[Does childhood obesity affect sexual development?]. / Beeinflusst die kindliche Adipositas die Pubertätsentwicklung?

The process of pubertal development is only partly understood and is influenced by many different factors. During the twentieth century there was a general trend toward earlier pubertal development. Fat mass is thought to be a major inducer of puberty. Owing to the rising epidemic of childhood obesity, the relationship between body composition in children and the rate and timing of puberty needs to be investigated. Some studies suggest that central obesity is associated with an earlier onset of pubertal development. Rapid weight gain in early life is linked to advanced puberty in both sexes. A clear correlation exists between increasing body mass index (BMI) and earlier pubertal development in girls. In boys the data are controversial: The majority of studies propose that there is an earlier puberty and voice break in obese boys, but some studies show the opposite. There are several factors and mechanisms that seem to link obesity and puberty, for example, leptin, adipocytokines, and gut peptides. Important players include genetic variation and environmental factors (e.g., endocrine-disrupting chemicals). This article presents the latest studies and evidence on this topic, underlining the inconsistencies in the data and, therefore, the need for further research in this area.

Leucocytes are a major source of circulating nicotinamide phosphoribosyltransferase (NAMPT)/pre-B cell colony (PBEF)/visfatin linking obesity and inflammation in humans.

AIMS/HYPOTHESIS: Nicotinamide phosphoribosyltransferase (NAMPT) is a multifunctional protein potentially involved in obesity and glucose metabolism. We systematically studied the association between circulating NAMPT, obesity, interventions and glucose metabolism and investigated potential underlying inflammatory mechanisms. METHODS: Fasting morning NAMPT serum levels were measured in cohorts of lean vs obese children, cohorts of intervention by lifestyle, exercise and bariatric surgery, and during an OGTT. In addition, mRNA expression, protein production and enzymatic activity of NAMPT were assessed from isolated leucocytes and subpopulations. RESULTS: Circulating NAMPT was significantly elevated in obese compared with lean children and declined after obesity interventions concomitantly with the decline in BMI, high-sensitivity C-reactive protein (hsCrP) and leucocyte counts. Circulating NAMPT significantly correlated with glucose metabolism and cardiovascular variables in univariate analyses, but only the association with glucose response during an OGTT was independent from BMI. We therefore assessed the NAMPT dynamic following an oral glucose load and found a significant decline of NAMPT levels to 77.0 ± 0.1% as a function of time, and insulin-to-glucose ratio during an OGTT in obese insulin-resistant adolescents. Circulating NAMPT was, however, most strongly associated with leucocyte counts (r = 0.46, p < 0.001). The leucocyte count itself determined significantly and independently from BMI insulin resistance in multiple regression analyses. We systematically evaluated NAMPT expression among several tissues and found that NAMPT was predominantly expressed in leucocytes. In subsequent analyses of leucocyte subpopulations, we identified higher NAMPT protein concentrations in lysates of granulocytes and monocytes compared with lymphocytes, whereas granulocytes secreted highest amounts of NAMPT protein into cell culture supernatant fractions. We confirmed nicotinamide mononucleotide enzymatic activity of NAMPT in all lysates and supernatant fractions. In monocytes, NAMPT release was significantly stimulated by lipopolysaccharide (LPS) exposure. CONCLUSIONS: Leucocytes are a major source of enzymatically active NAMPT, which may serve as a biomarker or even mediator linking obesity, inflammation and insulin resistance.

Vaspin is related to gender, puberty and deteriorating insulin sensitivity in children.

BACKGROUND: Visceral adipose tissue-derived serine protease inhibitor (vaspin) has been suggested as a novel adipocytokine related to obesity and insulin sensitivity in adults. DESIGN: We quantified vaspin serum concentrations in 65 lean and 67 obese children and aimed to evaluate the relationship of vaspin with physical development, obesity, and metabolic and cardiovascular phenotypes in children. We further assessed the acute vaspin response to glucose provocation in 20 obese adolescents and evaluated tissue expression patterns of vaspin in humans. RESULTS: Vaspin levels were significantly higher in girls than in boys. In girls, vaspin increased with age and pubertal stage, whereas there was no change with development in boys. Obese girls had lower vaspin serum levels than those of lean controls, but there was no significant correlation with body mass index (BMI). Independent of sex, age and BMI, lower vaspin was associated with better insulin sensitivity, with higher systolic blood pressure and impaired endothelial function. In response to glucose provocation during an oral glucose tolerance test, vaspin serum levels declined by approximately 25% in adolescents with hyperinsulinemia, whereas there was no significant decline in normoinsulinemic patients. In support of our clinical data, we not only confirmed vaspin mRNA expression in adipose tissue but also found consistent expression of vaspin in the liver and indications for expression in the pancreas and the skin. CONCLUSION: We showed that gender differences in circulating vaspin levels develop during pubertal progression in girls. Although vaspin's association with obesity remains controversial, vaspin was increased with worsening insulin resistance already in children and was acutely down-regulated following glucose provocation in insulin-resistant adolescents independent of obesity. Besides adipose tissue, vaspin expression in the liver and the pancreas may potentially contribute to circulating vaspin levels and their regulation.

Early weight gain and outcome in Henoch-Schönlein nephritis.

BACKGROUND: Intrauterine growth restriction seems to be a risk factor for an aggravated course of secondary renal diseases in children. Catch-up growth after birth may play a critical role. We tested if there is an association between an aggravated course of nephritis in Henoch-Schönlein Purpura (PSHN) and low birth weight or early weight gain during infancy. PATIENTS: We retrospectively analysed the clinical course of 34 children with PSHN. METHODS: Patients were sorted according their birth weight standard deviation score (SDS) in tertiles. Early weight gain was defined as gain of weight standard deviation score >0.67 between birth and 2 years of age. RESULTS: Patients with higher birth weight needed Cyclophosphamide in a higher rate than low birth weight children. In the high weight gain group (SDS gain >0.67) 9 of the 11 patients compared to 7 of 22 patients in the low weight gain group (SDS gain <0.67) presented with arterial hypertension during the initial manifestation of PSH nephritis (p=0.01). Median systolic blood pressure SDS in the high weight gain group was 1.54 (-1.39-4.71) versus 0.29 (0.52-4.05) in the low weight gain group (p=0.008). Nevertheless, other clinical parameters during first manifestation and follow-up were not relevantly different. CONCLUSION: In contrast to the data of children with idiopathic nephrotic syndrome or IgA nephropathy, this study does neither provide evidence for an association between low birth weight nor early weight gain and the later course of PSHN. Interestingly, early weight gain was associated with a higher systolic blood pressure during the initial manifestation of PSHN.

Considering laparoscopic salvage options--is pre-emptive omentectomy necessary in paediatric peritoneal patients?

BACKGROUND: In paediatric peritoneal dialysis patients, pre-emptive omentectomy is discussed controversially and literature provides only little data concerning this issue. Our aim was to evaluate the rate of omentum-majus-related problems in our patients, in whom omentectomy was generally not performed. Furthermore, we were interested in the success rates of laparoscopic adhesiolysis. PATIENTS AND METHODS: Between 09/2006 and 03/2008, we regularly saw 18 peritoneal dialysis patients in whom we retrospectively analysed medical records to determine the rate of catheter-related complications. In addition, we evaluated the success rates of laparoscopic adhesiolysis. RESULTS: During 355 dialysis months in 18 patients, we observed 7 omentum-majus-related obstructions in 6 patients (1/50.7 PM). The median age of the patients affected was 9 years, median filling volume at the time of the obstruction was 671 ml/m (2). Laparoscopic adhesiolysis was successful in 4 out of 7 episodes. In 3 cases, the catheter lumen was plugged by necrotic portions of the omentum and the catheters had to be replaced. CONCLUSION: Our data confirm omentum-majus-related catheter obstruction as a major cause of catheter dysfunction. However, in comparison to literature, it remains unclear to which extent omentectomy can reduce the incidence of catheter obstruction in general (including e. g. obstruction due to coagulation). Thus, the decision to perform an omentectomy should be taken individually after careful consideration. In case of omentum-majus-associated obstruction, early but not late laparoscopic intervention proved to be a successful, minimally invasive technique to restore catheter function.

[Topical anesthesia before vascular access in children. Comparison of a warmth-producing lidocaine-tetracaine patch with a lidocaine-prilocaine patch]. / Topische Anästhesie vor Venenpunktion bei Kindern. Vergleich eines wärmenden Lidocain-Tetracain- mit einem Lidocain-Prilocain-Pflaster.

BACKGROUND: Venepuncture is one of the most stressful situations for children during induction of general anesthesia. Therefore, many clinicians use a local anesthesia patch (EMLA) containing a mixture of lidocaine and prilocaine in order to reduce the stress for pediatric patients. This study compared the effect of a new heated topical anesthesia delivery system containing lidocaine and tetracaine (Rapydan) with the lidocaine/prilocaine patch EMLA. METHODS: The study design was prospective, randomized, single-blinded and monocenter. A total of 200 children aged from 3 to 13 years were randomized into group E (EMLA) or group R (Rapydan). The primary endpoint of the study was the overall incidence of pain. Additionally, the intensity of pain during venous puncture was evaluated by means of an investigator-based 4 point pain score: 0 no reaction, 1 gentle movement/grimacing, 2 moderate withdrawal of the arm/crying and 3 strong withdrawal/screaming. Furthermore, erythema of the skin, visibility of the veins and success rate of the punctures were assessed. RESULTS: Mean contact time of the patch with the skin was 35 min in both groups. The overall incidence of pain was 46% in group E and 12% in group R (p<0.001). The intensity of pain also differed significantly between the groups. A pain score of 1 was observed in 24% (group E) versus 10% (group R), a score of 2 was documented in 13% (group E) versus 1% (group R) and a score of 3 was observed in 9% (group E) versus 1% (group R; p<0.001). Erythema of the skin was observed more frequently in group R (p<0.001). Visibility of the veins and success rate of venous puncture did not differ significantly. CONCLUSIONS: After a contact time of 35 min the Rapydan patch led to superior analgesia during venous puncture than the EMLA patch. With regard to visibility of the veins and success rate of the punctures, differences between the two patches were not observed.

Experience with mycophenolate mofetil as maintenance therapy in five pediatric patients with severe systemic lupus erythematosus.

Maintenance therapy of severe pediatric systemic lupus erythematosus (SLE) usually consists of azathioprine and prednisone . In adult SLE patients mycophenolate mofetil (MMF) is successfully used, superiority to azathioprine has not been shown yet. We hypothesized that a maintenance therapy with MMF is able to decrease disease activity as well as the dose of glucocorticoid needed in children and adolescents with SLE. Five girls with a mean age of 13.9 (range 12-15) years were treated with 1.2+/-0.20 g/m (2) MMF daily on individual medical decision. Three patients had severe renal (WHO IV) and one severe cerebral involvement. Three patients with frequent flares on azathioprine maintenance therapy were switched to MMF, two patients with severe renal and cerebral manifestation received MMF additionally after induction therapy. Flares, steroid dosage, and disease activity (SLEDAI) were monthly registered in all patients. The number of flares decreased from 1.28 to 0.25 episodes per patient year during a mean follow-up period of 39 (range 36-42) months after MMF initiation. In parallel prednisone dose could be reduced from 10.80+/-5.25 to 3.25+1.18 mg/d (p<0.01). SLEDAI score dropped from 15.20+/-2.8 before MMF to 3.60+/- 0.9 at the last visit under MMF (p<0.001). No severe adverse event occurred. In our cohort of five pediatric patients MMF was effective and safe for maintenance therapy of SLE over a period of 3.5 years. MMF seems to be successful in preventing flares even in adolescents having unfavorable course on azathioprine treatment before. This observation should be confirmed by a randomized multicenter clinical trial.

Patient with antibody-negative relapse of Goodpasture syndrome.

Smoking in young men may trigger anti-GBM disease manifesting with hemoptysis. We present a male adolescent in whom hemoptysis was mistaken to be a sign of airway infection for several months and who later on underwent an unusual antibody-negative relapse. The 16-year-old patient had a history of smoking and therapy-refractant hemoptysis and, later, acute macrohematuria with renal insufficiency necessitating hemodialysis (initial creatinine 4.2 mg/ dl). Chest X-ray showed diffuse lung infiltration. Renal biopsy revealed linear IgG deposits along the glomerular basement membrane (GBM) and cellular crescents in 13/16 glomeruli, simultaneously increased anti-GBM antibodies were detected. Thus, anti-GBM glomerulonephritis was diagnosed. After treatment with prednisone, oral cyclophosphamide and plasmapheresis, chest X-ray and hemoptysis improved, but renal failure persisted. Anti-GBM antibodies were negative. 4 weeks later, the patient presented again with a clinical relapse of severe hemoptysis and respiratory insufficiency after smoke exposition. Despite negative anti-GBM antibodies, he was treated similarly to a relapse and after the second course of plasmapheresis the patients' general condition improved and hemoptysis subsided. During the next 10 months the patient was stable with negative antibodies. He was under intermittent hemodialysis until laboratory measurements showed improved renal function. Now, 30 months after the acute episode, the patient is off dialysis for 17 months with stable creatinine values of 1.9 - 2.4 mg/dl, and is currently being treated with antihypertensive medicaments, calcitriol, calciumacetate, natriumhydrogencarbonate and allopurinol. The prognosis of anti-GBM glomerulonephritis depends on serum creatinine and the need of dialysis at initial presentation. In these patients, one-year survival rate is 67% and 5% for kidney function. Of note, despite the unfavorable prognosis in our patient, renal function recovered after 1 year of hemodialysis treatment. It is important to consider that in patients with anti-GBM disease antibody-negative relapses are possible.

Detection of proliferating cell nuclear antigen in diagnostic histopathology.

We describe the effects of tissue preservation, fixation time, and hydrolytic treatment on the detection of proliferating cell nuclear antigen (PCNA) by immunoperoxidase staining with three commercial anti-PCNA antibodies (19A2, 19F4, PC10). Our goal was to provide guidelines for PCNA immunohistochemistry in formalin-fixed, paraffin-embedded specimens. In proliferative cell compartments, nuclear staining was achieved with all three antibodies. In some cases PCNA was also expressed in non-proliferative, histologically normal tissues associated with tumors or other lesions elsewhere. In most autopsy specimens PNCA immunoreactivity was markedly diminished as compared with similar surgical specimens. Incubation overnight with primary antibody at 4 degrees C enhanced PCNA immunoreactivity over incubation at 42 degrees C for 45 min. Pre-treatment with 2 N HCl did not increase staining. Staining with the PC10 antibody was much better preserved than staining with the antibodies 19A2 and 19F4 after prolonged formalin fixation of surgical specimens and in tissues obtained at autopsy. With all three antibodies, however, PCNA immunoreactivity was well preserved during formalin fixation for 8-24 hr and during fixation delays for 8 hr at room temperature. This indicates that PCNA is stable under conditions routinely encountered in diagnostic surgical pathology and facilitates its potential use as a diagnostic proliferation marker.

Long-term outcome after open treatment of severe intra-abdominal infection and pancreatic necrosis.

BACKGROUND: Outcome assessment after surgical treatment of intra-abdominal infections and pancreatic necrosis has concentrated on postoperative complications and survival, while long-term results have received little attention. OBJECTIVES: To evaluate hospital costs and long-term outcome for patients undergoing open treatment of intra-abdominal infection or pancreatic necrosis and to determine whether results justify costs. DESIGN: Cohort study and cost-effectiveness analysis. SETTING: Referral center. PATIENTS: From January 1, 1988, through June 30, 1996, we used open treatment for 147 patients with pancreatic necrosis (n=75; group 1), severe intra-abdominal infections due to benign diseases (n=50; group 2), and infections due to malignant neoplasm (n=22; group 3). All surviving patients (n=92) were followed up. Fifty-seven patients in group 1, 25 patients in group 2, and 10 patients in group 3 survived. INTERVENTIONS: The effective costs of treatment per surviving patient (including restorative surgery) were calculated. The patients were interviewed, and the residence location, medical treatment, degree of recovery, functional state, and employment status were assessed. We assessed the quality of life by using the short general health survey (SF-36). MAIN OUTCOME MEASURES: Costs, survival, and long-term outcome. RESULTS: The effective costs per survivor studied were $175000 (group 1) and $232400 (groups 2 and 3). Most patients experienced good long-term results, ie, employment status was unchanged for 69 (75%) of the patients, and the functional state was unchanged for 81 (88%) of the patients. Readmission to a hospital was necessary for 14 (15%) of the patients, and 5 (6%) required care in nursing homes. Of the patients studied, 75% described their quality of life as good. Patients in group 3 had significantly worse results for survival, functional status, and quality of life (P<.01, log-rank test). CONCLUSIONS: Our study demonstrated that open treatment of severe intra-abdominal infection and pancreatic necrosis is a cost-effective treatment with good long-term results for most patients. However, patients with malignant neoplasms did not benefit from this therapy and, therefore, should not be treated by laparostomy.

Does reoperation for abdominal sepsis enhance the inflammatory host response?

OBJECTIVE: To determine the effect of reoperation for severe abdominal sepsis on the course of proinflammatory mediators and hemodynamic factors. DESIGN: Inception cohort. SETTING: A university hospital and a secondary care hospital. PATIENTS AND METHODS: Fifteen patients suffering from severe peritonitis due to intestinal perforation or infected necrotizing pancreatitis were studied following 19 subsequent operations. Plasma samples were obtained immediately before and after reoperation, as well as at 1, 3, 6, 12, and 24 hours after operation to determine endotoxin, tumor necrosis factor alpha, and interleukin-6 levels. Clinical factors and therapeutic support were recorded at the corresponding times. MAIN OUTCOME MEASURES: Postoperative hemodynamic instability as defined by changes of the mean arterial pressure, pulmonary capillary wedge pressure, and vasopressor support. Courses of proinflammatory mediators were correlated to the hemodynamic findings. RESULTS: Mean arterial pressure decreased from 94 mm Hg postoperatively to 80 mm Hg at 3 hours (P = .006) and 81 mm Hg at 6 hours postoperatively (P = .005). Pulmonary capillary wedge pressure dropped from 14 mm Hg postoperatively to 12 mm Hg at 1 hour (P = .05). Vasopressor support significantly increased from 1 to 6 hours postoperatively (P = .02). Neither endotoxin nor tumor necrosis factor alpha levels showed significant changes in the postoperative course. Interleukin-6 levels continously increased from 586 pg/mL preoperatively to 910 pg/mL at 1 hour (P = .02) and 931 pg/mL at 3 hours postoperatively (P = .04). Overall interleukin-6 levels (R = -0.38, P = .003) and especially early postoperative interleukin-6 levels inversely correlated with postoperative mean arterial pressure. CONCLUSIONS: Reoperation for abdominal sepsis frequently causes substantial hypotension, and is, thus, potentially harmful to the patient. Reoperative trauma may induce an early postoperative increase in interleukin-6 levels. Because this increase occurs before the development of hypotension, a relationship between the kinetics of this cytokine and the observed hemodynamic instability may be present.

Stimulation of neuropeptide Y release in rat pheochromocytoma cells by nitric oxide.

Neuropeptide Y and nitric oxide (NO) synthase are colocalized in nervous tissues. We tested the hypothesis whether or not NO might be involved in the release of neuropeptide Y. Neuropeptide Y concentration in the supernatant of PC12 rat pheochromocytoma cells, shown to express NO synthase I by immunohistochemistry, rose threefold in a time- and dose-dependent manner following sodiumnitroprusside and 3-morpholinosydnonimine (SIN-1) incubation. Neuropeptide Y mRNA expression was induced by NO-donors as a function of incubation-time. Neuropeptide Y production rose fivefold with zaprinast, an inhibitor of the phosphodiesterase V and threefold with nerve growth factor (NGF). Combined application of zaprinast and NGF did not further increase neuropeptide Y production while combination of zaprinast and sodiumnitroprusside potentiated the NO effect on neuropeptide Y release. The data suggest that NO regulates neuropeptide Y secretion of PC12 pheochromocytoma cells on the mRNA level.

Highly selective vagotomy plus Jaboulay: a possible alternative in patients with benign stenosis secondary to duodenal ulceration.

BACKGROUND: The treatment of patients with duodenal ulcers has undergone radical changes in recent years. Symptomatic stenotic obstruction of the gastric outlet, however, has remained a specific indication for elective operation, with gastric resection (Billroth I or II) and vagotomy often used as options for intervention. STUDY DESIGN: The present report describes the results of highly selective vagotomy (HSV) in combination with lateral Jaboulay gastroduodenostomy in the treatment of patients with benign stenosis secondary to duodenal ulceration. Functionality of results and patient satisfaction have been focal aspects in our assessment. RESULTS: During a period of five years, HSV plus Jaboulay was performed upon 19 patients (14 men and five women, with an average age of 55 years). No operative mortality was seen. The postoperative follow-up period ranged from 12 to 60 months. There were no ulcer recurrences, the functional results (roentgenographic double-contrast technique) were excellent, and patient satisfaction was high (Visick grade I, 67 percent; Visick grade II, 33 percent). CONCLUSIONS: As evidenced by the results, HSV plus Jaboulay seems to represent a convincing alternative to gastric resection in the treatment of patients with benign stenosis secondary to duodenal ulceration.

Scintillation proximity assay for calcitriol in serum without high pressure liquid chromatography.

A rapid isolation step for 1,25-dihydroxyvitamin D3 without high pressure liquid chromatography (HPLC) and a sensitive radioimmunoassay (RIA) have been developed. The time required for extraction and isolation with a combination of Extrelut-1-minicolumns and Sep-Pak silica cartridges from as little as 0.5 ml serum is only 2 h. The assay can be counted after 8 h of incubation. It is performed in the vial that collects the eluate, thus eliminating transfer losses and errors. No separation of bound and free hormone is necessary before beta-counting in the scintillation proximity assay. The detection limit of the assay is 2.7 ng/l. The intra-assay coefficients of variation are 7.3% and 5.2% for samples with calcitriol concentrations of 31 and 148 ng/l, respectively. The inter-assay coefficients of variation are 11.3%, 13.3% and 16.1% for low (16 ng/l), medium (30 ng/l) and high (148 ng/l) control pool samples, respectively. Normal values for calcitriol range from 32 to 80 ng/l. Elderly subjects, patients with reduced kidney function and pregnant women were also evaluated for their calcitriol levels. This assay correlates well with a RIA employing HPLC prepurification and charcoal separation of bound/free calcitriol (r = 0.94).

Immunochemiluminometric assay with two monoclonal antibodies against the N-terminal sequence of human parathyroid hormone.

We have developed an immunochemiluminometric assay (ICMA) with two monoclonal antibodies for the N-terminal sequence of human parathyroid hormone (hPTH). One monoclonal antibody (A1-70) was physically adsorbed onto polystyrene beads, the other (B1-70) was labelled with acridinium ester and synthetic hPTH (1-38) was used as standard. This assay has cross-reactions with synthetic hPTH (1-34) and hPTH (1-84) but no cross-reactions with hPTH (4-16), (28-48), (39-84), (44-68), (53-84) and hPTH-rP (1-86). The assay detection limit is 0.4 pmol/l. The normal range is 1.3-12 pmol/l based on 72 normal volunteers. About 91% of study patients (n = 58) with surgically proven primary hyperparathyroidism (1 degree HPT) had PTH values above normal and one of them showed a low normal intact PTH value but elevated PTH values with use of this assay. After immunoabsorption of plasma samples from patients with secondary hyperparathyroidism (2 degrees HPT) on hemodialysis with polystyrene beads containing antibodies against hPTH (39-84), some patients still showed significant amounts of PTH in this new ICMA but not intact PTH. The data reveal that significant amounts of amino-terminal immunoreactive PTH fragments rarely exist in 1 degree HPT but are present in some patients with 2 degrees HPT. The major advantage of this assay is to measure both amino-terminal PTH fragments and intact PTH with no interference from carboxy-terminal PTH fragments because two anti-N-terminal hormone sequence monoclonal antibodies are used.

Molecular absorption spectrometry (MAS) by electrothermal evaporation in a graphite furnace-XIII Determination of traces of fluoride by mas of AlF after liquid-liquid extraction of fluoride with triphenylantimony(V) dihydroxide.

The determination of traces of fluoride by means of the molecular absorption of AlF volatilized in graphite cuvettes is described. An extraction method for separation and preconcentration of the fluoride has been developed, to avoid matrix effects. The fluoride is extracted with 10(-3)M triphenylantimony(V) dihydroxide in M1BK, and stripped with 0.025M barium hydroxide. The method is sensitive and specific for fluoride. The detection limit is about 0.3 ng of fluoride, and the fluoride content of 6 ml of 10(-7)M solution can be determined. The determination is possible in presence of various ions, but it is estimated that usage of trace matrix separation leads to a considerable improvement in the relative detection limits (by 2-3 orders of magnitude), levels as low as 0.01 ppm being detectable in some matrices.

Investigations of trace analysis of A(III)B(V) semiconductor microsamples by atomic spectroscopy-VII Investigation of trace and thin-layer analysis of doping elements (Ag, Au, Bi, Cd, Sn, Tl) in InAs by atomic-absorption with electrothermal evaporation.

Etching procedures for separation of thin layers of InAs (up to 1.4 mum thick) have been developed and optimized. A solid-state microtome has been used for cutting layers thicker than 1mum. AAS/ETA methods for determination of traces of Ag, Au, Bi, Cd, Sn, and Tl have been developed. The matrix interferences of nitric add, hydrobromic acid, and As(3+) or In(3+) in nitric or hydrobromic acid have been studied. The main causes of the matrix interference are the formation of diatomic molecules between the trace and matrix components, and the effect of the evaporation processes. By use of the platform technique with special platforms some matrix interferences could be minimized. For the determination of traces of Sn, matrix modification with Ni(NO(3))(2) as additive gave the best analytical values. For the trace determination of Au, separation of In from Au by evaporation of InBr(3) from 0.6M HBR medium in the AAS ashing phase was developed. The detection limits are in the 10(16) atoms/cm(3) region for layers of 1 mum thickness and surface area 1 cm(2).

Graphite-furnace AAS with ultrasonic nebulization.

A technique combining ultrasonic nebulization of solutions and graphite-furnace atomic-absorption spectrometry is described. The analytical possibilities of two different techniques are shown. In one the nebulized samples are continuously introduced into a graphite tube operated at constant temperature, and in the other deposited on the inner wall of the graphite tube and heated discontinuously. The method chosen influences the absorption values for several elements. The sensitivity for determination by continuous sampling lies between the values for the normal electrothermal AAS injection technique and flame AAS. Higher sensitivities are obtained with the deposition technique.

Interference caused by indium in the atomization of Ag, Bi, Cd, Sn, and Tl in ETA-AAS.

The depression of the signals for Ag, Bi, Cd, Sn, and Tl trace determination by ETA-AAS, which occurs in the presence of hydrobromic acid (with or without indium present), has been investigated by use of a new combined atomization equipment, molecular absorption measurements and thermodynamic calculations. The results show that all these elements form easily volatile bromides and more or less stable diatomic molecules of MBr type. These diatomic molecules, formed in the gaseous phase, are removed from the observation volume by diffusion, before their dissociation is complete. These two effects-formation of easily volatile compounds and stable diatomic molecules-are the main reasons for the depression of the atomic-absorption signals.

Molecular absorption spectrometry (MAS) by electrothermal evaporation in a graphite furnace-IX Determination of traces of bromide by mas of AlBr after liquid-liquid extraction of bromide with triphenyltin hydroxide.

The determination of traces of bromide by molecular absorption spectrometry (MAS) of AlBr (with electrothermal volatilization) is described. It is possible to determine 25 ng of bromide. Many problems are caused by various matrices, so an extraction method for separation (and also preconcentration) was developed. The combination of bromide extraction with triphenyltin hydroxide, stripping with 0.025M barium hydroxide and determination of the extracted bromide by MAS of AlBr (after addition of aluminium ions) gives a very sensitive and selective method for determination of traces of bromide in micro or macro samples, in the presence of large amounts of other species, including chloride and iodide.