Law Plots Research Articles

Purity characterization of 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS) monomer by UV–vis spectroscopy

The purity of the disulfonated monomer, 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS), is very important for obtaining high molecular weight disulfonated poly(arylene ether sulfone) random or block copolymers, which are promising candidates for proton exchange membrane (PEM) fuel cells. For commercialization purposes, direct use of unrecrystallized SDCDPS monomer with known purity in the copolymerization favorably influences its economics relative to the traditional recrystallization purification process. In this paper, a novel method to characterize the purity of the prepared unrecrystallized SDCDPS has been developed using UV–vis spectroscopy. The purity of the comonomer was determined from a Beers Law calibration curve developed using a highly purified SDCDPS sample. High molecular weight poly(arylene ether sulfone) random copolymers, based on this unrecrystallized SDCDPS monomer, 4,4′-dichlorodiphenyl sulfone (DCDPS), and 4,4′-biphenol monomers, were successfully synthesized. The molecular weight obtained from gel permeation chromatography (GPC) (Mn>45kgmol−1) was high enough to allow tough films for PEMs to be solvent cast. This confirmed that the purity characterization method was relatively accurate and applicable. The effect of storage and drying time of SDCDPS were also studied using Beer's Law plots.

Spectrophotometric Determination of Some Fluoroquinolone Derivatives in Dosage Forms and Biological Fluids Using Ion‐Pair Complex Formation

A simple, rapid, sensitive, and reproducible procedure for assaying norfloxacin (NOR), ciprofloxacin (CIP), and ofloxacin (OFL) was investigated. The procedure is based on the reaction of selected drugs with Sudan II (I), Congo red (II), and Gentian violet (III) in universal buffer to give soluble ion‐pair complexes. The effects of various parameters have been studied. Beer's law plots were obeyed in the concentration ranges 0.5–11 µg ml−1, whereas Ringbom optimum ranges were 0.7–9.5 µg ml−1. The apparent molar absorptivity (6.4×104 L mol−1 cm−1), Sandell sensitivity (4.99 ng cm−2), detection (0.13 µg ml−1), and quantification (0.44 µg ml−1) limits were calculated. The relative standard deviation for ten determinations, for samples containing 4.0 µg ml−1, was found to be 1.40%. The influence of commonly employed excipients in the determination of the studied drugs was examined. There was no interference from degradate product results from thermal and hydrolytic treatments. The results obtained by the proposed procedure were statistically validated. The developed procedure was successfully applied to the determination of the studied drugs in dosage forms and biological fluids.

Kinetic studies of water uptake and loss in glass-ionomer cements

The water sorption and desorption behaviour of three commercial glass-ionomer cements used in clinical dentistry have been studied in detail. Cured specimens of each material were found to show slight but variable water uptake in high humidity conditions, but steady loss in desiccating ones. This water loss was found to follow Fick's law for the first 4-5 h. Diffusion coefficients at 22 degrees C were: Chemflex 1.34 x 10(-6) cm(2) s(-1), Fuji IX 5.87 x 10(-7) cm(2) s(-1), Aquacem 3.08 x 10(-6) cm(2) s(-1). At 7 degrees C they were: Chemflex 8.90 x 10(-7) cm(2) s(-1), Fuji IX 5.04 x 10(-7) cm(2) s(-1), Aquacem 2.88 x 10(-6) cm(2) s(-1). Activation energies for water loss were determined from the Arrhenius equation and were found to be Chemflex 161.8 J mol(-1), Fuji IX 101.3 J mol(-1), Aquacem 47.1 J mol(-1). Such low values show that water transport requires less energy in these cements than in resin-modified glass-ionomers. Fick's law plots were found not to pass through the origin. This implies that, in each case, there is a small water loss that does not involve diffusion. This was concluded to be water at the surface of the specimens, and was termed "superficial water". As such, it represents a fraction of the previously identified unbound (loose) water. Superficial water levels were: Chemflex 0.56%, Fuji IX 0.23%, Aquacem 0.87%. Equilibrium mass loss values were shown to be unaffected by temperature, and allowed ratios of bound:unbound water to be determined for all three cements. These showed wide variation, ranging from 1:5.26 for Chemflex to 1:1.25 for Fuji IX.

Spectrophotometric determination of pefloxacin mesylate in pharmaceuticals

A spectrophotometric method is described for assay of pefloxacin mesylate (PFM) in bulk drug and in tablets. The method is based on back extraction of the bromophenol blue dye at pH 5.2 from the dye-drug ion pair followed by measurement of the dye absorbance at 590 nm. The working conditions of the method were investigated and optimized. Beer's law plot showed a good correlation in the concentration range of 0.15-1.25 microg mL(-1). Sensitivity indices such as molar absorptivity, limits of detection and quantification are reported. Intra-day and inter-day precision, and accuracy of the methods were established according to the ICH guidelines, and the er values were in the range of -1.7 to 1.8% with RSD values ranging from 1.0 to 1.1%. The method was successfully applied to the assay of PFM in tablet preparations with recoveries varying from 97.5 to 101.9%, with standard deviation in the range of 0.6 to 1.9. The results were statistically compared with those of the reference method by applying Student's t-test and F-test. Accuracy evaluated by means of the spike recovery method, range from 97.0 to 106.0%, with precision better than 3%.

Extractive liquid–liquid spectrophotometric procedure for the determination of thiocyanate ions employing the ion pair reagent amiloride monohydrochloride

An accurate, inexpensive and less laborious liquid–liquid extractive spectrophotometric procedure for the determination of thiocyanate ions in aqueous media has been developed. The method has been based upon the formation of a yellow colored complex ion associate of the ion-pairing reagent 1-(3, 5 -diamino -6 -chloropyrazinecarboxyl) guanidine hydrochloride monohydrate, namely amiloride hydrochloride, DPG +·Cl − and the thiocyanate ions in aqueous media containing HNO 3 (0.5 mol L −1) and subsequent extraction with 4-methyl-2-pentanone. The absorption electronic spectrum of the ion associate showed one well-defined peak at λ max 366 nm. The stoichiometric mole ratio of DPG +·Cl − to the thiocyanate ions is 1:1.The effective molar absorptivity ( ɛ) of the ion associate at λ max 366 nm is 1.1 ± 0.1 × 10 4 L mol −1 cm −1. The extraction constants ( K d, K ex, and β) enabled a simple and convenient use of the developed binary ion associate for the extractive spectrophotometric determination of traces of thiocyanate ions in the aqueous media. Beer's law and Ringbom's plots are obeyed in the concentration range 0.05–10 and 0.1–7 μg mL −1 of the thiocyanate ions, respectively with a relative standard deviation of ±2.3%. The calculated lower limits of detection (LOD) and quantitation (LOQ) of the developed procedure for the thiocyanate ions were found equal to 0.02 and 0.066 μg mL −1, respectively. The developed method has been applied for the determination of trace amounts of thicyanate ions in tap-, waste- and natural water samples and compared successfully with the reported methods at the 95% confidence level. The proposed method was also applied successfully for the determination of thiocyanate ions in saliva samples.

Chemical equilibria and sequential extractive spectrophotometric determination of selenium(IV) and (VI) using the chromogenic reagent 4,4′-dichlorodithizone

The chromogenic reagent 4,4′-dichloro(3-mercapto-1,5-diphenylformazan), Cl2H2D Z , forms a yellow–red-coloured complex with selenium(IV). The produced complex species was extracted quantitatively into n-hexane, and its absorbance was measured at 416 nm. The chemical composition of the extracted selenium(IV)-Cl2H2D Z chelate and the molar absorptivity at 416 nm were found to be [SeO (Cl2HD Z )2] and 9 × 104 L mol−1 cm−1, respectively. The values of the extraction constants (K D, K ex, β) enable a convenient application of the proposed system for the liquid–liquid extraction procedure and sequential spectrophotometric determination of traces of inorganic selenium(IV) and/or selenium(VI) after reduction of the later to selenium(IV) with HCl (6 M). Beer's law and Ringbom's plots were obeyed in the concentration range 0.01–20 and 0.5–19 µg mL−1 of selenium(IV), respectively, with a relative standard deviation of 2.2%. The proposed method has been successfully applied to the determination of selenium(IV) or (VI) and total inorganic selenium(IV) and (VI) in tap and freshwater samples.

Using Visible Absorption To Analyze Solutions of Kool-Aid and Candy

This article describes a set of materials and a brief description of a technique that may be used to introduce concepts of color and visible absorption to students. Because everyday food items are used, the activity may be presented to high school students, nonscience majors, or may be used with science majors to help them develop good analytical techniques without worry about hazardous waste. A description is given of the use of Kool-Aid solutions to prepare a Beer's law plot, from which an unknown's concentration can be determined. Although a scanning spectrophotometer was used at our institution, a Spectronic 20 would be usable as well. Also, solutions of Kool-Aid, MandMs, and Skittles are compared in terms of their visible absorption band shapes. Students use these candy spectra to determine whether the dyes used to color these food items might be the same.

Comparative Study of the Copolymerization Kinetics of Mono and Divinylbenzyl p-tert-Butylcalix[4]arene Derivatives and Styrene

A study of the copolymerization kinetics of 25,27-bis-(4-vinyl-benzyloxy)-26,28-dihydroxy-p-tert-butylcalix[4]arene (1) and 25,26,27-tripropoxy-28-(4-vinyl-benzyloxy)-p-tert-butylcalix[4]arene (2) with styrene (St) was undertaken. The radical copolymerizations were carried out in THF in the presence of benzoyl peroxide at 75°C for a certain period. Six molar feed ratios, ranging from 1:1 to 1:20 (1 or 2 to St), were used to calculate the reactivity parameters. The copolymer composition was determined by FT-IR spectroscopy using a Beer's law plot obtained from the corresponding homopolymers. The reactivity ratio calculations were performed with the linearization methods of Fineman-Ross (F-R) and Kelen-Tüdös (K-T), assuming the validity of the so-called terminal model. In the copolymerization of the monoene 2, similar reactivity ratios were found for the comonomers (ca. 1.2; K-T). On the other hand, the reactivity ratios calculated for the copolymerization of 1 with St yielded r St = 0.67 and r calix = 3.0 (K-T method). The higher reactivity of monomer 1 as compared to styrene is discussed in connection with our previously postulated cyclocopolymerization route.

Comparison of spectrophotometric and high performance liquid chromatographic methods in the bioavailability studies of aspirin and salicylic acid in healthy human volunteers

The aim of the work was to develop a simple, rapid and accurate multiple component spectrophotometric method for the determination of aspirin and its major metabolite, salicylic acid, in plasma and the results obtained compared with the results of the same analysis using HPLC method. With HPLC, the drugs aspirin, salicylic acid and paracetamol (as internal standard) were eluted with 10μm reversed phase C18-support column at ambient temperature with a mobile phase consisting of methanol: 5% acetic acid (25:75) adjusted to pH 3.45 with glacial acetic acid, at a flow rate of 1.5ml/min with U.V detection at 280nm. Each analysis required no longer than 10min. Quantitation was achieved by measurement of the peak-height ratio and the relative and absolute recoveries varied from 90 to 98%. For U.V. spectrophotometric analysis, Beer's law plots were prepared using standard solutions of each of the salicylates (aspirin and salicylic acid) in 0.1M HCl and plasma. Extraction recoveries in plasma and 0.1M HCl (as control) were developed and the relative and absolute recoveries varied from 90 to 98%. The methods were applied for the determination of the pharmacokinetic parameters of aspirin and its major metabolite salicylic acid. Comparing the bioavailability of the drug under the two analytical methods employed in the study, it was observed that higher concentrations were observed with HPLC than U.V. Spectrophotometric method. However, the results obtained from these two analytical methods correlate with each other with the degree of probability (0.05

Resolution of Three Fluorescence Components in the Spectra of all-trans-1,6-Diphenyl-1,3,5-hexatriene under Isopolarizability Conditions

all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence in solution consists of emissions from the S1 (2(1)A(g)) and S2 (1(1)B(u)) states of the s-trans,s-trans conformer (s-t-DPH) and emission from the S1 state of the s-cis,s-trans conformer (s-c-DPH). The contribution of s-c-DPH fluorescence increases upon excitation at longer wavelengths, and both minor emissions, s-c-DPH and 1(1)B(u) s-t-DPH fluorescence, contribute more at higher temperatures (Ts). Resolution of a spectrothermal matrix of DPH fluorescence spectra by principal component analysis with self-modeling (PCA-SM) is hampered by T-dependent changes in the spectra of the individual components. We avoided differential polarizability-dependent spectral shifts by measuring the spectra in n-alkanes (Cn, C8 to C16 with n even) at T values selected to keep the index of refraction constant, hence under isopolarizability conditions. Compensation of the spectra for T-induced broadening allowed resolution of the spectral matrix into its three components. The optimum van't Hoff plot gives Delta H = 2.83 kcal/mol for s-c-DPH/s-t-DPH equilibration, somewhat smaller than the 3.4 kcal/mol calculated value, and the optimum Boltzmann distribution law plot gives Delta E(ab) = 4.09 kcal/mol for 1(1)B(u)/2(1)A(g) equilibration. The 1(1)B(u) fluorescence spectrum bears mirror-image symmetry with the DPH absorption spectrum, and the energy gap, 1431 cm(-1), is consistent with the 1615 cm(-1) difference between the lowest energy bands in the 1(1)B(u) and 2(1)A(g) fluorescence spectra. The results give V(ab) = 198 +/- 12 cm(-1) for the vibronic matrix coupling element between the 2(1)A(g) and 1(1)B(u) states. Fluorescence quantum yields and lifetimes under isopolarizability conditions reveal an increase in the effective radiative rate constant of s-t-DPH with increasing T.

Gas-Phase Databases for Quantitative Infrared Spectroscopy

The National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) are each creating quantitative databases containing the vapor-phase infrared spectra of pure chemicals. The digital databases have been created with both laboratory and remote-sensing applications in mind. A spectral resolution of approximate, equals 0.1 cm(-1) was selected to avoid degrading sharp spectral features, while also realizing that atmospheric broadening typically limits line widths to 0.1 cm(-1). Calculated positional (wave- number, cm(-1)) uncertainty is </=0.005 cm(-1), while the 1sigma statistical uncertainty in absorbance values is <2% for most compounds. The latter was achieved by measuring multiple (typically >/=9) path length-concentration burdens and fitting a weighted Beer's law plot to each wavenumber channel. The two databases include different classes of compounds and were compared using 12 samples. Though these 12 samples span a range of polarities, absorption strengths, and vapor pressures, the data agree to within experimental uncertainties with only one exception.

TGA Investigation of Xylenes' Steric Effect During Their Adsorption and Diffusion in NaX Adsorbent

Separation processes using selective adsorption on zeolite are widely applied in chemical industries. The X zeolite is especially used for the separation of xylenes isomers. The objective of this workbased on NaX adsorbent known by its selectivity exclusively geometric to xylene isomersis a contribution to the comprehension of the separation mechanisms and of the steric effect parameters. Adsorption of o-xylene, m-xylene, p-xylene, and trimethylbenzene was studied in thermobalance at 100, 250, and 420 °C and at a constant pressure of 700 Pa. The results show that the adsorption and diffusion process are strongly influenced by the molecules' sizes. Using the Fick law plot, disruption phenomena owing to the steric effect were observed when the supercages of NaX adsorbent were filled.

Estimation of Generation Power of Wind Turbine due to Doppler SODAR Assessment

This paper describes the wind assessment of high layer for siting the wind turbine on the complex terrain, which is based on the data measured by the use of Doppler SODAR. Although a rough estimation of the wind assessment using standard meteorological anemometers at low layer are cost effective and easy to be installed, it is necessary to measure the wind condition at hub height for accurate assessment. Comparison between measured data by Doppler SODAR and the data predicted from observation of the wind condition at low layer is performed. Large difference is seen in the measured wind profile and calculated power law plots of the wind. Estimation of generation power of wind turbine due to SODAR measurement agrees well with the actual turbine generation power. In the complex terrain, it can be said that observation of the low layers does not suffice to assess accurately the wind, while Doppler SODAR measurement is useful.

Extractive spectrophotometric determination of fluoroquinolones and antiallergic drugs in pure and pharmaceutical formulations.

A simple, rapid and sensitive spectrophotometric procedure has been proposed for the assay of fluoroquinolones viz., ciprofloxacin (CPF) and norfloxacin (NRF), and antiallergic drugs viz., methdilazine hydrochloride (MDH) and isothipendyl hydrochloride (IPH) in bulk and pharmaceutical formulations. The method is based on the reaction of selected drugs with Brilliant Blue G (BBG) in NaOAc-AcOH buffer of pH 4.0 for CPF and NRF or in neutral medium for MDH and IPH to give chloroform soluble ion-association complexes. The effects of various parameters have been studied. The ion-association complexes exhibited absorption maxima at 610 nm for CPF, at 614 nm for NRF and MDH, and at 612 nm for IPH. Beer's law plots were obeyed in the concentration ranges of 0.5-6.0, 0.4-8.0, 0.1-6.0 and 0.2-6.1 (mg ml(-1) for CPF, NRF, MDH and IPH, respectively, with correlation coefficients not less than 0.9969. Molar absorptivity values as calculated from the Beer's law data were found to be 2.86 x 10(4), 2.64 x 10(4), 3.13 x 10(4) and 5.51 x 10(4) mol(-1) cm(-1) for CPF, NRF, MDH and IPH, respectively. The influence of commonly employed excipients in the determination of the studied drugs has been studied. The results obtained by the proposed method were statistically validated.

Determination of minocycline by oxidative coupling and diazocoupling reactions in pharmaceutical formulations

Simple and sensitive spectrophotometric methods (M 1–M 4) by the application of oxidative coupling and diazocoupling reactions for the assay of minocycline (MC) in pure form and pharmaceutical formulations have been described. Methods M 1 and M 2 involve the oxidative coupling reactions of MC with 3-methyl-2-benzothiozolinone hydrazone (MBTH) (method M 1, λ max 440 nm) or 4-aminophenazone (4-AP) (method M 2, λ max 520 nm) in the presence of periodate. Methods M 3 and M 4 are based on the formation of diazocoupling products of MC with diazotised p-nitroaniline (DPNA) (method M 3, λ max 420 nm) or diazotised sulfanilic acid (DSAC) (method M 4, λ max 420 nm). Regression analysis of Beer's law plot showed good correlation in the concentration range of 8–48, 20–120, 4–20 and 8–40 μg ml −1 for methods A, B, C and D, respectively. The molar absorptivities fell within the range of 2.23×10 3–1.51×10 4 l mol −1 cm −1.The recoveries range from 99.02 to 100.61%.

Aqueous Complexation Equilibria of meso-Tetrakis(4-carboxyphenyl)porphyrin with Viologens: Evidence for 1:1 and 1:2 Complexes and Induced Porphyrin Dimerization

UV−vis spectra of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) have been studied in dilute (1.0 μM) aqueous solution at pH 7.0 as a function of added electrolytes, including phosphate buffer, methyl viologen dichloride (MV), and propyl viologen sulfonate (PVS). At concentrations ≤1.0 μM and pH ≥ 7.0, TCPP is considered to be tetraanionic and unaggregated. It shows a strong B (Soret) band at 414.2 nm that can be decomposed into three Gaussians, and follows Beer's law with ε = 4.8 × 105 M-1 cm-1 at pH 7.0 in 5.0 mM phosphate buffer. Deviations from Beer's law appear above 2 μM under the above conditions; linear regions for Beer's law plots depend on the pH, temperature, and ionic strength. Even around 1 μM, the Soret absorption strength is a very sensitive function of electrolyte concentration; for example, ε = 3.6 × 105 M-1 cm-1 at pH 7.0 in 62 mM phosphate buffer, and ε = 5.1 × 105 M-1 cm-1 in aqueous solution of minimal ionic strength (0.1 mM NaOH, pH 10). In the titration of TCPP with MV, two types of experiments were performed, at low ionic strength (which necessarily increased in the later stages of the titration) or at high (effectively constant) ionic strength. In 5.0 mM phosphate buffer at pH 7.0 two isosbestic points are observed, at 418.4 nm (in the range of 40−300 μM MV) and at 421.5 nm (15−90 mM MV), considered to represent the formation of 1:1 and 1:2 complexes (porphyrin−viologen). By nonlinear regression analysis, the complexation constants are calculated to be K1 = 3350 M-1 and K2 = 68 M-1. Application of principal component analysis identifies the spectra of both complexes and gives K1 = 2200 M-1 and K2 = 100 M-1. The complexation constants, the spectra of the complexes, and the positions of the isosbestic points vary with the buffer concentration. At 62 mM phosphate buffer, K1 = 600 M-1 and K2 = 40 M-1 by nonlinear regression analysis (K1 = 1200 M-1 and K2 = 140 M-1 by principal component analysis). 1H NMR spectra indicate that both TCPP and MV undergo concentration-dependent resonance shifts that can be correlated with the calculated complexation constants. Similar titration of TCPP with PVS also shows evidence for 1:1 and 1:2 complexes, but with lower equilibrium constants compared to those from titration with MV. At high PVS concentrations (>25 mM) a blue-shifted Soret band attributed to TCPP dimer is observed. The same spectrum is observed under a variety of other conditions, including the presence of a cationic surfactant (4 μM CTAB), very high ionic strength (3 M NaCl), or a polycationic complexing agent. These effects illustrate the variety of influences that affect the porphyrin absorption spectrum in aqueous solution and offer cautions about the conditions of experimental control and data analysis that are necessary to extract meaningful titration data.

Application of quinone reactions for the assay of amiodarone and ondansetron in pure and pharmaceutical formulations

Three simple, sensitive and reproducible visible spectrophotometric methods (A-C) are described for the determination of amiodarone (as hydrochloride, AD) or ondansetron (as hydrochloride, OST) in pure samples and pharmaceutical formulation. Methods A, B and C are based on the formation of charge-transfer complexes between AD or OST and chloranil, chloranilic acid or DDQ with λ m a x 540, 540 or 455 nm, respectively. Regression analysis of Beer's law plots showed good concentration ranges (20-300, 25-300), (30-300, 15-150) and (15-150, 5-60) μg ml - 1 for (AD, OST) in methods A, B and C, respectively. The applicability of the methods has been examined by analyzing tablets of AD or OST.

Validation of a high-performance liquid chromatography method for the determination of pancuronium in Pavulon injections

A new high-performance liquid chromatography (HPLC) method was developed for the quality control of pancuronium bromide and its degradation products. The HPLC method used a 5-μm Supelcogel ODP-50 (150×4 cm) column with acetonitrile–CH 3OH–water–F 3CCOOH (20.5:74.9:0.1, v/v) as the mobile phase (pH value 2.0 adjusted with trifluoroacetic acid) at a flow-rate 0.8 ml/min and UV detection at 210 nm. The Beer’s law plots were found to be linear over the concentration range 0.4–1.2 mg/ml of pancuronium bromide and 0.04–0.08 mg/ml of desacetyl degradation products ( R 2=0.9995). The RSD of the peak areas was 1.09% and the recovery was 102.43%. The RSD value shows good precision, acceptable accuracy and reproducibility of the new method for the determination of pancuronium bromide in presence of its desacetyl degradation products. The method is rapid and sensitive enough to be used for Pavulon injection analysis.

Color Changes in Indicator Solutions. An Intriguing and Elucidative General Chemistry Experiment

The simple dilution of an aqueous solution of the indicator (In) bromocresol green is proposed as an intriguing experiment for students of chemistry. As the solution is diluted with water, its color changes strikingly from reddish to pale blue. These changes are related to changes in the absorption bands in the visible electronic spectra. The pKIn can be determined through the Henderson-Hasselbalch equation by plotting the pH values as a function of log([In-]/[HIn]). The concentration, in mol L-1, of the HIn species can be determined by measuring the absorbance at 440 nm and using the e value determined from the Beer's law plot. [In-] is calculated from the difference between the initial HIn concentration and the observed [HIn]. Students will be able to conclude that the dissociated fraction of a weak acid increases with dilution.

Quantitative Determination of Copper: Combining Project-Based Laboratories with Single-Analyte Detection

A multiweek experiment is presented for use in undergraduate instrumental analysis courses. The experiment combines project-based laboratories and single-analyte detection to provide students with experience in method development and validation, and to give them a more realistic experience in the analytical laboratory. Working together as a team, students develop methods for the detection of an analyte (i.e., copper) in water samples using at least two spectroscopic instruments (e.g., ICP-AES, AA, UV-vis, fluorescence). Student teams are given only topical information about their projects, and must research and plan the analyses, learn the instrumental methods to be used, obtain figures of merit (e.g., detection limits) from Beer’s law plots, analyze commercial water samples, and produce a standard operating protocol for one of their methods, which will be validated by another team during a subsequent laboratory. Goals of this approach include promoting teamwork and building student confidence in approaching and operating unfamiliar instrumentation. Even more importantly, students are placed in the position of being scientists and having to make decisions and recommendations. Each step of the analytical process must be carefully considered, and its significance assessed as there are no recipes to follow as they develop their methods and make comparisons between different techniques for the determination of a single analyte.