Static and scanning array detection in capillary electrophoresis-mass spectrometry.

An array detection system based on position- and time-resolved ion counting was evaluated for capillary electrophoresis-mass spectrometry using continuous-flow fast atom bombardment and a liquid-junction coupling. Peptides with molecular masses up to 3200 were measured. A 100-1000-fold improvement over conventional detection was demonstrated by applying the array detector in scanning and static modes. Absolute detection limits in the range 1-5 fmol are achievable.

Direct chemical ionization-pattern recognition: characterization of bacteria and body fluid profiling.

Direct chemical ionization is ideally suited for profiling purposes because it is a relatively soft ionization method, easy to operate, reproducible and with a high sample throughput. Moreover, for non-volatile matrices the method combines pyrolysis with an optimal pyrolysate transfer to the ionization region enabling the detection of high molecular weight compounds. Application of the technique to urine analysis of women with a premenstrual syndrome and characterization of Salmonella bacteria illustrates its usefulness. Optimal information extraction from the profiles is, because of their complex nature, only possible using pattern recognition techniques. A new approach based on the data analysis of trend spectra is discussed.

LC/MS determination of bromazepam, clopenthixol, and reserpine in serum of a non-fatal case of intoxication.

Combined liquid chromatography and mass spectrometry (LC/MS) with a moving belt interface can be used as a rapid method for the determination of bromazepam, clopenthixol, and reserpine in serum samples obtained from cases of acute overdoses with combinations of these drugs. Low resolution detection limits are about 100 pg for the three drugs, while in high resolution mode the detection limit for bromazepam is shown to be at least 35 pg. Accurate masses were obtained in a serum sample within 5 ppm using high voltage scanning over a narrow mass range for about 10 ng of bromazepam and clopenthixol, respectively. Chemical deactivation of the belt was shown to effectively reduce memory effects and to improve the desorption characteristics of the belt leading to higher yields of evaporated intact molecules.

Derivatization and mass spectrometric behaviour of catecholamines and their 3-O-methylated metabolites.

A method has been developed for the derivatization of both catecholamines (dopamine, noradrenaline and adrenaline) and their 3-O-methylated metabolites (3-methoxytyramine, normetanephrine and metanephrine) in a single run. The compounds were first incubated with methanolic hydrochloric acid to methylate those compounds that contain a benzylic hydroxyl group and were subsequently converted into their pentafluoropropionyl derivatives. The derivatives thus prepared, showed good gas chromatographic and electron-impact mass spectrometric properties and can be analysed in a single gas chromatographic run. The effect of the derivatization on exchange reactions in the aromatic ring was investigated because standard compounds with deuterium label in that part of the molecule are often used in isotope dilution measurements. The exchange of deuterium for hydrogen in the aromatic ring under derivatization conditions was found to be limited.

The early recognition of the 21-hydroxylase deficiency variety of congenital adrenal hyperplasia.

The urinary steroids excreted by three newborn infants with 21-hydroxylase deficiency and by 15 healthy newborns aged two days have been compared after analysis by gas liquid chromatography (GLC). The identity of each steroid was carefully checked by gas chromatography/mass spectroscopy (GC-MS). The enzyme deficiency leads to the elevated excretion of urinary precursor metabolites, mainly 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan, 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan-11-one and 3alpha,17alpha-dihydroxy-5beta-pregnan-20-one. In the search for a quick and firm confirmation of suspected 21-hydroxylase deficiency in a newborn baby by means of a GLC-profile of urinary steroids, most attention has up to now been paid to 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan. However, 3alpha,17alpha-dihydroxy-5beta-pregnan-20-one is a better indicator, as it enables one to confirm the existence of this disease soon after birth directly from the GLC-profile without further analyses by GC-MS.

Determination of eight volatile nitrosamines in thirty cured meat products with capillary gas chromatography-high-resolution mass spectrometry: the presence of nitrosodiethylamine and the absence of nitrosopyrrolidine.

Five samples each of six cured meat products were analysed for the presence of eight volatile nitrosamines. A combined steam distillation-extraction step at pH 8-9 plus a concentration step were used for preparation of extracts. These were analysed, without further clean-up, using a coupled capillary GC-HRMS system at a resolution of 4 000. The MS was used in the fixed mass mode, but after the retention time of each nitrosamine the mass adjustment was tuned to the mass of the next nitrosamine. This combination allowed not only an unambiguous identification of the nitrosamines but also their direct quantitative determination. The products investigated were cooked ham, fermented sausage, raw bacon, mildly fried bacon, fried minced mean and smoked meat. Only one nitrosamine, NDEA, was sometimes found to be present in relatively large amounts. It occurred in two of the bacon samples; the concentration increased during mild frying from 4 and 13 mug/kg to 16 and 43 mug/kg, respectively. It was also present in two of the smoked meat samples in amounts of 7 and 91 mug/kg, respectively. Its identity was further confirmed on a second and third capillary column also coupled to the MS, and by direct introduction of the extracts into the MS at a resolution of 15 000. A silicon compound with practically the same retention time and mass as NDMA, which originates from the antifoam agents used as shown by other investigators, was found in the extracts in amounts corresponding to abuot 2 mug/kg of product. Nevertheless, seven samples were found positively to contain NDMA in amounts of 2-6 mug/kg. NMEA, NMPA, NMBA and NDPA could not be detected in any of the samples, nor could NPip or NPy. That no NPy (i.e., less than 50 mug/kg) was found in the fried bacon samples may be due to the mild frying method used. The use only of capillary GC with a nitrogen-selective detector, without further sample clean up, would have led to many false-positive results due to the presence of other nitrogen-containing compounds.