ABSTRACT
This study aimed to conduct measurement uncertainty assessment of a new method for determination of Sudan colorants (Sudan I, II, III and IV) in food by high performance liquid chromatography (HPLC). Samples were extracted with organic solvents (hexane, 20% acetone) and first purified by magnesium trisilicate (2MgO·3SiO2). The Sudan colorants (Sudan I-IV) were also initially separated on C8 by gradient elution using acetonitrile and 0.1% (v/v) formic acid aqueous solution as the mobile phases and detected with diode-array detector (DAD). The uncertainty of mathematical model of Sudan I, II, III and IV is based on EURACHEM guidelines. The sources and components of uncertainty were calculated. The experiment gave a good linear relationship over the concentration from 0.4 to 4.0 μg/mL and spiked recoveries were from 74.0% to 97.5%. The limits of determination (LOD) were 48, 61, 36, 58 μg/kg for the four analytes, respectively. The total uncertainty of Sudan colorants (Sudan I, II, III and IV) was 810±30.8, 790±28.4, 750±27.0, 730±50.0 μg/kg, respectively. The recovery uncertainty was the most significant factor contributing to the total uncertainty. The developed method is simple, rapid, and highly sensitive. It can be used for the determination of trace Sudan dyes in food samples. The sources of uncertainty have been identified and uncertainty components have been simplified and considered.
Subject(s)
Humans , Azo Compounds , Chemistry , Chromatography, High Pressure Liquid , Methods , Food Analysis , Methods , Food Coloring Agents , Chemistry , Limit of Detection , Magnesium Silicates , Chemistry , Naphthols , ChemistryABSTRACT
A new, simple and sensitive method was developed for the determination of silicon tetrahydride in the air of workplace in this study. The alkaline resin-based spherical activated carbon was used to collect sample of silicon tetrahydride at workplace. Silicon tetrahydride was then desorbed from active carbon in 100°C hot water. After reacting with ammonium molybdate, oxalic acid and 1,2,4-trichlorobenzene alpha-naphthol amino sulfonic acid under acid condition, silicon tetrahydride was transformed into silicon molybdenum blue. The absorbance of silicon molybdenum blue was quantitatively measured at the wavelength of 680 nm. The results showed that the average sampling efficiency and desorption efficiency were 97.53% and 94.94%, respectively by this method. Detection limits were 0.054 μg/mL for the spectrophotometric method and 0.14 mg/m(3) for the determination of silicon tetrahydride in the air of workplace (sampling volume was 7.5 L). The conversion rate of silicon tetrahydride gradually decreased when storage time of samples was extended. The descent rate of sample was less than 10% when the sample was sealed for 7 days in the room temperature. It was concluded that this spectrophotometric method can be successfully used to determine silicon tetrahydride in the worksites.
ABSTRACT
A new, simple and sensitive method was developed for the determination of silicon tetrahydride in the air of workplace in this study. The alkaline resin-based spherical activated carbon was used to collect sample of silicon tetrahydride at workplace. Silicon tetrahydride was then desorbed from active carbon in 100°C hot water. After reacting with ammonium molybdate, oxalic acid and 1,2,4-trichlorobenzene alpha-naphthol amino sulfonic acid under acid condition, silicon tetrahydride was transformed into silicon molybdenum blue. The absorbance of silicon molybdenum blue was quantitatively measured at the wavelength of 680 nm. The results showed that the average sampling efficiency and desorption efficiency were 97.53% and 94.94%, respectively by this method. Detection limits were 0.054 μg/mL for the spectrophotometric method and 0.14 mg/m(3) for the determination of silicon tetrahydride in the air of workplace (sampling volume was 7.5 L). The conversion rate of silicon tetrahydride gradually decreased when storage time of samples was extended. The descent rate of sample was less than 10% when the sample was sealed for 7 days in the room temperature. It was concluded that this spectrophotometric method can be successfully used to determine silicon tetrahydride in the worksites.
Subject(s)
Humans , Air Pollutants, Occupational , Limit of Detection , Reproducibility of Results , Silanes , Spectrophotometry , Methods , WorkplaceABSTRACT
Experiment teaching is a most important item of college teaching, and plays a vital and unexchangeable role to train students for their ability to practice and to innovate. To construct a feasible and scientific examination system of experiment teaching, will significantly help deepen the reformation of experiment teaching and improve the teaching quality. So according to the request for cultivating qualified ap- plication person, we preliminarily constitute the valuation system throughout the whole course and in the final, of theoretic examination and practice examination, and combined with students’ self-valuation and valuation from teachers. In fact, the system works well with a perfect effect.
ABSTRACT
<p><b>OBJECTIVE</b>To examine the antigenicity of hepatitis C virus (HCV) F protein and investigate serum prevalence of anti-F in HCV-infected patients.</p><p><b>METHODS</b>Eleven pairs of overlapping primers were used to synthesize the full-length HCV f gene, from which the truncated HCV f65 gene fragment was amplified by PCR. HCV f65 gene was then cloned into pET32a(+), and transformed into E. coli strain Plyss (DE3). This recombinant E.coli was induced by IPTG for the production of HCV F65 protein. The expressed HCV F65 protein, purified by Ni-NTA agarose, was further used in ELISA to detect serum anti-F, and to immunize rabbits for making polyclonal anti-F. The rabbit polyclonal anti-F was purified by Staphylococcus aureus protein A agarose.</p><p><b>RESULTS</b>After recombinant pET32a(+)-f65 was constructed successfully, HCV F65 protein was expressed and purified. The purified HCV F65 protein was used as a capture antigen in ELISA to detect serum anti-F in HCV infected patients (n = 30). The result showed that the mean A450 value and the positive rate of serum anti-F were 0.125+/-0.061 and 63.3%, respectively. The rabbit-derived polyclonal anti-F reacted specifically with HCV F65 protein, of which the titer was 1:30,000.</p><p><b>CONCLUSION</b>Our expressed HCV F65 protein is of antigenicity, and can be used to determine serum anti-F. Anti-F IgG does exist in the sera of the HCV-infected patients. Moreover, the rabbit-derived polyclonal anti-F can be used to detect HCV F protein.</p>