Determination of indole-3-acetic acid and indole-3-butyric acid in mung bean sprouts using high performance liquid chromatography with immobilized Ru(bpy)3-KMnO4 chemiluminescence detection

A novel method for determination of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) in an extract from mung bean sprouts using high performance liquid chromatography (HPLC) with chemiluminescence (CL) detection is described. The method is based on the CL reaction of auxin (indole-3-acetic acid and indole-3-butyric acid) with acidic potassium permanganate (KMnO₄) and tris(2,2′-bipyridyl)ruthenium(II), which was immobilized on the cationic ion-exchange resin. The chromatographic separation was performed on a Nucleosil RP-C18 column (i.d.: 250 mm × 4.6 mm, particle size: 5 μm, pore size: 100) with an isocratic mobile phase consisting of methanol-water-acetic acid (45:55:1, v/v/v). At a flow rate of 1.0 mL min⁻¹, the total run time was 20 min. Under the optimal conditions, the linear ranges were 5.0 × 10⁻⁸ to 5.0 × 10⁻⁶ g mL⁻¹ and 5.0 × 10⁻⁷ to 1.0 × 10⁻⁵ g mL⁻¹ for IAA and IBA, respectively. The detection limits were 2.0 × 10⁻⁸ g mL⁻¹ and 2.0 × 10⁻⁷ g mL⁻¹ for IAA and IBA, respectively. The relative standard deviation (RSD) of intra-day were 3.1% and 2.3% (n = 11) for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA; The relative standard deviations of inter-day precision were 6.9% and 4.9% for 2 × 10⁻⁶ g mL⁻¹ IAA and 2 × 10⁻⁶ g mL⁻¹ IBA. The proposed method had been successfully applied to the determination of auxin in mung bean sprouts.     

Polydopamine-based permanent coating capillary electrochromatography for auxin determination

A novel, simple, and economical method for the preparation of open-tubular capillary column using polydopamine coating was reported for the first time. After the capillary was filled with dopamine solution for 20h, polydopamine was formed and deposited on the inner wall of capillary as permanent coating via the oxidation of dopamine by the oxygen dissolved in the solution. Moreover, the electroosmotic flow of the coated capillaries was measured to be dependent on the repetitive coating times. The performance of the polydopamine-coated capillary electrochromatography was validated by the analysis of four auxins, indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (dCPAA), indole-3-acetic acid (IAA), and phenoxyacetic acid (PAA). The precisions (RSD, n=5) were in the range of 1.6-2.4% for migration time, 4.0-6.5% for peak area response, and 3.6-4.7% for peak height response for the four auxins at 1microgmL(-1) level. The detection limits were 0.185, 0.172, 0.177, and 0.259microg/mL for IBA, dCPAA, IAA, and PAA, respectively. The method was successfully used to the determination of IAA in the culture media of IAA-producing bacteria.     

Diamino moiety functionalized silica nanoparticles as pseudostationary phase in capillary electrochromatography separation of plant auxins

A novel and simple method for the preparation of silica nanoparticles having surface-functionalized diamino moiety (dASNPs) was reported in our paper and characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, and thermogravimetry techniques. To test this method practically, in this contribution we describe the enhanced separation of four plant auxins - indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (dCPAA), and 2-(1-naphthyl) acetic acid (NAA) - by capillary electrochromatography using diamino moiety functionalized silica nanoparticles as pseudostationary phase (PSP) in the running buffer. The effect of pH, buffer concentration, and diamino moiety functionalized silica nanoparticles concentration on the selectivity of separation was investigated. A combination of the nanoparticles and running buffer reversed the electroosmotic direction making possible the rapid and efficient separation of the auxins from the auxins migrated in the same direction with the EOF under optimum experimental conditions. A good resolution of four auxins was obtained within 5.5 min under optimum experimental conditions. The precision (RSD, n = 5) was in the range of 0.72-0.91% and 1.89-2.23% for migration time and peak area response, respectively. The detection limits were 0.48, 0.44, 0.46, and 0.42 μM for NAA, IBA, IAA, and dCPAA, respectively. Furthermore, the method was successfully tested for the determination of IAA in the grapes.     

Isolation of novel indole-3-acetic acid conjugates by immunoaffinity extraction

An analytical protocol for the isolation and quantification of indole-3-acetic acid (IAA) and its amino acid conjugates was developed. IAA is an important phytohormone and formation of its conjugates plays a crucial role in regulating IAA levels in plants. The developed protocol combines a highly specific immunoaffinity extraction with a sensitive and selective LC-MS/MS analysis. By using internal standards for each of the studied compounds, IAA and seven amino acid conjugates were analyzed in quantities of fresh plant material as low as 30 mg. In seeds of Helleborus niger, physiological levels of these compounds were found to range from 7.5 nmol g⁻¹ fresh weight (IAA) to 0.44 pmol g⁻¹ fresh weight (conjugate with Ala). To our knowledge, the identification of IAA conjugates with Gly, Phe and Val from higher plants is reported here for the first time.     

液相色谱-串联质谱法测定水稻中生长素及其氨基酸结合物

建立了同时测定水稻中吲哚-3-丁酸(IBA)、吲哚-3-乙酸(IAA)及其7种氨基酸结合物的液相色谱-串联质谱( HPLC - MS/MS)检测方法.样品在4℃下于80％甲醇中浸提12 h后,经混合阴离子交换反相固相萃取(MAX)净化,以5 mmol/L的甲酸铵溶液和甲醇为流动相,在C18柱上进行液相色谱分离,电喷雾正...     

Multi-walled carbon nanotube as a solid phase extraction adsorbent for analysis of indole-3-butyric acid and 1-naphthylacetic acid in plant samples

In this work,a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples.Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube(MWCNT) was chosen as the adsorbent for the extraction of auxins from plant samples.In this study,two important auxins were selected as model analytes,namely indole-3-butyric acid(IRA) and 1-naphthylacetic acid(NAA).They could be extracted and concentrated due to theirπ-πstacking interactions with MWCNT.Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment.Factors that may affect the enrichment efficiency were investigated and optimized.Comparative studies showed that MWCNT was superior to C18 for the extraction of the two analytes.Validation experiments showed that the optimized method had good linearity(0.9998 and 0.9960),high recovery(81.4%-85.4%),and low detection limits(0.0030 mg/L and 0.0012 mg/L).The results indicated that the novel method had advantages of convenience,good sensitivity,high efficiency, and it was feasible for the determination of auxins in plant samples.     

Development of sample preparation method for auxin analysis in plants by vacuum microwave-assisted extraction combined with molecularly imprinted clean-up procedure

A novel sample preparation method for auxin analysis in plant samples was developed by vacuum microwave-assisted extraction (VMAE) followed by molecularly imprinted clean-up procedure. The method was based on two steps. In the first one, conventional solvent extraction was replaced by VMAE for extraction of auxins from plant tissues. This step provided efficient extraction of 3-indole acetic acid (IAA) from plant with dramatically decreased extraction time, furthermore prevented auxins from degradation by creating a reduced oxygen environment under vacuum condition. In the second step, the raw extract of VMAE was further subjected to a clean-up procedure by magnetic molecularly imprinted polymer (MIP) beads. Owing to the high molecular recognition ability of the magnetic MIP beads for IAA and 3-indole-butyric acid (IBA), the two target auxins in plants can be selectively enriched and the interfering substance can be eliminated by dealing with a magnetic separation procedure. Both the VMAE and the molecularly imprinted clean-up conditions were investigated. The proposed sample preparation method was coupled with high-performance liquid chromatogram and fluorescence detection for determination of IAA and IBA in peas and rice. The detection limits obtained for IAA and IBA were 0.47 and 1.6 ng/mL and the relative standard deviation were 2.3% and 2.1%, respectively. The IAA contents in pea seeds, pea embryo, pea roots and rice seeds were determined. The recoveries were ranged from 70.0% to 85.6%. The proposed method was also applied to investigate the developmental profiles of IAA concentration in pea seeds and rice seeds during seed germination.     

全自动在线固相萃取-液相色谱-串联质谱法同时检测水稻中6种内源性植物激素

建立了同时检测水稻中6种内源性植物激素脱落酸( Abscisic acid,ABA)、吲哚-3-乙酸( Indole-3-acetic acid, IAA)、水杨酸( Salicylic acid,SA)、茉莉酸( Jasmonic acid,JA)、吲哚-3-丙酸( Indole-3-propionic acid, IPA)和吲哚-3-丁酸( Indole-3-butyric acid,IBA)的全自动在线固相萃取-液相色谱-串联质谱方法。植物样品经过甲醇提取,采用C18固相萃取柱富集净化,流动相将待测物洗脱至C18分析色谱柱进行分离,最终使用串联四极杆质谱进行检测。方法的线性范围为8~320μg/L,相关系数为R2≥0.99;方法的检出限(S/N=3)范围为0.1~0.8μg/kg;实际样品中方法回收率范围为71.2%~126%,RSD<13%。应用本方法快速、准确地检测了水稻幼穗中多种内源性植物激素的含量,并与目前植物学领域内常用的检测方法进行了比较。同时,本方法对水稻受伤叶片的内源植物激素含量变化进行了定量分析,其含量随受伤时间的变化趋势与其生物背景的实验结果相吻合。     

A Comparative Study of Diamine-Modified and Amine-Modified Silica Nanoparticles as Pseudo-Stationary Phases for CE Separation

The use of silica nanoparticles with surface modification in different applications is a topic of growing interest. This article provides a systematic comparison of diamine-modified and amine-modified silica nanoparticles as pseudo-stationary phases (PSPs) in capillary electrophoresis. The different electrophoretic behavior of these PSPs was evaluated by analysis of four auxins, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (dCPAA), and 2-(1-naphthyl)acetic acid (NAA). As expected, fast separation of the auxins was achieved, because they migrate in the same direction as the electro-osmotic flow under the optimum experimental conditions. However, the two nanoparticles had different selectivity and efficiency in the separation of the auxins, which could be related to the primary and secondary amines in their structures. The results indicated that even slight structural changes of the functional groups of the nanoparticles have pronounced effect on the interactions between the pseudo-stationary phase and the analytes.     

Simultaneous determination of several phytohormones in natural coconut juice by hollow fiber-based liquid–liquid–liquid microextraction-high performance liquid chromatography

A simple, selective, sensitive and inexpensive method of hollow fiber-based liquid–liquid–liquid microextraction (HF-LLLME) combined with high performance liquid chromatography (HPLC)-ultraviolet (UV) detection was developed for the determination of four acidic phytohormones (salicylic acid (SA), indole-3-acetic acid (IAA), (±) abscisic acid (ABA) and (±) jasmonic acid (JA)) in natural coconut juice. To the best of our knowledge, this is the first report on the use of liquid phase microextraction (LPME) as a sample pretreatment technique for the simultaneous analysis of several phytohormones. Using phenetole to fill the pores of hollow fiber as the organic phase, 0.1 mol L⁻¹ NaOH solution in the lumen of hollow fiber as the acceptor phase and 1 mol L⁻¹ HCl as the donor phase, a simultaneous preconcentration of four target phytohormones was realized. The acceptor phase was finally withdrawn into the microsyringe and directly injected into HPLC for the separation and quantification of the target phytohormones. The factors affecting the extraction efficiency of four phytohormones by HF-LLLME were optimized with orthogonal design experiment, and the data was analyzed by Statistical Product and Service Solutions (SPSS) software. Under the optimized conditions, the enrichment factors for SA, IAA, ABA and JA were 243, 215, 52 and 48, with the detection limits (S/N = 3) of 4.6, 1.3, 0.9 ng mL⁻¹ and 8.8 μg mL⁻¹, respectively. The relative standard deviations (RSDs, n = 7) were 7.9, 4.9, 6.8% at 50 ng mL⁻¹ level for SA, IAA, ABA and 8.4% at 500 μg mL⁻¹ for JA, respectively. To evaluate the accuracy of the method, the developed method was applied for the simultaneous analysis of several phytohormones in five natural coconut juice samples, and the recoveries for the spiked samples were in the range of 88.3–119.1%.     

Preparation of magnetic indole-3-acetic acid imprinted polymer beads with 4-vinylpyridine and β-cyclodextrin as binary monomer via microwave heating initiated polymerization and their application to trace analysis of auxins in plant tissues

Auxin is a crucial phytohormone for precise control of growth and development of plants. Due to its low concentration in plant tissues which are rich in interfering substances, the accurate determination of auxins remains a challenge. In this paper, a new strategy for isolation and enrichment of auxins from plant tissues was obtained by the magnetic molecularly imprinted polymer (mag-MIP) beads, which were prepared by microwave heating initiated suspension polymerization using indole-3-acetic acid (IAA) as template. In order to obtain higher selective recognition cavities, an enhanced imprinting method based on binary functional monomers, 4-vinylpyridine (4-VP) and β-cyclodextrin (β-CD), was adopted for IAA imprinting. The morphological and magnetic characteristics of the mag-MIP beads were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and vibrating sample magnetometry. A majority of resultant beads were within the size range of 80-150μm. Porous surface morphology and good magnetic property were observed. Furthermore, the mag-MIP beads fabricated with 4-VP and β-CD as binary functional monomers exhibited improved recognition ability to IAA, as compared with the mag-MIP beads prepared with the individual monomer separately. Competitive rebinding experiment results revealed that the mag-MIP beads exhibited a higher specific recognition for the template than the non-imprinted polymer (mag-NIP) beads. An extraction method by mag-MIP beads coupled with high performance liquid chromatography (HPLC) was developed for determination of IAA and indole-3-butyric acid (IBA) in plant tissues. Linear ranges for IAA and IBA were in the range of 7.00-100.0μgL(-1) and 10.0-100.0μgL(-1), and the detection limits were 3.9 and 7.4μgL(-1), respectively. The analytical performance was also estimated by seedlings or immature embryos samples from three different plant tissues, pea, rice and wheat. Recoveries were in the range of 70.1-93.5%. The results show that the present imprinting method is a promising approach for preparation of selective adsorbents for sample preparation of auxin analysis in plant tissues.     

Rapid and sensitive detection of auxins and flavonoids in plant samples by high-performance liquid chromatography coupled with tandem mass spectrometry

Simultaneous determination of indole-3-acetic acid and methyl indole-3-acetic acid ester in small amounts of plant tissue is essential for elucidating their mutual transformation mechanism and the in vivo function of methyl indole-3-acetic acid ester. Rapid quantification of flavonoids in the same sample is important for clarifying their roles in the transport of auxins and other phytohormones. Herein, we describe a simple method for the simultaneous determination of indole-3-acetic acid and its methyl ester in the roots of the Arabidopsis thaliana seedlings and a protocol for the rapid extraction and quantification of quercetin and kaempferol in these seedlings. High-performance liquid chromatography coupled with electrospray ionization time-of-flight tandem mass spectrometry was used for the detection of all the compounds. Negative data for indole-3-acetic acid and positive data for methyl indole-3-acetic acid ester were collected in two successive files with a single injection of the extracted sample. Under optimized conditions, the limit of detection for the four compounds was 2 ng/mL for indole-3-acetic acid, 0.5 ng/mL for methyl indole-3-acetic acid ester, 5 ng/mL for quercetin, and 1 ng/mL for kaempferol, respectively. Because of the high sensitivity of the assay, only 2-10 mg of the plant material was required to obtain quantitative results.     

Dual-cloud point extraction as a preconcentration and clean-up technique for capillary electrophoresis speciation analysis of mercury

A novel dual-cloud point extraction (dCPE) technique is proposed in this paper for the sample pretreatment of capillary electrophoresis (CE) speciation analysis of mercury. In dCPE, cloud point was carried out twice in a sample pretreatment. First, four mercury species, methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) formed hydrophobic complexes with 1-(2-pyridylazo)-2-naphthol (PAN). After heating and centrifuging, the complexes were extracted into the formed Triton X-114 surfactant-rich phase. Instead of the direct injection or analysis, the surfactant-rich phase containing the four Hg species was treated with 150 microL 0.1% (m/v) l-cysteine aqueous solution. The four Hg species were then transferred back into aqueous phase by forming hydrophilic Hg-l-cysteine complexes. After dCPE, the aqueous phase containing the Hg-l-cysteine complexes was subjected into electrophoretic capillary for mercury speciation analysis. Because the concentration of Triton X-114 in the extract after dCPE was only around critical micelle concentration, the adsorption of surfactant on the capillary wall and its possible influence on the sample injection and separation in traditional CPE were eliminated. Plus, the hydrophobic interfering species were removed thoroughly by using dCPE resulted in significant improvement in analysis selectivity. Using 10 mL sample, 17, 15, 45, and 52 of preconcentration factors for EtHg, MeHg, PhHg, and Hg(II) were obtained. With CE separation and on-line UV detection, the detection limits were 45.2, 47.5, 4.1, and 10.0 microg L(-1) (as Hg) for EtHg, MeHg, PhHg, and Hg(II), respectively. As an analysis method, the present dCPE-CE with UV detection obtained similar detection limits as of some CE-inductively coupled plasma mass spectrometry (ICPMS) hyphenation technique, but with simple instrumental setup and obviously low costs. Its utilization for Hg speciation was validated by the analysis of the spiked natural water and tilapia muscle samples.     

Micelle-mediated cloud point extraction and spectrophotometric determination of rhodamine B using Triton X-100

A new micelle-mediated cloud point extraction method is described for sensitive and selective determination of trace amounts of rhodamine B by spectrophotometry. The method is based on the cloud point extraction of rhodamine B from aqueous solution using Triton X-100 in acidic media. The extracted surfactant rich phase is diluted with water and its absorbance is measured at 563 nm by a spectophotometer. The effects of different operating parameters such as concentration of surfactant and salt, temperature and pH on the cloud point extraction of rhodamine B were studied in details and a set of optimum conditions were obtained. Under optimum conditions a linear calibration graph in the range of 5-550 ng mL⁻¹ of rhodamine B in the initial solution with r = 0.9991 (n = 15) was obtained. Detection limit based on three times the standard deviation of the blank (3S_b) was 1.3 ng mL⁻¹ (n = 10) and the relative standard deviation (R.S.D.) for 50 and 350 ng mL⁻¹ of rhodamine B was 2.40 and 0.87% (n = 10), respectively. The method was applied for the determination of rhodamine B in soft pastel, hand washing liquid soap, matches tip and textile dyes mixture samples.     

Simultaneous determination of angiotensins II and 1-7 by capillary zone electrophoresis in plasma and urine from hypertensive rats

We describe the procedure developed for the simultaneous detection and quantification of angiotensin II and angiotensin-(1-7), by capillary zone electrophoresis with UV detection by photodiode-array, at a wavelength of 200 nm, in the plasma and urine from hypertensive rats. Optimal separation was achieved with a 100 mM boric acid + 3 mM tartaric acid + 10 fM gold (III) chloride electrolyte solution at pH 9.80. The applied voltage was 30 kV and the capillary temperature was kept constant at 20 °C. The method was over the concentration range of 0.01-500 pmol/mL. All determination coefficients were higher or equal to 0.9985. Limits of detection and quantification for angiotensin II were 0.0110 pmol/mL (S/N = 3) and 0.0195 pmol/mL (S/N = 5), respectively. While for angiotensin-(1-7), the limits were 0.0112 pmol/mL (S/N = 3) and 0.0193 pmol/mL (S/N = 5), respectively. The present method offers a time-saving way to simultaneous determination of angiotensin II and angiotensin-(1-7), since it can be completed in 10 min, compared to other methodologies reported in the literature for capillary electrophoresis and liquid chromatography, which require more than 1 h for analysis of complex matrices, such as plasma and urine. The procedure is illustrated by experiments that quantify simultaneously angiotensin II and angiotensin-(1-7) in plasma and urine from hypertensive and normotensive rats, with and without antihypertensive treatment. The levels of angiotensin II and angiotensin-(1-7) detected in the experimental model, resulted in a recovery of 99.00-106.01% and a reproducibility of less than 10%. The proposed analytical method is a use full tool for the simultaneous detection of angiotensin II and angiotensin-(1-7) implicated in vascular remodeling in pathologies such as hypertension.     

A disposable electrochemical sensor for the determination of indole-3-acetic acid based on poly(safranine T)-reduced graphene oxide nanocomposite

A disposable electrochemical sensor for the determination of indole-3-acetic acid (IAA) based on nanocomposites of reduced graphene oxide (rGO) and poly(safranine T) (PST) was reported. The sensor was prepared by coating a rGO film on a pre-anodized graphite electrode (AGE) through dipping-drying and electrodepositing a uniform PST layer on the rGO film. Scanning electron microscopic (SEM) and infrared spectroscopic (IR) characterizations indicated that PST-rGO formed a rough and crumpled composite film on AGE, which exhibited high sensitive response for the oxidation of IAA with 147-fold enhancement of the current signal compared with bare AGE. The voltammetric current has a good linear relationship with IAA concentration in the range 1.0 × 10⁻⁷-7.0 × 10⁻⁶ M, with a low detection limit of 5.0 × 10⁻⁸ M. This sensor has been applied to the determination of IAA in the extract samples of several plant leaves and the recoveries varied in the range of 97.71-103.43%.     

Simultaneous Determination of Phytohormones in Plant Extracts using SPME and HPLC

Solid-phase microextraction followed by HPLC was used for the determination of indole-3-acetic acid (IAA), abscisic acid (ABA), indole-3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) in plant samples. Parameters influencing performance, including pH, salinity, extraction time, fiber coating and temperature, were optimized. A Carbowax-coated fiber was chosen for determination due to much higher extraction efficiency compared to polyacrylate fibers. The dynamic ranges spanned over three orders of magnitude. The LOD/(LOQ) values of the target compounds in pure water were 0.149(0.497), 0.442(1.472), 0.121(0.403), 0.058(0.193) μg L⁻¹ for IAA, ABA, IBA and NAA respectively. The method was successfully applied to the analysis of xylem fluid from Musa basjoo stem obtaining recoveries of 98.85% (IAA), 94% (IBA) and 94.30% (NAA). The method was also successfully applied to the analysis of these four target compounds in the hyperaccumulating plant, Viola baoshanensis. The results matched quite well with ones obtained by solid phase extraction followed by HPLC. The method developed was superior when applied to liquid samples because matrix effects could be eliminated.     

Detection of albiflorin and paeoniflorin in Paeoniae Radix by reversed-phase high-performance liquid chromatography with pulsed amperometric detection

We have developed a reversed-phase high-performance liquid chromatography-pulsed amperometric detection (RP-HPLC-PAD) method for the detection of albiflorin and paeoniflorin in Paeoniae Radix and Wu-ji-san. Albiflorin and paeoniflorin were completely separated using 10% acetonitrile in 5 mM sodium phosphate buffer (pH 3.0) as an eluent and detected by PAD under alkaline conditions after using a post-column delivery system. The limit of detection (S/N = 3) and the limit of quantification (S/N = 10) were 0.10 and 0.35 ng for albiflorin, and 0.20 and 0.50 ng for paeoniflorin, respectively. The coefficients of linear regression were 0.9995 and 0.9999 for concentrations between 0.035 and 100 μg/mL. The intra- and inter-day precision (RSDs) was less than 3.56% in Paeoniae Radix and Wu-ji-san. The average recoveries from Paeoniae Radix and Wu-ji-san were 99.01–100.94% and 99.46–100.64%. This method shows higher selectivity than HPLC–UV method for analyzing albiflorin and paeoniflorin in Chinese medicinal preparation.     

Simultaneous determination of four plant hormones in bananas by molecularly imprinted solid-phase extraction coupled with high performance liquid chromatography

A highly selective molecularly imprinted solid-phase extraction (MISPE) combined with liquid chromatography-ultraviolet detection was developed for the simultaneous isolation and determination of four plant hormones including indole-3-acetic acid (IAA), indole-3-propionic acid (IPA), indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA) in banana samples. The new molecularly imprinted microspheres (MIMs) prepared by aqueous suspension polymerization using 3-hydroxy-2-naphthoic acid and 1-methylpiperazine as mimic templates performed with high selectivity and affinity for the four plant hormones, and applied as selective sorbents of solid-phase extraction could effectively eliminate the interferences of the banana matrix. Good linearity was obtained in a range of 0.04-4.00 μg g(-1) and the recoveries of the four plant hormones at three spiked levels ranged from 78.5 to 107.7% with the relative standard deviations (RSD) of less than 4.6%. The developed MISPE-HPLC protocol obviously improved the selectivity and eliminated the effect of template leakage on quantitative analysis, and could be applied for the determination of plant hormones in complicated biological samples.     

Quantitation of atorvastatin in human plasma using directly suspended acceptor droplet in liquid-liquid-liquid microextraction and high-performance liquid chromatography-ultraviolet detection

A simple and sensitive methodology based on liquid-liquid-liquid microextraction (LLLME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) has been successfully developed for the determination of atorvastatin (AT) in human plasma. AT was first extracted from 4.5 mL acidic aqueous sample (diluted plasma, donor phase, pH 1) at temperature 45 °C through 400 μL 1-octanol for 4.5 min, while being agitated by a stirring bar at 1250 rpm. Then, a 5.5 μL free suspended basic aqueous droplet (acceptor phase, pH 10) was delivered to the top-center position of the organic membrane. The mixture was stirred at 650 rpm for 7.5 min and the analyte was back-extracted into the droplet. Finally, the acceptor phase was taken into a microsyringe and injected directly into the HPLC. An enrichment factor of 187 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1-500 ng mL⁻¹ with regression coefficient corresponding to 0.996. Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.4 and 1 ng mL⁻¹, respectively. A reasonable relative recovery (91%) and satisfactory intra-assay (4.4-7.0%, n = 6) and inter-assay (4.9-7.7%, n = 8) precision illustrated good performance of the analytical procedure. This technique was eventually applied for the determination of AT in human plasma after oral administration of 40 mg single dose of drug. The protocol proved to be highly cost-effective and reliable for the screening purpose.