Professor of Chemistry & Biochemistry at DePauw University
David T. Harvey is a Professor Emeritus of Chemistry and Biochemistry at DePauw University in Greencastle, Indiana, where he has been a dedicated faculty member since 1986. Over his nearly four-decade career, Dr. Harvey has established himself as a leading voice in analytical chemistry education, renowned for his commitment to making high-quality learning resources accessible to students worldwide.
This site offers an introductory course (as a MOOC) on the estimation of measurement uncertainty specifically related to chemical analysis (analytical chemistry).…
View Resource →The data set available here provides spectra for a solution of benzene in methanol recorded from 230-290 nm using a Perkin-Elmer Lambda…
View Resource →Control charts were originally developed in the 1920s as a quality assurance tool for the control of manufactured products. Although there are…
View Resource →Illustrated here is an example of a prescriptive approach to quality assurance for laboratories monitoring waters and wastewaters, adapted from Environmental Monitoring and…
View Resource →When an analyst performs a single analysis on a sample the difference between the experimentally determined value and the expected value is…
View Resource →In many cases the underlying theoretical relationship between the response and its factors is unknown. We can still develop a model of…
View Resource →One strategy for improving the efficiency of a searching algorithm is to change more than one factor at a time. A convenient…
View Resource →A simple algorithm for optimizing the response for a system is to adjust independently each factor. Consider a response that depends on…
View Resource →If we know the equation for a response surface, then it is relatively easy to find the optimum response. Unfortunately, we rarely…
View Resource →One of the most effective ways to think about an optimization is to visualize how a system’s response changes when we increase…
View Resource →Dialysis and gaseous diffusion are accomplished by placing a semipermeable membrane between the carrier stream containing the sample and an acceptor stream. Shown…
View Resource →The heart of a flow injection analyzer is the transport system that brings together the carrier stream, the sample, and any reagents…
View Resource →A propelling unit moves the carrier stream through the flow injection analyzer. Although several different propelling units have been used, the most…
View Resource →The basic components of a flow injection analyzer are shown below and include a pump for propelling the carrier stream and reagent…
View Resource →An FIA curve, or fiagram, is a plot of the detector’s signal as a function of time. The illustration below shows a…
View Resource →When we first inject a sample into an FIA’s carrier stream it has the rectangular flow profile of width w as shown…
View Resource →Flow injection analysis (FIA) was developed in the mid-1970s as a highly efficient technique for the automated analyses of samples. Unlike a…
View Resource →The figure below illustrates how we can use a kinetic analysis to determine the concentration of two analytes, A and B, provided…
View Resource →When an inhibitor interacts with an enzyme it decreases the enzyme’s catalytic efficiency. An irreversible inhibitor covalently binds to the enzyme’s active…
View Resource →For an enzyme–substrate reaction following a simple mechanism E + S ↔ E–S ↔ E + P consisting of the initial formation of an enzyme–substrate…
View Resource →Enzymes are highly specific catalysts for biochemical reactions, with each enzyme showing a selectivity for a single reactant, or substrate. For example,…
View Resource →A significant experimental problem when the reaction’s kinetics are fast is ensuring that we rapidly and reproducibly mix the sample and the…
View Resource →Monitoring a kinetic reaction is straight-forward, provided that the reaction does not proceed to a appreciable extent during the time it takes…
View Resource →In a rate method we use the differential form of the rate law to determine the analyte’s concentration. As shown here, the…
View Resource →Shown here is one useful scheme for classifying chemical kinetic methods of analysis. Methods are divided into two main categories: direct-computation methods…
View Resource →Another approach to separating neutral species is capillary electrochromatography, CEC. In CEC the capillary tubing is packed with 1.5–3 μm particles coated…
View Resource →One limitation to capillary electrophoresis is its inability to separate neutral species. Micellar electrokinetic capillary chromatography, or MEKC, overcomes this limitation by…
View Resource →We can reverse the direction of electroosmotic flow in capillary electrophoresis by adding an alkylammonium salt to the buffer solution. As shown…
View Resource →When a analyte’s concentration is too small to detect reliably, it may be possible to introduce it in a manner that increases…
View Resource →Most of the detectors used in HPLC also find use in capillary electrophoresis. Among the more common detectors are those based on…
View Resource →The basic instrumentation for capillary electrophoresis is shown here and includes a power supply for applying the electric field, anode and cathode…
View Resource →In capillary electrophoresis we inject the sample into a buffered solution retained within a capillary tube. When an electric field is applied…
View Resource →When an electrical field is applied to a capillary filled with an aqueous buffer we expect the buffer’s ions to migrate in…
View Resource →In ion-exchange chromatography (IEC) the stationary phase is a cross-linked polymer resin, usually divinylbenzene cross-linked polystyrene, with covalently attached ionic functional groups.…
View Resource →The figure below provides a block diagram of a typical liquid chromatography-mass spectrometer (LS–MS) instrument. As illustrated here, a three component mixture is injected…
View Resource →Another common group of HPLC detectors are based on electrochemical measurements such as amperometry, voltammetry, coulometry, and conductivity. The illustration below, for…
View Resource →One popular HPLC detector takes advantage of an analyte’s UV/Vis absorption spectrum. These detectors range from simple designs, in which the analytical…
View Resource →The operating pressure of an HPLC is sufficiently high that we cannot inject the sample into the mobile phase by inserting a…
View Resource →A typical HPLC includes between 1–4 reservoirs for mobile phase solvents. The mobile phase solvents are pulled from their reservoirs by the action…
View Resource →The illustration below shows the gradient elution separation of a mixture of flavonoids. Mobile phase A is an aqueous solution of 0.1%…
View Resource →One strategy for finding the best mobile phase for an HPLC separation is to use the solvent triangle, which allows us to…
View Resource →The most common type of HPLC column is a stainless steel tube with an internal diameter between 2.1 mm and 4.6 mm…
View Resource →The photo below shows an example of a typical HPLC instrument with insets showing close-up views of the pumps that move the mobile…
View Resource →In a GC analysis the area under the peak is proportional to the amount of analyte injected onto the column. The peak’s…
View Resource →The figure below provides a block diagram of a typical gas chromatography-mass spectrometer (GC–MS) instrument. As illustrated here, a three component mixture enters the…
View Resource →Shown here is a schematic diagram of electron capture detector (ECD) for gas chromatography. The detector consists of a β-emitter, such as…
View Resource →The schematic diagram below shows a flame ionization detector for gas chromatography. The eluent from the column mixes with H2 and is…
View Resource →One of the earliest gas chromatography detectors takes advantage of the mobile phase’s thermal conductivity. As the mobile phase exits the column…
View Resource →Shown here is a schematic diagram of a heated GC injector port for use with packed columns. The needle from the syringe…
View Resource →Shown here is an example of a syringe for injecting samples into a gas chromatograph. This syringe has a maximum capacity of…
View Resource →Solid-phase microextraction (SPME) is an attractive method for isolating an analyte prior to injecting it into a gas chromatograph. In one approach, which…
View Resource →Shown here is an example of a packed column for gas chromatography. This column is made from stainless steel and is 2…
View Resource →Photograph showing an example of a typical gas chromatograph with insets showing the heated injection ports—note the symbol indicating that it is…
View Resource →One way to improve a separation is to decrease the height of a column’s theoretical plate. The figures here consider four contributions…
View Resource →The illustration below shows how the mobile phase pH in liquid chromatography affects our ability to separate a mixture of four substituted…
View Resource →Adjusting the retention factor to improve the resolution between one pair of solutes may lead to unacceptably long retention times for other…
View Resource →The ideal chromatographic peak has a Gaussian profile, which occurs if the solute’s partition coefficient, KD, between the stationary phase and mobile…
View Resource →The goal of chromatography is to separate a mixture into a series of chromatographic peaks, each representing a single component of the…
View Resource →A solute’s chromatographic peak may be characterized in many ways, two of which are shown in this figure. Retention time, tr, is…
View Resource →The most common method for bringing the stationary phase and the mobile phases into contact is to hold the stationary phase within…
View Resource →In chromatography, a separation occurs because there is a difference in the equilibrium partitioning of solutes between the mobile phase and the…
View Resource →As illustrated below, in chromatography we pass a sample-free phase, which we call the mobile phase, over a second sample-free stationary phase…
View Resource →Shown here is an illustration outlining the progress of a traditional liquid–liquid extraction (LLE) using two identical extractions of a single sample…
View Resource →Voltammetry is a particularly attractive technique for the analysis of samples containing two or more analytes. Provided that the analytes behave independently,…
View Resource →In amperometry we apply a constant potential to the working electrode and measure current as a function of time. Because we do…
View Resource →In a cyclic voltammetry experiment, scanning the potential in both directions provides with the opportunity to explore the electrochemical behavior of species…
View Resource →In cyclic voltammetry (CV) we scan the potential in both the cathodic and anodic directions. The illustration below shows a typical potential-excitation…
View Resource →As illustrated here, anodic stripping voltammetry (ASV) consists of two steps. The first step is a controlled potential electrolysis in which we…
View Resource →Normal polarography has been replaced by various forms of pulse polarography, several examples of which are shown here. Normal pulse polarography (a),…
View Resource →The first important voltammetric technique to be developed—polarography—uses the dropping mercury electrode as the working electrode. As shown here, the current flowing…
View Resource →In voltammetry we measure current as a function of the applied potential. The shape of a voltammogram is determined by several experimental…
View Resource →Let’s assume we have a solution that is 1.0 mM in Fe(CN)63– is 1.0 mM. The standard state potential for the reduction…
View Resource →A typical arrangement for a voltammetric electrochemical cell is shown here. In addition to the working electrode, the reference electrode, and the…
View Resource →Schematic diagram showing a solid electrode. The electrode is fashioned into a disk and sealed in the end of an inert polymer…
View Resource →The approximate potential windows for mercury, platinum, and carbon (graphite) electrodes in acidic, neutral, and basic aqueous solvents are shown here. The…
View Resource →Three examples of mercury electrodes are illustrated here: (a) hanging mercury drop electrode, or HMDE; (b) dropping mercury electrode, or DME; and…
View Resource →Shown here is one example of a device for the external generation of oxidizing agents and reducing agents for controlled-current coulometry. A…
View Resource →A second approach to coulometry is to use a constant current in place of a constant potential, which produces the current–time profile…
View Resource →Coulometry is based on an exhaustive electrolysis of the analyte. By exhaustive we mean that the analyte is completely oxidized or reduced…
View Resource →Schematic diagram of a disposable ion-selective electrode created by screen-printing. In (a) a thin film of conducting silver is printed on a…
View Resource →The photo below provides a demonstration of the difference between activity and concentration using the indicator methyl green. The indicator is yellow…
View Resource →A gas-sensing electrode can be modified to create a potentiometric electrode that respond to a biochemically important species, such as enzymes. One example…
View Resource →A number of membrane electrodes respond to the concentration of a dissolved gas. The basic design of a gas-sensing electrode consists of…
View Resource →Another class of ion-selective electrodes uses a hydrophobic membrane containing a liquid organic complexing agent that reacts selectively with the analyte. Three…
View Resource →Schematic diagram of a solid-state electrode, the membrane for which is either a polycrystalline inorganic salt or a single crystal of an…
View Resource →Schematic diagram showing a combination glass electrode for measuring pH. The indicator electrode consists of a pH-sensitive glass membrane and an internal…
View Resource →Shown here is a schematic diagram of a typical potentiometric cell that includes a membrane electrode (in this case, an ion-selective membrane).…
View Resource →In a potentiometric electrochemical cell one half-cell provides a known reference potential and the potential of the other half-cell indicates the analyte’s…
View Resource →A junction potential develops at the interface between two ionic solution if there difference in the concentration and mobility of the ions.…
View Resource →Shown here is the schematic diagram of a typical potentiometric electrochemical cell. The electrochemical cell consists of two half-cells, each consisting of…
View Resource →Shown here is a family tree that highlights a number of interfacial electrochemical techniques. The specific techniques are shown in red, the…
View Resource →A potentiostat is used to set and control the potential of a working electrode. A schematic diagram for a manual potentiostat is shown…
View Resource →A galvanostat is used to control the current flowing through an electrochemical cell. A schematic diagram of a constant-current galvanostat is shown…
View Resource →To measure the potential of an electrochemical cell under a condition of zero current we use a potentiometer. Shown here is a…
View Resource →In electrochemistry, there is an important distinction between the concentration of a species at the electrode’s surface and its concentration at some…
View Resource →Turbidimetry and nephelometry are two techniques based on the elastic scattering of radiation by a suspension of colloidal particles: (a) in turbidimetry…
View Resource →Elastic scattering is divided into two types: Rayleigh, or small-particle scattering, and large-particle scattering. Rayleigh scattering occurs when the scattering particle’s largest…
View Resource →Flame emission is subject to the same types of chemical interferences as atomic absorption. These interferences are minimized by adjusting the flame’s…
View Resource →The most important spectral interference in emission spectroscopy is broad, background emission from the flame or plasma, and emission bands from molecular…
View Resource →The illustration below provides a schematic diagram of an inductively coupled plasma source (ICP), which consists of three concentric quartz tubes surrounded…
View Resource →Illustration showing how slit orientation changes the volume from which fluorescence is measured: (a) vertical slit orientation; (b) horizontal slit orientation. Suppose…
View Resource →Except for a few metal ions, most notably UO2+, most inorganic ions are not sufficiently fluorescent for a direct analysis. Many metal…
View Resource →The basic instrumentation for monitoring fluorescence and phosphorescence—a source of radiation, a means of selecting a narrow band of radiation, and a…
View Resource →A photoluminescence spectrum is recorded by measuring emission intensity as a function of either the excitation wavelength or the emission wavelength. An…
View Resource →Shown here is an illustration of the energy level diagram for a molecule exhibiting pathways for the deactivation of an excited state:…
View Resource →Photoluminescence is divided into two categories: fluorescence and phosphorescence. A pair of electrons occupying the same electronic ground state have opposite spins…
View Resource →The photo below shows a typical multielemental hollow cathode lamp. The cathode in this lamp is fashioned from an alloy containing Co,…
View Resource →A typical electrothermal atomizer, also known as a graphite furnace, consists of a cylindrical graphite tube approximately 1–3 cm in length and…
View Resource →The illustration below shows a cross-section through a typical flame looking down the burner’s slot along the source radiation’s optical path. The primary…
View Resource →Where within the flame one measures absorbance is critical as two competing processes affect the concentration of free atoms in the flame.…
View Resource →The photos below shows a typical assembly for flame atomization with close-up views of several key components. In the unit shown here,…
View Resource →As shown here, the relative uncertainty in determining absorbance (and thus in determining concentration) is greater at very high and very low…
View Resource →In absorption spectroscopy, precision is limited by indeterminate errors—primarily instrumental noise—introduced when measuring absorbance. Precision is generally worse for low absorbances where…
View Resource →An alternative to the method of continuous variations for determining the stoichiometry of metal-ligand complexes is the mole-ratio method in which the…
View Resource →The method of continuous variations, also called Job’s method, is used to determine the stoichiometry of a metal-ligand complex. In this method…
View Resource →With the availability of computerized data acquisition and storage it is possible to build digital libraries of standard reference spectra. The identity…
View Resource →A quantitative analysis based on the absorption of infrared radiation, although important, is less frequently encountered than those for UV/Vis absorption. One…
View Resource →The illustration below shows an FT-IR spectrometer equipped with a diamond ATR sample cell. The inserts show a close-up photo of the…
View Resource →The photo below shows several examples of sample cells for UV/Vis spectroscopy. From left to right (with path lengths in parentheses): rectangular…
View Resource →Examples showing the effect of signal averaging on a spectrum’s signal-to-noise ratio. From top to bottom: spectrum for a single scan; average…
View Resource →Several of the posts in the Analytical Image and Video Exchange include schematic diagrams of spectrophotometers. Gathered here are jpeg files for…
View Resource →The illustration here shows a schematic diagram of a diode array spectrophotometer, in which we replace a single photomultiplier detector with an array…
View Resource →The illustration below shows a diagram of a scanning, double-beam spectrophotometer. A chopper directs the source’s radiation, using a transparent window to…
View Resource →The illustration here shows a diagram of a single-beam spectrophotometer that uses a monochromator to select the wavelength. The analyst manually selects the…
View Resource →The illustration below is a diagram of a simple filter photometer, which uses an absorption filter (shown here) or interference filter to isolate a…
View Resource →Beer’s law suggests that a calibration curve is a straight line with a y-intercept of zero and a slope of εb. In many…
View Resource →Absorbance is the more common unit for expressing the attenuation of radiation because it is a linear function of the analyte’s concentration. When…
View Resource →As light passes through a sample, its power decreases as some of it is absorbed. This attenuation of radiation is described quantitatively…
View Resource →The energy of ultraviolet and visible electromagnetic radiation is sufficient to cause a change in an atom’s valence electron configuration. Sodium, for…
View Resource →The illustration here shows two electronic energy levels (E0 and E1), each with five vibrational energy levels (ν0–ν4). Absorption of ultraviolet and visible…
View Resource →A photomultiplier contains a photosensitive surface that absorbs radiation in the ultraviolet, visible, or near IR, producing an electrical current proportional to…
View Resource →An interferometer provides an alternative approach for wavelength selection. Instead of filtering or dispersing the electromagnetic radiation, an interferometer allows source radiation…
View Resource →An absorption filter has one significant limitation—because a filter has a fixed nominal wavelength, if you need to make measurements at two…
View Resource →The simplest method for isolating a narrow band of radiation is to use an absorption filter, which work by selectively absorbing radiation…
View Resource →In Nessler’s original colorimetric method for ammonia, developed in the 1850s before the advent of spectrophotometers, the sample and several standard solutions…
View Resource →A source of electromagnetic radiation must provide an output that is both intense and stable. Sources of electromagnetic radiation are classified as…
View Resource →The illustration here is a simplified energy diagram showing the absorption and emission of a photon by an atom or a molecule.…
View Resource →Illustration of plane-polarized electromagnetic radiation showing the oscillating electric field in red and the oscillating magnetic field in blue. The radiation’s amplitude,…
View Resource →The most important class of indicators for redox titrations are substances that do not participate in the redox titration, but whose oxidized…
View Resource →For an acid–base titration or a complexometric titration, the equivalence point is almost identical to the inflection point near the middle of…
View Resource →If at least one species in a complexation titration absorbs electromagnetic radiation, we can identify the end point by monitoring the titrand’s…
View Resource →Most indicators for complexation titrations are organic dyes—known as metallochromic indicators—that form stable complexes with metal ions. The indicator, Inm–, is added…
View Resource →Structures of (a) EDTA, in its fully deprotonated form, and (b) in a six-coordinate metal–EDTA complex with a divalent metal ion.
View Resource →The illustrations below show two approaches to titrating very small samples. In the first experimental design, samples of 20–100 µL were held by…
View Resource →In an acid–base titration the volume of titrant needed to reach the equivalence point is proportional to the moles of titrand. Because…
View Resource →Another application of acid–base titrimetry is the determination of equilibrium constants. Consider, for example, a solution of acetic acid, CH3COOH, for which…
View Resource →An alternative to using a visual indicator to locate a titration’s end point is to continuously monitor the titration’s progress using a…
View Resource →The illustration below shows the relationship between pH and an indicator’s color. The ladder diagram defines pH values where each of the…
View Resource →For most acid–base titrations the inflection point, the point on a titration curve having the greatest slope, very nearly coincides with the…
View Resource →This set of illustrations shows the steps for quickly sketching an good approximation of the titration curve for the titration of 50.0…
View Resource →A simple illustration of a typical volumetric buret. The stopcock is in the open position, allowing the titrant to flow into the…
View Resource →An acid-base reaction is exothermic, which means we can follow the titration by monitoring the titration mixture’s temperature as a function of…
View Resource →Examples of titration curves: (a) complexation titration of 25.0 mL of 1.0 mM Cd2+ with 1.0 mM EDTA at a pH of…
View Resource →Typical acid–base titration curve showing how the titrand’s pH changes with the addition of titrant. The titrand is a 25.0 mL solution…
View Resource →Illustration showing four possible mechanisms for the solid-state extraction of an analyte: (a) adsorption onto a solid substrate; (b) absorption into a…
View Resource →In a thermogravimetric analysis we measure the mass of a sample while heating the sample over time. The top photo shows a…
View Resource →Illustration showing the equipment for filtering a precipitate through a filtering crucible. Suction from a vacuum, often from a water aspirator, pulls…
View Resource →Illustration showing how to prepare a filter paper cone for gravity filtration. The filter paper circle in (a) is folded in half…
View Resource →Two methods for coagulating a precipitate of AgCl are illustrated here: (a) because of electrostatic repulsion, coagulation will not take place if…
View Resource →Two precipitates of PbCrO4 are shown in this photo. The precipitate in the beaker on the left was formed by pouring quickly a…
View Resource →Mixing solutions of 1.5 M KNO3 and 1.5 M HClO4 produces a white precipitate of KClO4. If permanganate ions, MnO4–, are present,…
View Resource →Three examples of impurities that may form during precipitation. The cubic frame represents the precipitate and the blue marks are impurities: (a)…
View Resource →Ball-and-stick diagram showing the lattice structure of AgCl. Each silver ion in the lattice’s interior binds with six chloride ions, and each…
View Resource →Illustration showing the solubility of CaF2 as a function of pH, represented by the solid blue curve. The predominate form of fluoride…
View Resource →Illustration showing the solubility of AgCl, SAgCl, as a function of pCl. The dashed red line shows SAgCl if one assumes incorrectly that the…
View Resource →Schematic diagram of a purge-and-trap system for extracting volatile analytes. The purge gas releases the analytes, which subsequently collect in the primary…
View Resource →In a Soxhlet extraction, the extracting solvent is placed in the lower reservoir and heated to its boiling point. Solvent in the…
View Resource →In a solid-phase extraction of a liquid sample, we pass the sample through a cartridge containing a solid adsorbent. A typical separation…
View Resource →Illustration showing a liquid–liquid extraction using a separatory funnel: (a) before the extraction, 100% of the analyte is in phase 1; (b)…
View Resource →When a sample is a solid, sublimation may provide a useful method for separating an analyte from an interferent. The sample is…
View Resource →Two experimental set-ups for distillations are shown in this figure. The simple distillation apparatus shown on the left does not produce a…
View Resource →When an analyte and interferent are miscible liquids, a separation by distillation is possible if their boiling points are significantly different. The…
View Resource →Photo of a dialysis cassette used to separate analytes from interferents based on size. The dialysis membrane in this unit has a…
View Resource →Three types of membrane filters are used to separate an analyte from interfering species that may be present in the sample solution.…
View Resource →One method for bringing a sample into solution is a chemical digestion, often aided by heating the sample and the digesting solution.…
View Resource →For a heterogeneous material consisting of large particulates, the original (or gross) sample may be too large to analyze. For example, a…
View Resource →A sample thief is used for sampling smaller particulate materials, such as powders. A typical sample thief consists of two tubes that…
View Resource →For particulate materials, particle size often determines the sampling method. Larger particulate solids, such as ores, are sampled using a riffle, which…
View Resource →This figure shows a schematic diagram of a gravity corer in operation. The corer’s weight is sufficient to penetrate into the sediment…
View Resource →This figure shows a systematic–judgmental sampling plan for monitoring the leaching of pollutants from a landfill. The sampling sites, shown as red…
View Resource →According to the Nyquist theorem, to accurately determine a periodic signal’s true frequency, we must sample the signal at least twice during…
View Resource →The overall variance in an analysis, s2, is the sum of the variances arising from the method, (smeth)2, and the variance due…
View Resource →When a manufacturer lists a chemical as ACS Reagent Grade, they must demonstrate that it conforms to specifications set by the American…
View Resource →The data set available here contains masses for 100 circulating U. S. pennies. All pennies in these data sets were minted between…
View Resource →The effect of a inert salt on a reaction’s equilibrium position is shown by the solutions in these two beakers. The beaker…
View Resource →Scale showing the pH value for representative solutions. Milk of Magnesia is a saturated solution of Mg(OH)2.
View Resource →The figure below shows how the masses of Ca2+ and CaCO3 change as a function of time during the precipitation of CaCO3.…
View Resource →The three plots below show the residual error in the signal, Sstd, as a function of the concentration of analyte, Cstd for…
View Resource →The figure here illustrates the basis of a linear regression analysis. The points in blue are the experimental data and the points…
View Resource →One approach for preparing standard additions is to spike equal volumes of the sample with different volumes of a standard and diluting…
View Resource →Sometimes the solution matrix in which the analyte resides affects the relationship between the signal and the analyte’s concentration, as shown below.…
View Resource →When using a single-point standardization, we must assume that there is a linear relationship between the signal and the analyte’s concentration. When…
View Resource →The figure below shows the probability of type 1 and type 2 errors for the IUPAC detection limit. (a) The normal distribution…
View Resource →A data point that is not consistent with the remaining data is called an outlier. Consider, for example, an experiment in which…
View Resource →The figure below shows the relationship between confidence intervals and the result of a t-test. (a) The shaded area under the normal…
View Resource →Example showing (a) a two-tailed, and (b and c) a one-tailed, significance test of an sample’s experimental mean relative to the population’s…
View Resource →According to the central limit theorem, when an analysis is subject to a variety of indeterminate errors, the distribution of results for…
View Resource →A binomial distribution describes a population whose members have only certain, discrete values. This is the case with the number of 13C…
View Resource →A binomial distribution describes a population whose members take on only certain, discrete values. This is the case, for example, with the…
View Resource →Indeterminate errors are random in nature and affect the reproducibility and repeatability of analytical measurements. We can assign indeterminate errors to several sources,…
View Resource →The magnitude of a constant determinate error is the same for all samples and is more significant when analyzing smaller samples. Analyzing…
View Resource →Analyzing a sample generates a chemical or physical signal proportional to the amount of analyte in the sample. This signal may be…
View Resource →Choosing an analytical methods requires a consideration of three potential limitations: the amount of sample available for the analysis, the expected concentration…
View Resource →Two determinations of the concentration of K+ in serum, showing the effect of precision on the distribution of individual results. The data…
View Resource →Suppose you are asked to develop an analytical method to determine the concentration of lead in drinking water. How would you approach…
View Resource →To measure volumes accurately and precisely, analytical chemists use volumetric pipets and volumetric flasks. A volumetric pipet is the choice when needing…
View Resource →An electronic balance is the most common method for determining a sample’s mass. Here is how the electronic balance works. An electromagnet…
View Resource →When the concentration of a species spans many orders of magnitude, it is difficulty to display how that species’ concentration changes during…
View Resource →What is the analytical perspective? Many analytical chemists describe this perspective as an analytical approach to solving problems. Although there probably are as…
View Resource →One distinction between analytical chemistry and chemical analysis is that analytical chemists work to improve and extend established analytical methods. For example,…
View Resource →This experiment describes the construction of a simple apparatus for effecting the electrodeposition of nickel onto a tared copper electrode. Results are…
View Resource →Students determine the amount of cranberry juice (as a volume percent) in mixtures of cranberry juice and apple juice by measuring the…
View Resource →Food storage containers may contain micro-particles of Ag, which serves as an anti-microbial agent to limit the growth of molds, fungi, and…
View Resource →The kinetics of the dephosphorylation of sodium p-nitrophenol using the enzyme bovine alkaline phosphatase is studied by measuring the reaction’s velocity spectrophotometrically…
View Resource →In this experiment students use diffusion-ordered NMR spectroscopy (DOSY) to determine the viscosity of a solution by measuring the diffusion coefficient (D)…
View Resource →Using a flatbed scanner to measure the reflectance from samples of a white polyester fabric impregnated with linseed oil, students determine detergent…
View Resource →Students determine the concentration of sodium sesquicarbonate in an alkaline laundry detergent though a combination of an acid-base titration and thermal gravimetry,…
View Resource →Students use DRIFT spectra and multivariate analysis to characterize sands collected from different locations. A principal component analysis shows that the scores…
View Resource →This experiment uses a novel approach to introduce students to the method of standard additions. To approximate the contribution of shell fragments…
View Resource →This experiment describes a quantitative UV-Vis analysis of mixtures of diesel/ethanol and diesel/biofuel based on the absorption of a solvochromatic probe dye.…
View Resource →The surface-enhanced Raman scattering (SERS) capabilities of silver nanoparticles is studied in this experiment by estimating the their analytical enhancement and surface…
View Resource →In this experiment students complete four tasks: monitoring the production of biodiesel by a transesterification of a commercial oil; quantifying mixtures of…
View Resource →The illustration below shows one method for making a standard addition. The volumetric flask on the left contains a portion of the…
View Resource →The photo below shows a typical example of a packed column for gas chromatography. This column is made from stainless steel and…
View Resource →Shown below is a schematic diagram of a thermal conductivity detector. This is one of a matched pair of cells. The sample…
View Resource →Shown below is a schematic diagram of a heated GC injector port for use with a packed column. The needle pierces a…
View Resource →Shown at the top is a reagent blank (far left) and a set of five external standards for Cu2+ with concentrations increasing…
View Resource →Shown at the top is a set of six standard additions for the determination of Mn2+. The flask on the left is…
View Resource →Suppose you are working at your local sewage treatment facility. One of your responsibilities is to monitor the effluent’s biological oxygen demand…
View Resource →One method for determining the concentration of glucose in fruit juices is to take advantage of its enzymatic oxidation in the presence…
View Resource →Trace levels of manganese can be determined by measuring its catalytic effect on the oxidation of diethylamine by sodium periodate. The rate…
View Resource →Shown below is a plot of initial rate vs. substrate concentration for an enzyme-substrate reaction that follows Michaelis-Menton kinetics. An analyst developing…
View Resource →The graph shown below is a plot of retention time vs. pH for the reverse-phase HPLC separation of a mixture containing phenacetin,…
View Resource →In ion-exchange chromatography, a solution containing a mixture of compounds is passed through a column packed with a resin containing covalently attached…
View Resource →A paper in the Journal of Chemical Education describes an experimental method for determining the concentrations of both insoluble metal sulfides, such…
View Resource →One method for determining copper is the “Neocuproine Method”. In this method, copper in a +1 oxidation state reacts with neocuproine (2,9-dimethyl-1,10-phenanthroline)…
View Resource →The spectrophotometric methods for analyzing Mn and for analyzing glucose use a chemical reaction to produce a useful signal. In the analysis for…
View Resource →Suppose you need to prepare a set of calibration standards for the spectrophotometric analysis of acetone at a wavelength of 211 nm…
View Resource →Shown below is a titration curve for a mixture of two monoprotic weak acids, HA and HB, where pKa,HA = 4.00 and…
View Resource →Shown below is a potentiometric titration curve for a 0.050-g sample of an amino acid dissolved in water and titrated with 0.100…
View Resource →The quantitative titrimetric analysis of amino acids often is complicated by the high pKa of the —NH4+ group, which produces a titration…
View Resource →In the EDTA titration for CaO in limestone, the pH of the sample is made sufficiently basic so any magnesium thatis present…
View Resource →Once upon a time, a common method for determining phosphorous was to convert it to phosphate, precipitate it as magnesium ammonium phosphate,…
View Resource →One of the hazards of strip mining is that water passing through the mine’s “tailings” (the piles of discarded material) is often…
View Resource →You may know that there is a growing interest in the ginkgo tree because herbal supplements using extracts of ginkgo are believed…
View Resource →When leaded gasoline was available, automobiles were a significant source of the total yearly environmental emission of Pb. During internal combustion lead…
View Resource →Imagine you have an aqueous sample containing a weak acid analyte, HA, and a weak base interferent, HI. The following information about…
View Resource →Carry out the following “experiment” to test the validity of the sampling constant equation mR2 = Ks where m is the sample’s…
View Resource →To determine the concentration of Cu2+ in a sample of water obtained from a local pond, the following solutions were prepared: Solution…
View Resource →A paper by Yan, et. al. [Yan, X.-P.; Sperling, M.; Welz, B. Anal. Chem. 1999, 71, 4216-4222] describes a newly developed analytical…
View Resource →Mechanical micropipets are commonly used to dispense small (μL) volumes of reagents. A recent “Application Note” [Am. Lab. June 1999] contains the…
View Resource →The %w/w Cu in a synthetic basic copper carbonate may be found by reducing and isolating the copper as Cu metal. To…
View Resource →In a recent paper [J. Chem. Educ. 1997, 74, 1108-1111], Snow, Dunn and Patel describe the experimental determination of fat in a…
View Resource →In determining the concentration of HCl by titrating against the primary weak base TRIS, the molarity of HCL is calculated using the…
View Resource →Errors effecting analytical work are broadly classified as determinate or indeterminate. Briefly explain the difference between a determinate and an indeterminate error,…
View Resource →A glucometer is a portable device used to monitor glucose levels in blood. Of concern for users is repeatability between units of…
View Resource →One concern in any analysis is the impact of the sample’s matrix. A method for an analyte that is known to work…
View Resource →Concentrated HCl is 37.2% w/w HCl (±0.5% w/w) and has a density of 1.19 g/mL (±0.01 g/mL). Suppose that you need to…
View Resource →Suppose you have a bottle of 53.4% w/w NaOH (the density of which is 1.52 g/mL) from which you are to prepare a…
View Resource →During lab you need to prepare a solution that is 5.00 x 10-2 M Fe(CN)63- using K3Fe(CN)6. (a) Explain how to make…
View Resource →Parathion, C10H16NO5PS, is a toxic organophosphorous pesticide. A recently published method [Sacks, et al. Anal. Chem. 2000, 72, 2055-2058] for parathion reports…
View Resource →Milk of Magnesia, or MOM, is a suspension of Mg(OH)2. One method for determining the amount of Mg(OH)2 in MOM is to…
View Resource →In an editorial published in American Laboratory (November 2000), Ira S. Krull states that in “any science, then, one must present at…
View Resource →Gratzel et. al. [Anal. Chem. 1999, 71, 2751-2756] describe the use of a diffusional microburet to transfer solutions to very small droplets…
View Resource →As part of the study of how humans age, there is an interest in learning how the chemical composition of tissues change…
View Resource →Have you ever wondered how atomic weights are determined? The National Institute of Standards and Technology (NIST) is one of several research…
View Resource →The April edition of the Journal of Chemical Education has an interesting experiment that introduces students to the fabrication of a microfluidic…
View Resource →The importance of visually examining a regression line relative to the data on which the regression is based is a point that…
View Resource →The data set available here is from the HPLC analysis of of riboflavin in urine. The Excel spreadsheet contains chromatographic data using…
View Resource →The following set of images show how samples are injected onto an HPLC column. Click on any image to expand the image…
View Resource →What happens if an institution does not have a quantitative analysis course? Where are students introduced to the concepts of analytical chemistry…
View Resource →This site provides an introduction to principal component analysis, beginning with a glossary of important terms before taking the reader through the…
View Resource →Means, standard deviation, and deciding if two results are different at some level of statistical significance is the basis for analytical decision…
View Resource →This site provides a java-based demonstration of how a least-squares analysis works. The applet opens with a set of data points with…
View Resource →This site provides a comprehensive electronic handbook on statistics for scientists and engineers. Topics include graphical approaches for exploratory data analysis, the…
View Resource →This site contains methods and exact solutions for a multitude of mathematical equations, including algebraic, differential, partial differential, integral, and functional equations.…
View Resource →This site is devoted to statistical tests and demonstrations of their use and was created with the support of the National Science…
View Resource →This site provides a brief reference on statistics that both analytical faculty and students will find useful. The site includes a series…
View Resource →This site provides a clear introduction to the principle component analysis (PCA) without overwhelming the student. The tutorial includes a brief introduction…
View Resource →This site contains a JavaScript “Uncertainty calculator,” which determines the uncertainty of a calculated result given the uncertainties for the measurements. The…
View Resource →This site provides a basic introduction to probability and statistics. There is a detailed explanation of the normal distribution, with associated mathematics,…
View Resource →This site provides a Java-based simulation that uses a random number generator to demonstrate the principles of probability. The website is available…
View Resource →The freely available software package uses a nonlinear least-squares regression analysis to fit chemical kinetic, enzyme kinetic, or ligand-receptor binding data to…
View Resource →This electronic textbook on statistics provides both extensive and in depth coverage of statistics. Although an excellent reference for analytical chemistry students…
View Resource →Showing 12 of 284 resources