Influence of pressure on the determination of palladium by graphite furnace atomic absorption spectrometry using resonance and non-resonance lines

Atomization under pressure considerably influences the absolute and relative sensitivities of resonance and non-resonace lines. Whereas for resonance lines the peak height and area senstitivities decrease with increasing pressure, for non-resonance lines the sensitivity initially increases probably because the increase of the temperature of the atomic vapor compensates for the Lorentz broadening and the red shift. At higher pressures probably absorption line broadening and red shift effect become predominant so that the sensitivity of the non-resonance lines becomes poorer. In spite of this the relative sensitivity of the non-resonance lines as compared to the resonance lines under the same conditions. improves steadily with increasing pressure. It is possible that the absorption profiles of the resonance and the non-resonance lines are affected differently by pressure. The peak characterization times differ considerably for the resonance and non-resonance lines. Calibration curves become more linear with increasing pressure. The improvement is more pronounced for the resonance line.     

Data Acquisition and Processing for High Speed Liquid Chromatography

Abstract

The effect of sampling rate and digital smoothing on data acquired from high speed liquid chromatography (HSLC) is explored. The amount of data required per peak is determined from the precision of area, height, and retention time measurements. The correct sampling rate is related mathematically to column characteristics and operating conditions. The effect of a modified moving average digital smoothing routine on peak width and height is investigated. Digital smoothing functions are shown to behave similarly to analog noise filters. The merits of raw data storage and post analysis processing are discussed in light of the short analysis times in HSLC and the decreased cost of computer memory.     

An ESR Method for Determination of Serum Lipase Activity

Abstract

An ESR method for determination of serum lipase is described in principle and demonstrated in practice. A lipid soluble nitroxide is dissolved in an olive oil emulsion. When the intensity of the ESR signal of the nitroxide in the aqueous phase is monitored as a function of time after an aliquot of lipase is added a linear plot of peak height as a function of enzyme concentration is obtained.     

Further studies on the influence of pressure on spectral line overlaps in electrothermal atomic absorption spectrometry

The purge gas nature and pressure determines the shift, shape and width of absorption lines in graphite furnaces. Depending on the nature of the gas, red or blue shifts will occur. Absorption line shifts may be used to advantage in several analytical situations. Atomization in argon or nitrogen causes a red shift and broadening of absorption lines. Atomization under pressure enhances these effects. The commercial graphite furnaces are non-isobar in space and time. It is speculated that using Ar/He or Ar/H₂; mixtures, a better overlap is possible between the analyte emission line from a hollow cathode lamp and the absorption line from a graphite furnace. The consequence would be an improvement in sensitivity.     

Influence of Atomizer Nature on Precision in Graphite Furnance - Atomic Absorption Spectrometry

Abstract

The graphite nature used for confectioning the graphite furnaces influences considerably the peak shapes. With the use of normal graphite the evolution of the peak is much slower and the shape is also altered. As a consequence the instrument has a better chance to “catch” and measure the peak height and area, this resulting in an overall better precision and accuracy.     

Der Einflu? von Salzen auf die anodische Spitzenh?he in der inversen Voltammetrie

Zusammenfassung Der Einfluß verschiedener Salzzusätze auf die anodische Spitzenhöhe bei der invers-voltammetrischen Bestimmung des Cadmiums wird untersucht. In allen Fällen tritt eine beträchtliche Abnahme der Spitzenstromstärke ein. Mögliche Ursachen und praktische Folgerungen dieser Salzeffekte werden diskutiert.

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Summary The influence of different salts on the peak height in anodic stripping voltammetry of cadmium is investigated. In all cases a remarkable decrease of peak height is found. Possible reasons and practical consequences are discussed.

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Herrn Prof. Dr. F. Strassmann zum 65. Geburtstag gewidmet.

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VI. Mitteilung: diese Z. 224, 276 (1966).

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Diese Untersuchungen wurden in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbandes der Chemischen Industrie ermöglicht.     

Catalytic-Fluorimetric Determination of Ti(IV) by Flow Injection Analysis

Abstract

Two flow injection analysis catalytic-fluorimetric methods for the determination of titanium are suggested, based on the measurement of the peak height and of the peak width, respectively. Both methods allow the determination of titanium at the ng.mL^?1 level with good selectivity. A comparison between both method is also established.     

On the Use of the Knox Equation. II. the Efficiency Measurement Problem

Abstract

The Knox equation, which relates the reduced plate height, h, to the reduced linear velocity, v, has a great importance in column and stationary phase testing. Significant A, B, and C terms of the Knox equation cannot be obtain with erroneous plate heights, h. Four methods for efficiency determination, the inflection (0.6H) method, the height/area method, an asymmetry based (0.1H) method and the moment method, were critically compared using 200 real chromatograms. Efficiency obtained using Gaussian assuming methods were highly overestimated, while the asymmetry based method gave quite acceptable results. Using the exponentially modified Gaussian model, it is demonstrated that the b/a ratio (the sum b + a is the peak-width at 10% of the peak height) is not an empirical figure of merit but can be related to a “peak skew” expression.     

Determining Trace Concentrations of Copper in Water by Cathodic Film Stripping Voltammetry with Adsorptive Collection

Abstract

A technique is presented for the determination of trace concentrations of copper (II) in natural water samples by cathodic stripping voltammetry of a film of copper-catechol complex ions adsorbed on the hanging mercury drop electrode. The peak height of the copper-catechol reduction peak is linearly dependent upon the copper (II) concentration between 10^?10 and 10^?7 M. The detection limit of the technique is below 10^?10 M copper (II) for a collection time of 3 minutes, but the sensitivity can be further increased four-fold by collecting for 15 minutes. The sensitivity is reduced by high concentrations of competing trace metals and of surfactants, which necessitate the use of standard additions to the sample.     

Determination by High Performance Liquid Chromatography of Stability of Tetrahydro-β-carbolines at Different Ambient Temperatures

Abstract

To determine the stability of tetrahydro-β-carboline compounds over time and at different temperatures, a reversed-phase high pressure liquid chromatography system with electrochemical detection was utilized. Noreleagnine (1,2,3,4-tetrahydro-β-carboline) and tetrahydroharman (1-methyl-1,2,3,4-tetrahydro-β-carboline) were dissolved in water or ascorbate (0.1 mg/ml) vehicle and stored at ?20°C, 22°C, or 37°C for one, seven or 12 days. After each solution was injected in the column in a concentration of 400–600 ng/10 μl, peak height values were obtained for the compound under each condition. Analysis of percent recovery showed that the two β-carbolines were relatively stable with a maximal degradation of 14% occurring only at the 12-day assay interval. These results suggest that this class of compound can be used in pharmacological studies in which they can be dispensed from a mini-pump implanted in tissue. Further, an HPLC system with electrochemical detector provides a valid and reliable procedure for quantification of indoleamine-aldehyde condensation products.     

Determination of Hydroxy-Testos-Terones by Isocratic,High-Performance Liquid Chromatography with an Internal Standard

Abstract

A simple, isocratic, reverse-phase HPLC method to separate nine oxidative metabolites of testosterone is described. An internal standard, adrenosterone, was used to quantltate metabolites by the peak height method. An application of this method to the metabolism of testosterone by rat lung microsomes is presented.     

Determination of silver by graphite furnace—atomic absorption spectrometry with atomization under pressure

Summary When determined with pressurized atomization silver shows a lower peak height sensitivity than under normal conditions. Peak area is less influenced by pressure. The peak parameters are somewhat changed as compared to normal atomization. Notable is the prolongation of the mean residence time and peak time. Interferences are reduced with atomization under pressure.The linearity of the calibration curves is extended with atomization under pressure.

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Silberbestimmung im Graphittiegel. Atomabsorptions-Spektrometrie nach Zerstäubung unter Druck

Zusammenfassung Bei Zerstäubung unter Druck zeigt Silber eine geringere Empfindlichkeit der Peak-Höhe. Die Peak-Fläche wird durch Druck weniger stark beeinflußt. Im Vergleich zur Normalzerstäubung sind die Peak-Parameter etwas verändert, die Störungen sind bei Zerstäubung unter Druck geringer, die Eichkurven verlaufen über größere Strecken geradlinig.

     

Determination of Lysine in Nutrition Sample by Adsorption Voltammetry

Abstract

Lysine can be determined by adsorptive voltammetry after derivatization with acetaldehyde in 1.3 x 10^?2mol/ L borax-NaOH buffer solution (containing 4 x 10^?3mol/ L of CH₃CHO at pH10). The Schiff's base product of the derivation can be adsorbed on a hanging mercury electrode and reduced with peak potential of about -1.33v (vs.SCE) after 120s pre-concentration time. The derivative peak height is linearly proportional to the concentration for lysine in the range 6.0 x 10^?7-1.0 x 10^?5mol/ L. The detection limit is 4.0 x 10^?7mol/ L. Using this method, we have directly determined lysine in nutrition samples without any pre-separation step.     

High Pressure Liquid Chromatographic Determination of Mecillinam in Human Plasma and Urine

Abstract

A simple, specific, rapid and sensitive method for the analysis of mecillinam in plasma and urine using high pressure liquid chromatography is described. The assay is performed by direct injection of a plasma protein free supernatant or a dilution of urine. A μBondapak phenyl column with an eluting solvent of 16% CH₃CN-0.2% H₃PO₄ was used, with UV detection of the effluent at 220 nm. Desacetyl-cephalothin was used as the internal standard and quantitation was based on peak height ratio of mecillinam to that of the internal standard. The lowest concentration detectable without extraction was 0.25 μg/ml for plasma and 8.9 μg/ml for urine. No interference from plasma and urine was noted.     

Molybdenum Catalysed Polarographic Reduction of Iodate

Abstract

Polarographic catalytic reduction of iodate by molybdenum (VI) is investigated in an acetate-acetic acid solution of pH 5. The catalytic wave consisted of a peak at around -1.6 V vs SCE. The effect of pH, metal ion concentration, oxidant concentration, mercury column height, surfactants and neutral salt on the wave characteristics is studied. Probable explanations are offered.     

Degradation Characteristics of Two Tetrahydroisoquinolines at Room and Body Temperatures: HPLC Determination with Electrochemical Detection

Abstract

Reversed-phase high-pressure liquid chromatography (HPLC) was utilized to determine the stability of tetrahydropapaveroline (THP) and salsolinol at two ambient temperatures and over varying time intervals of up to 27 hr. Although ascorbate, an antioxidant, was shown to retard the temporally contingent degradation of THP at both 22°C and 37°C, the breakdown of the tetrahydrosoquinoline product was more pronounced at 37°C. Salsolinol was virtually stable under all conditions. The formation of detectable by-products of THP was demonstrated by the presence of secondary peaks in the THP-water assay which were strikingly absent in the THP-ascorbate aliquots. Finally, the HPLC profiles of five THP samples obtained from four different sources revealed the presence of similar secondary peaks which varied considerably in shape and peak height from one sample to another. The implications of this lack of uniformity of THP for pharmacological studies of addictive processes is discussed.     

31P NMR and HPLC Investigations of the Cyclophosphamide Metabolite,Phosphoramide Mustard

Abstract

Phosphoramide mustard (PM), a key active metabolite of the widely used anticancer drug cyclophosphamide (CP), can exist in several closely-related ionized, cyclized and substituted forms. We have developed a high pressure liquid chromatographic (HPLC) method for analysing serum concentrations of PM in order to relate these serum concentrations to toxicity and efficacy of treatment of CP. ³¹p NMR spectroscopy is used to verify the HPLC peak homology of the proposed PM peak.     

HPLC Determination of Carbendazim in Formulations

Abstract

A rapid high performance liquid chromatographic method has been developed to determine Carbendazim (methyl 2-benzimidazole carbamate) in formulations using reverse phase μ Bondapak C₁₈ column and ultraviolet detection. The sample is extracted from formulations with methanol, carbaryl is used as an internal standard. Absorbance is measured at 254 nm and the compound is quantitated by peak height ratios. The method is simple and recoveries averaged between 91–93%.     

Separation and Quantitation of O-Phthalaldehyde Derivatives of Taurine and Related Compounds in a High Performance Liquid Chromatography (HPLC) System

Abstract

A sensitive specific assay for taurine using high performance liquid chromatograpy and fluorescence measurement is described. The method employs precolumn derivatization with o-phthalaldehyde in the presence of ethanethiol. Taurine is clearly separated from other amino acids including its precursors hypotaurine and cysteine sulfinic acid. The fluorescence peak height is linear between 1 and 100 picomoles of taurine. There is clear separation of taurine from a contaminant of other taurine assays, α-glycerophosphoryl ethanolamine.     

An Evaluation of Eluent Recycling and Column Life for HPLC Analysis of Carbohydrates

Abstract

The length of service of amine modified silica columns for the automated analysis of carbohydrates in food and beverages typically exceeds 500 sample injections. Excessive accumulation of carbohydrate in the recirculated eluent results in a gradual decrease in peak height. Detector response is independent of injection volume over the range of 1–50 μl. These results suggest critical parameters for use in automated carbohydrate analysis systems.