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Purpose: Blood-flow restriction (BFR) endurance training may increase endurance performance and muscle strength similar to traditional endurance training while requiring a lower training intensity. We aimed to compare acute cardiorespiratory responses to low-intensity interval exercise under BFR with moderate-intensity traditional interval exercise (TRA)., Methods: We conducted a randomized crossover study. The protocol involved three cycling intervals interspersed with 1 min resting periods. With a 48-h washout period, individuals performed the protocol twice in random order: once as BFR-50 (i.e., 50% incremental peak power output [IPPO] and 50% limb occlusion pressure [LOP]) and once as TRA-65 (65% IPPO without occlusion). TRA-65 intervals lasted 2 min, and time-matched BFR-50 lasted 2 min and 18 s. Respiratory parameters were collected by breath-by-breath analysis. The ratings of perceived breathing and leg exertion (RPE, 0 to 10) were assessed. Linear mixed models were used for analysis., Results: Out of the 28 participants initially enrolled in the study, 24 healthy individuals (18 males and 6 females) completed both measurements. Compared with TRA-65, BFR-50 elicited lower minute ventilation (VE, primary outcome) (-3.1 l/min [-4.4 to -1.7]), oxygen consumption (-0.22 l/min [-0.28 to -0.16]), carbon dioxide production (-0.25 l/min [-0.29 to -0.20]) and RPE breathing (-0.9 [-1.2 to -0.6]). RPE leg was significantly greater in the BFR-50 group (1.3 [1.0 to 1.7])., Conclusion: BFR endurance exercise at 50% IPPO and 50% LOP resulted in lower cardiorespiratory work and perceived breathing effort compared to TRA at 65% IPPO. BFR-50 could be an attractive alternative for TRA-65, eliciting less respiratory work and perceived breathing effort while augmenting perceived leg muscle effort., Trial Registration: NCT05163600; December 20, 2021., (© 2024. The Author(s).)

We report the extension of the common β-diketimine proligand class, RAr nacnacH (HC(RCNAr) 2 H), where R is an alkyl group such as Et or iPr, plus Ph, and Ar is a sterically demanding aryl substituent such as Dip = 2,6-diispropylphenyl, Dep = 2,6-diethylphenyl, Mes = 2,4,6-trimethylphenyl or mesityl, Xyl = 2,6-dimethylphenyl, via one-pot condensation procedures. When a condensation reaction is carried out using the chemical dehydrating agent PPSE (polyphosphoric acid trimethylsilylester), β-diketiminate phosphorus(V) products such as ( iPrMes nacnac)PO 2 can also be obtained, which can be converted to the respective proligand iPrMes nacnacH via alkaline hydrolysis. The RAr nacnacH proligands can be converted to their alkali metal complexes with common methods and we have found that deprotonation of iPrDip nacnacH is significantly more sluggish than that of related β-diketimines with smaller backbone alkyl groups. The basicity of the RAr nacnac - anions can play a role in the success of their salt metathesis chemistry and we have prepared and structurally characterised the EtDip nacnac-derived silicon(II) compounds ( EtDip nacnac)SiBr and ( EtDip nacnac')Si, where EtDip nacnac' is the deprotonated variant MeCHC(NDip)CHC(NDip)Et.

Soai's asymmetric autocatalysis represents a highly remarkable example for spontaneous symmetry breaking and enantioselective amplification in the enantioselective alkylation of pyrimidine-5-carbaldehydes to the corresponding chiral pyrimidine alcohols. Recently, zinc hemiacetalate complexes, formed from pyrimidine-5-carbaldehydes and the chiral product alcohol, were identified by in situ high-resolution mass spectrometric measurements as highly active transient asymmetric catalysts in this autocatalytic transformation. To study the formation of such hemiacetals and their stereodynamic properties, we focused on the synthesis of coumarin homolog biaryl systems with carbaldehyde and alcohol substituents. Such systems are able to form hemiacetals by intramolecular cyclization. An interesting feature of the substituted biaryl backbone is that tropos and atropos systems can be obtained, enabling or disabling the intramolecular cyclization to hemiacetals. Biaryl structures with various functional groups were synthesized, and the equilibrium and stereodynamics between the closed and open structures were investigated by dynamic enantioselective HPLC (DHPLC). The enantiomerization barriers ΔG ǂ and activation parameters ΔH ǂ and ΔS ǂ were determined from temperature dependent kinetic measurements., (© 2023 The Authors. Chirality published by Wiley Periodicals LLC.)

Introduction: Dyspnea is one of the most common symptoms in patients with lung diseases. The term "dyspnea" refers to the subjective sensation of uncomfortable breathing, which is experienced and described very differently between individuals. Because of this, diagnosis can be very challenging and similar to pain, no true objective measurement parameters of dyspnea exist. A detailed symptom history and clinical examination are critical in establishing the diagnosis, but the severity of pulmonary functional impairment does not always correlate with the clinical picture. The diagnosis of lung diseases is led by pulmonary function tests and imaging techniques, which measure the response to therapy and assess the prognostic course of the disease. The purpose of this article is to review the causes of pulmonary dyspnea, present a guide to diagnostic work-up, and introduce common differential diagnoses., (© 2023 Aerzteverlag medinfo AG.)

Study Objectives: To assess altitude-induced sleep and nocturnal breathing disturbances in healthy lowlanders 40 y of age or older and the effects of preventive acetazolamide treatment., Methods: Clinical examinations and polysomnography were performed at 760 m and in the first night after ascent to 3100 m in a subsample of participants of a larger trial evaluating altitude illness. Participants were randomized 1:1 to treatment with acetazolamide (375 mg/day) or placebo, starting 24 h before and while staying at 3100 m. The main outcomes were indices of sleep structure, oxygenation, and apnea/hypopnea index (AHI)., Results: Per protocol analysis included 86 participants (mean ± SE 53 ± 7 y old, 66% female). In 43 individuals randomized to placebo, mean nocturnal pulse oximetry (SpO2) was 94.0 ± 0.4% at 760 m and 86.7 ± 0.4% at 3100 m, with mean change (95%CI) -7.3% (-8.0 to -6.5); oxygen desaturation index (ODI) was 5.0 ± 2.3 at 760 m and 29.2 ± 2.3 at 3100 m, change 24.2/h (18.8 to 24.5); AHI was 11.3 ± 2.4/h at 760 m and 23.5 ± 2.4/h at 3100 m, change 12.2/h (7.3 to 17.0). In 43 individuals randomized to acetazolamide, altitude-induced changes were mitigated. Mean differences (Δ, 95%CI) in altitude-induced changes were: ΔSpO2 2.3% (1.3 to 3.4), ΔODI -15.0/h (-22.6 to -7.4), ΔAHI -11.4/h (-18.3 to -4.6). Total sleep time, sleep efficiency, and N3-sleep fraction decreased with an ascent to 3100 m under placebo by 40 min (17 to 60), 5% (2 to 8), and 6% (2 to 11), respectively. Acetazolamide did not significantly change these outcomes., Conclusions: During a night at 3100 m, healthy lowlanders aged 40 y or older revealed hypoxemia, sleep apnea, and disturbed sleep. Preventive acetazolamide treatment improved oxygenation and nocturnal breathing but had no effect on sleep duration and structure., Trial Registration: The trial is registered at Clinical Trials, https://clinicaltrials.gov, NCT03561675., (© The Author(s) 2022. Published by Oxford University Press on behalf of Sleep Research Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Pulmonary vascular diseases (PVDs), defined as arterial or chronic thromboembolic pulmonary hypertension, are associated with autonomic cardiovascular dysregulation. Resting heart rate variability (HRV) is commonly used to assess autonomic function. Hypoxia is associated with sympathetic overactivation and patients with PVD might be particularly vulnerable to hypoxia-induced autonomic dysregulation. In a randomised crossover trial, 17 stable patients with PVD (resting PaO 2 ≥ 7.3 kPa) were exposed to ambient air (FiO 2 = 21%) and normobaric hypoxia (FiO 2 = 15%) in random order. Indices of resting HRV were derived from two nonoverlapping 5-10-min three-lead electrocardiography segments. We found a significant increase in all time- and frequency-domain HRV measures in response to normobaric hypoxia. There was a significant increase in root mean squared sum difference of RR intervals (RMSSD; 33.49 (27.14) vs. 20.76 (25.19) ms; p < 0.01) and RR50 count divided by the total number of all RR intervals (pRR50; 2.75 (7.81) vs. 2.24 (3.39) ms; p = 0.03) values in normobaric hypoxia compared to ambient air. Both high-frequency (HF; 431.40 (661.56) vs. 183.70 (251.25) ms 2 ; p < 0.01) and low-frequency (LF; 558.60 (746.10) vs. 203.90 (425.63) ms 2 ; p = 0.02) values were significantly higher in normobaric hypoxia compared to normoxia. These results suggest a parasympathetic dominance during acute exposure to normobaric hypoxia in PVD.

Asymmetric synthesis constitutes a key technology for the preparation of enantiomerically pure compounds as well as for the selective control of individual stereocenters in the synthesis of complex compounds. It is thus of extraordinary importance for the synthesis of chiral drugs, dietary supplements, flavors, and fragrances, as well as novel materials with tunable and reconfigurable chiroptical properties or the assembly of complex natural products. Typically, enantiomerically pure catalysts are used for this purpose. To prepare enantiomerically pure ligands or organocatalysts, one can make use of the natural chiral pool. Ligands and organocatalysts with an atropisomeric biphenyl and binaphthyl system have become popular, as they are configurationally stable and contain a C 2-symmetric skeleton, which has been found to be particularly privileged. For catalysts with opposite configurations, both product enantiomers can be obtained. Configurationally flexible biphenyl systems initially appeared to be unsuitable for this purpose, as they racemize after successful enantiomer separation and thus are neither storable nor afford a reproducible enantioselectivity. However, there are strategies that exploit the dynamics of such ligands to stereoconvergently enrich one of the catalyst enantiomers. This can be achieved, for example, by coordinating an enantiomerically pure additive to a ligand-metal complex, which results in deracemization of the configurationally flexible biphenyl system, thereby enriching the thermodynamically preferred diastereomer. In this Account, we present our strategy to design stereochemically flexible catalysts that combine the properties of supramolecular recognition, stereoconvergent alignment, and catalysis. Such systems are capable to recognize the chirality of the target product, leading to an increase in enantioselectivity during asymmetric catalysis. We have systematically developed and investigated these smart catalyst systems and have found ways to specifically design and synthesize them for various applications. In addition to (i) reaction product-induced chiral amplification, we have developed systems with (ii) intermolecular and (iii) intramolecular recognition, and successfully applied them in asymmetric catalysis. Our results pave the way for new applications such as temperature-controlled enantioselectivity, controlled inversion of enantioselectivity with the same chirality of the recognition unit, generation of positive nonlinear effects, and targeted design of autocatalytic systems through dynamic formation of transient catalysts. Understanding such systems is of enormous importance for catalytic processes leading to symmetry breaking and amplification of small imbalances of enantiomers and offer a possible explanation of homochirality of biological systems. In addition, we are learning how to target supramolecular interactions to enhance enantioselectivities in asymmetric catalysis through secondary double stereocontrol. Configurationally flexible catalysts will enable future resource-efficient development of asymmetric syntheses, as enantioselectivities can be fully switched by stereoselective alignment of the stereochemically flexible ligand core on demand.

Introduction: We evaluated whether exposure to high altitude impairs visuomotor learning in lowlanders with chronic obstructive pulmonary disease (COPD) and whether this can be prevented by acetazolamide treatment. Methods: 45 patients with COPD, living <800 m, FEV1 ≥40 to <80%predicted, were randomized to acetazolamide (375 mg/d) or placebo, administered 24h before and during a 2-day stay in a clinic at 3100 m. Visuomotor performance was evaluated with a validated, computer-assisted test (Motor-Task-Manager) at 760 m above sea level (baseline, before starting the study drug), within 4h after arrival at 3100 m and in the morning after one night at 3100 m. Main outcome was the directional error (DE) of cursor movements controlled by the participant via mouse on a computer screen during a target tracking task. Effects of high altitude and acetazolamide on DE during an adaptation phase, immediate recall and post-sleep recall were evaluated by regression analyses. www.ClinicalTrials.gov NCT03165890. Results: In 22 patients receiving placebo, DE at 3100 m increased during adaptation by mean 2.5°, 95%CI 2.2° to 2.7° ( p < 0.001), during immediate recall by 5.3°, 4.6° to 6.1° ( p < 0.001), and post-sleep recall by 5.8°, 5.0 to 6.7° ( p < 0.001), vs. corresponding values at 760 m. In 23 participants receiving acetazolamide, corresponding DE were reduced by -0.3° (-0.6° to 0.1°, p = 0.120), -2.7° (-3.7° to -1.6°, p < 0.001) and -3.1° (-4.3° to -2.0°, p < 0.001), compared to placebo at 3100 m. Conclusion: Lowlanders with COPD travelling to 3100 m experienced altitude-induced impairments in immediate and post-sleep recall of a visuomotor task. Preventive acetazolamide treatment mitigated these undesirable effects., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Scheiwiller, Furian, Buergin, Mayer, Schneider, Mademilov, Lichtblau, Muralt, Sheraliev, Sooronbaev, Ulrich and Bloch.)

Prediction of adverse health effects at altitude or during air travel is relevant, particularly in pre-existing cardiopulmonary disease such as pulmonary arterial or chronic thromboembolic pulmonary hypertension (PAH/CTEPH, PH). A total of 21 stable PH-patients (64 ± 15 y, 10 female, 12/9 PAH/CTEPH) were examined by pulse oximetry, arterial blood gas analysis and echocardiography during exposure to normobaric hypoxia (NH) (FiO2 15% ≈ 2500 m simulated altitude, data partly published) at low altitude and, on a separate day, at hypobaric hypoxia (HH, 2500 m) within 20−30 min after arrival. We compared changes in blood oxygenation and estimated pulmonary artery pressure in lowlanders with PH during high altitude simulation testing (HAST, NH) with changes in response to HH. During NH, 4/21 desaturated to SpO2 < 85% corresponding to a positive HAST according to BTS-recommendations and 12 qualified for oxygen at altitude according to low SpO2 < 92% at baseline. At HH, 3/21 received oxygen due to safety criteria (SpO2 < 80% for >30 min), of which two were HAST-negative. During HH vs. NH, patients had a (mean ± SE) significantly lower PaCO2 4.4 ± 0.1 vs. 4.9 ± 0.1 kPa, mean difference (95% CI) −0.5 kPa (−0.7 to −0.3), PaO2 6.7 ± 0.2 vs. 8.1 ± 0.2 kPa, −1.3 kPa (−1.9 to −0.8) and higher tricuspid regurgitation pressure gradient 55 ± 4 vs. 45 ± 4 mmHg, 10 mmHg (3 to 17), all p < 0.05. No serious adverse events occurred. In patients with PH, short-term exposure to altitude of 2500 m induced more pronounced hypoxemia, hypocapnia and pulmonary hemodynamic changes compared to NH during HAST despite similar exposure times and PiO2. Therefore, the use of HAST to predict physiological changes at altitude remains questionable. (ClinicalTrials.gov: NCT03592927 and NCT03637153).

Question Addressed by the Study: To investigate exercise performance and hypoxia-related health effects in patients with pulmonary hypertension (PH) during a high-altitude sojourn., Patients and Methods: In a randomised crossover trial in stable (same therapy for >4 weeks) patients with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) with resting arterial oxygen tension ( P aO 2 ) ≥7.3 kPa, we compared symptom-limited constant work-rate exercise test (CWRET) cycling time during a day-trip to 2500 m versus 470 m. Further outcomes were symptoms, oxygenation and echocardiography. For safety, patients with sustained hypoxaemia at altitude (peripheral oxygen saturation <80% for >30 min or <75% for >15 min) received oxygen therapy., Results: 28 PAH/CTEPH patients (n=15/n=13); 13 females; mean±sd age 63±15 years were included. After >3 h at 2500 m versus 470 m, CWRET-time was reduced to 17±11 versus 24±9 min (mean difference -6, 95% CI -10 to -3), corresponding to -27.6% (-41.1 to -14.1; p<0.001), but similar Borg dyspnoea scale. At altitude, P aO 2 was significantly lower (7.3±0.8 versus 10.4±1.5 kPa; mean difference -3.2 kPa, 95% CI -3.6 to -2.8 kPa), whereas heart rate and tricuspid regurgitation pressure gradient (TRPG) were higher (86±18 versus 71±16 beats·min -1 , mean difference 15 beats·min -1 , 95% CI 7 to 23 beats·min -1 ) and 56±25 versus 40±15 mmHg (mean difference 17 mmHg, 95% CI 9 to 24 mmHg), respectively, and remained so until end-exercise (all p<0.001). The TRPG/cardiac output slope during exercise was similar at both altitudes. Overall, three (11%) out of 28 patients received oxygen at 2500 m due to hypoxaemia., Conclusion: This randomised crossover study showed that the majority of PH patients tolerate a day-trip to 2500 m well. At high versus low altitude, the mean exercise time was reduced, albeit with a high interindividual variability, and pulmonary artery pressure at rest and during exercise increased, but pressure-flow slope and dyspnoea were unchanged., Competing Interests: Conflict of interest: S.R. Schneider has nothing to disclose. Conflict of interest: L.C. Mayer has nothing to disclose. Conflict of interest: M. Lichtblau has nothing to disclose. Conflict of interest: C. Berlier has nothing to disclose. Conflict of interest: E.I. Schwarz has nothing to disclose. Conflict of interest: S. Saxer has nothing to disclose. Conflict of interest: L. Tan has nothing to disclose. M. Furian has nothing to disclose. Conflict of interest: K.E. Bloch has nothing to disclose. Conflict of interest: S. Ulrich reports grants from Johnson and Johnson SA, Switzerland, during the conduct of the study; and grants from the Swiss National Science Foundation and Zurich Lung, grants and personal fees from Orpha Swiss, and personal fees from Actelion SA and MSD SA, outside the submitted work., (Copyright ©The authors 2021.)

Background: Many patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PH) wish to travel to altitude or by airplane, but their risk of hypoxia-related adverse health effects is insufficiently explored., Research Question: How does hypoxia, compared with normoxia, affect constant work-rate exercise test (CWRET) time in patients with PH, and which physiologic mechanisms are involved?, Study Design and Methods: Stable patients with PH with resting Pao 2  ≥ 7.3 kPa underwent symptom-limited cycling CWRET (60% of maximal workload) while breathing normobaric hypoxic air (hypoxia; Fio 2 , 15%) and ambient air (normoxia; Fio 2 , 21%) in a randomized cross-over design. Borg dyspnea score, arterial blood gases, tricuspid regurgitation pressure gradient, and mean pulmonary artery pressure/cardiac output ratio (mean PAP/CO) by echocardiography were assessed before and during end-CWRET., Results: Twenty-eight patients (13 women) were included: median (quartiles) age, 66 (54; 74) years; mean pulmonary artery pressure, 41 (29; 49) mm Hg; and pulmonary vascular resistance, 5.4 (4; 8) Wood units. Under normoxia and hypoxia, CWRET times were 16.9 (8.0; 30.0) and 6.7 (5.5; 27.3) min, respectively, with a median difference (95% CI) of -0.7 (-3.1 to 0.0) min corresponding to -7 (-32 to 0.0)% (P = .006). At end-exercise in normoxia and hypoxia, respectively, median values and differences in corresponding variables were as follows: Pao 2 : 8.0 vs 6.4, -1.7 (-2.7 to -1.1) kPa; arterial oxygen content: 19.2 vs 17.2, -1.7 (-3 to -0.1) mL/dL; Paco 2 : 4.7 vs 4.3, -0.3 (-0.5 to -0.1) kPa; lactate: 3.7 vs 3.7, 0.9 (0.1 to 1.6) mM (P < .05 all differences). Values for Borg scale score: 7 vs 6, 0.5 (0 to 1); tricuspid pressure gradient: 89 vs 77, -3 (-9 to 16) mm Hg; and mean PAP/CO: 4.5 vs 3.3, 0.3 (-0.8 to 1.4) Wood units remained unchanged. In multivariable regression, baseline pulmonary vascular resistance was the sole predictor of hypoxia-induced change in CWRET time., Interpretation: In patients with PH, short-time exposure to hypoxia was well tolerated but reduced CWRET time compared with normoxia in association with hypoxemia, lactacidemia, and hypocapnia. Because pulmonary hemodynamics and dyspnea at end-exercise remained unaltered, the hypoxia-induced exercise limitation may be due to a reduced oxygen delivery causing peripheral tissue hypoxia, augmented lactic acid loading and hyperventilation., Trial Registry: ClinicalTrials.gov; No.: NCT03592927; URL: www.clinicaltrials.gov., (Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: Pediatric hematology, oncology, and hematopoietic cell transplantation (HCT) patients are at increased risk for bloodstream infections. The authors sought to evaluate the influence of a standardized best practice central venous catheter (CVC) maintenance bundle on the burden of and risk factors for mucosal barrier injury (MBI) and non-MBI central line-associated bloodstream infections (CLABSIs) across a common inpatient and ambulatory continuum in this high-risk population., Methods: A retrospective cohort study of patients with underlying malignancy, hematologic disorders, and HCT recipients with a CVC in place at the time of CLABSI diagnosis in both inpatient and ambulatory settings from January 1, 2012 to December 31, 2016. Descriptive, nonparametric statistics were used to describe patient characteristics and outcomes. Logistic regression analyses were applied to identify potential risk factors for inpatient versus ambulatory and MBI versus non-MBI CLABSI., Results: During the 5-year period, 118 of 808 (14.6%) patients had 159 laboratory-confirmed CLABSIs for ambulatory and inpatient CLABSI rates of 0.27 CLABSI/1000 and 2.2 CLABSI/1000 CVC days, respectively. CLABSI occurred more frequently in hospitalized patients after HCT and with underlying leukemia, most frequently caused by Gram-negative bacteria. MBI CLABSI accounted for 42% of all CLABSI with a 3-fold higher risk in hospitalized patients. Having multiple CVC or a CVC that was not a port independently associated with higher CLABSI risk., Conclusions: In our cohort, non-MBI CLABSI continued to account for the majority of CLABSI. CVC type is independently associated with higher overall CLABSI risk. Further studies are needed to reliably define additional prevention strategies when CLABSI maintenance bundles elements are optimized in this high-risk population.

A Good Laboratory Practices (GLP) validated, multiresidue analytical method is presented for the determination of the chloroacetanilide herbicides metolachlor, acetochlor, and alachlor, the chloroacetamide herbicide dimethenamid, and their respective ethanesulfonic (ESA) and oxanillic (OA) acid degradates in ground and surface water. A 50-mL water sample is subjected to purification using a C-18 SPE column. The four parent components and their eight ESA and OA degradates are isolated using 80/20 methanol/water (v/v) for elution. The eluate is reduced to < 1.0 mL and reconstituted in 10/90 acetonitrile/water (v/v) to the desired final fraction volume. Final analysis is accomplished using liquid chromatography/electrospray ionization-mass spectrometry/mass spectrometry in the + (parent compounds) and - (ESA and OA degradates) ion modes by monitoring appropriate precursor/product ion pairs for each of the 12 analytes. The method limit of quantification is 0.10 ppb and the limit of detection is 0.125 ng injected for each analyte. Average procedural recovery data range from 95 to 105% for fortification levels of 0.10-100 ppb. The method validation study was performed following GLP guidelines.

A method is reported for the determination of cyromazine and melamine residues in soil. Soil samples are extracted twice via mechanical shaking, each time with 70% acetonitrile/30% 0.050 M ammomium carbonate for 30 min. An aliquot portion of the pooled extracts is subjected to strong cation exchange (SCX) purification on AG 50W-X4 resin. Final analysis is accomplished using liquid chromatography-ultraviolet (LC-UV) detection at a wavelength of 214 nm. Confirmatory analyses can be performed using gas chromatography-mass selective detection (GC-MSD) in the selected ion monitoring (SIM) mode. The limit of detection (LOD) is 2.5 ng injected and the limit of quantification (LOQ) is 10 ppb when using LC-UV for the analysis of N-cyclopropyl-1,3,5-triazine-2,4, 6-triamine (cyromazine) and 1,3,5-triazine-2,4,6-triamine (melamine). The LOD is 0.050 ng injected and the LOQ is 10 ppb when using GC-MSD for confirmatory analyses. The mean procedural recoveries were 97 and 95% and the standard deviations were 16 and 11% for cyromazine and melamine, respectively (n = 24), when using LC-UV. The mean procedural recoveries were 107 and 92% and the standard deviations were 9.9 and 16% for cyromazine and melamine, respectively (n = 29), when using GC-MSD. The method validation study was conducted under U.S. EPA FIFRA Good Laboratory Practice Guidelines 40 CFR 160. The method also passed an Independent Laboratory Validation (ILV) as per U.S. EPA FIFRA Subdivision N.