Search

Relative Response Factors (RRFs) can be used for quantitation of one compound against another and it is widely used for Impurity analysis of pharmaceutical products; however, the application in potency assay is limited. Through an extensive study shown in this paper, it can be concluded that using the “RRF methodology” for potency assay is much more challenging compared to impurity analysis, due to the much tighter criteria required for potency analysis. The effects of instrument settings, which are rarely discussed or recognized in current HPLC analytical method development and quality release testing, are discussed. These factors impact the RRF just as much as other commonly recognized HPLC parameters. The effects of UV detector settings, i.e. Slit Width, Step Width, Band Width, and Data Collection Module, have been explored. This phenomenon has been demonstrated using three compounds to observe the impact of their quantitation due to the significant RRF variations. Finally, principles to reduce RRF variations have been discussed, and practical considerations of RRF application to method development and method transfer are provided.

The present work deals with the broadening of rotational lines of the carbon monoxide 2–0 band by both argon and hydrogen chloride. A high resolution grating spectrometer with a spectral slit width of 0.07 cm(−1) was used, necessitating only a small correction in observed half-width values. Sufficiently small contributions of CO self-broadening were obtained by using long pathlength cells of 12 meters for CO-argon mixture and 1 meter for CO-HCl mixture. Half-width results, which are considered accurate to within ±5 percent, are presented in the form of a table and by a graph.

A high-performance thin-layer chromatographic method was developed and validated for simultaneous determination of thiocolchicoside and ketoprofen in combined dose tablet formulation. The chromatography was performed on pre-coated silica gel 60 F 254 plates using methanol-toluene-benzene 2.5:3.5:4.0 (v/v/v ) as mobile phase. The plates were developed to a distance of 8.0 cm at ambient temperature. Experimental conditions such as band size, chamber saturation time, migration of solvent front, slit width, etc. were critically studied and the optimum conditions were selected. A TLC scanner set at 260 nm was used for direct evaluation of the chromatograms in reflectance/absorbance mode. The drugs were satisfactorily resolved with R F 0.34 for thiocolchicoside and 0.65 for ketoprofen. Method was validated according to the ICH guidelines The calibration plot was linear between 125-750 ng per band for THC and 1000-6000 ng per band for KET. The LOD and LOQ for THC were 17.43 and 52.82 ng per band, for KE...

An important step in the validation of an analytical procedure is the study of its robustness. In the case of spectrofluorimetric determinations, quenching introduces specific problems which are approached in this paper for the particular case of tetracyclines determination in milk. Quenching can be detected with excitation emission matrices (EEM) signals and a three-way Parallel Factor (PARAFAC) decomposition and modelled by means of a four-way PARAFAC decomposition which reproduces the physical model of this effect. The robustness of the method is evaluated by including changes in seven experimental variables: trichloroacetic acid (TCA) volume solution used in the precipitation of milk proteins, revolutions per minute, time and temperature in the centrifugation step, pH and emission–excitation slit width in the fluorimetric analyte determination and the analyst. The robustness analysis is carried out by means of a Plackett–Burman experimental design as it is suggested by European Decision 2002/657/EC (European Decision (EC) No. 2002/657/EC of 12 August 2002, implementing Council Directive 96/23/EC, concerning the performance of analytical methods and the interpretation of results, Off. J.L 221, 17/8/2002, 8). The analyte concentration will be taken as response in the Plackett-Burman experimental design instead of the signal as it is habitual in these cases. Therefore, a three-way Partial Least Squares (3-PLS) calibration models with EEM signal is needed. When an analogous study is carried out for tetracycline (TC) in the absence of chlorotetracycline (CTC) as interferent, univariate calibration is employed, being able to conclude that in the robustness analysis, different factors are significantly active when quenching exists.

The pressure dependence of a 129 Xe chemical shift (δ) and the local density of xenon adsorbed in activated carbon fiber (ACF) with slit-pore widths of 11.71.I nm was investigated using in-situ high-pressure 129 Xe NMR. 129 Xe chemical shift values below 0.025 MPa change linearly with equilibrium pressure. The initial slope of the pressure dependence of δ led to a shift value at zero pressure, δ s ', which approximately reflects the xenon-wall interaction. A statistical model incorporating the xenon-wall interaction well interprets the dependence of δ s ' on the pore width. Furthermore, in a higher-pressure region, the density dependence of the chemical shift led to the xenon-xenon interaction via the virial coefficients of the chemical shift up to the second order on density (the third-virial coefficient). The second-virial coefficient (a coefficient for the linear term of density) depended on the pore width. Increasing the slit width from 0.7 to 1.1 nm increased the second-virial coefficient, δ 1 , from 42 x 10 -3 to 78 x 10 -3 ppm kg -1 m 3 , suggesting that the space accessible by the surrounding xenon atoms increases when the slit width increases. This aspect reveals the size effect of the xenon-xenon interaction in nanospace.

This paper presents a comparison of quantification of thin-layer chromatographic plates with slit-scanning densitometry and with two image-analysing systems. Camag test dye mixture III was used as a sample. The influence of different measuring beam dimensions (slit width and slit length) on the quantitative evaluation of thin-layer chromatograms was studied in the reflectance as well as in the transmission mode. The slit length has a much higher influence on the reproducibility of the measured areas than the slit width. The results obtained with both CCD cameras show linear correlation between response area and concentration of Camag test dye mixture III in a higher concentration range than the densitometrically obtained results. The sensitivity of the used image-analysing systems was much lower than that of the slit-scanning densitometer.

A simple technique for estimating the slit width of a spectrometer from the ratio of the observed (Δν1/2)R and (Δν1/4)R of a Raman line profile was developed by calculating a set of corresponding values of Z=(Δν1/4)R/(Δν1/2)R and X=S/(Δν1/2)R based on the exact numerical evaluation of the Voigt profile. This technique was applied to some selected Raman lines and was found to give accurate values of the slit width in almost all cases where the slit distortion is appreciable and the band is isolated. Another technique for calculating the fractional Lorentzian character from the observed Raman spectra is also suggested. © 1997 by John Wiley & Sons, Ltd.

In order to enhance research in the field of low‐temperature photophysics or photochemistry, a convenient multiple‐purpose spectrophotometer system was constructed. This system enabled us to measure the emission (and/or its excitation) and absorption (even under steady‐state photolysis) spectra of liquid and solid samples at a temperature ranging from 10 up to 313 K. The spectral resolutions (or the peak separations) were estimated to be ∼0.10–0.31 and ∼1.0–7.3 nm for an emission and its excitation spectra, respectively, recorded at a slit width between 0.05 and 0.5 mm. For an absorption spectrum recorded at a slit width of 0.5 mm, the resolution was still better than that recorded by a commercial spectrophotometer with a bandwidth of 0.2 nm. By recording a number of emission spectra (normalized by the excitation‐light intensities at various excitation wavelengths), a contour mapping for the simultaneous intensity representation of the emission and its excitation spectra was also possible.

Relationship between the condition of the high pressure water jet and the produced powder was investigated to understand the mechanism of fine powder production by high pressure water atomization. The water flow rate and the slit width of water nozzle were directly measured in three different initially set nozzle configurations under various water pressures (up to 80MPa). Also, the suction pressure above the conical water jet and the staticpressure difference of the jet interior were investigated.The water flow rate and the configuration of the water nozzle increased comparably as the water pressure increased, but the suction pressure formed a peak. The shape and size of powders change up to the value of water pressure where the peak suction pressure appeared. The characterization of powders did not change considerably when atomized in the water pressure which exceed the value of Peak suction pressure.

A method is described to avoid the effects of sample heterogeneity in Raman measurements on solid samples. A Hadamard multiplex multichannel system with a bifurcated fiber-optic bundle for excitation and collection is used. The Hadamard mask employs a 7-element code with a unit slit width of 400 μm. Results are reported for samples prepared by mixing cytosine and 5-methylcytosine powders.

To investigate the internal structure changes in virgin black human hair keratin fibers due to aging, the structure of cross-sections at various depths of virgin black human hair (sections of new growth hair: 2 mm from the scalp) from a group of eight Japanese females in their twenties and another group of eight Japanese females in their fifties were analyzed using Raman spectroscopy. For the first time, we have succeeded in recording the Raman spectra of virgin black human hair, which had been impossible due to high melanin granule content. The key points of this method are to cross-section hair samples to a thickness of 1.50-microm, to select points at various depths of the cortex with the fewest possible melanin granules, and to optimize laser power, cross slit width as well as total acquisition time. The reproducibility of the Raman bands, namely the alpha-helix (alpha) content, the beta-sheet and/or random coil (beta/R) content, the disulfide (--SS--) content, and random coil content of two adjoining cross-sections of a single hair keratin fiber was clearly good. The --SS-- content of virgin black human hair from the Japanese females in their fifties for the cortex region decreased compared with that of the Japanese females in their twenties. On the other hand, the beta/R and alpha contents of the cortex region did not change.

This article reports on the separation and determination of Cr(III) and Cr(VI) with cation-exchange chromatography and flame atomic absorption spectroscopy. A sample containing the two ions is added to a column containing a cation-exchange resin; the Cr(VI) ions are not retained by the resin and are collected in the effluent. The Cr(III) ions are retained by the resin and eluted with an HCl solution. The separated ions are aspirated into an air/acetylene flame and the absorbance measurements are made at λ = 357.9 nm and 0.2-nm slit width. The experiment has been implemented in a quantitative methods of analysis course. The results of the analysis of synthetic water samples obtained by students majoring in various areas of science are presented. The data showed that 58% of the Cr(VI) and 39% of the Cr(III) values had relative errors in the range of ±5%. The evaluation of the precision of the student results revealed that 48% of the Cr(III) and 81% of the Cr(VI) reported values had RSD ≤ 4%. This experiment...

Students are introduced to screening and sequential experimentation using simulations and experimentation. The work begins with spreadsheet simulations and practice with the experimental design software. Students learn how to use the graphical output, normal quantile plots, to recognize the specific factors that affect the result of an experiment. In the laboratory, students make a preliminary investigation of the effect of six variables (flame observation height, flame stoichiometry, acetic acid, lamp current, wavelength, and slit width) on the atomic absorption signal for silver. This requires only sixteen experiments. Two or three active variables and an interaction of two variables are typically observed. Following this 26-2 fractional factorial design experiment, students investigate the effect of two active variables in more detail. This typically requires 16 to 25 experiments. The complexity of the system becomes apparent when flame observation height and percentage of acetic acid are studied. Most, but not all, of the observations are consistent with descriptive material that would be found in a typical instrumental methods text.

The Raman spectrum of gaseous N2F4 at a pressure of 760 Torr was recorded with a spectral slit width of 3 kaysers. Ten of the expected eleven fundamentals of the symmetric motions of both the gauche and trans isomers give rise to strongly polarized Raman lines. These new data require a reassignment of some of the fundamentals for both the C2 and C2h conformers. The Raman of the solid at 18 K was also recorded. Both conformers were found in the solid even after annealing the sample for 9 hr at a temperature of 101.6 K and 3 hr at a temperature of 106.8 K. Bands attributable to the gauche isomer became more intense relative to those for the trans isomer after several hours of annealing.

1. 1. Some confusion has recently developed concerning the “correct” molar absorptivity (e) for use with the Ellman reagent, 5,5'-dithiobis (2-nitrobenzoate). 2. 2. For any compound E is dependent upon the experimental conditions under which it is determined and is correct for that system alone. 3. 3. General acceptance and use of a single reported value is invalid and can lead to inaccuracies. 4. 4. In support of this we discuss the effect on e of slit width, stray light, wavelength and photometric accuracy and the presence or absence of the parent compound in the analytical solution. 5. 5. We conclude that for any colorimetric reagent, a single “correct” e value should not be sought but rather that internal standardization should be the rule.

A technique for calibrating slit width for straight spectrometer slits based on the diffraction of laser radiation is described. Related slit properties and calibration apparatus are discussed.

The original papers of Walsh and L'vov anticipated that atomic absorption spectroscopy would be capable of absolute, or standardless analyses. This paper shows that the modern graphite furnace technique provides standardless analyses in varied and complex matrices within about 10–20% accuracy. Some of the conditions that control the remaining variability are the atomization temperature and spectroscopic variables such as spectral slit width and lamp current. Nevertheless, characteristic mass data collected from nominally similar conditions in different laboratories for many elements show a spread of about ±15%, in spite of all the variables. A group of materials was analysed for several elements using only characteristic mass data for calibration and the results were compared with previous analyses of these materials. The results supported the 10–20% accuracy of this approach

The purpose of this study was to use the optical Doppler velocimeter of Borders and Granger [(1984), Microvasc. Res. 27, 117–127] to determine the ratio of centerline red cell velocity to mean velocity of blood flowing in small glass tubes. Red blood cell suspensions were perfused at different rates through capillary tubes (15–100 μm, id) while measuring centerline velocity ( V meas ). Mean red cell velocity ( V mean ) was calculated from measurements of volume flow in the tubes. With the effective slit width (sensor size) of the velocimeter set at 9.0 μm, the ratio of V meas V mean averaged 1.54 ± 0.03 (mean ± SEM), and was essentially independent of tube size. When the slit width was increased, the ratio of V meas V mean was significantly lower and appeared to vary as a function of tube diameter. These results are compared with previous measurements using other velocimeters, and the relationship between relative sensor size and ratio of V meas V mean is discussed.

A spectrochemical procedure to determine the ratio of the concentration of argon in a sample slightly different from air to the concentration of argon in air was developed using an electrodeless discharge tube and a 22-foot direct-reading optical spectrometer. A precision of ±0.43% at the 95% confidence level was obtained for a single determination made in 1 minute. A method of relative precisions to obtain optimum adjustments of the equipment is described. This method was used to determine the optimum discharge tube pressure and the optimum entrance slit width.

The E1cm.1% values of infra-red absorptions of picolines in cyclohexane solution vary with the concentration of the solutes. Variation of the E values due to slit width effects is not the only factor contributing to the failure of Beer's Law; a second factor is interaction between the solute molecules. Serious errors in infra-red absorption analysis of picoline mixtures are demonstrated when such interactions are not taken into account.

Flame photometric determination of 0.001% Na in primary standard potassium iodate by applying the “ Linear Extraporation Method ” is reported.By reason of the working curve of Na in 1% KIO3 solution being linear up to 1 p.p.m. Na content and its background flat, the above method becomes applicable.Under the condition of oxygen pressure 13 psi, acetylene pressure 3.5 psi, slit width 0.02 mm, and by using Beckman DU flame photometer with photomultiplier, 0.001% Na in KIO3 was determined with good precision. If sufficient care is taken to prevent the intrusion of Na, this method is more simple and more rapid as compared with the usual method.

A spectrophotometric method for the determination of plutonium in the range of 0.2–140 mg/1 is described. The method is based on the measurement of the absorption of plutonium (VI) at 831 nm. A recording spectrophotometer with variable slit width, 10-cm cells and scale expansion facilities, is necessary. Uranium up to 20 g/1 does not interfere.

The band (v 1 + v 4) of gaseous HCCl3 has been remeasured with a spectral slit width of about 0,06 cm-1. By using the technique of computer simulation the following constants have been evaluated: (v 1 + v 4)0, α C (1+4), α B (1+4) and ξ Z (1+4).

The infrared absorption due to localized vibrations of H− and D− ions in NaF and LiF is measured between 20 and 300 °K. The oscillator strengths are temperature independent. Measurements with uniaxial pressure show that the frequency of the local mode in NaF:H− is shifted by lattice distortions of the symmetry of Γ and Γ but not of Γ. In NaF:D−, LiF:H−, and LiF:D− two-phonon decays are allowed resulting in relatively large halfwidths at low temperatures. In NaF:H− a two-phonon decay is not possible and the halfwidth becomes smaller than the minimum spectral slit width of the grating spectrometer. The temperature dependence can be described by a scattering process in NaF:H− and by a composition of a scattering process with a two-phonon decay process in the other systems. The anharmonic frequency shift is calculated to a first approximation. In a simple density approximation the side band spectra can be described better by anharmonicity than by nonlinear dipole moments. Die Ultrarotabsorption lokalisierter Schwingungen von H−-und D−-Ionen in NaF und LiF wird zwischen 20 und 300 °K gemessen. Die Oszillatorenstarken sind temperaturunabhangig. Messungen mit uniaxialem Druck an NaF:H− zeigen, das die Frequenz der lokalisierten Schwingung durch Gitterverzerrungen der Symmetrien Γ und Γ, aber nicht durch Γ verschoben wird. In NaF:D−, LiF:H− und LiF:D− sind Zweiphononen-Zerfallsprozesse erlaubt, so das man bei tiefen Temperaturen relativ grose Halbswertsbreiten erhalt. In NaF:H− ist ein solcher Zerfall nicht moglich, und die Halbwertsbreite wird kleiner als die spektrale Spaltbreite des Gitterspektrometers. Der Temperaturverlauf kann in NaF:H− durch einen Streuprozes, in den anderen drei Systemen durch Uberlagerung eines Zweiphononen-Zerfallsprozesses mit einem Streuprozes erklart werden. Die anharmonische Frequenzverschiebung wird in erster Naherung berechnet. Mit einer einfachen Dichtenaherung konnen die Seitenbanden durch Anharmonizitat besser beschrieben werden als durch nichtlineare Dipolmomente.

Although the Davis Halide Meter is one of the best portable instruments so far encountered for the evaluation of health hazards which may result from the inhalation of organic chloride vapors, it has not been completely free of difficulties. These problems are described along with corrective measures which have been developed. A partial list of items considered includes: effect of water vapor, inability to zero the instrument, effect of slit width, effects of high concentrations of organic halide vapors upon subsequent use and required calibration.

The experimental determination of the resolving power of infrared spectrometers by means of sharp absorption lines is discussed. Under certain conditions the convolution of the true line profile with the monochromator function approximates completely to the latter, from where the spectral slit width can be obtained immediately. Some suitable lines in the absorption spectra of small gas molecules are suggested for calibration purposes.

A rapid sensitive (1 p.p.m.) ultraviolet method of analysis has been developed and successfully applied to the determination of repellent in cloth and on glass plates. The absorbance of a sample in ethanol is read on a spectrophotometer at 230 mµ with the slit width maintained constant. The concentration is determined from a calibration curve relating absorbance to concentration. Absorption spectra of the purified ortho, meta, and para isomers have no peaks, but at constant slit width their absorbances at 230 mµ, obey Beer’s Law. Insufficient differences in the spectra of the three isomers precluded a satisfactory mathematical determination of the individual isomers.

The best experimental conditions for zinc determinations by atomic absorption spectrophotometry, air pressure, slit width and concentration limits have been established. The precision of the method is calculated on the basis of error calculus of absorption measurements. If solutions containing 30–120 ppm of Zn 2+ are measured, the relative errors are lower than ±0.5%. Interferences of anions and cations have been investigated, and found in most cases to be negligible.

The Raman spectra of benzene in the liquid and vapour states have been photographed alongside each other under identical conditions of slit width and illumination. While the 600 and 992 Raman lines show no shift, the line at 3061 shifts to 3069 as we pass from the liquid to the vapour. The Raman line at 3047 observed in the liquid has either completely disappeared or considerably weakened in the vapour. The rotation wings accompanying the Rayleigh lines in the liquid show no intensity maximum separated from the centre whereas there is a distinct maximum in the case of the vapour. This result is demonstrated with the help of microphotometric records. The distribution of intensity within the wings in the case of the liquid is very different from that obtained in the case of the vapour. When judged by comparing with the 992 Raman line, a very considerable fall in the absolute intensity of the wings is noticed as we pass from the vapour to the liquid. The significante of this result is discussed.

An infrared spectrophotometric micromethod, specific for endrin, has been developed which quantitatively measures 1–2 μg of endrin in solutions containing endrin-dieldrin-aldrin. Endrin was determined by: a) reference to a standard curve based on the 748 cm −1 (13.37 μ) absorbance band unique to endrin, or b) use of a constant based on the ratio of the 748 cm −1 absorbance band of endrin to the 1179 cm −1 (8.48 μ) absorbance band common to all three compounds. Sensitivity and accuracy were attained with micro cells. The measurements were made with controlled slit width and instrument conditions. The base-line technique was used to measure the intensities.

This paper describes simple methods for determining spectral bandwidth by measurement and by calculation. We measured the spectral bandwidth of the monochromator from the Beckman Enzyme Analyzer TR, and found it to be 3.5-4.0 nm (av 3.8) by two different methods. We visually estimated it to be 4 nm. Using the specifications for the diffraction grating, focal length, and fixed slit width, we calculated the theoretical spectral bandwidth to be 3.6 nm.

The importance of narrow slits in the spectrophotometric determination of extinction coefficients has been demonstrated. Care is needed in the B.P. 1958 spectrophotometric tests or assays of apomorphine hydrochloride, chloroquine phosphate, chloroquine sulphate, diiodohydroxyquinoline, naphazoline nitrate, papaverine hydrochloride and especially procyclidine hydrochloride, to avoid spuriously low results.

Tres parámetros de operación de un espectrofotómetro UV-visible (velocidad de barrido, ancho de ranura del monocromador e intervalo de muestreo) fueron optimizados utilizando un diseño factorial fraccionado. Cuatro espectros de absorción de óxido de holmio fueron registrados en una porción de la región visible (560-610 nanómetros) usando diferentes combinaciones de niveles “altos”y “bajos” para los parámetros ya mencionados. Las combinaciones fueron provistas por un diseño 23-1. De los resultados se deduce que el espectro de más alta calidad es proporcionado por la siguiente combinación: alta velocidad de barrido, ancho de ranura del monocromador pequeño (0.2 nanómetros) e intervalo de muestreo pequeño (un punto por cada 0.1 nanómetro). Este trabajo ilustra la utilidad del diseño factorial fraccionado como una herramienta de optimización en el laboratorio de química analítica

The Raman spectra of benzene in the liquid and vapour states have been photographed alongside each other under identical conditions of slit width and illumination. While the 600 and 992 Raman lines show no shift, the line at 3061 shifts to 3069 as we pass from the liquid to the vapour. The Raman line at 3047 observed in the liquid has either completely disappeared or considerably weakened in the vapour. The rotation wings accompanying the Rayleigh lines in the liquid show no intensity maximum separated from the centre whereas there is a distinct maximum in the case of the vapour. This result is demonstrated with the help of microphotometric records. The distribution of intensity within the wings in the case of the liquid is very different from that obtained in the case of the vapour. When judged by comparing with the 992 Raman line, a very considerable fall in the absolute intensity of the wings is noticed as we pass from the vapour to the liquid. The significante of this result is discussed.

A simple convenient method is described by which radioactivity on thin layer chromatoplates can be scanned rapidly. Depending on the coating thickness and the slit width and time constant of the scanner, the efficiency was about 2%. The continuous scanning system is described. (P.C.H.)

THE infra-red absorption bands of nine organic liquids have been studied in the 3.5μ region. The spectrometer employed made use of an eschelette grating, which had a resolving power of 10,000 as compared with approximately 170 for a 3-inch rock-salt prism in this region. The dispersion was such that, with the slits 0.25 mm. wide, one slit width contained a portion of the spectrum only 25 A. wide. The wave-lengths as given below are believed to be accurate to ±0.003μ.

Recently the Py solvent scale has been introduced and a large body of data has been generated using fluorescence measurements. Numerous problems exist in the correct determination of these values, including instrumental and chemical artifacts. Among the instrumental problems associated with correct Py assignments are slit width effects, inner filtering and efficiencies associated with double-pass vs. single-pass cell compartment designs. These instrumental problems, together with chemical artifacts related to adequate blank correction and temperature control, were investigated in the work reported in this paper.