Zhongyin Ji

Accurate Determination of Amino Acids in Serum Samples by Liquid Chromatography–Tandem Mass Spectrometry Using a Stable Isotope Labeling Strategy

An accurate and sensitive liquid chromatography-tandem mass spectrometry method was developed for the analysis of amino acids (isoleucine, leucine, valine, tyrosine, phenylalanine and tryptophan) in serum samples using a stable isotope labeling strategy. Amino acid samples and standards were, respectively, derivatized by 10-methyl-acridone-2-sulfonyl chloride (d0-MASC) and its deuterated counterpart d3-MASC to form isotopic pairs which co-eluted and were detected by an MS detector at the same time. Accurate internal standard-based quantification was thereby achieved without the use of any internal standard analogy. The labeling reaction of MASC with amino acids is fast, simple and robust. Besides, derivatization increased the molecular weight of amino acids, and therefore they were shifted out of the background noise which was often observed in low mass region. The instrument LODs were in the range of 1.0-2.5 nmol/L. Linearities calculated by comparing theoretical peak area ratios of d0-/d3-MASC derivatives with the experimental peak area ratios were excellent with correlation coefficients of >0.995. The proposed method was successfully applied to the analysis of amino acids in serum samples with high sensitivity and accuracy.

Rapid, Selective, and Sensitive Analysis of Triterpenic Acids in Hippophae rhamnoides L. Using HPLC with Pre-Column Fluorescent Derivatization and Identification with Post-Column APCI-MS

Hippophae rhamnoides L., a fruit which is rich in natural chemical ingredients, has become an important raw material of health food, medicine, and cosmetics. In the present work, a method using 2-(5-benzoacridine)ethyl-p-toluenesulfonate as pre-column derivatization reagent with high sensitivity, selectivity, and short separation time was developed to analyze triterpenic acids (TTAs) in H. rhamnoides L. by HPLC with fluorescence detection and simultaneously confirmed by post-column atmospheric pressure chemical ionization-mass spectrometry. The method was validated by linearity, limits of detection (LODs) and lower limits of quantification (LLOQs), precision, and accuracy. Good linear correlations were observed for all TTAs with correlation coefficients greater than 0.9996. LODs and LLOQs were in the range of 1.71–2.14 and 7.45–8.23 ng mL−1, respectively. The method was successfully employed to analyze TTAs in H. rhamnoides L. from various origins in the Qinghai–Tibetan plateau with trace amount of samples within 15 min. A systemic mapping of the TTAs in H. rhamnoides L. of different origins was established. The results indicated that H. rhamnoides L. is rich in TTAs, especially in oleanolic and ursolic acids, and the content of TTAs varies across origins. This work will support the research on pharmaceutical applications of H. rhamnoides L. and provide information for quality control.

DETERMINATION OF FATTY ACIDS IN THREE NITRARIA SPECIES BY PRECOLUMN FLUORESCENCE LABELING FOR HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AND ATMOSPHERIC PRESSURE CHEMICAL IONIZATION-MASS SPECTROMETRY

A novel fluorescence method using 2-(7-methyl-1H-pyrazolo-[3,4-b] quinoline-1-yl) ethyl-4-methyl benzenesulfonate as the labeling reagent was established for high-performance liquid chromatography determination of fatty acids. The conditions were optimized, including the identity of the organic solvent, identity, and amount of catalyst, amount of derivatization reagent, derivatization temperature, and derivatization time. The results indicated that quantitative yields of derivative were obtained with a five-fold molar excess of reagent at 90°C for 30 min using 25 mg of potassium carbonate as the catalyst. Atmospheric pressure chemical ionization mass spectrometry results indicated that collision-induced dissociation of protonated fatty acid derivatives produced fragments at m/z 228.2, m/z 210.2, and m/z 183.8. The method was validated in terms of linearity, limits of detection, limits of quantification, precision, and accuracy, and the results showed that the method exhibited excellent sensitivity, selectivity, and reproducibility. Limits of detection and limits of quantification were in the ranges of 0.52–2.34 ng mL−1 and 1.23–6.63 ng mL−1, respectively. This method was successfully applied to the determination of fatty acids in sarcocarps, seeds, and leaves of Nitraria tangutorum Bobr., Nitraria sibirica Pall., and Nitraria roborowskii Kom. The results indicated that the main components were oleic, linoleic, linolenic, and hexadecanoic acids. However, the composition of fatty acids in the tissues varied considerably.

Stable isotope labeling assisted liquid chromatography–tandem mass spectrometry for the analysis of perfluorinated carboxylic acids in serum samples

A new stable isotope labeling (SIL) reagent pair, 10-methyl-acridone-2-sulfonohydrazide (MASH) and its deuterated counterpart d3-MASH was synthesized and successfully applied to the analysis of perfluorinated carboxylic acids (PFCAs) in serum samples. The limits of detection (LODs) were in the range of 0.07-0.42μg/L, and the limits of quantitation (LOQs) were in the range of 0.25-1.38μg/L. Besides ionization enhancing effect, MASH also showed excellent fluorescence property. Therefore, the mass spectrometer operation cost was greatly lowered by carrying out parameter optimization experiments on HPLC which is easier to operate and maintain. The SIL strategy was confirmed to be effective in reducing matrix effect. The developed multiple-reaction monitoring (MRM) condition of PFCAs was also suitable for other carboxylic acid due to the introduction of MASH which is more prone to fragmentation than the analytes. With the MRM conditions obtained from PFCAs, fatty acids were also found in serum samples. This feature made the proposed method show powerful potential in the identification of acidic compounds in complex samples in the absence of corresponding standard.

Synchronous determination with double-wavelength by RP-HPLC-UV and optimization of ultrasound-assisted extraction of phenolic acids from Caragana species using response surface methodology

&NA; The utilization of Caragana korshinskii Kom. (CK) is currently concentrated on its ecological and fuel functions. Little attention has been devoted to the analysis of their phenolic acid (PA) components. To obtain more data for further utilization of CK, a new analysis protocol was tested to determine PAs synchronously by RP‐HPLC‐UV with double‐wavelength (280 nm and 320 nm) detection. Specifically, separation of PA components was performed on a Hypersil Gold C18 reverse phase column with gradient elution. A four‐factor‐three‐level Box‐Behnken design was implemented for optimization of PA extraction. The results demonstrated that CK were rich primarily in chlorogenic acid, vanillic acid, caffeic acid and rosmarinic acid. The total content of PAs in CK leaves was the highest compared with its other parts. The distribution of total flavonoid content of CK was leaves > flowers > bark, while that of the total phenolic content of CK was flowers > leaves > bark. Graphical abstract Figure. No caption available. HighlightsA new protocol of synchronous determination of phenolic acids (PAs) was proposed by RP‐HPLC‐UV with double‐wavelength.The validated results demonstrated that the proposed method was feasible to determine PAs in plant samples.The protocol was applied for analysis PAs in Caragana korshinskii Kom. which was mainly rich in chlorogenic acid, vanillic acid, caffeic acid and rosmarinic acid.Total content of PAs in leaves was the highest compared with that of flowers and bark.

A sensitive pre-column derivatization method for the analysis of free fatty acids by RP-HPLC with fluorescence detector and its application to Caragana species

Caragana korshinskii Kom. (CK), one of afforestation tree species, is widely planted in northwest region of China. To compare the constituents as references for further utilization of CK, C. microphyll Lam. (CM) and C. jubata L. (CJ), been used as traditional Chinese medicine, were taken into consideration. To obtain more information on CK for further utilization, a sensitive and stable pre-column derivatization method for the analysis of fatty acids (FAs) was established using a novel labeling reagent 2-(5H-benzo[a]-carbazol-11(6H)-yl)ethyl hydrazine-carboxylate (BCEHC) by HPLC with fluorescence detector. The derivatives exhibit predominant fluorescence property at excitation and emission wavelengths of 330nm and 380nm, respectively. 16 derivatives of FAs including 13 saturated FAs and 3 unsaturated FAs are separated on a reversed-phase column with gradient elution within 30min. The validation of method indicated that all FAs were given excellent linear responses with good linear coefficient of correlation being equal to or greater than 0.9985. The limits of detection (LODs) at a signal-to-noise ratio of 3 varied from 63.12 to 116.21ngL-1. The developed method was successfully applied to determine the contents of free FAs (FFAs) in flowers, leaves and bark of CK and the samples were extracted by a green and simple method of gas purge microsyringe extraction. The results show that the contents of linoleic acid and linolenic acid are high in flowers and leaves while the bark is rich in linoleic acid. The total content of FFAs in all parts of CK is higher than that of CM. The distribution of FFAs in plants is obviously different even in the congeneric among different species.

A highly sensitive and selective method for determination of phenoxy carboxylic acids from environmental water samples by dispersive solid-phase extraction coupled with ultra high performance liquid chromatography-tandem mass spectrometry

A rapid and efficient method for extraction of 12 phenoxy carboxylic acids (PCAs) in environmental water samples was established based on metal-organic framework MIL-101 assisted dispersive solid phase extraction (DSPE). 12 PCAs were labeled by d0-10-methyl-2-(piperazin-1-ylsulfonyl)anthracen-9(10H)-one(d0-MASPz) and d3-10-methyl-2-(piperazin-1-ylsulfonyl)anthracen-9(10H)-one(d3-MASPz), allowing each analyte to have an isotope internal standard. A stable isotope-coded strategy for the detection of 12 PCAs was developed under optimized extraction conditions and UHPLC-MS/MS conditions. All PCAs analytes were in good linearity in the concentration range of 5-1000 ng/L, and the calibration function was verified by the Mandel fitting test with a 95% confidence level. The LODs and LOQs were estimated by the IUPACs recommendations. The LODs ranged from 0.18 to 0.88 ng/L, and LOQs ranged from 0.59 to 2.90 ng/L. The intra-day and inter-day precision in three spiked levels (5, 50 and 100 ng/L) were in the range of (1.40 ± 0.14) %- (2.76 ± 0.12) % and (2.60 ± 0.26) %- (3.83 ± 0.32) %, respectively. The developed method has been successfully applied to the determination of PCAs in environmental water samples with recoveries ranging from 95.3% to 105.5%. All of the precision and recovery analyses were done in triplicate.

Simultaneous Determination of Five Triterpenic Acids in Four Corydalis Herb Medicines by Reversed-Phase High Performance Liquid Chromatography-Fluorescence-mass Spectrometer (RP-HPLC-FLD-MS) Based on Pre-Column Derivatization

ABSTRACT A rapid and sensitive reversed-phase high performance liquid chromatography– fluorescence-mass spectrometer (RP-HPLC–FLD-MS) method based on pre-column derivatization using 2-(5-benzoacridine)ethyl-p-toluenesulfonate (BAETS) as labelling reagent has been developed for simultaneous determination of five triterpenic acids (asiatic acid (AA), maslinic acid (MA), corosolic acid (CA), oleanolic acid (OA), and betulinic acid (BA). The presented method was validated for linearity (correlation coefficient R2 > 0.9994), precision (RSD 2.1%–3.9%) and reproducibility (RSD 0.01%–2.1%). The limits of detection (LODs) and the limits of quantitation LOQs were within the range of 0.71–1.02 ng mL−1 and 2.28–3.24 ng mL−1, respectively. The proposed method was successfully applied to simultaneously determine five triterpenic acids of four Corydalis plants and showed satisfactory reproducibility and credibility. Moreover, several main parameters affecting extraction procedure and derivatization efficiency were investigated by response surface methodology (RSM), respectively. Triterpenic acid content in four Corydalis plants was measured according to the established method and the results indicated that triterpenic acid contents were various in different organs and herbs. GRAPHICAL ABSTRACT