A simple and sensitive cloud point extraction method for the preconcentration of ultra-trace amounts of nickel as a prior step to its determination by graphite furnace atomic absorption spectrometry was proposed. It is based on the reaction of nickel with 2-(5-bromo-2-pyridylazo)-5-dimethylaminoaniline (5-Br-PADMA) in HAc–NaAc buffer media and mixed micelle-mediated extraction of the complex using the anionic surfactant sodium dodecyl sulfate sodium (SDS) and non-ionic surfactant (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene (Triton X-114). The optimal reaction and extraction conditions such as pH, concentration of 5-Br-PADMA, SDS and Triton X-114, equilibrium temperature, incubation, and centrifuge time were evaluated and optimized. Under the optimal conditions, the calibration graph was linear over the range 0.1–5.5 ng/mL of nickel with a correlation coefficient of 0.9942. The detection limit obtained was 0.031 ng/mL, and the relative standard deviation was 2.1% for nickel (c = 2 ng/mL, n = 6). The proposed method was successfully applied to the determination of nickel in water samples.

Water-soluble polysaccharide from tea plant flower (TFP) was screened for its biological and biophysical effects. TFP-1, one of the major constituents, yielded after removing the proteins and purification by Sephadex G-100 (Sigma-Aldrich Pty Ltd., Castle Hill, Australia). It was subjected to chemical identification and the result indicated its average molecular weight (132 kDa) and its formation which consisted of xylose, glucose, arabinose and galactose with the molar ratio of 1.0: 2.9: 4.6: 21.8. Presence of TFP-1 displayed reactive oxygen radicals scavenging activity and it showed dose-dependent antioxidant activity by comparing with three commonly used antioxidants. The research showed that administration of TFP-1 for 28d continuously was found not only to be protective on liver lipid peroxidation induced by bromobenzene in mice through increasing the activity of superoxidase dismutase, total antioxidant capacity, but also markedly to attenuate the enhancement of malondialdehyde content in dose-dependent manner. Altogether, these results suggest that TFP-1 could be considered as a potential antioxidant. PRACTICAL APPLICATIONS The resources of tea (Camellia sinesis) flower is abundant in China with low utilization, as tea farmers buried their trim and had little utilization of them. Tea flower is rich in proteins, tea polysaccharides, amino acids, vitamins and other active substances, and its toxicological safety and pesticide residues in volume come up to European standards. At present, commonly low-grade tea is preferred to tea flowers to extract the tea polysaccharide. To make full use of the abandoned tea flower resource to extract polysaccharides can greatly reduce the cost of tea products. Moreover, the research on antioxidant activity of tea flower polysaccharide provides a scientific basis for tea flower as a cheap and effective antioxidant product, additives in food and cosmetic. Secondly, the use of tea flower can also reduce the consumption of tea nutrient and make it turn to vegetative growth, which can improve yield and quality of tea.

A novel method is reported for the determination of cobalt using thermal lens spectrometry with cloud point extraction using 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminoaniline as the chelating agent and octylphenoxypolyethoxyethanol (Triton X-114) as the extractant. Optimized conditions for cloud point extraction included a pH of 5.0 in acetic acid/sodium acetate buffer, 4.0 × 10⁻⁶ molar of the chelating agent, 0.08 percent Triton X-114 (w/v), and equilibration for twenty minutes at 60 degrees Celsius. After separation, the surfactant-rich phase was dissolved in 0.45 milliliter of 2 molar HCl-ethanol for determination. A single mode helium:neon laser at 632.8 nanometers was used for excitation and as the probe. Using the optimized conditions, a linear calibration curve was obtained from 0.2 to 4 nanograms per milliliter cobalt and the limit of detection was 0.02 nanogram per milliliter. The sensitivity was enhanced by approximately 500-fold compared to conventional spectrophotometry. The method was used for the determination of cobalt in water.

A new method for the determination of ultra-trace cobalt in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction using 2-(5-bromo-2-pyridylazo)-5-di methylaminoaniline (5-Br-PADMA) as the chelating agent and Triton X-114 as the extractant was established. The main parameters affecting extraction, such as pH, concentration, chelating agent, surfactant, equilibrium temperature and time, were investigated in detail. The optimized CPE conditions were as follows: pH = 5.5 HAc–NaAc buffer solution, 80 μL 5 × 10⁻⁴ mol L⁻¹ 5-Br-PADMA, 0.6 mL 1.0% (w/v) Triton X-114, and heat-assisted at 60 °C for 10 min. Under optimum conditions, the analytical curve was linear in the range of 0.05–1.0 ng mL⁻¹ and the detection limit was 0.004 ng mL⁻¹ for cobalt, the relative standard deviation was 3.3% (c = 0.5 ng mL⁻¹, n = 6), and the recovery was 96.7–104.0%. The method was applied to the determination of ultra-trace cobalt in water with satisfactory results.

A novel catechol (CA) biosensor was developed by embedding tyrosinase (Tyr) onto in situ electrochemical reduction graphene (EGR) on choline-functionalized gold nanoparticle (AuNPs-Ch) film. The results of UV-Vis spectra indicated that Tyr retained its original structure in the film, and an electrochemical investigation of the biosensor showed a pair of well-defined, quasi-reversible redox peaks with E_pa = −0.0744 V and E_pc = −0.114 V (vs. SCE) in 0.1 M, pH 7.0 sodium phosphate-buffered saline at a scan rate of 100 mV/s. The transfer rate constant k_s is 0.66 s⁻¹. The Tyr-EGR/AuNPs-Ch showed a good electrochemical catalytic response for the reduction of CA, with the linear range from 0.2 to 270 μM and a detection limit of 0.1 μM (S/N = 3). The apparent Michaelis-Menten constant was estimated to be 109 μM.

A highly sensitive method for the determination of ultra-trace levels of cobalt using cloud point extraction (CPE) coupled with thermal lens spectrometry was proposed. It is based on the complexation of cobalt with a suitable chelating agent, 2-(5-iodio-2-pyridylazo)-5-dimethylaminoaniline (5-I-PADMA), and subsequent micelle-mediated extraction of the product using non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) as an extracting agent. The effects of experimental conditions such as pH, concentration of 5-I-PADMA and Triton X-114, equilibration temperature and time on CPE were studied. After phase separation, the surfactant rich phase containing the complex was dissolved with HCl–acetone solution prior to its analysis by thermal lens spectrometry. A single mode He–Ne laser with λ = 632.8 nm was used to produce both excitation and probe beams. Under optimal conditions, the calibration plot was linear in the range of 0.2–6.0 ng mL⁻¹ cobalt, with a correlation coefficient of 0.9975. The detection limit obtained under optimum conditions was 0.02 ng mL⁻¹. The sensitivity was enhanced by 331 times compared to that of the conventional spectrophotometric method. The proposed method was successfully applied to the extraction and determination of cobalt in water and wheat flour samples.