Optimized Dispersive Liquid–Liquid Microextraction and Determination of Sorbic Acid and Benzoic Acid in Beverage Samples by Gas Chromatography

A new rapid method for direct determination of trace levels of sorbic and benzoic acids was developed by dispersive liquid–liquid microextraction and gas chromatography with flame ionization detection. In the proposed approach, the separation procedure of sorbic and benzoic acids was performed on a general chromatographic column without any prior derivatization processes. Some effective parameters on the microextraction recovery were studied and optimized utilizing multilevel factorial and central composite experimental designs. The best concurrent extraction efficiency acquired using ethanol and chloroform as dispersive and extraction solvents. Central composite design (CCD) resulted in the optimized values of microextraction parameters as follows: 1.0 mL of dispersive and 0.1 mL of extraction solvents, ionic salt concentration of 50 g?L^?1 at pH 4. Under optimum conditions, the calibration curve was linear over the range 0.5–20 mg L^?1. Relative standard deviation was 11% and 13% for five repeated determinations for sorbic and benzoic acids, respectively. Limits of detection were acquired as 0.2 mg L^?1 for sorbic acid and 0.5 mg L^?1 for benzoic acid. The average recoveries were 31% and 39% for sorbic and benzoic acids, respectively. The method was successfully applied to the determination of sorbic and benzoic acids as preservatives in beverage samples.     

Automated Magnetic Solid-Phase Extraction for Synthetic Food Colorant Determination

A new automated magnetic solid-phase extraction (MSPE) method was developed and combined with high-performance liquid chromatography (HPLC) and spectrophotometry for off-line and on-line quantitative enrichment and determination of synthetic food colorants in food samples. Fe₃O₄-poly (ionic liquid) core-shell microspheres were prepared as a sorbent to quickly extract analytes from aqueous samples. The entire MSPE process, including extraction, separation, elution, and cleaning, was automated using common equipment. The main parameters affecting the performance of MSPE and the automated process, such as absorbent, sample pH, eluent, flow rate, elution time, etc., were investigated in detail. Under the optimum experimental conditions, the limits of detection ranged between 4.1 and 14 ng/mL by off-line HPLC and were 220 ng/mL for the determination of amaranth by on-line spectrophotometry, with excellent reproducibility (intra- and inter-day relative standard deviations were less than 3.2 %). The developed method was successfully applied to the determination of colorants in food samples.     

Characterization of nutritionally important phytoconstituents in bitter melon (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.) fruits by HPLC–DAD and GC–MS

Bitter melon (Momordica charantia L.) is the traditional vegetable used as medicinal food, in different parts of the world, including Korea and China. Little is known about its bioactive composition aside from its health-promoting properties. Therefore, the present work aimed to determine the content of carotenoids, tocopherols, folates and fatty acids in bitter melon fruits. Using HPLC–DAD, six major carotenoids were quantified in fruits; all-E-lutein was recorded in highest quantity, followed by all-E-β-carotene and α-carotene, with 79.5, 17.6 and 1.5 % of total carotenoids, respectively. A high content of α-tocopherol (42.93 μg/g FW) and total folate (0.724 µg/g FW) was also recorded in fruits using HPLC–DAD and microbiological assay, respectively. The total lipid content of 1.79 % was recorded in fresh fruits (FW). Using GC–MS, sixteen fatty acids were identified in lipid fraction; α-linolenic acid (ALA; C18:3) was found in highest quantity (44.33 %) followed by palmitic acid (C16:0) (29.64 %), and linoleic acid (C18:2) (10.32 %). Melon fruits contain a low amount of saturated fatty acid and high-mono and polyunsaturated fatty acids, in the form of ALA. Knowledge of bioactive composition in bitter melon fruit will be useful for proper diet recommendations and also for nutrient database updating.     

Determination of glyoxal and methylglyoxal in Thai fish sauce and their changes during storage test

Recently more research attention has been given to glyoxal (GO) and methylglyoxal (MG) in relevant to their role in biological and food systems. In this study, pre-column derivatization using 5,6-diamino-2,4-hydroxypyrimidine sulfate (DDP) for fluorescence detection on HPLC was optimized for fish sauce matrix. DDP–GO and DDP–MG derivatives detected had fluorimetric wavelengths coincided with the spectral characteristics reported. Standard addition experiment showed that the detection method was free from interference and matrix effect with good recovery (90–115 %) and precision (less than 8 % RSD at 88–242 ng/mL). Limit of detection for GO and MG were 11.7 and 10.9 ng/mL respectively. Prolonged storage of the fish sauce sample under 4, 25, 40, and 60 °C showed that GO increased at 40 and 60 °C while MG increased at 25, 40, and 60 °C. The results also suggested possible role of molecular oxygen in these formations. Together with GO and MO, browning development and Strecker aldehydes were also monitored.     

The UPLC–ESI–QqQLIT–MS/MS method for quantitative determination of phytochemicals in ethanolic extracts of different parts of eight Ficus species: Development and validation

Ficus and validation of the ultra performance liquid chromatography–electrospray ionization hybrid triple quadrupole–linear ion trap–tandem mass spectrometry (UPLC–ESI–QqQ_LIT–MS/MS) method in a multiple-reaction monitoring (MRM) mode for the quantitative determination of 19 phytochemicals. The chromatographic separation of targeted phytochemicals was performed using the Waters ACQUITY UPLC BEH? C18 column (1.7 μm, 2.1 mm × 50 mm) with 0.1% formic acid with water and acetonitrile as a mobile phase at a flow rate of 0.25 mL/min. The validation parameters showed the overall recoveries from 95.78?101.44% (RSD ≤ 3.25%), precision (intra-day: RSD ≤ 2.96%; inter-day: RSD ≤ 2.89%), linearity (R² ≥ 0.9982), limit of detection (8.60 × 10^–10?2.18 × 10^–6 mg/mL), and the limit of quantitation (2.60 × 10^–9–6.63 × 10^–6 mg/mL) in the concentration range from 0.5 to 1000 × 10^–6 mg/mL. This method was successfully applied in ethanolic extracts of different parts (fruits, leaves, and barks) of selected eight Ficus species. Quinic acid was predominant followed by rutin and chlorogenic acid among the studied nineteen phytochemicals. Ficus benjamina showed the maximum total content in fruits and leaves. The UPLC–ESI–QqQ_LIT–MS/MS method combined with principal component analysis (PCA) was successfully used for Ficus species discrimination on the basis of the contents of 15 compounds. The UPLC–ESI–QqQ_LIT–MS/MS method combined with PCA could be used for quality control.     

Characteristics of fat,and saponin and tannin contents of 11 varieties of rambutan (Nephelium lappaceum L.) seed

Rambutan seed is discarded during fruit processing. However, the seed contains a considerable amount of crude fat. Hence, the objective of this study was to determine two anti-nutritional constituents, namely saponin and tannin, and to characterize the fat of the seeds of 11 varieties of rambutan fruit. Results showed that the range of crude fat content is fairly narrow (36.13–39.13 g/100 g dried seeds). The iodine value and free fatty acid content of the fat were 38.50–50.61 g I₂/100 g fat and 0.99–2.18% as oleic acid, respectively. Oleic (33.35–46.64%) and arachidic (26.03–33.27%) acids were the main fatty acids in the fat. HPLC analysis showed that the fat comprised mainly five unknown triacylglycerols (83.94–95.33%). The melting and crystallization curves showed that the fat exhibited four to nine non-distinct peaks. The complete melting and crystallization onset temperatures of the fat were 24.8–50.6°C and 24.1–39.4°C, respectively, while the melting and crystallization enthalpies of the fat ranged from 71.2 to 141.7 J/g and from 60.4 to 88.9 J/g, respectively. At 0°C, the solid fat index of the fat ranged between 87.4% and 91.6% and the fats of some varieties melted completely at human body temperature. The saponin and tannin contents of the seed were 14.27–18.96 mg soya saponin/100 g and 4.40–26.68 mg catechin equivalent/100 g, respectively. Findings showed that rambutan seed fat has potential to be used in various sectors of food industry.     

HPLC Determination of Spectinomycin in Feed Premixes and Dosage Forms Using 1-Naphthyl Isocyanate Precolumn Derivatization with UV Detection

A new, simple, and sensitive HPLC method was developed for the determination of spectinomycin hydrochloride in dosage forms and feed premixes through derivatization with 1-naphthyl isocyanate. The separation was achieved on a C₁₈ column using a mobile phase consisting of acetonitrile/water (50:50 v/v, pH 3.2) in a flow rate of 1 mL/min with UV detection at 230 nm. The factors influencing the derivatization reaction yields were carefully studied and optimized. The method was linear over the concentration range of 10–100 μg/mL with a limit of detection 0.25 μg/mL and limit of quantitation 1.75 μg/mL. The developed method was successfully applied to the analysis the drug in the commercial dosage forms and spiked feed premix samples; the average recoveries were 99.79 and 99.56, respectively. The analytical performance of the method was fully validated and the results were satisfactory. A proposal of the reaction pathway was presented.     

Simultaneous Determination of Quercetin,Rutin, Naringin,and Naringenin in Different Fruits by Capillary Zone Electrophoresis

A fast and reliable capillary zone electrophoretic (CZE) method has been developed for the simultaneous determination of four fruit flavonoids using photodiode array (PDA) detector. The effects of CE parameters including concentration and pH of the running buffer, voltage, and injection time were optimized. Under the optimized conditions, all flavonoids were well determined in a 10 mM borate buffer of pH 8.5 within 10 min at an applied voltage of 25 kV. Naringin, naringenin, and quercetin were found to have linear response in the range of 3.12–200 μg/mL whereas rutin’s response was linear from 6.25 to 200 μg/mL. LOD was found to be 0.406, 0.314, 0.582, and 0.333 μg/mL and LOQ 1.355, 1.046, 1.941, and 1.11, respectively. Relative standard deviations (RSD) were found to be less than 3 % for both migration time and peak height which shows long-term stability and good reproducibility of the developed method. The method was successfully applied for the simultaneous determination of flavonoids from various fruit juice samples.     

RP-HPLC法测定东北地区6 种红树莓果实中有机酸组成

建立一种反相高效液相色谱法分离和测定6 种红树莓果实中草酸、酒石酸、柠檬酸、DL-苹果酸和乳酸5 种有机酸的方法。色谱条件为：采用SinoChrom DS-BP C18色谱柱（150 mm×4.6 mm,5 μm）,流动相为甲醇-0.01 mol/L KH2PO4溶液（pH 2.60,97∶3,V/V）,流速0.6 mL/min,柱温30 ℃,检测波长210 nm。结果表明：在此条件下5 种有机酸都被有效地分离,各种有机酸的质量浓度与峰面积在测定范围内呈良好的线性关系,标准曲线相关系数在0.999 3～0.999 9之间;精密度实验相对标准偏差在0.20%～1.53%（n=5）范围内;回收率为98.83%～105.42%,相对标准偏差为0.06%～1.00%。测得6 种红树莓果实中有机酸以柠檬酸为主,含量为1 058.41～1 825.45 mg/100 g,草酸、乳酸、DL-苹果酸含量较低,未检测到酒石酸。该方法简单、高效、准确、重复性好,可用于红树莓果实中有机酸的分离测定。     

Characterization of nutritionally important phytoconstituents in minimally processed ready-to-eat baby-leaf vegetables using HPLC–DAD and GC–MS

Ready-to-eat baby-leaf vegetable market has been rapidly growing and offering to consumers convenient and appealing products, rich in health beneficial bioactive compounds. In the present study, the composition of carotenoids, tocopherols, and fatty acids were analyzed in seven baby-leaf vegetables using HPLC–DAD and GC–MS. Among the vegetables, the maximum amount (μg/g FW) of All-E-violaxanthin (42.77), 9′-Z-neoxanthin (22.13), All-E-lutein (69.67), All-E-β-carotene (60.18), total carotenoids (195.21), γ-tocopherol (19.68) and total tocopherol (47.68) were found in Batavian lettuce (Lactuca sativa L. var. Acephala). In all the studied baby-leaf vegetables, α-linolenic acid (ALA, C18:3) was found in highest quantity (44.73–54.39 %) followed by palmitic acid (C16:0) (13.02–19.49 %), and linoleic acid (C18:2) (8.25–21.54 %). Significantly high amount polyunsaturated fatty acids (PUFA) were recorded in Batavian lettuce (74.33 %) and red Romaine (72.72 %), compared to other studied vegetables. In view of health benefits, baby-leaf vegetables contain a low amount of saturated fatty acids and high-mono and PUFA, which can enhance the health benefits of these vegetables. Carotenoids in most of these studied baby-leaf vegetables can be classified as very high. Knowledge of carotenoid, tocopherols and fatty acids composition in different baby-leaf vegetables will be useful to nutritional experts for selection of nutrient-dense plants for food fortification and proper diet recommendation. To our knowledge, this is the first report on fatty acids composition from baby-leaf vegetables.     

A Preconcentration Procedure for Determination of Ultra-Trace Mercury (II) in Environmental Samples Employing Continuous-Flow Cold Vapor Atomic Absorption Spectrometry

New functionalized magnetic nanoparticles as solid-phase sorbent were prepared and investigated for extraction of ultra-trace amounts of mercury from environmental samples. The Fe₃O₄ magnetic nanoparticles functionalized with dithizone were characterized by Fourier transform infrared spectrometer. X-ray diffraction and scanning electron microscopy confirmed the size of nanoparticles. Effects of several factors on the extraction procedure were investigated. The optimized conditions were established to be 80 mg of polymer, 8.5 for solution pH, 5 min for adsorption time, 5 min for desorption time, 2 mL for HCl (0.1 mol L^?1)/ thiourea 0.05 % as the eluent, 500 mL for breakthrough volume, and without addition of salt. Under the optimal conditions, the limit of detection, maximum capacity, and preconcentration factor were 0.05 ng mL^?1, 0.557 mmol g^?1, and 250, respectively. Limit of quantification was in the range of 0.2–2 ng mL^?1 for various matrices. Accuracy and precision of the method were about ±2.0 and below 11.1 %, respectively. Finally, the present method has been successfully applied to mercury determination in table salt, green tea, vegetables, toothpaste, and water samples. The mercury content found in the real samples was from 0.6 to 15.74 ng mL^?1 without addition of mercury.     

A High-Performance Liquid Chromatographic Method for Simultaneous Determination of 21 Free Amino Acids in Tea

Free amino acids are closely related to the savory taste and beneficial effects of tea, and high-performance liquid chromatography (HPLC) is the most widespread analytical approach for simultaneous determination of free amino acids in tea. However, the reported HPLC methods have drawbacks such as long run times, low resolution, or poor efficiency. In this study, a special amino acid analysis column was used to separate and verify 21 amino acids including l-theanine, the predominant amino acid in tea. The mobile phases, including the sodium acetate and acetic acid concentration in buffer B, and the pH and concentration of sodium acetate in buffer A were optimized. The elution gradients were optimized using DryLab 2000 Plus software. In this way, an online o-phthaldialdehyde precolumn derivatization HPLC-fluorescence detection method was developed for simultaneous determination of 21 amino acids. Comparison to other HPLC methods for simultaneous determination of free amino acids in tea showed that our method is easy (automated derivatization), quick (30 min), inexpensive, and green (using a minimum of solution). It has good resolution (≥1.8) and high selectivity (interpark time?≥?0.5 min). Free amino acids in six tea samples were analyzed. This work provides an HPLC method to simultaneously measure 21 amino acids in tea and potential in other food products.     

A Simple and Sensitive Nanocatalytic Fluorescence Method for the Determination of Folic Acid in Foods Using Fe3O4 Nanoparticle-K2S2O8 System

In pH 2.72 HCl-NaAc buffer solution at room temperature and in the presence of a nanocatalyst of Fe₃O₄ nanoparticles, potassium persulfate rapidly oxidized folic acid (FA) to form a product with strong fluorescence at 446 nm. The analytical conditions were considered, and a simple, rapid, and accurate fluorescence method was proposed for the determination of 0.007–8.0 mg/L FA, with a detection limit of 2.0 ng/mL FA. This method was applied to the analysis of FA in a real sample with satisfactory results that agree with the HPLC results.     

Determination of Zearalanol and Its Analog Zearalanone in Muscle Tissues by Amplified Luminescent Proximity Homogeneous Assay (AlphaLISA)

A homogenous light-induced chemiluminescence immunoassay (AlphaLISA) method was established for the determination of residues of zearalanol and its analog zearalanone in muscle tissue samples. AlphaLISA is a bead-based proximity assay. When donor and acceptor beads proximity, a cascade of chemical reactions begin. The end result is a greatly amplified signal that contributes to the detection sensitivity down to the attomole level. Compared with other methods, the AlphaLISA has characteristics of homogeneity, being free of cleaning, high sensitivity. The method showed a linear relationship in the range of 0.01–4 ng/mL (R ²?>?0.99); the sensitivity of the assay was 0.066 ng/mL. Cross-reactivity rate of zearalanol was 100 % and zearalanone was 82.1 %, and other compounds were not more than 40 %. The average recovery rates of Zearalanol at spiked levels of 1–4 ng/mL were 96.3 to 105.0 and 91.7 to 100.5 % for pork and bovine muscles; the intra-day precision ranged from 2.6 to 9.8 %, and the inter-day precision ranged from 8.7 to 17.5 %. These results indicated that the proposed method was successfully applied in the analysis of zearalanol and its analog zearalanone in muscle tissues.     

Simultaneous Determination of 13-HODE, 9,10-DHODE,and 9,10,13-THODE in Cured Meat Products by LC-MS/MS

A method was developed for simultaneous determination of 13-hydroxyoctadecadienoic acid (13-HODE), 9,10-dihydroxyoctadecenoic acid (9,10-DHODE), and 9,10,13-trihydroxyoctadecenoic acid (9,10,13-THODE) in cured meat products. The analytes, extracted with methanol and cleaned by solid phase extraction, were separated on an XBridge C18 column (150*4.6 mm, 5 μm) with a mobile phase consisting of 0.1 % formic acid in water and acetonitrile, followed by detection with an electrospray ionization tandem mass spectrometry in negative-ion mode. The proposed method produced satisfactory reliability, sensitivity, and accuracy. Recoveries of the three analytes within the spiking range of 0.5–40 μg/g were 80.0–97.8 %, and limits of quantification of 13-HODE, 9,10-DHODE, and 9,10,13-THODE were 0.4, 0.025, and 0.05 μg/g, respectively. The method was successfully employed to detect the three fatty acids with hydroxyl(s) in cured meat products. It was shown that all samples contained the three analytes simultaneously, with concentrations ranging 1.40–100.77 μg/g for 13-HODE, 0.13–1.82 μg/g for 9,10-DHODE, and 0.49–10.12 μg/g for 9,10,13-THODE, respectively. The analytical result also indicated there were isomers of analytes, and the real content of fatty acids with hydroxyl(s) from oxidation of LA might be much higher.     

A Comparative Study of the Ionization Modes in GC–MS Multi-residue Method for the Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Crayfish

A gas chromatography–mass spectrometry (GC–MS) multi-residue method with different ionization modes has been developed for the determination of 23 organochlorine pesticides and ten polychlorinated biphenyls (PCBs) in crayfish. The approach was based on an extraction with acetonitrile saturated by hexane (containing 0.1 % acetic acid), followed by a dispersed solid-phase extraction cleanup with primary secondary amine and octadecylsilane, and finally analyzed by GC–MS/MS operated in electron impact (EI) and positive chemical ionization (PCI), and GC–MS in negative chemical ionization (NCI), respectively. An isotope internal standard, DDT-D₈, was used for quantification. These three GC–MS procedures were validated and compared using crayfish samples fortified at three levels (5, 10 and 20 ng/g). Good linearity, accuracy, precision and sensitivity were achieved by all three ionization modes with recoveries in the range of 70 to 112 %, relative standard deviations (RSDs) below 10 % and limits of detection (LODs) in the range of 0.002 to 8 ng/g. Extremely high selectivity was obtained by both EI- and PCI-MS/MS, while PCI was more sensitive to compounds containing nitro and carbonyl groups, and EI was a better choice for dieldrin, endosulfan, and its metabolites. NCI-MS had the highest sensitivity but lower anti-interference ability and was not suitable for the determination of DDTs and PCBs. These three ionization modes can be used as complementary and alternative in routine GC–MS analysis of organochlorine pesticides and polychlorinated biphenyls in food.     

Amaranth seed varieties. A chemometric approach

In this work, the amino acid and fatty acid profiles were determined in two advanced lines of amaranth seeds: Amaranthus hypochondriacus × Amaranthus cruentus AH17a and Amaranthus cruentus AcG6/17a; as well as in two new varieties: Amaranthus cruentus var. Candil and Amaranthus hypochondriacus var. Dorado. The following contents were found: protein (18.76–26.00 %), dietary fiber (15.91–17.80 %) and total lipids (10.62–11.44 %), high concentrations of unsaturated fatty acids (77.80–82 % of total lipids), linoleic acid (41.94–55.50 % of total lipids) and lysine (47.3–68.6 mg g^?1 of protein) were also found. Based on these composition data, chemometric tools were used to classify these new varieties and lines by unsupervised methods—principal component analysis and cluster analysis; as well as by supervised methods—sequential discriminant analysis (DA) and partial least squares DA. It was possible to correctly classify all varieties and lines using 11 variables. In conclusion, it was found that new varieties and advanced lines of amaranth show proper nutritional quality, which reveals the potential of this genus as agro-food. Also, a complete chemometric assessment allowed us to distinguish between these new varieties and lines.     

Development of a Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assay for the Analysis of Diclazuril in Chicken Tissues

A highly sensitive and specific monoclonal antibody (Mab) against diclazuril was produced. The hapten with diclazuril coupled to diazotised 4-aminobenzoic acid was synthesized and conjugated to bovine serum albumin by the active ester method to form an immunogen for antibody generation. A novel diclazuril carboxymethyloxime derivative used in an ovalbumin conjugate was applied as a heterologous coating antigen and was expected to improve the immunoassay sensitivity. A sensitive and simple indirect competitive enzyme-linked immunosorbent assay (icELISA) based on the Mab for the determination of diclazuril was developed. Under the optimized conditions, the icELISA for diclazuril showed a half maximum inhibition concentration (IC₅₀) value of 1.8 ng/mL, with limit of detection of 0.24 ng/mL and negligible cross-reactivities with other coccidiostat compounds including toltrazuril, robenidine, nicarbazin, halofuginone, amprolium, monensin, and maduramycin. The icELISA was successfully applied to diclazuril residue analysis in spiked chicken tissues. The average recoveries, intra-assay, and inter-assay coefficients of variation were in a range from 77.6 to 103.7 %, 3.7 to 13.0 %, and 5.6 to 18.3 %, respectively.     

Indirect Competitive Enzyme-Linked Immunosorbent Assay for the Detection of Dibutyl Phthalate in White Wine,Compared With GC-MS

Plasticizer has attracted more and more attention in China for the past 3 years, especially in Taiwan district. In this study, an indirect competitive enzyme-linked immunosorbent assay (icELISA) has been developed for the determination of a plasticizer dibutyl phthalate (DBP) in white wine. Dibutyl 4-aminophthalate coupled with OVA was synthesized as an immunogen to produce polyclonal antibodies against DBP. The antibody exhibited negligible cross-reactivity with other related compounds. The influence of several physicochemical parameters, such as coating procedure, organic solvent, competitive reaction time, and pH was investigated. The limit of detection was 64.5 ng/mL, which was sensitive enough for a screening assay. The linear range was 64.5–1,606.2 ng/mL with a correlation coefficient (R ²) of 0.996. The method was successfully applied to the determination of DBP in white wine. Recoveries were between 83.1 and 101.7 %. This immunoassay was highly specific, sensitive, rapid, simple, and suitable for DBP monitoring. The results obtained were compared with those obtained using gas chromatography–mass spectrometry (GC-MS), and a satisfied correlation coefficient of 0.928 was obtained by real sample detection.     

Dispersive Micro Solid-Phase Extraction with Graphene Oxide for the Determination of Phenolic Compounds in Dietary Supplements by Ultra High Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry

This report described the use of graphite oxide (GO) as sorbent in dispersive micro solid-phase extraction (DMSPE), together with ultra high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS), for the determination of phenolic compounds (protocatechuic aldehyde, caffeic acid, and rosmarinic acid) in dietary supplements. The extraction conditions such as sample agitation, agitation time, sorbent amount, and type and volume of the eluent were optimized. The results showed that GO-assisted DMSPE exhibited higher enrichment factors for tested solutes as compared to the normal extraction. Under the most favorable conditions, good limits of detection (0.07–0.21 ng/mL) and repeatability of extraction (RSDs below 5.6 %, n?=?5) were obtained. The developed method was applied to determine phenolic analytes with satisfactory recoveries, which were 90.1–96.4 % for Danshen and 85.5–97.6 % for Danshen injection, respectively.