Pretreatment Column Research Articles

Determination of calcium pantothenate and panthenol in pharmaceutical preparations by high performance liquid chromatography.

A simple and rapid method was developed for the determination of calcium pantothenate(Pa-Ca) or panthenol(Pol) in pharmaceutical preparations by high performance liquid chromatography(HPLC). They could successfully be separated on a column of Nucleosil 5C18 with a mixture of 10 mM phosphate buffer (pH 3.0)-acetonitrile (97 : 3) as a mobile phase and detected at 208 nm. Aqueous extract from a preparation was applied to a Chemco-Sep ODS-A pretreatment column, and Pa-Ca and Pol were eluted with the above mobile phase. The eluate was made up to a constant volume and injected to HPLC system. The contents of Pa-Ca and Pol in the preparation were calculated by using calibration curves based on their peak heights on HPLC chromatogram. Several vitamin preparations were analyzed by the proposed method.

Quantitative investigation of rapid injector port derivatization of amphetamine using trifluoroacetic anhydride with packed and capillary column GC and GC/MS methods.

Direct injector port derivatization of amphetamine through coinjection of sample with trifluoroacetic anhydride was quantitatively investigated and found to be a rapid and more sensitive alternative to longer solution-based derivatization procedures. Under optimum conditions determined in this work, limits of detection were 1 ng using gas chromatography with flame ionization detection and 1 pg using single ion monitoring of ion 140.0 amu (M-91+) in gas chromatography/mass spectrometry methods. The previously reported derivatization period of over 12 hr was greatly reduced using instantaneous derivatization with a 100- to 1000-fold increase in limits of detection. Effects of inlet temperature, mass of trifluoroacetic anhydride, and column pre-treatment on chromatographic performance are reported. Application to analysis of serum from amphetamine-dosed rats was used for comparison to accepted solution-based derivatization.

Rapid measurement of oestradiol and oestriol by high-performance liquid chromatography after automatic pretreatment

A fluorometric liquid chromatographic method was developed for measurements of unconjugated oestradiol and oestriol in the serum of pregnant women. The serum samples are injected directly into the apparatus and pass to a pretreatment column, where oestrogens are adsorbed while hydrophilic components such as proteins and carbohydrates are not. The oestrogens then pass into a separation column containing a new type of polymer gel. The mobile phase consists of an acetonitrile—water mixture, and separation is achieved by a reversed-phase mechanism. The eluent is monitored for fluorescence. Data on the reproducibility and recovery by this method and the correlation of values with those obtained by radioimmunoassay are reported. Results on the increases of oestradiol and oestriol in the serum during pregnancy are also reported.

Determination of glucocorticoids by liquid chromatography. III. Application to ointments and a cream containing cortisone acetate, dexamethasone acetate, fluorometholone, and betamethasone valerate.

In order to separate cortisone acetate, dexamethasone acetate, fluorometholone, and betamethasone valerate in ointments and a cream from the base and excipients, a silica gel column pretreatment was carried out (pre-screening procedure) and then glucocorticoids were successfully determined by high-performance liquid chromatography on a LiChrosorb RP-18 column. By the use of the pre-screening procedure, the base, excipients, and other active ingredients (except glycyrrhetinic acid) in commercial preparations were almost completely removed, and hence a lowering of the efficiency of the LiChrosorb RP-18 column and blocking of the flow of the mobile phase in column caused by the base remaining on the top of the column could be avoided. The contents of glucocorticoids in various commercial preparations were found to be 95.7 to 102.5% of the labeled amounts.

Amino Acid Screening—An Objective Approach

In the amino acid screening of biologic specimens through the use of thin layer chromatography, the common approach has been to compare sample specimens to normal specimens, and then to interpret variations in spot patterns and intensities. Because normal specimens often contain ninhydrin-staining compounds other than amino acids, subjective reporting may result. This study compared sample specimens with a pure mix of standards. The concentrations of these standards were adjusted to approach minimum detection levels, which in most cases are far above the normal concentrations of amino acids found in body fluids. Any sample specimen showing significant ninhydrin spots on one-dimensional chromatography was then subjected to column pretreatment and two-dimensional chromatography to preclude the possibility of reporting false positives. With such a screening procedure, the presence of a ninhydrin spot in the sample indicated a positive result and its absence indicated a negative result. The procedure is suitable for the small clinical unit as well as large mass screening programs.

Simultaneous determination of iodide and thiocyanate in powdered milk using ion chromatography with mixed-mode column

The contents of iodide and thiocyanate are important detection items in powdered milk quality testing. Due to the complexity of the powdered milk matrix, chromatographic analysis is easily subjected to interference. Acclaim Mixed-Mode WAX-1 column incorporated both hydrophobic and weak anion-exchange properties was used to separate iodide and thiocyanate from interfering substances in powdered milk matrix, and detected by Ultraviolet (UV) detection. After powdered milk was dissolved in water, the protein was precipitated by acetonitrile. Then OnGuard RP pre-treatment column was used to remove the organic matters which might pollute the column. The eluent was acetonitrile-100 mmol/L phosphate buffer (pH 6)-water (45:5:50,v/v/v). The UV detection wavelength was 226 nm. The limits of detection of iodide and thiocyanate were 4.6 microg/L and 13.8 microg/L respectively, and the relative standard deviations of peak areas were 1.2% (n = 6) and 1.7% (n = 6) for 0.2 mg/L iodide and thiocyanate standard solutions. The method is accurate and reliable, and has wide linear range, low limit of detection. This method provides a viable approach for powdered milk quality dairy products.

Comparison of dynamically coated SE‐54, SP‐2250 and carbowax 20M wall‐coated open tubular (WCOT) glass capillary columns, prepared after surface pretreatment with Superox™‐4 or with BaCO3

AbstractA new surface pretreatment for the preparation of wall‐coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non‐extractable layer of Superox™‐4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox‐4 is stable at high temperatures (> 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE‐54, Carbowax 20M, and SP‐2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO3 procedure. The Superox‐4 pretreated columns were equal or superior in quality to the BaCO3 pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (Neff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.

Column deactivation for the analysis of picogram amounts of underivatized chlorophenols and chlorocresols by combined gas chromatography mass spectrometry

Picogram amounts of underivatized chlorophenols and chlorocresols are analysed by gas chromatography mass spectrometry using high resolution selected ion monitoring. Deactivation by pretreatment of columns with 2,4-dichlorophenoxyacetic acid gives long-term improvement in sensitivity and reproducibility.

Charcoal Column/Thin Layer Chromatographic Method for High Fructose Corn Sirup and Spectrophotometric Method for Hydroxymethylfurfural in Honey: Collaborative Studies

A new spectrophotometric method is described for determining hydroxymethylfurfural in honey in which interfering background absorption of honey is corrected for by use of a bisulfite-treated sample as blank. Two procedures for detecting high-fructose corn sirup (HFCS) in honey were also tested. In one, charcoal column pretreatment is used to concentrate trace oligosaccharides, followed by thin layer chromatography to differentiate those of HFCS from those of honey. The other method depends on measurement of the isomaltose/maltose ratio by gas-liquid chromatography. The charcoal/thin layer chromatographic method for HFCS has been adopted official first action. The bisulfite method for hydroxymethylfurfural has been adopted interim first action.

Isolation and determination of quaternary ammonium compounds by means of amberlite XAD-columns and thin layer chromatography.

The potentials of XAD-columns for the isolation of quaternary ammonium compounds from aqueous media have been investigated. When adequate amounts of counter ions (perchlorate, chloride, phosphate, nitrate) were added to the aqueous sample, to the column pretreatment fluid and to the aqueous washing fluid, most quaternary compounds investigated were retained on the column and could be recovered by elution with methanol. This approach proved also suitable for urine. Quantitation of quaternaries isolated in this way from urine samples could be performed on silicagel thin layer plates through visualization with iodine, followed by densitometric evaluation. For decamethonium detection limits were 0.1 micrograms/ml. Recoveries at the 1 micrograms/ml level were between 80--90% with variation coefficients of less than 10%.

A basic study of column adsorption chromatography : Part I. Standardization of adsorbent

The method of measuring f(I) values is proposed as a measure of the adsorption capacity of adsorbents. The f(I) value, a characteristic figure for a particular system, can be obtained chromatogiaphically by measuring the progression rate of zone and the degree of packing of the column. For a system involving a unit concentration of trasns- p-methoxyazobenzene in benzene as standard solution and alumina as adsorbent, optimum conditions for the measurement of f(I) were established. The effects of day-light, pretreatment of column, temperature, flow rate of solution, amount of adsorbent and degree and mode of packing were studied Under optimum conditions, the value of f(I) was reproducible within ±2%.