Column Solid-Phase Extraction with 2-Acetylmercaptophenyldiazoaminoazobenzene (AMPDAA) Impregnated Amberlite XAD-4 and Determination of Trace Heavy Metals in Natural Waters by Flame Atomic Absorption Spectrometry

A column solid-phase extraction (SPE) preconcentration method was developed for the determination of Cd, Co, Cu, Ni and Zn ions in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2-acetylmercaptophenyldiazoaminoazobenzene (AMPDAA) complexes on a short column of AMPDAA-XAD-4 resin from buffered sample solution and subsequent elution with hydrochloric acid plus sodium chloride. Important SPE parameters were optimized using model solutions. The loading half-time, t_1/2, for Cd, Co, Cu and Zn was found to be less than 5min, and for Ni the value was 12min. The detection limit for Cd, Co, Cu, Ni and Zn was 0.028, 0.064, 0.042, 0.023 and 0.16µgL^–1, respectively, and the quantification limit was 0.043, 0.11, 0.099, 0.044 and 0.29µgL^–1, respectively. The AMPDAA-XAD-4 resin has good selectivity for Cd, Co, Cu, Ni and Zn over several electrolytes, especially over earth alkaline metals with tolerance limits of 0.05molL^–1. The method was validated by analysing a standard reference material (GBW 08301), and it was found that the results agree with those quoted by the manufactures. The developed method was applied to the determination of trace metal ions in tap water and river water samples with satisfactory results.     

Determination of trace heavy metals in waters by flame atomic absorption spectrometry after preconcentration with 2,4-dinitrophenyldiazoaminoazobenzene on Amberlite XAD-2

A new column, solid-phase extraction (SPE), preconcentration method was developed for determination of Cd, Co, and Cu ions in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2,4-dinitrophenyldiazoaminoazobenzene (DNDAA) complex on a mini column of DNDAA-XAD-2 resin. The effects of pH, eluent type, eluent concentration, eluent volume, resin quantity, sample volume, sample flow rate, and matrix ions (Na, Ca, and Mg) were investigated on the recovery of the metals using model solutions. The detection limit for Cd, Co, and Cu was 0.062, 0.084, and 0.057 μg L⁻¹ and the quantification limit was 0.17, 0.24, and 0.12 μg L⁻¹ respectively. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was applied to the determination of trace metal ions in tap water, river water samples with satisfactory results.     

Selective solid phase extraction and preconcentration of trace mercury(II) with poly-allylthiourea packed columns

A new method for selective solid-phase extraction and preconcentration of trace mercury(II) from aqueous solution was developed by using poly-allylthiourea as a new extractant. The procedure is based on the retention of analyte in the form of thiourea complex on a mini column of polymer resin. The effects of pH, eluent type, eluent concentration, sample volume, sample flow rate, and foreign ions on the recovery of the analyte were investigated using model solutions. At optimal pH value, the extraction capacity of the new sorbent was 1.13 mmol g^?1. The adsorption behavior of mercury(II) on the sorbent can be described by a Langmuir adsorption isotherm equation. The method was validated by analyzing a certified reference material with the results being in agreement with those quoted by manufacturers. The method was applied to the determination of trace inorganic mercury(II) in natural water samples and vegetables with satisfactory results.     

Preparative separation and enrichment of four taxoids from Taxus chinensis needles extracts by macroporous resin column chromatography

An environment‐friendly method was established for the preparative separation and enrichment of four taxoids, namely 10‐deacetylbaccatin III (10‐DAB III), 7‐xylosyl‐10‐deacetyltaxol (7‐xyl‐10‐DAT), cephalomannine and paclitaxel from Taxus chinensis needles extracts. Characteristics of seven widely used macroporous resins for four taxoids were compared, AB‐8 resin offered better adsorption and desorption capacities than others. AB‐8 resin column chromatography was used to study the desorption process for four taxoids. The optimum parameters for desorption were 30% ethanol 5 RV for removing impurities, following 15 RV for 10‐DAB III, after the desorption of impurities with 35% ethanol 10 RV, 45% ethanol 30 RV for 7‐xyl‐10‐DAT, then 65% ethanol 10 RV for cephalomannine and paclitaxel, the flow rate was 6 RV/h. After separation on AB‐8 resin column chromatography, the contents of 10‐DAB III, 7‐xyl‐10‐DAT, cephalomannine and paclitaxel in the product reached 4.58, 13.17, 1.36 and 3.08%, respectively, which were 7.63‐, 3.68‐, 6.18‐ and 6.55‐fold to those in T. chinensis needles extracts. The recovery yields were 94.96, 77.32, 88.09 and 95.25%. In general, the AB‐8 resin column chromatography has the advantages of lower cost, high efficiency and simple procedure. Therefore, it may provide scientific references for the preparative separation and enrichment of taxoids from other T. species.     

Determination of paclitaxel and its analogues in the needles of Taxus species by using negative pressure cavitation extraction followed by HPLC‐MS‐MS

A new separation method, negative pressure cavitation (NPC) extraction followed by HPLC‐MS‐MS for the determination of paclitaxel and its analogues in the needles of Taxus species is described in this study. Compared with three conventional extraction methods, NPC is a more effective, economical, and facile method for the separation of nature compounds from herbal plants. In contrast to high‐temperature extraction, NPC at low temperature can minimize undesirable reactions such as thermal decomposition or degradation. In addition, the extraction mechanism of NPC was also illuminated. The effects of vacuum degree, extraction solvent, ratio of solid to liquid, time, and times extraction were studied and optimized. The optimum extraction conditions were as follows: vacuum degree –0.03 MPa, solvent 80% v/v alcohol, ratio of material to liquid 1:15 (g/mL), extraction time 60 min, extraction (×3). Using these conditions, the recoveries of 10‐deacetyl‐7‐xylosylpaclitaxel, 10‐deacetylpaclitaxel, cephalomannine, and paclitaxel were higher than 95.88, 95.82, 94.85, and 96.18%, respectively. The contents of paclitaxel, 10‐deacetyl‐7‐xylosylpaclitaxel, 10‐deacetylpaclitaxel, and cephalomannine for Taxus chinensis were 0.0053, 0.0467, 0.0132, and 0.0076%, and 0.0067, 0.0153, 0.0047, and 0.0064% for Taxus cuspidata, respectively. Furthermore, a comparison of SEM images observed the morphological changes of microstructures and cellular damage in yew needles.     

Spectrophotometric determination of lead in traditional Chinese medicines with dibromo<Emphasis Type="Italic">p</Emphasis>-methyl-acethylsulfonazo

A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-acethylsulfonazo (DBMASA) has been synthesized and purified. A method has been proposed for the spectrophotometric determination of lead with DBMASA in traditional Chinese medicines. The content of lead in the samples was low, so we used sulfhydryl cotton fiber (SCF) to separate and enrich trace Pb(II), which lead to a satisfactory result. In 0.25 M phosphoric acid medium, which greatly increased the selectivity, lead reacted with DBMASA to form a 1: 2 blue complex, having an intense absorption peak at 640 nm. Under the optimal conditions, Beer’s law is obeyed over the range 0.01–1.0 μg/mL of Pb(II) and the apparent molar absorptivity is 1.06 × 10⁵ L/mol cm. The detection limit and variation coefficient are found to be 2.1 ng/mL and 1.3%, respectively. The method has been applied to the determination of lead in traditional Chinese medicines with satisfactory results.     

Spectrophotometric determination of trace copper(II) in biological samples with 2,4-bis(4-phenylazophenylaminodiazo)phenol

A highly sensitive and selective chromogenic reagent 2,4-bis(4-phenylazophenylaminodiazo)phenol (BPPAAP) reacted with copper(II) to form a highly stable complex in the ethanolic solution at pH range of 9.0–12.0. The Cu(II)-BPPAAP complex showed maximum absorbance at 540 nm, with molar absorptivity being 1.86 × 10⁵ L/mol cm. Beer’s law was obeyed over the range 0–0.2 μg/100 mL of copper(II) and variation coefficient is found to be 2.4–4.8%. The detection and quantification limit of the method are 2.0 and 6.5 ng/mL, respectively. To eliminate the interference of foreign ions, a convenient and efficient method using a column packed with sulfhydryl dextrose gel as a solid-phase extractant was utilized with satifactory reults. The developed method has been successfully employed for the determination of copper(II) in the biological samples.     

Spectrophotometric determination of trace mercury(II) in cereals with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid

A simple and low cost method for the determination of mercury has been developed. The method was based upon the highly sensitive color reaction of mercury(II) ions with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid (BPPABSA). We found that in the presence of 2.0% Triton X-100, the reagent reacts with mercury to form a stable red complex in a borax buffer solution at pH 10.22. The formed complex shows an absorption maximum at 530 nm. The apparent molar absorptivity is 2.18 × 10⁵ L/mol cm. The content of mercury in the sample was low and some foreign ions might interfere with the determination of mercury(II), so we used sulfhydryl dextran gel (SDG) to separate and enrich trace mercury(II), which lead to a satisfactory result. Under the optimal conditions, Beer’s law is obeyed in the range of 0–15 μg/25 mL Hg²⁺, the detection limit and relative standard deviation are 0.86 ng/mL and 1.4–3.8%, respectively. The method has been applied to the determination of mercury in cereals with satisfactory results.     

Spectrophotometric determination of trace cadmium in vegetables with 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid

A new highly sensitive and selective chromogenic reagent, 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid (BPPABA) has been synthesized and applied to the determination of trace cadmium(II) in vegetables. The method is based on the color reaction between BPPABA and cadmium (II). In the presence of Triton X-100, cadmium(II) reacts with BPPABA in Na₂B₄O₇-NaOH buffer solution (pH 10.5), forming red complex with maximum absorption at 530 nm. Under the optimal conditions, Beer’s law is obeyed within 0–12 μg of cadmium within 25 mL of solution, and the apparent molar absorptive coefficient of the complex is 2.8 × 10⁵ L/mol cm. The detection limit and the relative standard deviation were found to be 0.92 μg/L and 1.0%, respectively. Interference of foreign ions was also investigated. Most of the metal ions are tolerated in considerable amounts except for Hg(II), Cu(II) and Ni(II). To eliminate the interference of foreign ions, metal ion imprinted polymer technique was utilized.