of catechin,epicatechin and procyanidin B2 in plant fruits.The sample was extracted with ethanol solution(6+4)by soxhlet extraction.The extract was purified by solid phase extraction and then was separated on a SinoChrom ODS C18 column with a mixture of acetonitrile and0.1%(φ)phosphoric acid solution as mobile phase.UV absorbance was measured at 280 nm.The linearity range of the mass concentration of the 3target analytes was 5.0-100.0mg·L-1,with detection limits(3S/N)in the range of 1.03-2.38 mg·L-1.The recovery rates measured by standard addition method were in the range of83.6%-98.5% with RSD(n=3)in the range of 0.4%-2.1%.
The bearing spring of lower part on a turbine of one power plant had fractured.By means of chemical compositions analysis,hardress test,metallographic inspection and fracture surface analysis,the fracture reasons of the bearing spring were researched.The results show that the fracture mechanism of the bearing spring was fatigue fracture.The fracture failure of the spring was due to original defect of spring surface and corrosive medium in the service environment.
Firstly,Ni-50 Cr alloy coating was prepared by high velocity arc spray(HVAS)on 20 Gsteel substrate.The high temprature oxidation resistance of the coating was compared with that of 20 G steel and Tafa 45 CT coating at 750 ℃.Optical microscopy(OM),scanning electron microscopy(SEM)and X-ray diffractometer(XRD)and X-ray energy dispersive spectrometer(EDS)were used to analyze the microstructure and oxidation produce of the coatings.The results show that the microstructure of Ni-50 Cr coating was the typical layer structure.Compared to 20 G steel and Tafa 45 CT coating,the high temprature oxidation resistance of Ni-50 Cr coating was increased by 85 times and 1.3times respectively.NiO,Cr2O3 and NiCr2O4 were identified as the main phases of the oxidated coatings.As the increasing of Cr content,the Cr2O3 content in the protective oxide scales was gradually increased,which resulted in a significant enhancement of the high temperature oxidation resistance.
The reversed-phase high performance liquid chromatography(RP-HPLC)combined with precolumn derivatization was used to determine chromium(Ⅵ)released from ceramic jewelry.The ceramic jewelry sample was extracted by artificial sweat. Chromium(Ⅵ)in the extraction was derivatized with 1,5-diphenylcarbazide under acidic condition.The derivative was separated using Waters SunFire ODS C18 column as stationary phase and a mixture of acetone and KH2PO4 solution of 10mmol·L-1 with pH 2.5as mobile phase for gradient elution.Absorbance at 540 nm was measured.The linear relationship between the peak area and the mass concentration of chromium(Ⅵ)was found in the range of 5.0-200.0μg·L-1,with correlation coefficient of0.999 1and detection limit(3S/N)of 0.037μg·L-1.Tests for recovery were made by standard addition,giving recovery rates in the range of 97%-101% and RSD(n=7)in the range of 1.9%-3.2%.
