Preparation of porous apatite granules from calcium phosphate cement.

A versatile method for preparing spherical, micro- and macroporous (micro: 2-10 and macro: 150-550 microm pores), carbonated apatitic calcium phosphate (Ap-CaP) granules (2-4 mm in size) was developed by using NaCl crystals as the porogen. The entire granule production was performed between 21 and 37 degrees C. A CaP cement powder, comprising alpha-Ca3(PO4)2 (61 wt.%), CaHPO4 (26%), CaCO3 (10%) and precipitated hydroxyapatite, Ca10(PO4)6(OH)2 (3%), was dry mixed with NaCl crystals varying in size from 420 microm to 1 mm. Cement powder (35 wt.%) and NaCl (65 wt.%) mixture was kneaded with an ethanol-Na2HPO4 initiator solution, and the formed dough was immediately agitated on an automatic sieve shaker for a few minutes to produce the spherical granules. Embedded NaCl crystals were then leached out of the granules by soaking them in deionized water. CaP granules were micro- and macroporous with a total porosity of 50% or more. Granules were composed of carbonated, poorly crystallized, apatitic CaP phase. These were the first spherical and porous CaP granules ever produced from a self-setting calcium phosphate cement. The granules reached their final handling strength at the ambient temperature through the cement setting reaction, without having a need for sintering.

Formation of apatitic calcium phosphates in a Na-K-phosphate solution of pH 7.4.

Poorly crystalline, apatitic calcium phosphate powders have been synthesized by slowly adding a Na- and K-containing reference phosphate solution with a pH value of 7.4 to an aqueous calcium nitrate solution at 37 degrees C. Nano-particulated apatitic powders obtained were shown to contain small amounts of Na and K, which render them more similar in chemical composition to that of the bone mineral. Precipitated and dried powders were found to exhibit self-hardening cement properties when kneaded in a mortar with a sodium citrate- and sodium phosphate-containing starter solution. The same phosphate solution used in powder synthesis was found to be able to partially convert natural, white and translucent marble pieces of calcite (CaCO3) into calcium-deficient hydroxyapatite upon aging the samples in that solution for 3 days at 60 degrees C. Sample characterization was performed by using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, inductively-coupled plasma atomic emission spectroscopy, and simultaneous thermogravimetry and differential thermal analysis.

Synthesis of biomimetic Ca-hydroxyapatite powders at 37 degrees C in synthetic body fluids.

An important inorganic phase for synthetic bone applications, calcium hydroxyapatite (HA, Ca10(PO4)6(OH)2), was prepared as a nano-sized (approximately 50 nm), homogeneous and high-purity ceramic powder from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts dissolved in modified synthetic body fluid (SBF) solutions at 37 degrees C and pH of 7.4 using a novel chemical precipitation technique. The synthesized precursors were found to easily reach a phase purity >99% after 6 h of calcination in air atmosphere at 90 degrees C, following oven drying at 80 degrees C. There was observed, surprisingly, no decomposition of HA into the undesired beta-TCP phase even after heating at 1,600 degrees C in air for 6 h. This observation showed the superior high-temperature stability of such 'biomimetic' HA powders as compared to those reported in previous studies. The former powders were also found to contain trace amounts of Na and Mg ions, originating from the use of SBF solutions instead of pure water during their synthesis. Characterization and chemical analysis of the synthesized powders were performed by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infra-red spectroscopy, scanning electron microscopy, and inductively coupled plasma atomic emission spectroscopy.

Characterization of virus infected cell cultures by pyrolysis/direct chemical ionization mass spectrometry.

The supernatants of Vero cell cultures after infection with a herpes simplex virus or a poliomyelitis virus as well as a blank were analysed by pyrolysis/direct chemical ionization mass spectrometry (Py/DCI MS). Informative pyrogrammes were obtained and used for characterization of viral proteins by applying pattern recognition methods. Differentiation of viral proteins was evaluated by analysing 'blind' samples. Herpes viruses could be classified correctly but the observed differences between the blank and the polio virus supernatants were too small for reliable classification of the polio viruses. Purification of the samples seems to be a prerequisite for further studies. The potential value of Py/DCI MS as a rapid non-invasive diagnostic method for viral meningoencephalitis is stressed.

Direct chemical ionization-mass spectrometric profiling of urine in premenstrual syndrome.

In search of the pathophysiological background of premenstrual syndrome, direct chemical ionization-mass spectrometric profiling was applied to urine samples from 17 patients and 18 control subjects, collected on days 11 and 25 of the menstrual cycle. Oestrogenic compounds and hippuric acid were found to be involved in differences between these groups. Quotient profiles calculated for each subject from their profiles of days 11 and 25 showed cycle day-dependent group differences. Masses accounting for these differences between patients and control subjects indicate the involvement of unsaturated heterocyclic compounds in premenstrual syndrome.

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.

Formation of odorous compounds from hydrogen sulphide and 2-butenal.

Strongly odorous compounds may be formed upon addition of hydrogen sulphide to unsaturated carbonyl compounds. The reaction between hydrogen sulphide and 2-butenal was studied, and the characteristics of the flavour, the structure and some of the physical chemical characteristics of the reaction products were determined. The influence of the pH on the type of components formed in dilute aqueous solution was investigated.

Reaction of hydrogen sulphide with 2-alkenals.

Depending on the types of solvent and catalyst, different products are formed in the reaction of hydrogen sulphide with 2-alkenals. The structures of many of these products have been elucidated, and the reaction sequences leading to them are proposed.