Comparison of nutritional composition between plant-based drinks and cow's milk

The high decline in liquid milk consumption in Western countries has been compensated by the increased consumption of processed dairy products and the rapidly increasing number of new plant-based beverages constantly introduced in the market, advertised as milk substitutes and placed on shelves near milk products. To provide better understanding about the nutritional value of these drinks compared with cow's milk, 27 plant-based drinks of 8 different species and two milk samples were purchased from two big retailers in Switzerland, and their composition regarding protein, carbohydrate, fat, vitamin, and mineral contents and residue load [glyphosate, aminomethylphosphonic acid (AMPA), and arsenic] was analyzed quantitatively and qualitatively. Energy and nutrient intakes were calculated and compared with the dietary reference values for Germany, Austria and Switzerland (D-A-CH). In addition, the digestible indispensable amino acid score (DIAAS) was calculated to estimate the quality of the proteins. Milk contained more energy; fat; carbohydrate; vitamins C, B₂, B₁₂, and A; biotin; pantothenic acid; calcium; phosphorus; and iodine than most plant-based drinks. Soy drinks provided slightly more protein and markedly more vitamins B₁ and B₆, folic acid, and vitamins E and D₂ (with supplemented vitamin D₂) and K₁, magnesium, manganese, iron, and copper than milk and the other plant-based drinks. However, with the exception of cow's milk and soy drinks, which had > 3% protein, most milk alternatives contained ≤ 1% protein; therefore, they cannot be considered good protein sources. In regard to protein quality, milk was outstanding compared with all plant-based drinks and exhibited higher calculated DIAASs. Our results show that the analyzed plant-based drinks are not real alternatives to milk in terms of nutrient composition, even if the actual fortification is taken into account. Improved fortification is still an issue and can be optimized using the most bioavailable and soluble derivatives. Complete replacement of milk with plant-based drinks without adjusting the overall diet can lead to deficiencies of certain important nutrients in the long term.

Molecular effects of the consumption of margarine and butter varying in trans fat composition: a parallel human intervention study

BACKGROUND

Whereas the dietary intake of industrial trans fatty acids (iTFA) has been specifically associated with inflammation, cardiovascular disease, and type 2 diabetes, understanding the impact of dietary fats on human health remains challenging owing to their complex composition and individual effects of their lipid components on metabolism. The aim of this study is to profile the composition of blood, measured by the fatty acid (FAs) profile and untargeted metabolome of serum and the transcriptome of blood cells, in order to identify molecular signatures that discriminate dietary fat intakes.

METHODS

In a parallel study, the molecular effects of consuming dairy fat containing ruminant TFA (rTFA) or margarine containing iTFA were investigated. Healthy volunteers (n = 42; 45-69 y) were randomly assigned to diets containing margarine without TFA as major source of fat (wTFA control group with 0.4 g TFA per 100 g margarine), margarine with iTFA (iTFA group with 4.1 g TFA per 100 g margarine), or butter with rTFA (rTFA group with 6.3 g TFA per 100 g butter) for 4 weeks. The amounts of test products were individually selected so that fat intake contributed to 30-33% of energy requirements and TFA in the rTFA and iTFA groups contributed to up to 2% of energy intake. Changes in fasting blood values of lipid profiles (GC with flame-ionization detection), metabolome profiles (LC-MS, GC-MS), and gene expression (microarray) were measured.

RESULTS

Eighteen FAs, as well as 242 additional features measured by LC-MS (185) and GC-MS (54) showed significantly different responses to the diets (P_FDR-adjusted < 0.05), mainly distinguishing butter from the margarine diets while gene expression was not differentially affected. The most abundant TFA in the butter, i.e. TFA containing (E)-octadec-11-enoic acid (C18:1 t11; trans vaccenic acid), and margarines, i.e. TFA containing (E)-octadec-9-enoic acid (C18:1 t9; elaidic acid) were reflected in the significantly different serum levels of TFAs measured after the dietary interventions.

CONCLUSIONS

The untargeted serum metabolome differentiates margarine from butter intake although the identification of the discriminating features remains a bottleneck. The targeted serum FA profile provides detailed information on specific molecules differentiating not only butter from margarine intake but also diets with different content of iTFAs in margarine.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00933322.

Quantitative LC/MS-MS Determination of Sulfonamides and Some Other Antibiotics in Honey

A simple and rapid method was developed for the determination of 20 antibiotics (sulfonamides, tetracyclines, and flumequine) in honey by liquid chromatography tandem mass spectrometry. The proposed method is sensitive (limit of detection 0.5 to 10 ppb for the various antibiotics) and selective. A hydrolysis step ensures the liberation of sugar-bound sulfonamides. The approach has been used to analyze some 300 honey samples. A number of them were found to have exceeded the Swiss limit of 50 ppb.

Determination of Clopidol Residues in Chicken Tissues by Liquid Chromatography: Collaborative Study

Eighteen laboratories participated in a collaborative study on the determination of clopidol residues in chicken muscle tissues by liquid chromatography. Of these, results from 16 laboratories which rigorously followed the method were subjected to statistical analysis. The method performance was assessed by all participants using 14 samples of chicken muscle fortified at concentrations ranging from 0.1 to 5.0 mg/kg. In addition, 9 participants each reported results for 6 clopidol-incurred samples in chicken muscle. Test portions were extracted with acetonitrile, and the extracts were purified with alumina and anion exchange resin solid-phase extraction cartridges in sequence. Clopidol was separated by reversed-phase liquid chromatography and quantified at 270 nm. Average recoveries ranged from 81.8 to 85.4%, reproducibility relative standard deviation (RSDR) ranged from 11.9 to 22.6%, and repeatability relative standard deviation (RSDr) ranged from 9.9 to 15.1%. For clopidol-incurred samples at concentrations of 0.100–0.687 mg/kg, the mean determination value range was 0.099–0.659 mg/kg; RSDR was 12.6–19.8%, RSDr was 3.1–8.5%; and HORRAT values were 0.7–1.1. The accuracy and precision of the method are in conformity with the requirements specified by AOAC INTERNATIONAL. The method was adopted Official First Action in April 2003.

Mass spectrometry data of in vitro and in vivo pig digestion of skim milk powder

The data in this article are related to the research article entitled “Physiological comparability of the harmonized INFOGEST in vitro digestion method to in vivo pig digestion” (Egger et al., 2012). In this article, proteins identified in the different sections of pig skim milk powder (SMP) digestion are presented. In addition to the exemplary β-casein profiles of the paper, the peptide patterns of the other most abundant milk proteins during in vivo digestion in individual pigs are shown as heatmaps and line graphs. These data clearly reveal the digestion resistant protein regions and illustrate the variability between the pigs in the different sampling sections. Moreover, peptide patterns of the same SMP proteins comparing the harmonized in vitro digestion (IVD) with pig in vivo digestion show the physiological relevance of the IVD protocol. Finally, correlation coefficients were calculated to indicate similarities between pig sampling sections and gastric and intestinal IVD endpoints.

Limited Associations between Keel Bone Damage and Bone Properties Measured with Computer Tomography, Three-Point Bending Test, and Analysis of Minerals in Swiss Laying Hens

Keel bone damage is a wide-spread welfare problem in laying hens. It is unclear so far whether bone quality relates to keel bone damage. The goal of the present study was to detect possible associations between keel bone damage and bone properties of intact and damaged keel bones and of tibias in end-of-lay hens raised in loose housing systems. Bones were palpated and examined by peripheral quantitative computer tomography (PQCT), a three-point bending test, and analyses of bone ash. Contrary to our expectations, PQCT revealed higher cortical and trabecular contents in fractured than in intact keel bones. This might be due to structural bone repair after fractures. Density measurements of cortical and trabecular tissues of keel bones did not differ between individuals with and without fractures. In the three-point bending test of the tibias, ultimate shear strength was significantly higher in birds with intact vs. fractured keel bones. Likewise, birds with intact or slightly deviated keel bones had higher mineral and calcium contents of the keel bone than birds with fractured keel bones. Calcium content in keel bones was correlated with calcium content in tibias. Although there were some associations between bone traits related to bone strength and keel bone damage, other factors such as stochastic events related to housing such as falls and collisions seem to be at least as important for the prevalence of keel bone damage.

Tolerance to 1,25 dihydroxyvitamin D3 glycosides from Solanum glaucophyllum by the growing pig

Solanum glaucophyllum leaves contain high levels of glycosidically bound 1,25 dihydroxyvitamin D₃, the most important vitamin D metabolite. The tolerance to this source was evaluated during six weeks with fifty weaned pigs fed increasing levels (0, 2.5, 5, 10 and 20μg 1,25(OH)₂D₃/kg diet). The diet contained, per kg, 9.7g Ca, 3.5g digestible P and 2000IU cholecalciferol. Ten additional pigs were fed a diet containing 1000IU cholecalciferol/kg, without 1,25(OH)₂D₃. Weekly plasma and final kidney, bone and urinary mineral contents, bone density and breaking strength served as indicators for possible adverse effects of the supplement. All animals grew well and remained clinically healthy. The measured parameters remained unchanged when 1000 replaced 2000IU cholecalciferol/kg and when 1,25(OH)₂D₃ was fed up to 10μg/kg. Twenty μg 1,25(OH)₂D₃ increased plasma Ca and decreased plasma P from the 2^nd and the 4^th experimental week onwards, respectively. Twenty μg 1,25(OH)₂D₃ increased final plasma Ca and 1,25(OH)₂D₃ and reduced final plasma P by respectively 19, 56 and 13%. Twenty μg 1,25(OH)₂D₃ also increased kidney Ca and urinary Ca by 43 and 69%, respectively, reduced bone breaking strength by 12% and tended to decrease bone ash by 3%. To conclude, 2000IU D₃ was not beneficial compared to 1000IU cholecalciferol; up to 10μg 1,25(OH)₂D₃ per kg diet did not lead to observed adverse effects; 20μg 1,25(OH)₂D₃ altered the homeostatic regulation of Ca and P thus, may lead to first signs of possible adverse effects, such as soft tissue calcification.

[New melanoma immunotherapies: mechanisms of action, efficiency and management of toxicities]

In recent years the therapy of metastatic melanoma has been revolutionized from a disease with very few efficient treatment options to one with access to multiple therapies which can impact on patient survival. Two main classes of therapies have been developed: 1. Immunotherapy by immune checkpoint inhibitors and 2. Small molecule inhibitors of the MAPK pathway. Immunotherapies achieved by either inhibition of CTLA-4 or the PD1/PD-Ll axes are impacting the overall survival in an important fraction of patients. In addition, the side effects of these immune therapy approaches require early detection by all the specialists involved as well as early management according to precise guidelines for optimal outcome.

Effects of benzoic Acid and dietary calcium:phosphorus ratio on performance and mineral metabolism of weanling pigs

In a 2×2 factorial experiment the hypotheses tested were that the metabolic acid load caused by benzoic acid (BA) added to the feed affects bone mineralization of weanling pigs, and that a wide dietary calcium (Ca) to phosphorus (P) ratio in phytase-supplemented feeds with a marginal P concentration has a positive effect on bone mineralization. The four experimental diets, which contained 0.4% P and were supplemented with 1,000 FTU phytase/kg, contained either 5 g BA/kg or no BA and either 0.77% Ca or 0.57% Ca. The 68 four-week-old Large White pigs were fed the experimental diets ad libitum for six weeks and were then slaughtered. Benzoic acid increased feed intake (p = 0.009) and growth rate (p = 0.051), but did not influence the feed conversion ratio (p>0.10). Benzoic acid decreased the pH of the urine (p = 0.031), but did not affect breaking strength and mineralization of the tibia (p>0.10). The wide Ca:P ratio decreased feed intake (p = 0.034) and growth rate (p = 0.007) and impaired feed the conversion ratio (p = 0.027), but increased the mineral concentration in the fat-free DM of the tibia (p = 0.013) without influencing its breaking strength (p>0.10). The observed positive effect of the wide Ca:P ratio on bone mineralization may be attributed, at least in part, to the impaired feed conversion ratio, i.e. to the higher feed intake and consequently to the higher mineral intake per kg BW gain. The negative impact on animal performance of the wide dietary Ca:P ratio outweighs its potentially positive effect on bone mineralization, precluding its implementation under practical feeding conditions.

[Melanoma: a new therapeutic era]

Melanoma is the cancer with the fastest incidence increase in Switzerland. 30% of the cases arise before the age of 50 years. Once metastatic, the median survival under current systemic therapies is about 8 months, with less than 5% of patients alive at 5 years. Many efforts in the understanding of cellular biology, intracellular signaling pathways, as well as the role of cellular immunity have been made in the recent years. This has resulted in the development of novel and very promising therapies. In this review, we will cover the results obtained with targeted therapies such as "tyrosin kinase inhibitors" (TKI), as well as those obtained with a monoclonal antibody directed against the CTLA-4 receptor of lymphocytes.

Sentinel lymph node involvement and a high Breslow index are independent factors of risk for early relapse of melanoma

AIM

The clinical relevance of sentinel lymph node (SLN) analysis was evaluated prospectively and compared with other known risk factors of relapse in early stage melanoma.

METHODS

Surgery was guided by lymphoscintigraphy, blue dye and gamma probe detection. SLN were analysed by haematoxylin eosin (HE) histochemistry and multimarker immunohistochemistry (IHC). Disease free survival (DFS) was evaluated with Kaplan-Meier plots according to different parameters and Cox analyses of variance.

RESULTS

From 210 patients a total of 381 SLN were excised. Lymphoscintigraphy identified all excised SLN with only 2 false positive lymphatic lakes. Fifty patients (24%) had tumour positive SLN. With a mean follow-up of 31.3 months, 29 tumour recurrences were observed, 19 (38%) in 50 SLN positive and 10 (6%) in 160 SLN negative patients. Strong predictive factors for early relapse (p < 0.0005) were SLN positivity and a high Breslow index.

CONCLUSION

SLN tumour positivity is an independent factor of high risk for early relapse with a higher power of discrimination than the Breslow index.

Pustulose exanthématique aiguë généralisée : premier cas décrit en relation avec une infection à Chlamydia pneumoniae

Skin reactions to drugs or infections can be very important.

CASE REPORT

A 14-year-old boy developed fever, a diffuse pustular rash and a respiratory distress. Chest X-rays and serology were consistent with an acute Chlamydia pneumoniae infection. A skin biopsy revealed an acute generalized exanthematous pustulosis.

CONCLUSION

Acute generalized exanthematous pustulosis (AGEP) is a disease manifested by a diffuse eruption of follicular sterile pustules. Most of the cases are drug induced, but they may be secondary to viral or bacterial infections. We report the first case of AGEP in a child with an acute C. pneumoniae infection.

Expression of Melan-A/MART-1 antigen as a prognostic factor in primary cutaneous melanoma

In this study we assessed the expression of the Melan-A/MART-1 antigen by immunohistochemistry using monoclonal antibody A103 in 73 primary cutaneous melanomas and its correlation with tumor staging and patient survival. Melan-A/MART-1 was expressed in 90% of primary tumors, with loss of expression increasing with Breslow thickness. Kaplan-Meier analysis demonstrated a significantly reduced disease-free interval and overall survival rate for patients not expressing this antigen. The poor prognosis of such patients was even worse for those presenting with a primary melanoma and a Breslow thickness of > or = 1 mm. Thus, Melan-A/MART-1 is not only a useful and specific additional marker for the diagnosis of primary cutaneous melanoma, but it may also help refine the prognosis of patients with malignant melanoma.

Thromboangiitis obliterans: a rare cause of a reversible Raynaud's phenomenon

A 25-year-old woman with progressive Raynaud's phenomenon and digital necrosis is presented. Systemic sclerosis and other connective tissue disorders as well as atherosclerosis and arterial emboli were excluded with appropriate laboratory examinations. Arteriography revealed multiple palmar and digital occlusions with corkscrew-shaped vessels. Based on these characteristic arteriographic and clinical findings, the diagnosis of thromboangiitis obliterans was finally retained. With intravenous perfusion of the prostacyclin analogue iloprost (2 ng/kg/min, 6 h daily during 21 days), a complete healing of Raynaud's phenomenon and of the digital necrosis was observed. There was no recurrence during the 1-year follow-up. This observation demonstrates that thromboangiitis obliterans is a potential reversible cause of severe Raynaud's phenomenon in young women even in the absence of lower limb involvement. Early recognition is important to avoid irreversible complications such as loss of digits.

Monosymptomatic Loa loa infection

We report the case of a 17-year-old student from Cameroon who presented an atypical, mono-symptomatic form of Loa loa infection, characterized only by rare subcutaneous movements of adult worms.

Norwegian scabies in a patient with acquired immunodeficiency syndrome

We report the case of a 42-year-old man with symptomatic HIV infection (C3 CDC stage) who presented widespread hyperkeratotic skin lesions diagnosed as Norwegian scabies. The CD4 count was 87 cells/mm3. The patient has been the source of a nosocomial outbreak (20 individuals affected). He was treated successfully with combined topical treatment (permethrin 5% cream plus keratolytic agents) and oral ivermectin.

[Erythema migrans with multiple lesions]

INTRODUCTION

Erythema migrans with multiple lesions is observed in Europe in only 5-20 p. 100 of Borrelia infections. The number of lesions observed simultaneously in one patient is less than 7, considering all the cases published in the literature to date.

CASE REPORTS

We report three patients who presented multiple macular, erythematous and centrifugal lesions localized on the trunk and the limbs. The first patient presented about thirty lesions, the second more than seventy, and the third about twenty. Serology investigation and immunoblots allowed to establish the diagnosis of a recent Borrelia Burgdorferi infection, with multiples lesions of erythema migrans. PCR performed on a skin biopsy of one of the patients confirmed the presence of Borrelia burgdorferi. Response to antibiotic therapy was immediate in all 3 patients.

DISCUSSION

These 3 cases are of particular interest because the number of simultaneous lesions is much higher than what is reported in the European literature. These observations remind the clinician that the diagnosis of erythema migrans with multiple lesions should be included, in Europe as well, in the differential diagnosis of multiple annular dermatoses.

Sunscreen use and duration of sun exposure: a double-blind, randomized trial

BACKGROUND

In epidemiologic studies, sunscreen use is associated with increased risk of cutaneous melanoma, basal cell skin cancer, and higher numbers of nevi. It has been proposed that sunscreens may encourage prolonged sun exposure because they delay sunburn occurrence. We examined whether, under habitual conditions of sunscreen use, the sun-protection factor (SPF) had an influence on sun-exposure duration.

METHODS

Before the 1997 summer holidays, we randomly assigned 87 French and Swiss participants who were 18-24 years of age to receive an SPF 10 or an SPF 30 sunscreen. Neither medical personnel nor study participants were aware of their sunscreen assignment. Participants were asked to complete daily records of their sun exposure. To avoid influencing the recreational sun-exposure habits of the study participants, no recommendation was made about sun exposure or sun protection. Furthermore, participants were told that the trial end point was the number of pigmented skin lesions before and after the holidays. One subject was lost to follow-up. All statistical tests were two-sided.

RESULTS

The SPF 10 (n = 44) and SPF 30 (n = 42) groups had equivalent mean holiday durations (19.4 days versus 20.2 days) and mean quantities of sunscreen used (72.3 g versus 71.6 g). The mean cumulative sun exposures for the two groups were 58.2 hours and 72.6 hours, respectively (P =.011). The mean daily durations of sunbathing were 2.6 and 3.1 hours, respectively (P =.0013), and, for outdoor activities, they were 3.6 and 3.8 hours, respectively (P =.62). There was no difference in sunburn experience between the two groups.

CONCLUSIONS

Use of higher SPF sunscreen seems to increase the duration of recreational sun exposure of young white Europeans.

Drug-induced linear IgA bullous dermatosis probably induced by furosemide

Linear IgA bullous dermatosis (LABD) is an autoimmune disease, characterized by linear deposition of IgA along the basement membrane zone. Drug-induced LABD is rare but increasing in frequency. A new case of drug-induced LABD associated with the administration of furosemide is described.

[Clinical aspects and pathology of melanoma]

The annual incidence of melanoma is continually increasing. Melanomas can easily be diagnosed because they are readily visible on the skin. The prognosis is excellent for melanoma when it is diagnosed in an early stage. The clinical diagnosis of melanomas is made by the simple A-B-C-D-E-rule. Clinically, we distinguish the following melanoma types by the order of frequency: the melanoma of the superficial spreading type (SSM), the melanoma with nodular type (NM), the lentigo maligna melanoma (LMM) and the acro-lentiginous melanoma (ALM). Other clinical subtypes of melanoma are congenital giant nevus and melanoma of the mucous membranes. With help of histogenesis, we can distinguish similar forms for melanoma of the SSM-type, melanoma of the NM-type, the lentigo maligna melanoma (LMM) and the melanoma of the ALM-type. In this case, it is preferable to use the terminology acanthotic-lentiginous melanoma since acro-lentiginous is the clinical expression and not a histopathological one. Further subtypes can be distinguished histopathologically such as the desmoplasic melanoma which has been recently described as melanoma from a dysplasic nevus as well as melanoma of the lichen cleanness type. Furthermore, due to histopathology other particular forms can be distinguished such as the melanoma of the nevus Spitz type and melanoma originating from a blue nevus. Most important for the histopathological report is the thickness of the melanoma in millimeters related to the Breslow index as well as the invasion level in the skin by the Clark classification since the melanoma thickness is the most important risk factor for the melanoma patient.

Chorioretinal vascular abnormalities associated with angioid streaks and pseudoxanthoma elasticum

OBJECTIVE

To analyze the retinal and choroidal vascular abnormalities in eyes with angioid streaks (AS) associated with pseudoxanthoma elasticum (PXE).

METHODS

Color photographs and fluorescein angiograms of 54 eyes of 27 consecutive patients with AS and PXE were examined retrospectively.

RESULTS

Four (7%) of the 54 eyes had a major vascular abnormality at the level of the disc; this took the form of a large vascular loop corresponding to an arteriovenous communication between retina and choroid in 3 eyes (6%) and an anastomosis between 2 retinal arteries in 1 eye (2%).

CONCLUSION

Analysis of the vascular network in these eyes showed several vascular abnormalities, among which chorioretinal arteriovenous communications appear to be the most dramatic.

Severe, chronic anorexia and extensive leg ulcerations as presenting signs of primary Sjögren's syndrome

We report the case of a 75-year-old woman with a 15-year history of inappetance resulting in weight loss of approximately 40 kg. On physical examination, the skin of the lower extremities was markedly hyperpigmented with a brown-greyish hue. In addition, the skin of the legs was infiltrated, erythematous, riddled with erosions and necrotic ulcers. Clinical and laboratory evaluation revealed sicca syndrome, a pronounced polyclonal hypergammaglobulinemia (60 g/l), high levels of antinuclear, anti-SSA and anti-SSB antibodies. Histological examination of involved skin demonstrated a leukocytoclastic vasculitis.

Meleda disease: report of two cases investigated by electron microscopy

We report 2 cases of clinically typical Meleda disease in a family from Herzegovina. Electron microscopy did not reveal major ultrastructural anomalies of keratinization; however, the transition from stratum granulosum to stratum corneum appeared to occur less abruptly than normally by a stepwise process suggesting a slowing down of terminal cornification.

Intraepidermal IgA pustulosis preceding a CD30+ anaplastic large T-cell lymphoma

We report the case of a 62-year-old patient with an extracutaneous CD30+ anaplastic large T-cell lymphoma which was preceded by intraepidermal IgA pustulosis (IEAP). The clinical picture was identical to Sneddon-Wilkinson disease and histologic examination showed subcorneal pustules with slight acantholysis. Direct immunofluorescence exclusively revealed IgAK deposits on the plasma membrane of suprabasal keratinocytes. Indirect immunofluorescence and immunoelectrophoresis showed no evidence of monoclonal IgA gammopathy. IEAP responded to dapsone treatment (100 mg/day). Two months after disappearance of active cutaneous lesions, the patient developed generalized lymphadenopathy due to CD30+ anaplastic T-cell lymphoma.

Methods for the determination of sulphonamides in meat

Sulphonamides, due to their important antibacterial effects, are widely used in veterinary practice and animal husbandry. Residues arising from administration without observing withdrawal time sufficiently are normally the parent compounds and the N4-acetyl derivatives, the latter being hydrolyzed to the parent compounds only during extraction under acidic conditions. It is therefore quite conceivable that many authors concentrate on determining these metabolites. In the past decade, we have witnessed a considerable increase in new analytical techniques dealing with the determination of sulphonamides. Among these procedures, especially the so-called multimethods using high-performance liquid chromatography--though sometimes including toilsome clean-up steps--can be mentioned. However, current approaches also utilize gas chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, supercritical fluid chromatography-mass spectrometry, thin-layer chromatography and immunological methods. For most of these techniques, a strong trend towards lowering the level of detectability (down to the sub-ppb range) and improving accuracy and reproducibility can be established.