Detection of trace amounts of citrinin in dried orange peel by using an optimized extraction method coupled with ultra‐performance liquid chromatography–tandem mass spectrometry

A fast and sensitive method involving ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) was introduced to detect citrinin in dried orange peel. A series of extraction, purification and chromatographic conditions was also systematically examined. With the proposed method, the obtained calibration graph was linear, with an R of 0.9996 within a concentration range of 0.5–10 ng/mL. The estimated limits of detection and quantification were 0.05 and 0.17 ng/mL, respectively. Under the selected conditions, the relative recoveries in different citrus products spiked with 1–10 ng/mL citrinin were 89.4–98.7% with RSDs of <2.5%. Compared with previously reported analytical methods, the newly developed UPLC–MS/MS method showed excellent sensitivity and good precision in detecting citrinin. The results indicated that it is a reliable and effective technique for the detection of trace citrinin in dried orange peel.     

Residues of 165 pesticides in citrus fruits using LC-MS/MS: a study of the pesticides distribution from the peel to the pulp

Abstract

A sensitive LC–ESI-MS/MS method was developed for the determination of 165 pesticides in 50 citrus fruit samples collected in Sicily. Moreover, an evaluation of pesticides levels in the citrus layers (peel, albedo, and pulp) was carried out. The method presented acceptable trueness, precision, and linearity with LOQ of 5?μg/kg. The results obtained showed a high frequency of fungicides class pesticides in all the citrus samples examined (>95%) with the highest concentrations in the peel (4468?µg/Kg). A significant difference of concentrations was found between the layers of the citrus fruits analysed (p?<?0.05). In particular, the peel and albedo present higher pesticides significantly higher than the pulp. Our findings confirming the widespread use of these substances in citrus cultivation and suggesting the importance of pesticides analysis in all the citrus fruit layers separately, considering the different interactions between the physicochemical characteristics of the matrices and the pesticides.     

A Validated HPLC Method for Simultaneous Determination of 2-Hydroxy-4-methoxybenzaldehyde and 2-Hydroxy-4-methoxybenzoic Acid in Root Organs of Hemidesmus indicus

A reverse phase HPLC method was developed and validated for the simultaneous determination of 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-4-methoxybenzoic acid in the root extracts of Hemidesmus indicus. A comprehensive validation of the method including sensitivity, linearity, reproducibility, accuracy, limit of detection (LOD) and limit of quantification (LOQ) was conducted using the optimized chromatographic conditions. The method was found to be linear (r > 0.998) in the range of 5–350 μg mL⁻¹ for 2-hydroxy-4-methoxybenzaldehyde and for 2-hydroxy-4-methoxybenzoic acid (r > 0.999) in the range 10–300 μg mL⁻¹. The method was found to be precise with inter-day precision values (% RSD) in the ranges of 0.61–1.76% for 2-hydroxy-4-methoxybenzaldehyde and 1.3–2.8% for 2-hydroxy-4-ethoxybenzoic acid while intra-day precisions (% RSD) of two analytes were in the range of 0.41–1.07 and 0.95–2.5%. The limits of detection (LODs) for 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-4-methoxybenzoic acid were 0.84 and 2.34 μg mL⁻¹. The described method was fast, sensitive and reproducible, and thus well suited for routine analysis of these two compounds from root extracts of H. indicus and other plants.     

QuEChERS-液相色谱-串联质谱法同时检测土壤和柑橘中吡唑醚菌酯、甲基硫菌灵及其代谢物多菌灵的残留

建立了QuEChERS-液相色谱-串联质谱法(LC-MS/MS)检测土壤和柑橘中吡唑醚菌酯、甲基硫菌灵及其代谢物多菌灵的分析方法。样品经甲醇或乙腈提取,N-丙基乙二胺(PSA)净化后,用液相色谱分离,电喷雾正离子多反应监测(MRM)模式进行质谱测定,以基质匹配标准溶液进行外标法定量。吡唑醚菌酯、甲基硫菌灵和多菌灵的定量限(LOQ,S/N=10)分别为5.8~7.0μg/kg、9.3~14.1μg/kg和2.1~2.6μg/kg。样品的加标回收率为75.48%~109.18%,相对标准偏差(RSD)为0.60%~5.11%(n=5)。该法快速简便,定量准确,用基质配制标准溶液能够有效、准确地校正LC-MS/MS测定吡唑醚菌酯、甲基硫菌灵和多菌灵残留的基质效应,满足土壤、橘皮、橘肉和柑橘全果实际样品的检测需求。     

Dissipation,residues and risk assessment of spirotetramat and its four metabolites in citrus and soil under field conditions by LC‐MS/MS

A modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for the simultaneous determination of spirotetramat and its four metabolite residues in citrus, peel, pulp and soil was developed and validated by liquid chromatography with tandem mass spectrometry (LC‐MS/MS). The samples were extracted with acetonitrile (1%, glacial acetic acid, v/v) and purified using primary secondary amine and octadecylsilane. The limit of detection was 0.01–0.13 mg/kg, whereas that of quantification was 0.02–0.40 mg/kg for spirotetramat and its metabolites. The average recoveries of spirotetramat, spirotetramat‐enol, spirotetramat‐mono‐hydroxy, spirotetramat‐enol‐glucoside and spirotetramat‐ketohydroxy in all matrices were 73.33–107.91%, 75.93–114.85%, 76.44–100.78%, 71.46–103.19% and 73.08–105.27%, respectively, with relative standard deviations < 12.32%. The dissipation dynamics of spirotetramat in citrus and soil followed first‐order kinetics, with half‐lives of 2.3–8.5 days in the three sampling locations. The terminal residues of spirotetramat in four matrices at the three locations were measured below the 1.0 mg/kg maximum residue limit set by China, and residues were found to be concentrated on the peel. The risk assessment of citrus was evaluated using risk quotients. The risk quotient values were found to be significantly <1, suggesting that the risk to human health was negligible when using the recommended doses of spirotetramat in citrus. These results could provide guidance for the safe and proper application of spirotetramat in citrus in China.     

超高效液相色谱-三重四极杆-离子阱质谱法检测柑橘中螺虫乙酯及其4种代谢产物

建立了超高效液相色谱-三重四极杆-离子阱质谱定量检测柑橘中螺虫乙酯及其4种代谢产物残留的分析方法。样品以QuEChERS技术为前处理方法进行净化、浓缩,在电喷雾电离（ESI）源、正离子模式下,采用MRM监测模式分析,以基质匹配外标法定量。螺虫乙酯及其4种代谢产物在2~1000 μg/L线性范围内具有良好的线性关系,相关系数（R²）>0.99;方法的检出限（LOD）为0.08~0.49 μg/kg,定量限（LOQ）为0.26~1.62 μg/kg;空白样品添加回收率为94.0%~98.7%,相对标准偏差为1.1%~5.3%。田间试验结果表明,在施药最高推荐量60 mg/kg （有效成分）下,柑橘果肉、果皮、全果样品中螺虫乙酯及其4种代谢产物残留总量分别为5.93~14.20、11.30~17.86和1.30~16.51 μg/kg,残留量均低于国家标准最大残留限量值1.00 mg/kg。该方法操作简便,快速准确,灵敏度高,分离效果好,能够有效降低基质干扰效应,准确度与精密度均能达到定量分析要求,适用于柑橘中螺虫乙酯及其代谢产物残留的定性定量检测。     

电感耦合等离子体发射光谱法测定柑桔类水果及果皮中多种微量元素

采用HNO_3-HClO_4体系湿法消解样品,利用电感耦合等离子体发射光谱仪同时测定了柑桔类水果及果皮中Al、B、Ba、Ca、Cu、Fe、K、Mg、Mn、Na、Sr、Zn 12种微量元素的含量。分析结果的相对标准偏差0.35%~3.26%,加标回收率85.5%~107.0%,该法简单、快速、可靠、灵敏度高。实验表明,大部分柑桔类水果果皮中微量元素含量高于其果肉中含量。柚子内皮和外皮中微量元素含量有少许差异,柚子外皮中的K、Ca、Mg含量最高,而柚子内皮中Fe、Na的含量较高。该结果为有效利用柑桔类水果果皮的药用功效提供了定量参考依据。     

The development of sequential injection analysis coupled with lab-on-valve for copper determination

A sequential injection analysis (SIA) using lab-on-valve with air segmentation and spectrophotometric detection was designed for copper(II) determination. It is based on the reaction of copper(II) and 2-carboxy-2′-hydroxy-5′-sulfoformazyl benzene (Zincon) in a weak alkaline solution between the air zones. Beer's Law was obeyed over the range of 0.1-2.0 mg L⁻¹ copper(II) with a correlation coefficient 0.9985 and a slope of 0.2893 absorbance unit/mg L⁻¹. The relative standard deviation was 2.0% for a series of 10 measurements of 0.5 mg L⁻¹ copper(II) solution. The detection limit (3 S/N) and the limit of quantification (LOQ) were 0.05 and 0.17 mg L⁻¹ respectively. This method has been successfully applied to determination of copper(II) in wastewater with a sample throughput of 120 h⁻¹. The method is superior to the batchwise method in that it provides fully automation, rapidity, less reagents and sample consumption with little waste generation.     

Solid-phase microextraction coupled to gas chromatography for the determination of 2,3-dimethyl-2,3-dinitrobutane as a marking agent for explosives

This paper investigates the detection of 2,3-dimethyl-2,3-dinitrobutane (DMNB), a marking agent in explosives, by gas chromatography (GC) with electron capture detection using solid-phase microextraction (SPME) as a sample preparation technique. The 25,27-dihydroxy-26,28-oxy (2′,7′-dioxo-3′,6′-diazaoctyl) oxy-p-tert-butylcalix[4]arene/hydroxy-terminated silicone oil coated fiber was highly sensitive to trap DMNB from ammonium nitrate matrix. The analysis was performed by extracting 2 g of explosives for 30 s at room temperature and then immediately introducing into the heated GC injector for 1 min of thermal desorption. The method showed good linearity in the range from 0.01 to 1.0 μg/g. The relative standard deviations for these extractions were <8%. The calculated limit of detection for DMNB (S/N = 3) was 4.43 × 10⁻⁴ μg/g, which illustrates that the proposed systems are suitable for explosive detection at trace level. This is the first report of an SPME-GC system shown to extract marking agent in explosives for subsequent detection in a simple, rapid, sensitive, and inexpensive manner.     

A novel liquid chromatography-fluorescence method for the determination of delafloxacin in human plasma

Delafloxacin is a novel fluoroquinolone antibiotic that was approved by the European Medicine Agency to treat bacterial infections of the skin and underlying tissues, and community-acquired pneumonia. Despite being in the market since 2019 in the European Union, there is no published liquid chromatography-fluorescence method for delafloxacin quantification in biological samples. A novel, rapid, and sensitive high-performance liquid chromatographic method was developed to determine delafloxacin in human plasma using its native fluorescence. Plasma delafloxacin concentrations were determined by reverse-phase chromatography with fluorescence detection at 405/450 nm of excitation/emission wavelengths. Delafloxacin was separated on a Kromasil C18 column 250 × 4.6 mm id, 5 µm using isocratic elution. The mobile phase was a mixture of 0.05% trifluoroacetic acid/acetonitrile (52/48). Retention times were 5.4 and 11.6 min for delafloxacin and valsartan (internal standard), respectively. Regression calibration curves were linear over the range of 0.1–2.5 µg/mL. The lower limit of detection was 0.05 µg/mL, and the lower limit of quantification was 0.1 µg/mL. Accuracy and precision were always <11%, and the limit of quantification was <16%. Mean recovery was 98.3%. This method can be applied to determine delafloxacin in human plasma and could be useful to perform pharmacokinetic studies.     

A highly sensitive enzyme immunoassay for evaluation of 2′-deoxycytidine plasma level as a prognostic marker for breast cancer chemotherapy

A highly sensitive competitive enzyme immunoassay (EIA) has been developed and validated for the determination of the plasma level of 2′-deoxycytidine (dCyd), the potential prognostic marker for breast cancer chemotherapy. This assay employed a monoclonal antibody that recognizes dCyd with a high specificity, and 5′-succinyl-dCyd (5′sdCyd) conjugate of bovine serum albumin (5′sdCyd-BSA) immobilized onto microplate wells as a solid phase. The assay involved a competitive binding reaction between dCyd, in plasma sample, and the immobilized 5′sdCyd-BSA for the binding sites of the anti-dCyd antibody. The bound antibody was quantified with horseradish peroxidase-labeled anti-immunoglobulin second antibody and 3,3′,5,5′-tetramethylbenzidine as a peroxidase substrate. The concentration of dCyd in the sample was quantified by its ability to inhibit the binding of the antibody to the immobilized 5′sdCyd-BSA and subsequently the color formation in the assay. The assay limit of detection was 8 nM and the effective working range at relative standard deviations (R.S.D.s) of ≤10% was 20-800 nM. No cross-reactivity from the structurally related nucleobases, nucleosides, and nucleotides was observed in the proposed assay. Mean analytical recovery of added dCyd was 98-100 ± 3.2-8.2%. The precision of the assay was satisfactory; R.S.D. was 3.4-4.2 and 4.3-8.9% for intra- and inter-assay precision, respectively. The proposed EIA was compared favorably with HPLC method in its ability to accurately measure dCyd spiked into plasma samples. The analytical procedure is convenient, and one can analyze 200 samples per working day, facilitating the processing of large-number batch of samples. The proposed EIA is expected to contribute in further evaluation of dCyd as a prognostic marker for breast cancer chemotherapy and elucidation of the role of dCyd in various biological and biochemical systems.     

Ion-pair high-performance liquid chromatography with diode array detection coupled to dual electrospray atmospheric pressure chemical ionization time-of-flight mass spectrometry for the determination of nucleotides in baby foods

A liquid chromatography with diode array detection coupled to dual electrospray atmospheric pressure chemical ionization time-of-flight mass spectrometry (HPLC/ESI-APCI-TOF-MS) method is described for the rapid determination of five monophosphate nucleotides (cytidine 5′-monophosphate, uridine 5′-monophosphate, adenosine 5′-monophosphate, inosine 5′-monophosphate and guanosine 5′-monophosphate) in baby foods. The method is based on the deproteinisation of foods and direct analysis of nucleotides by ion-pair HPLC using isocratic elution with a mobile phase of 5% (v/v) methanol and 95% (v/v) 0.1 M formate buffer (pH 5.5) containing 0.01 M N,N-dimethylhexylamine (DMHA) at a flow-rate of 0.7 mL min⁻¹. The HPLC was hyphenated with two different detection systems, photodiode-array (DAD) and ESI-APCI-TOF-MS in negative mode. The method was validated for linearity, detection and quantitation limits, selectivity, accuracy and precision. The recoveries obtained for spiked samples were satisfactory for all the analytes. The method was successfully applied to the analysis of nucleotides in different baby and/or functional food samples, as cereals, purees and dairy products. A study was also carried out on the stability of nucleotides in acidified dairy infant food with pasteurized yoghourt and follow-on formulae samples stored at room temperature and at 30 °C.     

Dual-cloud point extraction and tertiary amine labeling for selective and sensitive capillary electrophoresis-electrochemiluminescent detection of auxins

The low concentrations of the auxins in samples of plant tissue necessitate the use of selective and sensitive techniques for their quantification. Herein a selective and sensitive method based on dual-cloud point extraction (dCPE) and tertiary amine labeling for the quantification of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) by capillary electrophoresis-electrochemiluminescence (CE-ECL) is proposed. The procedure for dCPE included two cloud point processes with Triton X-114 as the extractant. The two auxins became hydrophobic in an acidic solution and were extracted into surfactant-rich phase after the first cloud point procedure. They were then back-extracted into the alkaline aqueous phase during the second cloud point step. The extracted auxins were reacted with 2-(2-aminoethyl)-1-methylpyrrolidine (AEMP) in acetonitrile that contained N,N′-dicyclohexylcarbodiimide and 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine to produce their AEMP-derivatives. The two auxin-AEMP-derivatives were subjected into CE and detected by Ru(bpy)₃²⁺-based ECL. The preconcentration factors for IAA and IBA with dCPE were 40.5 and 43.4, respectively. The on-capillary detection limits (S/N = 3) were 2.5 and 2.8 nM for IAA and IBA. This protocol presents a clear advantage in that it reduces the interference from the matrixes extensively and gives a high sensitivity for the detection of auxins. The proposed method was applied successfully to the detection of the two auxins in acacia tender leaves, buds, and bean sprout.     

Multiresidue method for the simultaneous determination of 16 acaricides by modified quick,easy, cheap,effective, rugged,and safe extraction and ultra‐high performance liquid chromatography coupled with tandem mass spectrometry in citrus

An ultra‐high performance liquid chromatography coupled with tandem mass spectrometry analytical method was developed for simultaneously determining 16 acaricides in citrus based on an optimized quick, easy, cheap, effective, rugged, safe strategy. Good linearities of the standard curve of 5–1000 μg/kg was obtained with regression coefficients higher than 0.9967. Recoveries for all compounds ranged from 72 to 111% with relative standard deviations lower than 14.4% at spiked levels of 5, 50, and 500 μg/kg. Low limits of detection and quantification were readily achieved ranging from 0.05 to 2.7 and 0.10 to 4.3 μg/kg, respectively. Matrix effects were also evaluated for 16 targets with most compounds achieved signal enhancement. Citrus peel gave the highest extent matrix effects, followed by whole citrus and pulp. Finally, this method was successfully applied to detect acaricides residues in real citrus samples. The results showed that pyridaben and quinalphos were the two most frequent and high‐concentration compounds with concentrations exceeding the maximum residue limits in five samples, suggesting that the use of these acaricides should be regulated in China in the future.     

Microdialysate analysis of monoamine neurotransmitters—A versatile and sensitive LC–MS/MS method

We have developed and validated a sensitive method for the simultaneous determination of some monoamine neurotransmitters like dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in rat brain microdialysate using high-performance liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). Sensitivity enhancement has been achieved by amine derivatization with the reagent (5-N-succinimidoxy-5-oxopentyl)triphenylphosphonium bromide (SPTPP) under mild conditions. The use of the selected reaction monitoring (SRM) mode has allowed detection of the analytes at a concentration of 30 pM (lower limit of quantification, LLOQ, signal-to-noise ratio higher than 5) with an accuracy of ≤3.80% and a precision of ±7.39 (%CV) for all neurotransmitters. Derivatization improves resolution and chromatographic retention times (3 min) by lipophilization. Linearity has been good (R > 0.99) over a large concentration range (30–50,000 pM). The intra and inter-batch accuracy and precision were not greater than 4.8% and 6.4%, respectively. Therefore, the method was successfully applied for monitoring the concentration changes of neurotransmitters in microdialysis samples deriving from striatum rat brain region after amphetamine administration (3 mg kg⁻¹, i.p.).     

Simple, Sensitive, and Rapid LC–ESI-MS Method for Quantification of Mitiglinide in Human Urine

A sensitive and specific liquid chromatographic method with electrospray ionization mass spectrometry (LC–ESI-MS) has been developed and validated for identification and quantification of mitiglinide in human urine. A simple liquid–liquid extraction procedure was followed by separation on a C₁₈ column with gradient elution, and detection using a single-quadrupole mass spectrometer in selected-ion-monitoring (SIM) mode. The method was tested using six different batches of urine. Linearity was established for the mitiglinide concentrations in the range 0.005–1.0 μg mL⁻¹, with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. Intra- and inter-day precision (as RSD, %) was below 10% and accuracy for mitiglinide ranged from 85 to 115%. The lower limit of quantification was reproducible at 0.002 μg mL⁻¹ for 500 μL urine. The proposed method enables unambiguous identification and quantification of mitiglinide in pre-clinical and clinical studies.     

Analytical approach to determine biogenic amines in urine using microextraction in packed syringe and liquid chromatography coupled to electrochemical detection

The goal of this work was to develop and validate an analytical method for the detection and quantification of the biogenic amines serotonin (5‐HT), dopamine (DA) and norepinephrine (NE), using microextraction in packed syringe (MEPS) and liquid chromatography coupled to electrochemical detection (HPLC‐ED) in urine. The method was validated according to internationally accepted guidelines from the Food and Drug Administration. Linearity was established between 50 and 1000 ng/mL for 5‐HT and between 5 and 1000 ng/mL for DA and NE, with determination coefficients (R²) >0.99 for all compounds. The limits of quantification and detection were respectively 50 and 20 ng/mL for 5‐HT, and 5 and 2 ng/mL for DA and NE. Within‐ and between‐run precision ranged from 0.84 to 9.41%, while accuracy ranged from 0.79 to 12.76% for all compounds. The intermediate precision and accuracy were 1.50–8.36 and 0.54–13.51%, respectively. The method was found suitable for clinical routine analysis of the studied compounds, using a sample volume of 0.5 mL. This is the first study employing a commercially available MEPS column for the simultaneous detection and quantification of 5‐HT, DA and NE in urine by coulometric detection. Copyright © 2012 John Wiley & Sons, Ltd.     

A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence detection and column switching for determination of MDMA-related compounds in hair

A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence (POCL) detection and column switching has been developed for simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA) and related compounds, for example 3,4-methylenedioxyamphetamine, methamphetamine, and amphetamine, in hair. After digestion of the hair with 1 mol L⁻¹ sodium hydroxide the compounds were extracted with n-heptane and derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. A mixture of hydrogen peroxide and bis(2,4,5-trichloro-6-carbopentoxyphenyl)oxalate in acetonitrile was used as post-column CL reagent. Calibration plots showed linearity was good (r = 0.999); detection limits were 0.02–0.16 ng mg⁻¹ hair at a signal-to-noise ratio of 3. The precision of the method, as RSD (n = 5), in intra-day and inter-day assays was better than 5.0 and 6.9%, respectively. The proposed method was sufficiently sensitive to detect low ng mg⁻¹ levels of MDMA and related compounds in hair, and could be used for quantification of the compounds in hair samples from patients treated in a chemical dependency unit.     

Ultra-sensitive quantification of lysozyme based on element chelate labeling and capillary electrophoresis–inductively coupled plasma mass spectrometry

In this study, an ultra-sensitive method for the quantification of lysozyme based on the Gd³⁺ diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid labeling and capillary electrophoresis–inductively coupled plasma mass spectrometry (CE–ICP–MS) was described. The Gd³⁺-tagged lysozyme was effectively separated by capillary electrophoresis (CE) and sensitively determined by inductively coupled plasma mass spectrometry (ICP–MS). Based on the gadolinium-tagging and CE–ICP–MS, the lysozyme was determined within 12 min with an extremely low detection limit of 3.89 attomole (3.89 × 10⁻¹¹ mol L⁻¹ for 100 nL of sample injection) and a RSD < 6% (n = 5). The proposed method has been successfully used to detect lysozyme in saliva samples with a recovery of 91–106%, suggesting that our method is sensitive and reliable. The success of the present method provides a new potential for the biological assays and sensitive detection of low-abundant proteins.     

Simultaneous Determination of Phenolics and Polymethoxylated Flavones in Citrus Fruits by Ultra-High Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (UHPLC-QqQ-MS)

Phenolic and polymethoxylated flavones are important bioactive components in citrus fruit. Here, a rapid and sensitive method based on ultra-high performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-QqQ-MS) was developed for the simultaneous determination of phenolic and polymethoxylated flavones in the peels and pulp of mandarins, tangelos, and oranges. Three phenolic acids and eight flavonoids, including polymethoxylated flavones, were separated and determined using positive and negative ion modes in a single chromatographic run of only 11?min using the multiple reaction monitoring detection mode. The method was validated with high recoveries from 96.1% to 103.5%, good precision with interday relative standard deviations less than or equal to 7.3%, intraday relative standard deviations ≤2.64%, low limits of detection from 1.0 to 18?µg L^–1, and low limits of quantitation in the range from 3.0 to 61?µg L^–1. The application of this UHPLC-QqQ-MS/MS method to the citrus extracts of three cultivars showed that mandarin fruits contained the highest total amounts of the 11 analytes, followed by tangelos and oranges. This study provides a reliable and quantitative method that can be used for the development of functional products and quality evaluation of citrus fruits.