Experiences described

It should be noted that a number of different enzyme preparations can now be purchased directly from manufacturing chemists. It must be emphasised that the activity of an enzyme, whether purchased or prepared in the laboratory, may vary between rather wide limits. The activity is dependent on the source of the enzyme, the presence of poisons and also on the temperature. It appears, for example, that the quality of horseradish peroxidase depends upon the season of the year at which the root is obtained from the ground. It cannot be expected therefore that all the experiments described below will work always with the precision characteristic of an organic reaction proceeding under accurately known conditions. 

The experiments described in Part I have been numbered, as they form a graded series to illustrate the chief manipulative processes employed in practical organic chemistry. The experiments in Parts II-V have not been numbered, as in general a selection must be made from them. In each part of the book, the experiments have been arranged as far as possible in logical order, although occasionally (as in Part IV) this is not necessarily the order of increasing difficulty. 

An experiment describing the analysis of the triglyc eride composition of several vegetable oils is described in the May 1988 issue of the Journal of Chemical Education (pp 464-466)... 

The following experiments describe homemade sampling devices for collecting samples in the field. 

This experiment describes the construction of an air sampler using an aquarium pump, a flow meter, a filter holder, and bottles that serve as traps for analytes. Applications include the determinations of SO2, NO2, HCHO, and suspended particulate matter. 

This experiment describes a simple gravimetric procedure for determining the %w/w Cl in samples of poly(vinyl chloride). 

This experiment describes a method for determining the acidity, reported as an equivalent molarity of H2SO4, of rain water. Because the volume of standard base needed to titrate a sample of rain water is small, the analysis is done by a standard addition. A 10.00-mL sample of nominally 0.005 M H2SO4 is diluted with 100.0 mL of distilled water and standardized by titrating with 0.0100 M NaOH. A second 10.00-mL sample of the sulfuric acid is mixed with 100.0 mL of rain water and titrated with the same solution of NaOH. The difference between the two equivalence point volumes... 

Most experiments involving EDTA as a titrant use Ga + and Mg + as an analyte. This experiment describes a... 

Einally, the last experiment describes an unustml precipitation titration. 

This experiment describes the application of multiwavelength linear regression to the analysis of two-component mixtures. Directions are given for the analysis of permanganate-dichromate mixtures, Ti(IV)-V(V) mixtures and Cu(II)-Zn(II) mixtures. 

This experiment describes a standard multicomponent analysis for two analytes based on measuring the absorbance at two wavelengths. Hexacyanoruthenate(II) is used as a complexing agent, forming a purple-blue complex with Fe(III) and a pale green complex with Cu(II). 

A dye used in the coloration of materials, such as fibers, must be present as the monomer if it is to adsorb to the material s surface. This experiment describes how spectrophotometry can be used to determine the equilibrium constant between a monomer and a dimer for the dye pinacyanol iodide in water. 

The analysis of APC tablets (a mixture of aspirin, phenacetin, and caffeine) has been a common undergraduate laboratory experiment. This experiment describes modifications to the standard analysis for APC tablets in which paracetamol (also known as acetaminophen) replaces phenacetin. 

This experiment describes a characterization analysis in which the degree of association, equilibrium constant, and hydrogen bond energy are measured for benzyl alcohol and phenol in CCI4. 

The next set of experiments describe suitable applications of atomic absorption spectroscopy. 

The following set of suggested experiments describes the preparation of solid-state and liquid ion-exchange ion-selective electrodes, as well as potentiometric biosensors. 

This experiment describes the preparation of liquid ion-exchange electrodes for Gk and Ga +. The liquid ion-exchange solutions are incorporated into PVG membranes and fixed to the end of glass tubing. The internal solutions are either NaGl or GaGk, and a Ag/AgGl reference electrode is situated in the internal solution. 

This experiment describes the preparation and evaluation of two liquid-membrane Na+ ion-selective electrodes, using either the sodium salt of monensin or a hemisodium ionophore as ion exchangers incorporated into a PVG matrix. Electrodes prepared using monensin performed poorly, but those prepared using hemisodium showed a linear response over a range of 0.1 M to 3 X 10 M Na+ with slopes close to the theoretical value. 

This experiment describes a semester-long project in which the concentration of several ions in a fresh water aquarium are monitored. Ions that are monitored using potentiometric electrodes include H+ (pH electrode), Gh (chloride electrode), HG03 (GO2 electrode), NH4+ (NH3 electrode), and N03 (NH3 electrode). Nitrate concentrations were determined following its conversion to ammonia. 

This experiment describes the use of coated graphite electrodes for the potentiometric monitoring of precipitation, acid-base, complexation, and redox titrations. 

The following four experiments describe useful and accessible applications of coulometry. 

This experiment describes the application of cathodic stripping voltammetry to the analysis of Ni and Co in fresh water and sea water. 

This experiment describes the determination of the stability (cumulative formation) constant for the formation of Pb(OH)3 by measuring the shift in the half-wave potential for the reduction of Pb + as a function of the concentration of OH . The influence of ionic strength is also considered, and results are extrapolated to zero ionic strength to determine the thermodynamic formation constant. 

This experiment describes the use of a commercially available amperometric biosensor for glucose that utilizes the enzyme glucose oxidase. The concentration of glucose in artificial... 

Commercially available kits for monitoring blood-glucose use an amperometric biosensor incorporating the enzyme glucose oxidase. This experiment describes how such monitors can be adapted to the quantitative analysis of glucose in beverages. 

The first set of experiments describes the application of gas chromatography. These experiments encompass a variety of different types of samples, columns, and detectors. Most experiments maybe easily modified to use available equipment and detectors. 

This experiment describes a quantitative analysis for the active ingredients in a prescription antipsychotic medication. The separation makes use of a cyanopropyl derivatized column and a mobile phase of 70% v/v acetonitrile, 5% v/v methanol, and 25% v/v 0.1 M aqueous KH2PO4. A UV detector set to 215 nm is used to measure the eluent s absorbance. 

This experiment describes the quantitative analysis of the asthma medication Quadrinal for the active ingredients theophylline, salicylic acid, phenobarbital, ephedrine HGl, and potassium iodide. Separations are carried out using a Gi8 column with a mobile phase of 19% v/v acetonitrile, 80% v/v water, and 1% acetic acid. A small amount of triethylamine (0.03% v/v) is included to ensure the elution of ephedrine HGl. A UV detector set to 254 nm is used to record the chromatogram. 

This experiment describes a quantitative analysis for caffeine, theobromine, and theophylline in tea, pain killers, and cocoa. Separations are accomplished by MEKC using a pH 8.25 borate-phosphate buffer with added SDS. A UV detector set to 214 nm is used to record the electropherogram. An internal standard of phenobarbital is included for quantitative work. 

Weber, P. L. Buck, D. R. Capillary Electrophoresis A Past and Simple Method for the Determination of the Amino Acid Composition of Proteins, /. Chem. Educ. 1994, 71, 609-612. This experiment describes a method for determining the amino acid composition of cyctochrome c and lysozyme. The proteins are hydrolyzed in acid, and an internal standard of a-aminoadipic acid is added. Derivatization with naphthalene-2,3-dicarboxaldehyde gives derivatives that absorb at 420 nm. Separation is by MEKC using a buffer solution of 50 mM SDS in 20 mM sodium borate. 

This experiment describes a kinetic method for determining the concentrations of Mn04 and Gt207 in a mixture. The analysis is based on a difference in the rate at... 

Most flow injection analyses use peak height as the analytical signal. When there is insufficient time for reagents to merge with the sample, the result is a split-peak, or doublet, due to reaction at the sample s leading and trailing edges. This experiment describes how the difference between the peak times can be used for quantitative work. 

This experiment describes the preparation of a flow-through potentiometric electrode assembly incorporating a valinomycin-PVC membrane in the transport tubing. The... 

This experiment describes the use of FIA for determining the stoichiometry of the Fe +-o-phenanthroline complex using the method of continuous variations and the mole-ratio method. Directions are also provided for determining the stoichiometry of the oxidation of ascorbic acid by dichromate and for determining the rate constant for the reaction at different pH levels and different concentration ratios of the reactants. 

This experiment describes the adaptation of the bicinchoninic acid (BCA) protein assay to a flow injection analysis. The assay is based on the reduction of Cu + to Cu+ by the protein, followed by the reaction of Cu+ with bicinchoninic acid to form a purple complex that absorbs at 562 nm. Directions are provided for the analysis of bovine serum albumin and rabbit immunoglobulin G, and suggestions are provided for additional analyses. 

This experiment describes the use of a fractional factorial design to examine the effects of volume of HNO3, molarity of AgN03, volume of AgN03, digestion temperature, and composition of wash water on the gravimetric analysis for chloride. 

This experiment describes a fixed-size simplex optimization of a system involving four factors. The goal of the optimization is to maximize the absorbance of As by hydride generation atomic absorption spectroscopy using the concentration of HCl, the N2 flow rate, the mass of NaBH4, and reaction time as factors. 

This experiment describes a variable-size simplex optimization of the quantitative analysis of vanadium as... 

This experiment describes a fractional factorial design used to examine the effects of flame height, flame stoichiometry, acetic acid, lamp current, wavelength, and slit width on the flame atomic absorbance obtained using a solution of 2.00-ppm Ag+. 

In the experiment described in Fig. 2.1, the bottom plate remains in place and the nonslip condition stipulated above requires that the layer of fluid adjacent to the bottom plate also have zero velocity. This situation clearly... 

During gc/ms or liquid chromatography/mass spectrometry (Ic/ms) acquisitions, it is possible to perform a mixture of the experiments described in Table 2 for different time windows, with the experimental parameters, such as the coUision energy, optimized for each analyte. 

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