摘要:

Disc electrophoresic can be used to determine if uncookee beef and beef products have Seen adulterated with meat from horses, hogs, deer, and buffalo.

ISSN:0003-2719    

DOI:10.1080/00032718308077150

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A method is described for the analysis of fluorine in geological samples involving the decomposition of the sample with phosphoric acid and the measurement of the fluoride ion concentration using an ion chromatograph. The detection limit is below 5 g F in the original sample. Multiple analyses of NBS-91 Opal Glass yielded a relative standard deviation of less than 2.5%. In excess of 30 samples can be analyzed in an 8 hour day. Potential interference from high carbon containing samples, such as oil shales, is discussed.

ISSN:0003-2719    

DOI:10.1080/00032718308077151

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A compression molded graphite-Teflon electrode is evaluated as a detector for the electrochemical detection of phenolic compounds, separated by reverse-phase high-performance liquid chromatography. Detection limits for these phenolic compounds range from 0.5–1 ng. Repetitive injections yield peak heights with RSDs less than 1%. Passivation of electrode surface by phenols is discussed. In addition, construction of a flow cell to be used in conjunction with graphite-Teflon electrode is also described.

ISSN:0003-2719    

DOI:10.1080/00032718308077152

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The use of a direct liquid introduction probe with a short guard column as the method of sample introduction is explored. This technique is an alternative to the conventional direct probe method. The method is rapid, involatile compounds can be analyzed, and volatile compounds are not lost in the vacuum lock. Screening for trichlorophenol in urine, by observing the loss of [M-HCOCI]+, is used to test the technique. The advantages and disadvantages of split and splitless direct liquid introduction probes and column concentration are discussed. Detection limits in the low nanograms were observed, and samples may be analyzed every 30 seconds.

ISSN:0003-2719    

DOI:10.1080/00032718308077153

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Aqueous samples of organic solutes often exhibit a delayed reaction in the indigo test for dissolved ozone which is similar to the reaction of ozone itself. This phenomenon has made timing critical in aqueous ozone measurements and has been observed in both laboratory situations with high organic carbon:ozone ratios and in a potable water treatment plant with low organic carbon:ozone ratios. Organic hydroperoxides, singlet oxygen, and Fenton's reagent but not triplet oxygen, hydrogen peroxide, nor p-benzoquinone were found to interfere. Addition of phenolic antioxidants was found to inhibit the interference. These results extend the utility of the indigo method to solutions of high organic carbon concentration.

ISSN:0003-2719    

DOI:10.1080/00032718308077154

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A new flow injection system for the determination of mercury by the cold vapor atomic fluorescence method is described. A sample solution (64 μ1) is injected into a stream of 0.1 M hydrochloric acid, which is mixed with a stream of 3% tin (II) chloride solution in a mixing joint. The combined stream is carried through a reaction coil for reduction of Hg (II) to Hg (0) and subsequently introduced into a specially designed gas-liquid separation vessel. Then the vaporized mercury is swept into a flow type fluorescence cell with a continuous flow of argon after removal of water in the gas phase through a condenser. Mercury is excited with an electrodeless discharge lamp as a source and the mercury fluorescence at both 184.9 and 253.7 nm is measured with a solar-blind photomultiplier. This method allows about 35 determinations of mercury in aqueous samples per hour. The calibration curve is linear over the 0–20 ppb range of mercury. The limit of detection (S/N = 3) is 0.008 ng (0.12 ppb × 64 μ1) and the coefficient of variation is below 1% for the 1–20 ppb solutions (n=10).

ISSN:0003-2719    

DOI:10.1080/00032718308077155

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A simple and accurate colorimetric method for determination of allyl isothiocyanate was developed. It involves formation of methylene blue by the reaction of an acid solution of N, N-dimethyl-p-phenylenediamine in the presence of ferric ion with the sulfide liberated by ethanolic base hydrolysis of allyl isothiocyanate in xylene. This method permits determination of microgram quantities of S in allyl isothiocyanate. The effects of alterations in reaction conditions on the color development were investigated. Tests with a range of sulfur-containing organic compounds (thiourea, cysteine, methionine, cysteic acid, thioacetamide, benzene sulfonamide, glucose-6-Sulfate, and sinigrin) showed that none of the compounds tested interfere with this method when the S concentration is ≤ 10 times that of S as allyl isothiocyanate.

ISSN:0003-2719    

DOI:10.1080/00032718308077156

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

By means of a special cell assembly, the prefilter, primary absorption, self-absorption, and postfilter effects of an analyte compound upon the signal of a fluorescent probe (aniline) could be evaluated. The experimental evaluation allowed us to model a possible mechanism of response of the negative fluorescence HPLC detector described by Syang Y. Su and co-workers and to indicate possible improvements in the flow cell design. The negative fluroescence detector's response seems to be largely based upon the prefilter, primary absorption, self-absorption, and postfilter effects of the analyte.

ISSN:0003-2719    

DOI:10.1080/00032718308077157

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The photodegradation of organophosphorus compounds has been studied using triethylphosphate as a model compound, A 150 W xenon lamp was used in conjunction with ammonium peroxydisulfate to achieve high yields of orthophosphate in a 100-second irradiation time. The effects of the pH of the reaction medium and the initial concentrations of a peroxydisulfate and triethylphosphate on the extent of reaction were determined. A survey of potential interferences was performed, Copper (II) ion was found to catalyze the reaction, The effect of varying the Cu (II) concentration and the pH dependence of the catalyzed reaction were determined, Organic solvents were found to interfere with the photo degradation, but the reaction shows good potential for incorporation into a post-column detection system for the liquid chromatographic determination of organophosphorus compounds where totally aqueous mobile phases can be used.

ISSN:0003-2719    

DOI:10.1080/00032718308077158

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A rapid method was developed for the analysis of paraquat dication (I) and diquat dication (II) as their diene reduction products (ID and IID respectively) in potatoes. Macerated potato tissue was spiked with various levels of the dications, 0.05, 0.5, and 5.0 ppm. The dications were reduced using a sodium borohydride/ethanol reduction procedure with reduction and simultaneous extraction in a single 50 ml glass-stoppered centrifuge tube. The diene reduction products were extracted into hexane and analyzed by gas-liquid chromatography (GLC) and a N/P-thermionic detector. Quantification by external standard method or internal standard method resulted in recoveries of 35, 38, 48 and 39,42, 64% for diquat and paraquat respectively. When a spiked macerate was well-mixed, recoveries were low due to adsorption; precision was within 5 5.4% (standard deviation). The importance of spiking technique was also illustrated. Upon thorough mixing and equilibration, of diquat spiked potatoes, recoveries were reduced dramatically. Adsorption of the dications and diene reduction products to glassware reduced recoveries and accounted for poorer precision; this latter effect was overcome by prior silanization of the glassware. Modification of existing NaBH4methods resulted in a procedure for I and II analysis requiring only 30 minutes per sample for complete analysis. Use of NaBH4reduction and analysis of I in potatoes has not been previously reported.

ISSN:0003-2719    

DOI:10.1080/00032718308077159

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor