Nitrogen-selective Detection Research Articles

Sensitive assay for amino sugars using capillary gas chromatography with nitrogen-selective detection

Sensitive assay for amino sugars using capillary gas chromatography with nitrogen-selective detection

An improved gas chromatographic method for the simultaneous determination of chloroquine and two metabolites using capillary columns

A gas chromatographic method for the simultaneous determination of therapeutic levels of chloroquine, and the metabolites deethyl chloroquine and bideethyl chloroquine in human whole blood, plasma and urine has been developed by use of the capillary column technique. The analytes were extracted as bases with n-hexane—1-pentanol (90:10) and re-extracted into an acidic aqueous phase. After a further extraction to a small volume of chloroform, the substances were injected by the falling needle technique onto a fused-silica capillary column followed by nitrogen-selective detection. Limits of determination using 2 ml of the sample were found to be 10 nmol/l (3 ng/ml) for chloroquine and deethyl chloroquine and 30–40 nmol/l (10 ng/ml) for bideethyl chloroquine with a coefficient of variation of < 15%. The precision of the method at the 100 nmol/l level was about 4% ( n = 8) for chloroquine.

An improved gas chromatographic method for the determination of urinary acetylpolyamines.

Our previous method for the determination of acetylpolyamines in human urine by gas chromatography has been improved. A urine sample fortified with the internal standard (monoacetylnorspermidine) was directly treated with ethyl chloroformate in an alkaline medium, thereby converting the acetylpolyamines to the N-ethoxycarbonyl derivatives. After extraction of the resulting derivatives with chloroform, the combined extract was applied to a silica gel minicolumn to remove interfering substances. The derivatives of acetylpolyamines thus isolated were determined by gas chromatography with nitrogen-selective detection under temperature-programmed conditions. Calibration curves for acetylpolyamines were linear over the range of 0.2-10 nmol examined. The sensitivity of this method is over 100-fold higher than that of the previous method, so that the acetylpolyamines in human urine could be accurately determined in a sample as small as 200 μl. The use of a nitrogen-selective detector and concomitant procedural modifications greatly reduced the time required for analysis.

Amino acid determination by capillary gas chromatography on chirasil-val : Enantiomer labelling nitrogen-selective detection

Amino acid analysis by enantiomer labelling and capillary gas chromatography on Chirasil-Val is superior to conventional gas chromatography and ion-exchange chromatography with respect to sensitivity, accuracy and speed. Employment of an alkali flame-ionization detector allows the selective detection of amino acids and suppression of background peaks; in addition, the delectability of amino acids is enhanced. Most nitrogen-selective detectors require meticulous adjustment of the operating conditions, but in combination with enantiomer labelling this is less critical. Maximum sensitivity and selectivity of the alkali-bead flame-ionization detector is achieved with a minimal flow of hydrogen. When using it as the carrier gas in capillary gas chromatography, flow control instead of the common pressure regulation is recommended to avoid a continuous fall of the baseline during temperature programming. Accurate flow control is achieved with a micro-aperture. The benefit of nitrogen-selective detection is especially apparent for histidine and arginine.

Determination of nitrated polynuclear aromatic hydrocarbons in particulate extracts by using capillary column gas chromatography with nitrogen selective detection

The highly complex matrix of a diesel particulate extract was analyzed for nitrated polynuclear aromatic hydrocarbons (nitro-PAH) by use of fused-silica capillary column GC/thermionic nitrogen-phosphorus (GC/NPD) analysis of HPLC fractions. These samples were found to contain at least 100 nitro-PAH. Positive isomer identification for 17 nitro-PAH has been made utilizing the GC retention times of authentic standards and low- and high-resolution mass spectra as criteria. An additional 45 nitro-PAH were tentatively identified by using one or more of these techniques. Quantitative GC/MS analysis of 1-nitropyrene, 1,3-dinitropyrene, 1,6-dinitropyrene, and 1,8-dinitropyrene was facilitated by the use of perdeuterated analogues of these compounds as internal standards. Detection limits by the GC/NPD method range between 0.2 and 0.5 ppm for the HPLC fractionated samples. 4 figures, 2 tables.

Determination of disopyramide and mono-N-desisopropyl-disopyramide in serum by gas-liquid chromatography with nitrogen-selective detection

A rapid, reliable assay is described for the quantitation of disopyramide (DP) and its metabolite, mono-N-desisopropyl-disopyramide (MNDP), in serum using p-chloro-disopyramide as the internal standard and aqueous standards for calibration. The procedure involves extraction of the serum sample with diethyl ether, derivatization of MNDP with acetic anhydride, and gas-liquid Chromatographic analysis with nitrogen-selective detection. The accuracy of the procedure is97.8 ± 10.3 (SD)% for DP over the concentration range, 0.25–10.00 μg/ml ( n = 37), and 99.6 ± 10.2 (SD)% for MNDP over the concentration range, 0.50–5.00 μg/ml ( n = 18). The within-day coefficient of variation is less than 8% for DP and 12% for MNDP. The lower limit of quantitative sensitivity is 0.25 μg/ml for DP and 0.50 μg/ml for MNDP, and the lower limit of detection is 0.6 ng and 1.6 ng, respectively, for DP and MNDP. This assay has been used to determine the time-course of DP and MNDP and the protein binding of DP (without requiring an in vitro protein binding curve) in the serum obtained from patients and laboratory animals during DP administration.

Determination of tricyclic antidepressant drugs by gas chromatography with the use of a capillary column

A universal gas chromatographic procedure for the determination of the commonly prescribed tricyclic antidepressant drugs in 1 mL of plasma is described. After the addition of internal standards the samples are washed with pentane at acidic pH and extracted with pentane at alkaline pH. The pentane extract is evaporated after the addition of acetic anhydride. Aliquots of a methanolic solution of the residue of evaporated extract are analyzed isothermally on a Durabond 30 m fused silica column. This column is well suited for use with a nitrogen selective detector. The liquid phase is not extracted by repeated injections of methanolic solutions of plasma extracts. When compared to a packed column, this column allows shorter analysis time.

Spontaneous Live Birth with a Maternal History of Intravenous Use of Pentazocine and Tripelennamine (T's and Blues)

A 24-year-old black female presented a live birth of six-months gestation. The 700-g neonate survived for 11 h. After toxicology revealed the presence of pentazocine and tripelennamine (T's and Blues), the mother admitted to using this combination intravenously 9 h previous to admission. Concentrations of pentazocine and tripelennamine were simultaneously determined by gas-liquid chromatography (GLC) combined with nitrogen selective detection. Analyses were performed on a 3% OV-101 column, with the added internal standard, dexbrompheniramine. Both pentazocine and tripelennamine were qualitatively confirmed by their electron impact mass spectra. Concentrations of pentazocine and tripelennamine in various fluids and tissues were determined.

Gas chromatography with nitrogen-selective detection of metoprolol from human plasma after reaction with phosgene

A method for the determination of therapeutic levels of metoprolol in human plasma is presented. Metoprolol and the internal standard are extracted from the buffered plasma sample to an organic phase containing 4 x 10 −3 M phosgene. After 10 min the organic phase is taken to dryness. The residue is dissolved in ethyl acetate and the formed oxazolidine derivatives are analyzed by gas chromatography with nitrogen-selective detection. With packed columns, rectilinear standard curves through the origin were obtained down to 80 nmoles/l of plasma. The precision of the method at 200 nmoles/l was 1.5% ( n = 8). The sensitivity of the method was improved by using capillary column gas chromatography. Linear standard curves were obtained down to 10 nmoles/1 of metoprolol in plasma. The precision of the method at the 50 nmoles/1 level was 2.2% ( n = 7). With this simple and straightforward method using extractive derivatization 30 samples can be handled in a day.

Isolation of polycyclic aromatic hydrocarbons and nitro derivatives in complex mixtures by liquid chromatography

A method has been developed for isolating polycyclic aromatic hydrocarbons (PAH) and their nitro derivatives in complex samples by means of normal-phase high-performance liquid chromatography (HPLC) using silica gel columns and n-hexane:benzane 3:1 as eluent. Experiments have revealed that ..pi..-bonding complex formation to benzene adsorbed on the surface of the column material and hydrogen bonding between free silanol groups on the surface and polar substituents in different types of polycylic organic matter affects the retention of these compounds. The PAH fraction is analyzed by gas chromatography (GC) with flame ionization detection. The NO/sub 2/-PAH fraction is analyzed by GC with nitrogen-selective detection. The method has been tested on samples of airborne particulate matter. 9-Nitroanthracene, 1-nitropyrene, and 10-nitrobenz(a)anthracene were identified and determined in airborne particulate matter. 4 figures, 4 tables.

Gas—liquid chromatographic determination of toloxatone in human plasma : Routine analysis of a wide range of drug concentrations using a nitrogen-selective detector

A selective and sensitive gas—liquid chromatographic (GLC) method has been developed for the measurement of toloxatone at therapeutic concentrations in plasma. The technique is based on a single extraction from plasma at pH 10, the preparation of a trimethylsilyl derivative and detection by a nitrogen-selective detector. The traditional calibration curve, peak-area ratio of toloxatone to internal standard versus toloxatone plasma concentration, was slightly concave for the wide concentration considered (10–3000 ng/ml). As a consequence, the linear least-squares regression analysis gave a negative intercept on the y-axis which affected quantitation accuracy of low plasma concentration values. A calibration method taking into consideration the non-linearity of the calibration curve is proposed. The characteristics of the detector were examined in order to analyse response linearity and sensitivity. A linear relationship was found between background current and detector sensitivity.

Trace analysis of amines and isocyanates using glass capillary gas chromatography selective detection : II. Determination of aromatic amines as perfluorofatty acid amides using nitrogen-selective detection

A method for the trace analysis of aromatic amines is presented. It involves derivatization of the amines to the corresponding amides by reaction with a perfluorofatty acid anhydride. The amides were separated by glass capillary gas chromatography, picogram amounts were quantitated using on-column injection and nitrogen-selective detection with a Varian thermionic specific detector. The method was applied to amines of interest from work environment health aspects and to polyurethane pyrolysis products. Detection limits were of the order 10–20 pg amine. Comparison with a recent gas chromatographic amine analysis method from this laboratory utilizing electron-capture detection was made, and differences between the two detection methods are discussed.

Determination of phosgene in methylene chloride after cyclisation with a 2-hydroxyamine and gas chromatography with nitrogen-selective detection

A convenient and simple method for the determination of phosgene in methylene chloride has been developed. An aliquot of the sample is mixed with a solution of metoprolol or 2-aminophenol, in an excess. After a reaction time of 10 min the solution is taken to dryness and the cyclic derivative analysed by gas chromatography with nitrogen-selective detection. The precisions (relative standard deviation) at the 40 and 10 ng ml–1 levels were 3.9 and 7.3% for metoprolol and 3.3 and 3.6% for 2-aminophenol, respectively. The absolute yields at the 40 ng ml–1 level were 91 and 95%, respectively. The present limit of detection is approximately 1 ng ml–1. Phosgene appeared in methylene chloride (>2 ng ml–1) stabilised with 20 p.p.m. of amylene within 3 d if stored in clear glass in the presence of daylight. After 15 d the 100 ng ml–1 level was reached.

Measurement of moclobamide, a new monoamine oxidase inhibitor, by gas chromatography with nitrogen-selective detection

Measurement of moclobamide, a new monoamine oxidase inhibitor, by gas chromatography with nitrogen-selective detection

Determination of the anti-ischaemic drug bepridil in human plasma using gas chromatography with nitrogen-sensitive detection

An assay has been developed to determine the anti-ischaemic drug bepridil (as its free base) in human plasma. The assay procedure comprises n-hexane extraction from basic plasma and gas chromatography using nitrogen-selective detection. An analogue of bepridil is used as internal standard. The accuracy and precision of the assay is determined by repeated analyses of drug-free plasma samples spiked with 5, 10, 20, 100, 400 and 1000 ng of bepridil per ml of plasma. The accuracy, defined as the relative difference between the mean bepridil concentration found and the true value, was 8% or better. The precision (relative standard deviation) was 13% at the 5 ng/ml level and 5% at the 1000 ng/ml level. The assay is suitable to monitor routinely bepridil plasma levels during clinical studies.

Cytokinin determination in tRNA by fused-silica capillary gas chromatography and nitrogen-selective detection

Cytokinin determination in tRNA by fused-silica capillary gas chromatography and nitrogen-selective detection

Gas chromatographic assay of codeine in human plasma utilizing nitrogen-selective detection

Gas chromatographic assay of codeine in human plasma utilizing nitrogen-selective detection

Gas chromatographic determination of bupivacaine in plasma using a support coated open tubular column and a nitrogen-selective detector.

A capillary gas chromatographic method for the quantitative determination of bupivacaine in plasma is described. Bupivacaine and an added internal standard were extracted from plasma with n-pentane. The extracted products were introduced into the gas chromatograph via a solid injection system. The combination of a support coated open tubular column and a nitrogen-selective detector insure a good selectivity and a high sensitivity. The coëfficient of variation at concentrations exceeding 3 ng bupivacaine/ml plasma is less than 6%. The detection limit is about 1 ng/ml.

Quantitative determination of n-dipropylacetamide in the plasma of epileptic patients by gas—liquid chromatography with nitrogen-selective detection

Quantitative determination of n-dipropylacetamide in the plasma of epileptic patients by gas—liquid chromatography with nitrogen-selective detection

Use of an Extended Torch with an Inductively Coupled Plasma for the Determination of Nitrogen in Aqueous Solutions

The inductively coupled argon plasma (ICP) has proved to be an excellent source for determining a variety of elements in various materials. The ICP has been used by several authors to determine nitrogen in various forms but not directly from a liquid sample. Alder, et al. determined low levels of ammonium by oxidation with sodium hypobromite in an alkaline medium. The resultant evolved nitrogen was then passed into an ICP and the emission of the NH band emission at 336.0 nm measured. Gaseous compounds containing nitrogen were analyzed by Northway et al. by injecting samples into the ICP and measuring the 868.027 nm N line. Brown et al. have reported the successful analysis of volatile organic liquids for nitrogen with the use of the ICP as a nitrogen selective detector for gas-liquid chromatography.