1.An Innovative Approach to Sensitive Artificial Sweeteners Analysis by Ion Chromatography-Triple Quadrupole Mass Spectrometry
Jianye GUI ; Wei SUN ; Chenling ZHANG ; Yongtao ZHANG ; Li ZHANG ; Fei LIU
Chinese Journal of Analytical Chemistry 2016;(3):361-366
Artificial sweeteners ( ASs ) have gained more and more attention by environmental scientists because some of them such as acesulfame, have the potential to be the ideal tracers of domestic wastewater for environmental monitoring. In contrast to the existing methods of artificial sweeteners, the analytical method of ASs as a new tracer for environmental samples requires better sensitivity and selectivity to avoid matrix interference. A highly sensitive method for the simultaneous determination of four frequently-used artificial sweeteners in water samples using solid-phase extraction and ion chromatography triple quadrupole mass spectrometer with an electrospray ionization source ( IC-MS/MS) in negative ion mode was developed. The separation effect of different separation columns was compared and a 2-mm ion chromatography column AS19 was chosen in the experiment. Chromatographic separation of all the 4 artificial sweeteners was carried out in 9 min in isocratic elution mode using 60 mmol/L sodium hydroxide as eluent. Different kinds of solid phase extraction cartridges were evaluated to obtain satisfactory recoveries of all of the analytes. Merk LiChrolut EN (200 mg, 3 mL) was preconditioned with 2 mL of methanol, followed by 2 mL of H2 O. About 200 mL of sample (pH<2. 0) was passed through the cartridge at a flow rate of 4 mL/min, and then the cartridge was eluted using 2 mL of methanol. 2 mm suppresser (75 mA) was used to reduce the background noise and to remove the matrix interference. The limits of detection were below 5. 0 ng/L for various artificial sweeteners based on 3-fold the S/N. The recoveries of different matrices in the samples were 65%-120%. The method described here is time-saving, accurate and precise, and is suitable for monitoring artificial sweeteners in different water matrices. The method has also the potential to trace other contaminants in groundwater.
2.Fast Detection of Carbonate and Bicarbonate in Groundwater and Lake Water by Coupled Ion Selective Electrodes
Nan ZHAN ; Yi HUANG ; Zhu RAO ; Xueliang ZHAO
Chinese Journal of Analytical Chemistry 2016;(3):355-360
The content of bicarbonate ( HCO-3 ) and carbonate ( CO2-3 ) ions in groundwater and lake water reflects a broad set of carbon cycling reactions associated with decomposition or synthesis of organic compounds with mineral dissolution or precipitation, which indicates the local geochemical environment. However, the content of HCO-3 and CO2-3 changes easily under the influence of pH, temperature, atmosphere pressure in the process of sampling, transportation and storage, so it has been a worldwide problem to determine the real content of HCO-3 and CO2-3 ions in groundwater and lake water. This article proposed a new way to solve the problem by fast field detection of HCO-3 and CO2-3 ions through the use of pH electrode combined with carbon dioxide electrode. Studies showed in the base solution of pH=4. 8 ± 0. 1, the detection range of HCO-3 ion was 0. 027-570 mg/L and that of CO2-3 was 1. 25 ×10-8-39. 7 mg/L. In the most case, the coexisting ions and weak acid ( K+, Na+, Mg2+, Cl-, SO2-4 <100 mg/L;HSO-3 , NO-2 , HOAc<50 mg/L) did not interfere with the analysis. The method was validated for real water samples and the recoveries were in the range of 95. 2%-99. 2% with the relative standard deviations (RSDs) of 2. 6%-3. 7%. Compared with the acid-base titration method, the accuracy of this method had proved to be good. However, the method could be affected by temperature, so the standard solution and samples should be measured at the same temperature. Above all, this method is suitable for fast field analysis for HCO-3 and CO2-3 ions in the nature water as it is sensitive, fast, economical, and the electrodes are easy to carry and operate. It has been successfully applied in the determination of HCO-3 and CO2-3 in groundwater and lake water in Qinghai Province. Experiment showed that the pH of the groundwater samples from Haidong district was 6 . 4-7 . 4 , with 234-4096 mg/L HCO-3 and 0. 16-1. 89 mg/L CO2-3 . The pH of the lake water samples was about 8. 7, with 1. 36-1. 86 g/L HCO-3 and 32. 3-43. 9 mg/L CO2-3 , which was consistent with the previous results.
3.Determination of Uric Acid Based on Chitosan/Ru(bpy) 2+3/Silica Nanoparticles Electrochemiluminescence Sensor
Xuemei FAN ; Shumin WANG ; Zhejian LI ; Xingwang ZHENG
Chinese Journal of Analytical Chemistry 2016;(3):342-347
Chitosan-Ru ( bpy ) 2+3 -SiO2 composite nanoparticles ( CRuS NPs ) were prepared by reverse microemulsion method, and based on the Nafion/MCNT composite membrane technology, CRuS NPs were effectively and steadily immobilize on the surface of a glassy carbon electrode to prepare the electrochemiluminescence sensor for uric acid determination. In 0. 1 mol/L PBS (pH 7. 4) buffer solution, when the actuation duration between uric acid and the modified electrode was 15 min, the electrochemiluminescence showed a good linear relationship to the negative logarithm of uric acid concentration in the range of 1. 0 × 10-10-1. 0 × 10-5 mol/L, the linear equation was IECL=-709. 52-202. 74lgC and the correlation coefficient was 0. 9936 with a detection limit of 6. 0 × 10-12 mol/L. The ECL sensor exhibited excellent repeatability and stability, and the RSD for 11 times determination of 1. 0 × 10-8 mol/L uric acid was 2. 9%. The recovery was 98. 5%-103. 5% in the determination of real Uric acid sample.
4.Direct Analysis of Phospholipids in Biological Tissues Using Internal Exlractive Electrospray Ionization Mass Spectrometry
Haiyan LU ; Jianyong ZHANG ; Wei ZHOU ; Yiping WEI ; Huanwen CHEN
Chinese Journal of Analytical Chemistry 2016;(3):329-334
Phospholipids and their metabolites play an important role in a variety of cellular processes including cell-cell adhesion, cell growth and differentiation, apoptosis, phagocytosis as well as storage of energy. In this study, the phospholipid composition of cancer tissue and adjacent normal tissue from humans and animals were analyzed by internal extractive electrospray ionization mass spectrometry ( iEESI-MS ) . Extractive solvent at high voltage (+5. 5 kV) was injected into tissue samples using a fused silica capillary at a flow rate of 0. 5-1 μL/min, producing fine charged droplets containing analytes of tissue samples at the tip of the sample. Charged droplets were directly sampled to the atmospheric inlet of a mass spectrometer. Out of 21 different ratios of CH3 OH ∶H2 O solvent mixture, the ratio CH3 OH ∶ H2 O=30∶70 ( V/V ) showed the optimal phospholipids extraction and visibility in MS. A large number of phospholipids from different tissue samples ( such as cancer tissue and adjacent normal tissue of lung cancer, esophageal cancer tissue, pork, beef, porcine heart and porcine lung) were obtained simultaneously by iEESI-MS analysis. The experimental results demonstrated that iEESI-MS was characterized by minimal sample pretreatment, low sample consumption, and rapid analysis ( the analysis time per sample was less than 1 min) , and the selectivity and sensitivity of iEESI-MS could be improved by choosing proper solvent. Importantly, the experimental results provided new information for further studies of phospholipids in biological tissues.
5.A Low Detection Limit Penicillin Electrochemical Biosensor Based on Penicillinase-Hematein Au/ZnO/Single Graphene Nanosheets
Zhizhong HAN ; Yueting WU ; Ying ZHOU ; Haibo PAN ; Jinghua CHEN ; Chunyan LI
Chinese Journal of Analytical Chemistry 2016;(3):377-384
ZnO nanoparticles ( ZnO NPs ) were obtained by a direct precipitation method. With the as-prepared ZnO NPs as seeds, Au/ZnO heterostructure was synthesized by seed-mediated growth method without any surfactant, and the diameters of ZnO NPs and Au NPs were about 50 nm and 10 nm, respectively. Then ionic liquids (ILs), trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide ([P(C6)3C14] [ Tf2 N] ) , and functionalized graphene ( GN ) were prepared under room temperature. The ILs as bridges could connect Au/ZnO heterostructure to form a new kind of graphene nanocomposite, Au/ZnO/GN. Then the penicillinase and hematein were immobilized on Au/ZnO/GN. And the biosensors based on penicillinase-hematein-Au/ZnO/GN (PH-AZG) were used for detecting penicillin G. In PBS buffer solution (pH 7. 0), PH-AZG exhibited a detection range from 2 . 5 × 10-14 to 3 . 3 × 10-6 mol/L with a detection limit of 1 . 5 × 10-14 mol/L (S/N≥3). Five PH-AZG electrodes were prepared with the same conditions, and the RSDs for their current response were less than 3. 2%. Furthermore, the standard curves were linear in the range of 5× 10-14-5×10-7 mol/L for milk. The average recoveries were 99. 7%-101. 4% with RSDs of 2. 3%-3. 5%(n=5). The method is sensitive and repeatable, and can be applied to the field of residue analysis about penicillins G with low concentration levels.
6.Solid Phase Extraction Technique Based on Electrospun Nanofibrous
Xiaoqing LI ; Jingjing LIU ; Feifei QI ; Biyi YANG ; Tian TIAN ; Qian XU
Chinese Journal of Analytical Chemistry 2016;(3):474-481
Nanofibers have been considered as a potential kind of sorbent for solid phase extraction, accordingly nanofiber-based solid phase extraction ( Nanofibers based solid phase extraction, NFs-SPE ) becomes a popular research point of sample pretreatment technique. This article reviewed in and abroad research status of practical application in food, environmental and biological sample preparation based on nanofibers mat, and proposed that there was a dual “structure”-“activity” relationship between target adsorption efficiency and the two structures ( nanometer morphological structure and molecular structure ) of nanofibers, which would be the key breakthrough to explore adsorption mechanism.
7.Optimization of Performance of Toroidal Ion Trap with Triangular Electrode by Theoretical Simulation
Haiyang YANG ; Chongsheng XU ; Lei YUE ; Sudakov MIKHAIL ; Yuanjiang PAN ; Chuanfan DING
Chinese Journal of Analytical Chemistry 2016;(3):482-488
The toroidal ion trap is an ideal candidate for miniaturized ion trap because it has much higher ion trapping capacity than a standard quadrupole ion trap of equal trapping dimensions. A novel toroidal ion trap mass analyzer with triangular electrode which contained a filament end cap, a detector endcap, an inner ring and an outer ring was reported. After designing and optimizing the electrodes by theoretical simulations, we found that the asymmetric triangle electrodes could reduce the affection from toroidal shape and improve the ion ejection rate and the mass resolution of the ion trap. The best design of the toroidal ion trap with a mass resolution of 1486 at m/z 609 was obtained.
8.Determination of Atmospheric Krypton and Xenon by Gas Chromatography-Mass Spectrometry in Direct Injection Mode
Zhanying CHEN ; Shujiang LIU ; Jianlong WANG ; Yinzhong CHANG
Chinese Journal of Analytical Chemistry 2016;(3):468-473
Volume concentration determination for atmospheric krypton and xenon is very important for krypton-85 and radioactive xenon isotopes monitoring. An injection setup integrated adjustable quantity sample injection and quantitative dilution function was designed. The effects of EI source parameters on the sensitivity of MS detector were studied. The optimized values were as following: ionization energy of 70 eV, emission current of 40 mA, cathode voltage of 27 mV, focus voltage of 85 mV and lens compensation of 20 V, respectively. A GC-MS method for the determination of krypton and xenon in atmosphere without of sample pretreatment was developed. The minimal detected concentrations for krypton and xenon were 3. 3×10-8(V/V) and 2. 6×10-9(V/V). Moreover, the krypton and xenon concentrations in the ground level air around our laboratory were measured with the results of 1 . 1 × 10-6 ( V/V ) and 9 . 3 × 10-8 ( V/V ) . The related combined standard uncertainties for krypton and xenon results were 2. 38% and 3. 15%, respectively.
9.Analysis of Staphyloxanthin Biosynthesis Using Single Cell Raman Spectroscopy
Zhanhua TAO ; Junxian LIU ; Deqiang SHI ; Jian KANG
Chinese Journal of Analytical Chemistry 2016;(3):456-461
Laser tweezers Raman spectroscopy ( LTRS ) was used to study the inhibitory effect of indol on staphyloxanthin biosynthesis in Staphylococcus aureus cells and the dynamic changes of this pigment content inside bacterial cells during batch cultivation. The Raman spectra of Staphylococcus aureus cells cultivated for different time and exposed to various doses of indol were acquired. The intensity of 1523 cm-1 band was used for the quantification of staphyloxanthin, in the meantime, the pigment was measured by UV spectrometry. The experimental result showed that an excellent linear relationship existed between the intensities of Raman peak at 1523 cm-1 of bacterial cells and the pigment contents estimated by UV spectrometry, with a correlation coefficient of 0 . 9772 . The spectral data at population level as well as single cell level revealed that indol could inhibit the production of pigment in dose-dependent manner, and the pigment content in bacterial cells incubated with indol decreased by 70%. Under the batch growth condition, the pigment amount in Staphylococcus aureus cells reached the maximum value during the middle exponential growth phase ( 12 h ) and the heterogeneity of pigment content in bacterial cells within certain populations at various time points was relatively small, with RSDs of 39. 2% to 61. 1%. This investigation indicates that LTRS can be served as a reliable method for the analysis of staphyloxanthin content at single cell level.
10.A Metabonomics Study of Childhood Pneumonia by Rapid Resolution Liquid Chromatography Quadrupole Time-of-flight Mass Spectrometry
Jing LI ; Xiaolei LIU ; Xu ZHAO ; Wei LI ; Yulin DAI ; Hao YUE
Chinese Journal of Analytical Chemistry 2016;(3):451-455
In this study, the rapid resolution liquid chromatography quadrupole time-of-flight mass spectrometry ( RRLC-QTOF/MS ) was used to profile the metabolites of urine samples from Childhood Pneumonia ( CP) patients and healthy controls and find the potential biomarkers which can support evidence to early diagnose and cure the disease. Choose 10 CP patients ( age 47. 72 ± 2. 35 months) and 10 healthy controls ( age 46 . 65 ± 1 . 97 months ) . The urine samples were analyzed by RRLC-QTOF/MS and then the resulting data matrices were analyzed by principal components analysis ( PCA ) to find the potential biomarkers. Urine samples of CP patients were successfully distinguished from those of healthy controls. A total of two significantly changed metabolites have been found and identified as potential biomarkers. It is suggested that the disorder of purine metabolism and amino acid metabolism may play an important role in the mechanism of CP.