bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarity change in capillary GC by serial‐column temperature optimization (SECAT mode in capillary GC)
Authors: Kaiser R. E. , Rieder R. I.
Published: May 2005

GC, including capillary GC, is rather inflexible, if a certain column length and stationary phase has been fixed for a given analytical problem. If the sample composition changes, one often has to change the column length and/or stationary phase, at least when something like optimum analytical conditions are needed. Temperature changes (or heating rates) can change the selectivity of a given column only within very limited ranges, due to the exponential effect of temperature on retention time. By serial coupling two chemically different capillaries, each run at another temperature, even the slightest changes of these two temperature values have a dramatic effect on the selectivity of the system for polar substances. We call this technique the SECAT mode of GC. Results are reported as retention index shifts, dependent on SECAT temperature data. This technique can in future easily be automated, thus enabling the analyst, for polar sample analysis, to adjust a given chroma‐tographic system to his specific sample composition without touching the instrument.
Multiple short pass glass capillary gas chromatography
Authors: Jennings W. , Settlage J. A. , Miller R. J.
Published: May 2005

A multiple repass system, utilizing an in‐line switching valve and suitable for use with small‐bore glass open tubular columns, is described. The advantages of the system, which include higher OPGV, large plate numbers and optimization of column “length”, are discussed.
A new surface roughening method for glass capillary columns. Sodium chloride deposition from suspension
Authors: de Nijs René C. M. , Rutten Gerard A. F. M. , Franken Josef J. , Dooper René P. M. , Rijks Jacques A.
Published: May 2005

A method is described for roughening the surface of glass capillary columns for subsequent coating with polar stationary phases. A suspension of sodium chloride, obtained by addition of a saturated solution of sodium chloride in methanol to 1,1,1‐trichloroethane, is passed through the column at velocities of 1–5 cm/s. During passage of the suspension, particles of sodium chloride deposit spontaneously on the column wall. The amount of sodium chloride deposited on the column wall is a function of the volume of the suspension passed through and of the contact time of the suspension and the column wall. Ultimately the amount of sodium chloride per unit surface area approaches a maximum. Columns covered with this maximum amount of sodium chloride were prepared with high reproducibility and coated with a number of polar stationary phases. Various factors that influence the stability of the suspension and the deposition of sodium chloride are discussed and minimum requirements are given. A theoretical model is proposed for the mechanism of deposition of sodium chloride particles on the glass wall.
Analysis of nitrosamines by GC2 with a photoionization detector
Authors: Meili J. , Brönnimann P. , Brechbühler B. , Heiz H. J.
Published: May 2005

The use of a photoionization detector (PID) coupled to a glass capillary gas chromatography (GC2) separation system for the detection of carcinogenic nitrosamines was investigated. The components analyzed gave a linear response with a lower detection limit of 50 to 100 pg with the 10.2 eV ionization source. No detector response was obtained with an ionization energy of 9.5 eV.

Chromatography of meat extracts indicated their complex molecular composition. Simple liquid chromatographic cleaning procedures significantly decreased the complexity of these samples, but not sufficiently for the accurate quantition of nitrosamine components.
HPLC with chemically bonded stationary phases. 1. ω‐hydroxyalkyl silicas
Authors: Matlin S. A. , Tinker J. S.
Published: May 2005

Grignard and trichlorosilane coupling methods have been applied to the synthesis of surface‐modified silicas carrying alkyl chains of varying length, terminally substituted by a hydroxyl group. The new phases have been characterized chromatographically using aromatic hydrocarbons, substituted anilines and metal acetylacetonates.
Design of a microprocessor‐controlled automated injection system for the analysis of gas phase cigarette smoke using glass capillary columns
Authors: Parrish Milton E. , Higgins Charles T. , Douglas D. R. , Watson Duane C.
Published: May 2005

An automatic injection system for the analysis of gas phase smoke has been designed and evaluated using the microprocessor‐controlled Hewlett‐Packard 5830 gas chromatograph. The cryogenic preconcentration trap was constructed from relatively inexpensive and readily available materials. It was determined that the use of the preconcentration trap, as opposed to condensing the smoke on the head of the cold (‐50°C) chromatographic column, significantly enhanced the resolution of the more volatile gas phase components. Data are presented which illustrate the injection system characteristics. In addition, chromatograms of gas phase smoke are presented which demonstrate the effectiveness of this technique.
A rapid, new and direct method for isolation and measurement of porphyrins in biological samples by high performance liquid chromatography
Authors: Englert Edwin , Wayne Anthony W. , Wales Eugene E. , Straight Richard C.
Published: May 2005

Reversed‐phase high performance liquid chromatography on microparticulate columns of octadecylsilane with elution by a gradient of acetonitrile in phosphate buffer, pH 7.5, separated porphyrin free acids directly in urine for the first time. Interfering fluorescence was removed with a precolumn of large particle size at acid pH. Peak area fluorescence by the method of standard addition was related linearly to amount of a porphyrin from 5 to 60 nanograms. The method was reproducible to ± 13%, able to detect 0.3 nanograms of a porphyrin in a 1 ml urine sample in 45 minutes, and capable of detecting the typical clinical patterns of normal and porphyrinuric urines. Modifications make the method applicable to measurements in other biological samples and to research separations. With the added rapidity of analysis, the method could expand porphyrin analysis in routine clinical medicine.
Analysis of polar compounds on PEG‐40M/KF glass capillary columns
Authors: Golovnya R. V. , Samusenko A. L. , Mistryukov E. A.
Published: May 2005

The chromatographic properties of potassium fluoride as an additive to the polyethylene glycol stationary phase were investigated. This unique base in organic chemistry was shown to succeed in yielding good results for the analysis of polar compounds, including the primary amines. Glass capillary columns of high selectivity for primary and secondary aliphatic amines were obtained by the “hexane plug” procedure by which a thin layer of KF is deposited on the inner surface of glass capillary columns. Some possible types of donor‐acceptor interactions occuring within the system PEG/KF/solute were considered.
The identification of tricyclic neuroleptics and sulphonamides by high‐performance thin‐layer chromatography
Authors: Po A. Li Wan , Irwin W. J.
Published: May 2005

Circular high‐performance thin‐layer chromatography (HPTLC) has been used to differentiate a series of twelve tricyclic neuroleptics, using both normal phase and reverse phase procedures. The use of normal phase systems also allows the resolution of geometric isomers of chlorprothixene, clopenthixol and flupenthixol. Thirteen sulphonamides and Trirnethoprim may also be distinguished using HPTLC.
Densitometric determination of unsaturated fatty acids with p‐hydroxybenzaldehyde by HPTLC
Authors: Gübitz
Published: May 2005

A rapid method for the detection and quantltatlve determlnation of unsaturated fatty acids by TLC is presented. After separation on HPTLC‐RP18‐plates, reaction wlth p‐hydroxybenzaldehyde is carried out by a dipping procedure. Nanogram amounts of unsaturated fatty acids can be determined with good reproducibility.
Separation and identification of lichen acids of the pulvinic acid series
Authors: Chawla H. M. , Gambhir I. , Kathuria L.
Published: May 2005

Lichen acids, pulvinic acid, vulpinic acid, pinastric acid, leprapinic acid, lsoplnastric acid and pulvinic acid dilactone, which occur in certain yellow varieties of lichens and are difficult to separate, have been successfully separated and identified by TLC on chlorobenzene‐impregnated silica gel plates.
Direct measurement of mass fragmentograms for eluents from a micro‐liquid chromatograph using an improved nebulizing interface
Authors: Yoshida Yu , Yoshida Hiromasa , Tsuge Shin , Takeuchi Tsugio , Mochizuki Koichi
Published: May 2005

An improved vacuum nebulizing interface with a very short counter nozzle was developed for direct coupling of a micro‐LC and a quadrupole MS with CI‐chamber. With the LC‐MS system using the nebulizing interface, it became possible to take mass fragmentograms for various less volatile compounds such as glutamic acid, steroids, aromatic amines and chlorine‐containing insecticides.
HPLC of fatty acid esters of mono‐ and polyhydric alcohols. Part 1: Analytical separation
Authors: Henke H. , Schubert J.
Published: May 2005

This paper shows how simply and yet very rapidly fatty acid esters of monohydric alcohols, but particularly partial and full fatty acid esters of fully hydric alcohols can be separated and determined by means of high‐pressure liquid chromatography on LiChrosorb RP‐8 with methanol/water. We have separated quantitatively the methylesters of the fatty acids C8:0 to C22:0 and C24:0, the i‐propyl‐, i‐butyl‐, n‐hexyl‐ and i‐octyl‐esters of the even‐numbered fatty acids C8:0 to C18:0, mono‐ and difatty acid esters of the 1,3‐bis‐(2‐hydroxyethyl)‐5,5‐dimethyl‐hydantoin, mono‐, di‐ and triesters of the trimethylolpropane as well as the tetraesters of the penta‐erythrite.
Separation of histamine and its metabolites using glass capillary gas chromatography and a nitrogen detector
Authors: Lieu Fong‐Yi , Jennings W.
Published: May 2005

Complete separation of the TMS derivatives of histamine, 1‐methyl histamine and 3‐methyl histamine was achieved in two minutes in a 7 m × 0.25 mm column coated with SP 2250. Using NPD, histamine was detectable at levels as low as 20 pg. This offers a rapid, sensitive procedure with potential for clinical diagnosis and food analysis.
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
Authors: Arrendale R. F. , Smith L. B. , Rogers L. B.
Published: May 2005

A 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.
Retention time and effective separation factor in series‐coupled columns with different stationary phases
Authors: Smuts T. W. , De Clerk K. , Du Toit T. G. , Buys T. S.
Published: May 2005

Basic expressions are derived for both the retention time and the effective separation factor in serially coupled GC columns. The retention time is determined by two main parameters. The first is the fractional time spent by an unretarded solute in each column which, in turn, is determined by the relative column lengths and flow velocities through each column. The second parameter is the relative mass distribution coefficient of a particular solute in each column; a variable that can be adjusted by changing the relative temperatures of the columns. The expression for the effective separation factor relates the measured separation factor for the series combination to the separation factors on the individual columns, the fractional time spent by an unretarded peak in each column, as well as the relative values of the mass distribution coefficients of a particular solute on the different columns.
Gas‐liquid chromatographic determination of moprolol (SD 1601) in human plasma and urine
Authors: Desager J. P.
Published: May 2005

1‐(o‐methoxyphenoxy)‐3‐isopropylamino‐2‐propanol hydrochloride (moprolol, OmeralR), is a new β‐adrenergic blocking agent. A gas chromatographic method for determining unchanged moprolol in human biological fluids has been developed. After solvent extraction, a bis‐trifluoroacetyl derivative was formed and measured by an electron capture detector. The quantification was checked by using an internal standard (pronethalol), which was added to all samples. The electron capture response was linear between 10 and 500 ng/ml. To avoid contamination of the peaks, careful extraction was imperative. The main advantages offered by the described method are: specificity, high sensitivity (10 ng.ml−1) and the small amount of biological fluids (1 ml plasma a. e.) required.
Identification of hydroquinone and catechol as impurities in reagent‐grade phenol using high performance liquid chromatography with ultraviolet and electrochemical detectors
Authors: Masoud A. N. , Dubes G. R.
Published: May 2005

Several impurities which were suspected to be present in commercial reagent‐grade phenol were separated using high performance liquid chromatography following sample concentration by steam distillation. A reverse‐phase, microparticulate column and 5 solvent systems containing 5% to 25% methanol in 0.05 M phosphoric acid were used. A variable wavelength ultraviolet detector and an electrochemical detector were connected in series, in that order, to the column. Capacity factors (ḱ) for pyrogallol, hydroquinone, resorcinol, catechol, orcinol and phenol were determined in the 5 solvent systems and compared to ḱ‐values of impurities present in the residue remaining from the steam distillation of phenol. Co‐chromatography of standards suspected as contaminants and possessing ḱ‐values similar to those of impurities were carried out in 3 solvent systems to confirm identical retention characteristics. Detector response ratios of contaminants and suspected standards, using various wavelengths and voltage potential settings, were utilized as major identification parameters. Two of the several contaminants separated were identified as hydroquinone and catechol.
Detection of an impurity (1%) at low resolution (0.25)
Authors: Rix H. , Malengé J. P.
Published: May 2005

The “Distribution Function Method”, which makes possible the measurement of systematic variations in the shape of signals, has been experimentally tested on the detection of two visually confounded gas chromatographic peaks, irrespective of the estimation of the resolution or the concentration ratio. Two detection procedures are suggested. The first compares directly, under the same experimental conditions, the shape of a pure peak and that of a peak suspected of contamination. The second makes use of variations of column temperature and gas flow rates to distinguish the behaviour of a pure substance from that of a contaminated substance. A marking procedure for the shape of a pure peak is then set up to dispense with the need of a reference standard. In practice, the two procedures make possible the detection of heptane as an impurity in n‐hexane at levels of one percent and under experimental conditions artificially chosen so as to make the resolution inferior to 0.25.
Steroid analysis by gas chromatography with SCOT and wide‐bore WCOT columns
Authors: Thomas B. S.
Published: May 2005

Glass capillary columns are ideal for analysis of urinary steroid profiles (i.e. the total steroid neutral fraction without prior separation into sub‐groups).

In this paper performance of both SCOT and wide‐bore WCOT columns has been compared, resulting in no significant quantitative difference on urine extracts run as trimethylsilyl ether derivatives. However, because of increased efficiency the WB‐WCOT column exhibited more sensitivity in measurement of small amounts of 11‐ox‐aetiocholanolone. Sensitivity of other steroids was greatly enhanced by use of either SCOT or WB‐WCOT, leading to an almost tenfold increase over conventional packed columns (e.g. androsterone and aetiocholanolone < 40 μg per 24 h urine sample). A simple splitless injection system (based on a design of Dr. W. Greenaway, Oxford University) is presented.

Experiments were also carried out using a SCOT column in conjunction with an FM‐electron capture detector. Whilst efficiency was impaired due to the design of the detector, use of He (carrier) and N2 (make up gas) showed that several steroid derivatives could be easily measured at well below the 10−10 g level with much more rapid retention times than with a 1½m packed column. Highly successful separation of 19 amino acids (as fluoro‐acyl derivatives) was achieved in 35 minutes using a SCOT (30 m) SP2100 column.
Assay of trimethoprim, sulfamethoxazole and its N4‐acetyl metabolite in biological fluids by high‐pressure liquid chromatography
Authors: Ascalone V.
Published: May 2005

A reversed‐phase HPLC assay method was developed to determine levels of the drugs trimethoprim, sulfamethoxazole and the N4‐acetyl metabolite of the latter in human blood plasma and urine. The organic substances are extracted with ethyl acetate by a single extraction at pH 6.8. The method is rapid, accurate, sensitive and precise and well suited to routine determination of these drugs on patients during clinical pharmacokinetic investigations.
Separation of enantiomers by high performance liquid chromatography using chiral eluents
Authors: Oelrich E. , Preusch H. , Wilhelm E.
Published: May 2005

Simple procedures are presented for separating the enantiomers of α‐methyldopa, 5‐hydroxytryptophan, tryptophan, triiodothyronine and thyroxine, which require neither special sorbents nor difficult‐to‐obtain or unstable reagents.

The method for α‐methyldopa, 5‐hydroxytryptophan and tryptophan is based on the use of L‐phenylalanine copper complex as the chiral constituent of the mobile phase; LiChrosorb® RP‐18 serves as the stationary phase. The procedure for triiodothyronine and thyroxine is grounded on the L‐proline copper complex as the chiral reagent and LiChrosorb® Si 60 as the stationary phase.

In all observed cases, the D‐enantiomer is eluted prior to the respective L‐enantiomer. Chirality inversion of the mobile phase (application of the D‐phenylalanine copper complex) reverses the order of elution; a racemic eluent (DL‐phenylalanine copper complex) leads to no separation. In addition to the enantiomers of α‐amino acids, the enantiomers of α‐hydroxy acids (mandelic acid) can be separated.
Gas‐chromatographic separation of underivatized steroids using a BPhBT liquid crystal stationary phase
Authors: Smith T. R. , Wozny M. E.
Published: May 2005

A gas‐chromatographic separation of underivatized steroids is described, in which the liquid crystal N,Ń‐bis(p‐phenylbenzylidene)α,α′‐bi‐p‐toluidine (BPhBT) was used isothermally at 265°C for the stationary phase. The nematic range of this crystal is 247 to 403°C. Use of the BPhBT crystal allowed operations in a temperature range where steroids are volatile and unlikely to display broad elution peaks and long retention times.

With columns precoated with 2.5 weight percent of BPhBT, steroids containing minor structural differences in the ring system were readily differentiated. For example, 5‐androsten‐17α‐ethinyl‐3β, 17β‐diol was found to elute more rapidly than its 3‐keto analog, ethisterone. Ethisterone was distinguished readily also from its 19‐nor analog, norethisterone. Additionally, differences in side‐chain functionality and resultant molecular dimensions facilitated the separation of steroids of identical ring structure, as in the comparison of cholesterol with methyl 3β‐hydroxy‐5‐cholenate and 25‐hydroxycholesterol.

An enhancement of separation according to the molecular length‐to‐breadth ratio was observed; in general, the larger this length‐to‐breadth ratio, the greater the retention period on the column.
Determination of the isomeric distribution and associated impurities in commercial diethylbenzenes by capillary gas chromatography
Authors: Kuchhal R. K. , Kumar B. , Kumar P. , Gupta P. L.
Published: May 2005

A capillary gas chromatographic method for the quantitative analysis of diethylbenzene fractions is described. Estimation of ortho‐, meta‐ and para‐isomers and other C9 and C10 aromatic impurities is covered. The conditions developed involve the use of a capillary column of Carbowax‐1540 (300 feet × 0.01 inch) under isothermal operation. The retention index data for a number of aromatics are presented at four temperatures (90, 100, 110 and 120°C). The method offers a good choice for any level of concentration both for isomers and impurities commonly encountered within a reasonable analysis time.
The Varigrad and similar apparatus in gradient liquid chromatography: A systematic computational approach. Part 1: Theoretical development
Authors: Said A. S.
Published: May 2005

Different methods for producing a pre‐assigned gradient in liquid chromatography are presented. A systematic approach to the calculations involved is given. The derived equations are mostly Poisson and Poisson summation distributions which are tabulated in the literature. The incremental method of gradient elution developed by Scott has been modified. In the modified apparatus two mixing chambers are used instead of one. This leads to an appreciable decrease in the number of reservoirs needed for the same precision in fitting a desired gradient. The application of the derived equations, together with other Varigrad modifications, will be given in Part 2 of this paper (to be published shortly in this Journal).
Glass capillary SCOT columns by a single‐step coating method
Authors: Chauhan Jasbir , Darbre André
Published: May 2005

A single‐step coating method for the preparation of glass capillary SCOT columns is described. It is reproducible and less time‐consuming than the well‐known two‐step coating procedures. Other methods attempted are discussed briefly. Both the flame ionization and electron capture detectors could be used in conjunction with temperature programming. The separations achieved with an “activity mixture”, phenols and phenolic acids, illustrate the resolution obtained. The columns are suitable for quantitative determinations and a comparison is made with a conventional packed column.
Glass capillary gas chromatography with simultaneous flame ionization (FID) and Hall® element‐specific (HECD) detection
Authors: McCarthy L. V. , Overton E. B. , Maberry M. A. , Antoine S. A. , Laseter J. L.
Published: May 2005

Two glass capillary gas chromatographic systems were equipped with inert effluent splitters which allowed simultaneous data acquisition using nonspecific and element‐specific detectors. Simultaneous detection was achieved using the nonspecific flame ionization detector (FID) and the Hall® electrolytic conductivity detector (HECD) operated in either the sulfur‐or the nitrogen‐specific mode. Typical application of the simultaneous detection system as applied to analysis of petroleum residues is briefly described. The Hall electrolytic conductivity detector can be made element specific for halogen‐, sulfur‐, or nitrogen‐containing compounds. Simultaneous detection enhances the information yield from a single sample injection and proves to be a powerful complementary technique when used with computerized gas chromatography/mass spectrometry.
Simultaneous gas chromatographic determination of pirimiphos‐methyl and malathion residues in peanuts, peanut hulls, peanut meats, and peanut oil
Authors: Simonaitis R. A. , Zehner J. M. , Redlinger L. M.
Published: May 2005

A gas chromatographic method developed for the simultaneous determination of residues of pirimiphos‐methyl (O‐[2‐(dimethyl‐amino)‐6‐methyl‐4‐pyrimidinyl] O,O‐dimethyl phosphorothioate) and malathion (diethyl mercaptosuccinate S‐ester with O,O‐dimethyl phosphorodithioate), in whole peanuts, peanut hulls, peanut meats, and peanut oil gives good recoveries and has a limit of detection for pirimiphos‐methyl and malathion of 0.04 ppm. Quantitative analysis for the two insecticides with electronic integration was reliable to 0.1 ppm.
Separation of isomeric and nonisomeric monoribonucleotides by isocratic ion pair high performance liquid chromatography
Authors: Al‐Moslih Moslih I. , Dubes George R. , Masoud Asaad N.
Published: May 2005

A simple, isocratic, high performance liquid chromatographic procedure is described for the first time for the separation of nine monoribonucleotides using the ion‐pairing technique. An aqueous mobile phase containing 100 mM KH2PO4 and 12.5 mM tetramethylammonium hydroxide as the solvophobic ion, pH 3.9, was used with a reverse phase RP‐18 column. The nine monoribonucleotides studied were separated and eluted in the following order: cytidine‐5′ ‐phosphate, uridine‐5′ ‐phosphate, cytidine‐3′ ‐phosphate, guanosine‐5′ ‐phosphate, uridine‐3′ ‐phosphate, uridine‐2′ ‐phosphate, adenosine‐5′ ‐phosphate, guanosine‐3′ ‐phosphate, and adenosine‐3′ ‐phosphate. Generally the 5′ nucleotides eluted faster than the 3′ and the order of elution within each series was: cytidine, uridine, guanosine, and adenosine. The only nucleotide where three isomers were studied was uridine, and the 2′ eluted later than the 3′. Baseline separation was attained for a mixture containing four 3′ nucleotides and uridine‐2′ ‐phosphate. When the four 5′ nucleotides were chromatographed, baseline separation was also obtained except between cytidine‐5′ ‐phosphate and uridine‐5′ ‐phosphate. The coefficient of variation of the retention characteristics, which reflected day‐to‐day variation, averaged 6.4%.
The dry‐packing of columns in liquid chromatography
Authors: Davies R. D.
Published: May 2005

This contribution comprises two parts, the one covering some variables in the dry‐packing of columns for liquid chromatography, the other the use of an automatic dry‐packer in liquid chromatography. A high‐pressure stainless steel column was dry‐packed using a 20‐44 μm size, irrregularly shaped, silica gel support. It was found that, when support was added in discrete amounts, lateral tapping produced a column of higher efficiency (HETP = 0.69 mm) than was the case for vertical tapping (HETP = 1.37 mm). Simultaneous vertical and lateral tapping produced an intermediate result. Bulk filling of the column followed by tapping was inferior to adding support in discrete amounts. An apparatus constructed to perform the vertical and lateral tapping operations automatically confirmed the above conclusions. It was concluded that commercially available dry‐packing apparatus do not offer the best action for packing an efficient column since they involve predominantly vertical tapping.
Rapid on‐line analysis of low molecular weight hydrocarbons using glass capillary gas chromatography
Authors: Glajch J. L. , Schunn R. A.
Published: May 2005

Rapid analysis is important for on‐line chromatography. Gaseous or vaporized samples have been injected via heated gas sampling valves of less than 500 μl dead volume. The critical sampling and split problems could be solved by temperature programming. The general analysis described could be successfully used inter alia in scouting reactions.
High‐performance liquid chromatography with continuous gradient elution in screening for unknown metabolites of butoprozine directly in dog bile
Authors: Overzet F. , Drenth B. F. H. , de Zeeuw R. A.
Published: May 2005

This paper describes the screening for metabolites of butoprozine, a new anti‐anginal drug, in dog bile by means of reverse‐phase HPLC. Although it does involve a simple clean‐up step to remove a substantial amount of endogenous bile compounds, this screening method nevertheless avoids extraction of metabolites and thus allows all metabolites to be introduced into the chromatographic system. A single run of 100 minutes from 100% water to 100% methanol in a linear gradient effects adequate separation of the great majority of metabolites without interference from remaining endogenous compounds.

Two methods of differentiating between metabolite peaks and endogenous peaks have been worked out. The first one makes use of 14C‐labeled butoprozine by measuring the amount of radioactivity in the column effluent while simultaneously recording the UV absorbance. The second method compares continuous gradient chromatograms of bile recorded before and after butoprozine administration under very similar conditions. The latter method can be applied to both radioactive and non‐radioactive materials.
Gas chromatographic resolution of carbohydrate enantiomers. A new chiral phase for pentoses
Authors: Benecke I. , Schmidt E. , König W. A.
Published: May 2005

New chiral polymers have been prepared by conversion of cyano groups of polysiloxanes XE‐60 and OV‐225 into carboxylic groups and subsequent coupling to give the respective S‐valine‐R‐α‐phenyl‐ethyl amide. In contrast to the corresponding stationary phases with S‐α‐phenylethyl amide groups, which have been used for the resoultion of trifluoroacetylated hexose derivatives, the new phase show high enantioselectivity for pentose and 6‐deoxyhexose derivatives.
A new method for the quantitative analysis of organochlorine pesticides and polychlorinated biphenyls
Authors: Godefroot M. , Stechele M. , Sandra P. , Verzele M.
Published: May 2005

A simple method is described for the quantitative determination of organochlorine pesticides and polychlorinated biphenyls (PCB's) in water at the sub‐ppb level. A micro gas‐phase extractor advantageously replaces other preconcentration and purification techniques. The extract is analyzed by capillary gas chromatography without further enrichment. The recovery at the ppb level was nearly 100% for organochlorine pesticides and more than 80% for PCB's. The complete procedure including sample preparation, steam distillation‐extraction, and capillary gas chromatographic analysis is carried out in less than four hours.
Structure elucidation of triglycerides by chromatographic techniques. Part 1: Capillary GC of ozonized triglycerides
Authors: Geeraert E. , De Schepper D.
Published: May 2005

Structure determination of triglycerides according to their number of unsaturated fatty acids (N.U.F.A.) is more easily achieved after ozonolysis of their mixtures (fats and oils) than by capillary gas chromatographic analysis of the mixture as such. Analyses performed before and after ozonolysis of cocoa buttel, hazelnut oil, and a mixture of both fats illustrate the potential of this approach to the structure elucidation of triglycerides by chromatographic techniques.
Static coating: An attempt to optimize a straightforward technique involving mechanical closure of the column
Authors: Grob K. , Grob G.
Published: May 2005

The static technique is commonly accepted as the most universal and scientific method of coating. At the same time, however, it is said to be experimentally demanding. Great efforts have therefore been made to render the method easier and safer, resulting in a wealth of recommendations confusing non‐experts. Over a period of two years we have practically applied most of the reported procedures with the aim of studying their practical convenience. We do not doubt that most procedures are comparably suitable in the hands of expert users, i. e. once the initiation efforts have been forgotten, or are otherwise of little interest. We have attempted to describe a method which is specifically suited for easy and quick introduction to beginners. The method is based on mechanical column closure. The principles of the method are discussed, and a comprehensive description of its practical application is given.
Influence of some inorganic salts on the polarity of apolar polymer phases in capillary gas chromatography
Authors: Traitler H. , Rossier M.
Published: May 2005

Different stationary phases were prepared by mixing a series of inorganic salts with dimethylsiloxane polymer (SE‐30) and then tested by capillary gas chromatography. It was demonstrated that the polarity (as evaluated by measurement of Rohrschneider constants) of the mixed stationary phases, which is inferior or equal to that of a medium‐polar OV‐25 phases, reached even lower values than SE‐30 alone. The influence of NaF, NaCl, NaBr, AgNO3, and other inorganic salts on the polarity of capillaries is reflected by a better resolution and shorter retention time of cis/trans isomers of fatty acid methyl esters (FAMES) as well as positional isomers of triglycerides.
Screening for unknown compounds by HPLC using a multichannel diode array UV‐VIS spectrophotometer: Application to drug metabolism
Authors: Ghijsen R. T. , Drenth B. H. F. , Overzet F. , de Zeeuw R. A.
Published: May 2005

This article describes the use of a multichannel UV‐VIS detector coupled on‐line to an HPLC instrument. Simultaneous measurements of the absorption of a compound over a full range of wavelengths (200–800 nm) makes this almost universal detector a useful tool in screening for unknown compounds. The procedures used to compute so‐called spectro‐chromatograms and to draw pseudo‐three‐dimensional plots are discussed. The experimental examples given include an application to screening for drug metabolites in biological fluids.
Evaluation of a rotary valve/cold trap/reinjection system for capillary columns
Authors: Jacobsson Sven , Berg Sven
Published: May 2005

This paper describes a cold trap/reinjection system for capillary columns which utilizes a flow switching rotary valve. Sample enrichment is performed in a liquid nitrogen‐cooled glass trap attached to the valve. Evaporation of enriched compounds is carried out with the aid of an electric heating coil. Parameters such as cryogenic trapping efficiency, reinjection rates, transference of sample, and adsorption, as well as overall performance, are examined. In addition, a comparison is made between the cold trap/reinjection technique and injection with a gas‐tight syringe.
High resolution HPLC
Authors: Verzele M. , Dewaele C.
Published: May 2005

In order to justify its classification as a “high resolution” technique, HPLC should show an improvement in efficiency by a factor of at least 10, should be easily achievable with separation times of less than 1 h, preferably in the reversed phase mode. This is accomplished by coupling three 25 × 0.46 cm columns packed with 5 μm spherical ROSiL‐C18‐D silica gel. Details of the method and some typical chromatograms are given.
Packing procedure of silica columns for HPLC with aqueous slurries
Authors: Claessens H. A. , Aben G. , Vonk N.
Published: May 2005

Successful packing of high quality HPLC columns is dependent upon a number of parameters. Especially when using slurry packing techniques, the absence of conglomerates of particles in the slurry and the wettability of the particles are important. The method described in this paper fulfills these conditions, imparting a ξ potential to the 5 and 10 μm silica particles by applying a pH gradient. This results in repulsive forces between the particles and hence leads to a well‐controlled monodisperse situation. Water is used as a slurry and displacement liquid; it combines the advantages of excellent wetting properties and non‐toxicity.
High resolution glass capillary columns for the gas chromatographic analysis of alditol acetates of neutral and amino sugars
Authors: Hudson J. R. , Morgan S. L. , Fox A.
Published: May 2005

The development of improved high resolulation glass capillary columns for separating the alditol acetates of neutral and amino sugars is described. Different capillary column treatments were evaluated for their activity toward amino sugar derivatives and for their effect on the efficiency of the completed column. The simple two‐step procedure of leaching with aqueous hydrochloric acid and dynamic coating with SP‐2330 was found to produce efficient and inert columns.
Mathematics for chromatography. Part I: Concentration distributions and their moments
Authors: Said A. S. , Al‐Ali H. , Hamad E.
Published: May 2005

Several distributions of interest in chromatography were studied. In each case, the moments up to 4th moment were evaluated and the skew and the excess were deduced. The distributions studied in this article are the normal, continuous Poisson, discrete Poisson, exponentially modified normal, and exponentially modified Poisson distributions.
Peak distortion in chromatography. Part 1: Concentration‐dependent behavior
Authors: Conder J. R.
Published: May 2005

Asymmetrical or tailed peaks are a common problem in chromatography. The causes of this distortion are described and classified. Each case is discussed from the point of view of first diagnosing the cause of asymmetry end then dealing with it appropriately; e.g. by removing the cause or, in applications to physicochemical measurement, by using more appropriate measures of retention than the residence time of the peak maximum. The classification of sources of asymmetry applies to both gas and liquid chromatography, allowing information derived from one field to be extended to the other.

Part 1 of this review covers nonlinear, concentration‐dependent behavior with and without nonideal band‐spreading. Part 2 will deal with sources of distortion controlled by the kinetics of transport or reaction processes, viz. apparatus effects, incomplete resolution, slow kinetic processes, chemical reaction, and column voids.
Peak distortion in chromatography. Part 2: Kinetically controlled factors
Authors: Conder J. R.
Published: May 2005

The review of the characterization, diagnosis, and treatment of peak distortion begun in Part 1 is concluded. Part 1 dealt with peak distortion caused by nonlinear (concentration‐dependent) chromatographic behavior in the column. The present part covers peak distortion due to either the apparatus, incomplete resolution, slow kinetic processes, reaction on the column, or column voids. All these sources are controlled by the kinetics of transport or reaction processes.
The use of silicon in the preparation of apolar glass capillary columns
Authors: Bertsch W. , Pretorius V. , van Niekerk G. C.
Published: May 2005

As an extention of previous reports, variables affecting the performance of columns modified by silicon deposition have been optimized. The aim of this work was to produce thermostable apolar glass capillary columns regardless of the glass type used and to maintain column performance under stressful conditions. The main parameters studied were the influence of glass type, leaching effects, and silicon layer thickness on column activity. Deactivation and stationary phase conditions were held constant. Both coated and uncoated columns were tested.

The thickness of the silicon layer was found to be relatively unimportant. There was no difference whether soft glass or borosiiicate glass was used and leaching before silicon deposition did not influence column activity. Bare silicon surfaces showed considerable activity especially in respect to interactions with free acids and bases.

There are indications that the surface consists of silicon oxide and other oxygenated forms of silicon rather than of the element. Treatment of the silicon layers with dilute hydrofluoric acid and the strict exclusion of traces of oxygen and water did not improve the situation. In spite of such specific interactions, silicon surfaces were easily deactivated by heat treatment with polysiloxanes.

Silicon surfaces deactivated by baking with octamethyltetrasiloxane at 400°C are inert and temperature stable and show characteristics similar to persilylated surfaces.
Derivatives of cholesterol cinnamate: A comparison of the separations of geometrical isomers when used as gas chromatographic stationary phases
Authors: Heath R. R. , Doolittle R. E.
Published: May 2005

Four para‐substituted cholesterol cinnamates were synthesized and evaluated for utility as gas chromatograph (GC) liquid crystal stationary phases. The capability of the phases to separate olefinic geometrical isomers was found to be dependent on the position of the olefinic bond. When unsaturation occurred at positions four carbons or greater from the terminal methyl of the compounds investigated, the relative ability of the phases to separate geometrical isomers was p‐Cl > p‐Me > cholesterol cinnamate > p‐MeO derivative > p‐NO2. When unsaturation occurred at positions four carbons or less from the terminal methyl the relative ability of the para‐derivatives of cholesterol cinnamate to separate geometrical isomers was reversed.
Structure elucidation of triglycerides by chromatographic techniques. Part 2: RP HPLC of triglycerides and brominated triglycerides
Authors: Geeraert E. , De Schepper D.
Published: May 2005

The structure determination of triglycerides by RP HPLC is discussed, and the importance of temperature and mobile phase composition demonstrated. The formation of brominated triglycerides followed by RP HPLC analysis allows rapid determination of cocoa butter equivalents (CBE ) in cocoa butter and chocolate products.
Optimization via liquid phase mixtures in capillary gas chromatography
Authors: Takeoka G. , Richard H. M. , Mehran Mehrzad , Jennings W.
Published: May 2005

The use of sequentially coupled columns to achieve a binary liquid phase mixture has been simplified by the availability of zero dead volume fittings compatible with fused silica columns. The extent to which the velocity gradient through the coupled column affects the “apparent” liquid phase ratio can be determined by graphic interpolation; the length ratio of the coupled column segments can then be adjusted so that the “apparent” liquid phase ratio actually experienced by the solutes agrees with the targeted value. The fact that the direction of flow through the coupled column affects the chromatographic dispersion suggests that accepted generalizations on flow optimization throughout the column may not be precisely correct.
An attempt to extend ordinary capillary gas chromatography to supercritical fluid chromatography (SFC)
Authors: Grob K.
Published: May 2005

Since capillary columns with well immobilized stationary phases are expected to withstand contact with supercritical fluids, we wished to study their amenability to SFC. Simultaneously, we wished to learn how far SFC can be accomplished with the ordianary tools of capillary GC.

The study demonstrates that truly supercritical, not just relatively high, pressure is required to ensure the typical effects of SFC. Results obtained with sub‐and supercritical pressure are compared and discussed. A comprehenshive study of the parameters permitting SFC with capillary GC equipment showed a clear preference for CO2 as a carrier, FID detection, and oncolumn sampling. While no additional equipment is required, a critical feature is the flow restrictor to be mounted on the end of the column. The production and properties of this restrictor are discussed in detail. It is reasonable to hope that SFC with 0.1 mm id capillary columns can be realized in the pressure range of 100–150 bar, where substances which cannot be eluted from a capillary colum under GC donditions are expected to be analyzed.
Cold trapping of volatile organic compounds on fused silica capillary columns
Authors: Pankow J. F.
Published: May 2005

A 30 m, 0.25 mm ID, fused silica capillary column at temperatures from –60 to –100°C has been shown to be a quantitative trap for organic compounds with volatilities ranging from that of 1, 1 ‐dichloroethene that of chlorobenzene. This type of “whole column cryotrapping” provided sharp peaks (peak width approximately 4–7 seconds) for all compounds at a trapping temperature of –80°C and with high carrier gas pressures and linear velocities (30 psi and 110 cm/s, respectively). Whole column cryotrapping possesses great simplicity, chromatographic efficiency (no trapping loop connections), and a built‐in indicator of quality assurance for trapping efficiency (i.e., peak shape). These advantages are extremely attractive and are indicative of the fact that the potential of this approach has not yet been fully appreciated.
Gradient separations of complex mixtures by micro high‐performance liquid chromatography
Authors: Takeuchi T. , Ishii D.
Published: May 2005

High‐performance micro packed fused‐silica and open‐tubular glass capillary columns were prepared and applied to separations of complex mixtures. Solvent‐gradient elution proved quite useful for the separation of solutes with wide polarity. Instruments and some applications are described.
Flexible soft glass capillary columns vs. flexible fused silica capillary columns for gas chromatography‐a critique
Authors: Lipsky S. R.
Published: May 2005

The gas chromatographic use of flexible thin walled soft glass capillary columns coated with non‐polar stationary phases is compared to similar columns made of fused silica glass. With non‐polar soft glass columns, the use of surface roughening viagaseous HCI followed by a Carbowax 20 M pretreatment gave adsorptive phenomena, and thermal instability. With very polar soft glass columns where a variety of cyanopropyl silicone phases were coated directly onto the NaCI crystal matrix, adsorptive effects were again prominent and frequent break‐down in film stability with time, was also observed. These undesirable effects were due to the presence of metal oxides in the soft glass. Attempts to remove these materials from the thin walled soft glass surface by means of acid leaching produced significant brittleness. This deleterious result was further increased by attempts at high temperature silylation or polysiloxane deactivation.

In sharp contrast, the fused silica surface was essentially free of metal oxides and the surface silanol groups are easily neutralized by silylation or polysiloxane deactivation techniques. No brittleness was observed following these procedures. An increasing series of high molecular weight, viscous, polymeric vinyl containing non‐polar and highly polar stationary phases have been produced which readily wet the surface of the fused silica and are easily crosslinked in the presence of free radical generators. These columns are essentially free of all the problems noted with flexible thin walled soft glass. When all of the parameters involved in the fabrication of a glass capillary column are assessed, it appears at this time, that the flexible fused silica glass column with cross linked phases approaches the “ideal” capillary column.
Solute focusing technique for on‐column injection in capillary gas chromatography
Authors: Hinshaw J. V. , Yang F. J.
Published: May 2005

A novel solute focusing technique for on‐column injection of liquid samples onto capillary GC columns is described. The focusing technique allows injection of 8.0 microliters or more of sample without producing the peak distortion or splitting observed under conventional on‐column injection conditions. The experimentally determined performance of the technique is given for a wide volatility range sample. Solute focusing is useful in situations where on‐column injection of 1.0 microliter or greater is required.
Prediction of gas chromatographic retention indices of linear, branched, and cyclic alkanes from their physicochemical properties
Authors: Bermejo J. , Guillén M. D.
Published: May 2005

Kováts retention indices for a series of linear, branched, and cyclic alkanes on squalane at any temperature, and on other stationary phases of different polarity at a given temperature, are related to physicochemical properties of the solutes, such as boiling point and molar refraction, by multiple regression analysis. The equations found permit calculation of the Kováts retention index for all alkanes, with standard deviations close to experimental error. The same equations can also be used for calculating the physicochemical parameters they contain.