Min Cycle Time Research Articles

A low thermal mass fast gas chromatograph and its implementation in fast gas chromatography mass spectrometry with supersonic molecular beams

A new type of low thermal mass (LTM) fast gas chromatograph (GC) was designed and operated in combination with gas chromatography mass spectrometry (GC-MS) with supersonic molecular beams (SMB), including GC-MS-MS with SMB, thereby providing a novel combination with unique capabilities. The LTM fast GC is based on a short capillary column inserted inside a stainless steel tube that is resistively heated. It is located and mounted outside the standard GC oven on its available top detector port, while the capillary column is connected as usual to the standard GC injector and supersonic molecular beam interface transfer line. This new type of fast GC-MS with SMB enables less than 1 min full range temperature programming and cooling down analysis cycle time. The operation of the fast GC-MS with SMB was explored and 1 min full analysis cycle time of a mixture of 16 hydrocarbons in the C(10)H(22) up to C(44)H(90) range was achieved. The use of 35 mL/min high column flow rate enabled the elution of C(44)H(90) in less than 45 s while the SMB interface enabled splitless acceptance of this high flow rate and the provision of dominant molecular ions. A novel compound 9-benzylazidanthracene was analyzed for its purity and a synthetic chemistry process was monitored for the optimization of the chemical reaction yield. Biodiesel was analyzed in jet fuel (by both GC-MS and GC-MS-MS) in under 1 min as 5 ppm fatty acid methyl esters. Authentic iprodion and cypermethrin pesticides were analyzed in grapes extract in both full scan mode and fast GC-MS-MS mode in under 1 min cycle time and explosive mixture including TATP, TNT and RDX was analyzed in under 1 min combined with exhibiting dominant molecular ion for TATP. Fast GC-MS with SMB is based on trading GC separation for speed of analysis while enhancing the separation power of the MS via the enhancement of the molecular ion in the electron ionization of cold molecules in the SMB. This paper further discusses several features of fast GC and fast GC-MS and the various trade-offs involved in having powerful and practical fast GC-MS.

Changes in drive phase lower limb kinematics during a 60 min cycling time trial

ObjectivesThe aim of this study was to evaluate changes in the three dimensional lower limb kinematics during a simulated cycling time trial. DesignRepeated measures. MethodsTen experienced male road cyclists performed a 60min cycling test at a workload based on previous onset of blood lactate accumulation (OBLA) testing. The time trial (TT) was divided into six 10min periods consisting of 8min cycling at steady state (88% of OBLA) followed by a 90s effort phase (140% of OBLA) and a 30s recovery phase (60% of OBLA). Three-dimensional kinematic data (200Hz) were recorded in the last minute of each steady state phase with specific attention directed at changes in range of motion (ROM) and consistency of orientation at the hip, knee and ankle joints during drive phase. Resultsfrom repeated measures ANOVA indicated a mean effect for test duration on the drive phase ROM in both hip extension (p=0.027) and ankle dorsi flexion (p<0.001). The SD of the mean tibial rotation during the drive phase was the only measure of movement consistency that showed an effect for test duration (p=0.031). ConclusionsThese findings indicated that participants tended to increase the ROM in hip extension and ankle flexion during drive phase at the end of a TT. Changes in the consistency of tibial rotation during the drive phase may be an important indicator of fatigue and should be monitored by coaches during training due to its possible relationship with injury and fatigue.

Deception of ambient and body core temperature improves self paced cycling in hot, humid conditions

We used incorrect visual feedback of ambient and core temperature in the heat to test the hypothesis that deception would alleviate the decrement in cycling performance compared to a no deception trial. Seven males completed three 30 min cycling time trials in a randomised order on a Kingcycle ergometer. One time trial was in temperate, control conditions (CON: 21.8 ± 0.6°C; 43.3 ± 4.3%rh), the others in hot, humid conditions (HOT: 31.4 ± 0.3°C; 63.9 ± 4.5%rh). In one of the hot, humid conditions (31.6 ± 0.5°C; 65.4 ± 4.3%rh), participants were deceived (DEC) into thinking the ambient conditions were 26.0°C; 60.0%rh and their core temperature was 0.3°C lower than it really was. Compared to CON (16.63 ± 2.43 km) distance covered was lower in HOT (15.88 ± 2.75 km; P < 0.05), but DEC ameliorated this (16.74 ± 2.87 km; P < 0.05). Mean power output was greater in DEC (184.4 ± 60.4 W) than HOT (168.1 ± 54.1 W; P < 0.05) and no difference was observed between CON and DEC. Rectal temperature and iEMG of the vastus lateralis were not different, but RPE in the third minute was lower in DEC than HOT (P < 0.05). Deception improved performance in the heat by creating a lower RPE, evidence of a subtle mismatch between the subconscious expectation and conscious perception of the task demands.

Effect of Central and Peripheral Fatigue on Maximal Voluntary Function

Exhaustive high intensity endurance exercise causes fatigue comprised of a central and a peripheral component. Each component's relative contribution to this phenomenon is unknown and difficult to separate during voluntary whole-body exercise. PURPOSE: We used fatiguing single-leg cycling to induce peripheral muscle fatigue in the working leg and to simultaneously facilitate central fatigue by increasing the central projection of locomotor muscle afferents. Our purpose was to evaluate the influence of a) central fatigue on maximum single-leg cycling power (Pmax) of the rested contralateral leg and b) central and peripheral fatigue on Pmax of the fatigued ipsilateral leg. METHODS: On separate days, 5 male cyclists performed 10min cycling time trials (TT) with either their left or right leg. Ratings of perceived exertion of the body (RPEbody) and of the leg (RPEleg) were evaluated during the final minute of TT. Fatigue was estimated by comparing exercise-induced changes in Pmax as quantified via inertial-load cycling before and again 1 and 3 min following TT. RESULTS: RPEbody and RPEleg during the left and right leg TT did not differ (17.6±0.9 vs. 17.8±0.7 and 19.6±0.5 vs. 19.6±0.5 scale units, respectively). One min after TT, contralateral Pmax was reduced by 14±5% (596±25 vs. 511±39W, p=0.03) and returned to pre-fatigue levels within 3min. One min after TT, ipsilateral Pmax was significantly reduced by 33±2% (575±23 vs. 387±26W p<0.01) and remained reduced by 18±2% (590±20 vs. 483±29W, p<0.01) 3min following TT. CONCLUSION: Our data suggest that central fatigue mechanisms primarily accounted for the reduction in the contralateral Pmax, however, central fatigue was only short lasting as contralateral Pmax was restored within 3min following TT. Increased firing of muscle afferents innervating the peripherally fatigued ipsilateral leg may have exerted inhibitory influences on central motor drive with the subsequent consequence of limiting Pmax in the rested contralateral leg. Furthermore, our results indicate that a combination of central and peripheral mechanisms initially compromised ipsilateral Pmax. However, 3min after TT, ipsilateral Pmax recovered by 15% suggesting that central fatigue had been restored and that the remaining reductions in ipsalateral Pmax were primarily due to peripheral fatigue.

High throughput analysis of 150 pesticides in fruits and vegetables using QuEChERS and low-pressure gas chromatography–time-of-flight mass spectrometry

A higher monitoring rate is highly desirable in the labs, but this goal is typically limited by sample throughput. In this study, we sought to assess the real-world applicability of fast, low-pressure GC–time-of-flight MS (LP-GC/TOFMS) for the identification and quantification of 150 pesticides in tomato, strawberry, potato, orange, and lettuce samples. Buffered and unbuffered versions of QuEChERS (which stands for “quick, easy, cheap, effective, rugged, and safe”) using dispersive solid-phase extraction (d-SPE) and disposable pipette extraction (DPX) for clean-up were compared for sample preparation. For clean-up of all sample types, a combination of 150 mg MgSO 4, 50 mg primary secondary amine (PSA), 50 mg C 18, and 7.5 mg graphitized carbon black (GCB) per mL extract was used. No significant differences were observed in the results between the different sample preparation versions. QuEChERS took <10 min per individual sample, or <1 h for two chemists to prepare 32 pre-homogenized samples, and using LP-GC/TOFMS, <10 min run time and <15 min cycle time allowed >32 injections in 8 h. Overall, >126 analytes gave recoveries (3 spiking levels) in the range of 70–120% with <20% RSD. The results indicate that LP-GC/TOFMS for GC-amenable analytes matches UHPLC–MS/MS in terms of sample throughput and turnaround time for their routine, concurrent use in the analysis of a wide range of analytes in QuEChERS extracts to achieve reliable quantification and identification of pesticide residues in foods.

Ultra-performance liquid chromatography for the determination of pesticide residues in foods by tandem quadrupole mass spectrometry with polarity switching

An ultra-performance liquid chromatographic (UPLC) electrospray ionisation tandem quadrupole mass spectrometric method has been developed for the determination of 52 pesticides in cereal-based baby foods, oranges and potatoes. The fast polarity switching capability of the mass spectrometer used enabled the determination of 44 of the compounds in the positive ionisation mode and 8 of the compounds in the negative ionisation mode in a single run. Prior to analysis, co-extractives were removed from acetonitrile extracts using dispersive solid-phase extraction with primary secondary amine (50 mg). The UPLC method separates all of the pesticides, resolves structural isomers (e.g. butocarboxim sulfoxide and aldicarb sulfoxide) and has a short (7 min) cycle time. Extracts spiked with pesticides at 0.10 and 0.01 mg kg −1 yielded average recoveries in the range of 66–124% with relative standard deviations less than 19% for the majority of the analytes.

Proteomic Detection of Beta Thalassaemia Trait Using Electrospray Mass Spectrometry-Mass Spectrometry.

Introduction Mass spectrometry has proved a valuable tool in the unequivocal characterisation of haemoglobin variants detected during routine haemoglobinopathy screening using High Performance Liquid Chromatography (HPLC) and/or isoelectric focusing. We have recently described a rapid and specific electrospray mass spectrometry-mass spectrometry (MSMS) method, using proteomic mutation targeting, for simultaneous detection of the clinically significant haemoglobinopathies; haemoglobin (Hb)S, HbC, HbE, HbDPunjab and HbOArab. Here we report additional transitions within the 1min cycle time, using delta chains as a surrogate HbA2, with the objective of detecting beta thalassaemia trait.Method Blood samples are digested using trypsin, which results in specific cleavage of globin chains at peptide bonds adjacent to lysine and arginine residues, to produce a series of well-characterised peptides. There is strong amino acid sequence homology between the beta and delta chains of haemoglobin, however tryptic digestion produces series of 15 (T1–T15) and 16 (T1–T16) peptides, for beta and delta chains respectively, with differences in T2, T3, T5, T10, T12, T13 and T14. In this report we have investigated the diagnostic utility of T2: beta sequence SAVTALWGK, average mass 932.1 daltons, delta sequence TAVNALWGK, average mass 959.1 daltons. In multiple reaction monitoring mode the respective T2 [M+2H]2+ ions, m/z 466.8 and 480.3, are selected, fragmented, and the singly charged ions of the informative peptide fragments, VTALWGK and VNALWGK, detected.Results The percentage area ratio of delta/(beta+delta) was calculated and compared with the classical percentage HbA2 value obtained by HPLC. 66 samples with HbA2 values within our normal range (mean 2.7%, range 1.8–3.4), and 58 with HbA2 values indicative of beta thalassaemia trait (5.2%, 4.2–7.9) were analysed by MSMS and the corresponding delta/(beta+delta) ratios were 1.7%, 0.9–2.3 and 3.4%, 2.5–6.0. In addition, in 2 further HbS beta thalassaemia zero compound heterozygote samples confirmed by beta gene sequencing the ratios were 4.1% and 3.7%.Conclusion This relatively small study provides evidence that beta thalassaemia trait may be diagnosed by MSMS and represents another step towards comprehensive MSMS population screening for clinically significant haemoglobinopathies.

A remote in situ monitor based on continuous flow analysis for the quantitation of sub-micromolar levels of hexavalent chromium in natural waters

We describe the design, optimization, and application of a small, lightweight, deployable monitoring instrument for accurately measuring parts-per-billion levels of hexavalent Cr in surface waters at hourly intervals. The monitor quantifies Cr(vi) using a standard molecular absorbance spectroscopic method, i.e. by formation of a complex with 1,5-diphenylcarbazide (DPC). The continuous flow analysis (CFA) design uses narrow conduits (0.90 mm) that are hot-forged onto poly(methyl methacrylate) ('Plexiglas') plates based on the method of Jannasch et al.(Anal. Chem., 1994, 66, 3352). The sample stream is drawn through the manifold at 25 microl min(-1) using a mini-peristaltic pump; osmotic pumps (10 microl h(-1)) are used to continuously inject reagent (2.0 mM DPC, 0.60 M HNO(3), 5.0% w/v acetone, and 0.10% w/v Brij-35) and to periodically introduce quality control standards and a cleaning solution (0.50 M HNO(3)). The 'Z-type' optical cell uses a liquid-core waveguide (10 mm) to collimate the light-emitting diode source beam (lambda(max) 574 nm) to a broadband photodiode detector. Figures of merit are: 7 min cycle time, response within 28 min and clear-down within 31 min, low waste generation (<40 ml d(-1)), detection limit (3sigma) of 48.4 microg l(-1) as Cr(vi) or 0.411 microM as chromic acid, 1.54% relative standard deviation at 100 microg l(-1), and selectivity for dissolved Cr(vi) in authentic surface water samples containing moderate levels (>0.21% w/v) of total particulate matter. Using a test chamber containing Milwaukee Harbor water that was periodically fortified with Cr(vi) standards, continuous testing over a 15 day period (354 h) yielded results that were in excellent agreement (<5% variation) with measurements made using an ICP-MS reference method. Drift in the calibration model over the test period was 1.23% and the variation in a 0.50 mg l(-1) Cr(vi) standard was 3.8%(n= 11). Known interferences to the DPC chemistry (Mo, V, and Hg at >5 mg l(-1)) were undetected in the harbor water by ICP-MS.

Comparison of W peak, VO 2peak and the ventilation threshold from two different incremental exercise tests: Relationship to endurance performance

This report presents data comparing the peak rate of oxygen consumption (VO2(peak)), peak power output (W(peak)) and the ventilation threshold (VT) obtained from two different incremental cycle exercise tests performed by nine well trained triathletes (Mean +/- SD age 32 +/- 3 yrs; body mass 77.4 +/- 4.9 kg and height 185 +/- 3 cm). Furthermore, the relationship between these variables and the average sustained power output (W) during a 90 min cycle time trial (TT) was also determined. The two incremental exercise tests involved a 'short' test, which commenced at 150 W with 30 W increments every 60 s until exhaustion. The second ('long') incremental test commenced at a power output representing 50% of the W(peak) obtained in the short test. The subjects were then required to increase the power output by 5% every 3 min until exhaustion. The results showed the W(peak) (W) in the short test was significantly (p < 0.01) higher than in the long test. However, there was no significant difference in the VO2(peak) (1 x min(-1)) between the two tests. There was a weak but significant correlation between W(peak) (W) and VO2(peak) (l x min(-1)) (r = 0.72: p < 0.05) in the short (60 s stage) test but not the long (3 min stage) test (r = 0.52). There were no significant differences and good agreement between for the heart rate (HR) (b x min(-1)) and oxygen consumption (VO2) corresponding to the VT. In contrast, the power output (W) corresponding to the VT was significantly different and not comparable between the long and short incremental tests. The cycle TT performance was most correlated to the W(peak) (W) (r = 0.94; p < 0.01) and the VT (W) (r = 0.75; p < 0.05) from the long test as well as the VO2(peak) (l x min(-1)) obtained from the short incremental test (r = 0.75; p < 0.01). These data suggest that the length of stages during incremental cycle exercise may influence the W(peak) and in turn the relationship of this variable to VO2(peak). Furthermore, the W(peak) obtained from a test incorporating 3 min stage increments represents the best indicator of 90 min cycle performance in well-trained triathletes.

An automated overlying water-renewal system for sediment toxicity studies

An automated water-renewal toxicity test system is described for exposing benthic invertebrates to whole sediments. The system will intermittently deliver laboratory or on-site water for overlying water replacement in sediment exposures. A range of cycle rates can be used to produce different volume additions of overlying water per day to exposure chambers. The system can be used with six different treatments and eight replicates per treatment producing 48 exposure chambers. Three formulated sediments with variable organic carbon (1.5%, 7.5%) and sand (14%, 63%) content were prepared to test the system exposing amphipods, Hyalella azteca and midges, Chironomus tentans in 10 day whole sediment tests. Intermittent water flow was used with a 90 min cycle time to create two volume additions of laboratory water per 24 h in exposure chambers (180 ml sediment, 320 ml water). Overlying water quality conditions, and survival and growth of both species were consistent and within acceptable limits for the testing requirements of the U.S. EPA guidelines for sediments with freshwater invertebrates.

High-throughput liquid chromatography ultraviolet/mass spectrometric analysis of combinatorial libraries using an eight-channel multiplexed electrospray time-of-flight mass spectrometer.

We report a high-throughput liquid chromatography/mass spectrometry (LC/MS) protocol for analyzing large combinatorial libraries using an eight-channel parallel LC/UV/MS (MUX-LCT) system. System configuration, linear response range in UV absorbance, LC column selection, and flow rate were optimized for 24 h/7 day unattended operations. Combinatorial libraries were analyzed on this system at a rate of 3200 compounds per day for a 3.5 min cycle time per injection. This parallel system is compared with a single-channel system in terms of performance and operation.

Chromatographic separation of whey proteins: Outinen, M., Harju, M., Tossavainen, O. and Antila, P. (Valio Oy, FIN-00100 Helsinki, Finland) PCT International Patent Application WO 95/ 19714

A perfusion reversed-phase (RP) HPLC method was developed for the rapid separation of the main bovine whey proteins: α-lactalbumin (α-LA), serum albumin (BSA) and the genetic variants of β-lactoglobulin (A and B) (β-LG A and β-LG B). For the method development, the influence of factors favouring structural changes of proteins (temperature and organic acid concentration in the mobile phase), gradient and other chromatographic conditions and the mass of protein injected was examined. The optimized method allowed the separation of proteins in about 1.5 min (cycle time 3.5 min) with resolution around 1.0 for the β-lactoglobulins. The method was applied to the determination of proteins in a whey from raw bovine milk. The precision of the determinations was ⩽3.75 mg per 100 ml (S.D.). With respect to the accuracy, errors ⩽7.0% in the determination on α-LA, β-LG A and β-LG B were obtained, compared with an RP-HPLC reference method. However, higher errors in the quantification of BSA were found owing to the lack of purity of the peak assigned. In addition, the proposed method has proved to be very useful in the detection of homologous whey proteins from different species (cow, sheep and goat) in milk mixtures.

THE INFLUENCE OF STARCH STRUCTURE ON GLYCOGEN RESYNTHESIS AND SUBSEQUENT CYCLING PERFORMANCE 7

The present study was designed to evaluate the influence of starch structure on muscle glycogen resynthesis and cycling performance. Eight male cyclists (22 ± 1 yr) completed an exercise protocol (DP) to decrease vastus lateralis glycogen concentration. This exercise consisted of 60 min cycling at 75% VO2max, followed by six 1-min sprints at ≈125%˙VO2max with 1 min rest intervals. In the 12 hr after the exercise each subject consumed ≈3000 kcal (65:20:15% carbohydrate, fat and protein). All of the carbohydrate (CHO) consumed was derived from one of four solutions: 1) glucose (G), 2) maltodextrin (M), 3) waxy starch (W) [100% amylopectin], or 4) resistant starch (R)[100% amylose]. Muscle biopsies were taken from the vastus lateralis muscle after DP and 24 hr later to determine glycogen concentrations. A 30 min cycling time trial (TT) was performed following the 24 hr post-DP muscle biopsy to examine the influence of the feeding regimen on total work output. The post-DP glycogen concentrations were similar among the four trials, ranging from 220.3±29.2 to 264.7 ± 48.3 mmol·kg-1 dry weight (d.w.) muscle. Twenty-four hours after DP, muscle glycogen concentration had increased less (p<0.05) in the R trial(+90.8 ± 12.8 mmol·kg-1 d.w.) than in the G (+197.7± 31.6 mmol·kg-1 d.w.), M (+136.7 ± 24.5 mmol·kg-1 d.w.) and W (+171.8 ± 37.1 mmol·kg-1 d.w.) trials. There were no differences in total work output during the TT, or blood lactate concentration immediately following the TT in any of the CHO trials. In summary, glycogen resynthesis was attenuated following ingestion of starch with a high amylose content, relative to amylopectin or glucose; however, short duration time trial performance was unaffected.

Perfusion liquid chromatography of whey proteins

A perfusion reversed-phase (RP) HPLC method was developed for the rapid separation of the main bovine whey proteins: α-lactalbumin (α-LA), serum albumin (BSA) and the genetic variants of β-lactoglobulin (A and B) (β-LG A and β-LG B). For the method development, the influence of factors favouring structural changes of proteins (temperature and organic acid concentration in the mobile phase), gradient and other chromatographic conditions and the mass of protein injected was examined. The optimized method allowed the separation of proteins in about 1.5 min (cycle time 3.5 min) with resolution around 1.0 for the β-lactoglobulins. The method was applied to the determination of proteins in a whey from raw bovine milk. The precision of the determinations was ⩽3.75 mg per 100 ml (S.D.). With respect to the accuracy, errors ⩽7.0% in the determination on α-LA, β-LG A and β-LG B were obtained, compared with an RP-HPLC reference method. However, higher errors in the quantification of BSA were found owing to the lack of purity of the peak assigned. In addition, the proposed method has proved to be very useful in the detection of homologous whey proteins from different species (cow, sheep and goat) in milk mixtures.

Evaluation of a new automated affinity-chromatographic method for the measurement of glycated hemoglobin

A new automated affinity-chromatographic method for the rapid determination of glycated hemoglobin is described. It has a four min cycle time, does not measure the labile fraction of glycosylated hemoglobin and is not interfered with by abnormal hemoglobins.

Mediation of Ventilatory Adaptations.

Mediation of Ventilatory Adaptations.

Circadian periodicity in cockroaches altered by high frequency light-dark cycles

The circadian period of the freerunning activity rhythm in the cockroach is systematically altered by high frequency light-dark cycles (HF-LD) according to the ratio of light to dark within each cycle. With a standard 10 min cycle time, brief (e.g., 0.5 min) exposure to light each cycle causes the free-running period to shorten significantly in comparison to its steady-state value in constant darkness. As the ratio of light to dark in HF-LD is increased, the period of the rhythm is progressively lengthened. These findings are discussed in terms of the general proposition that light, applied throughout the circadian cycle, predictably modifies periodicity according to the asymmetrical shape of the circadian phase response curve.

A directionally solidified Ni-base eutectic alloy reinforced by a mixed hafnium-zirconium monocarbide

The nickel-base eutectic alloy (Ni-10Cr-5Al-5Cr-8. 3Hf-1. 1Zr-0.7C, NASA HAFNIC-10) was directionally solidified to produce aligned refractory monocarbides in a nickel-rich matrix. The aligned carbides, (Hf, Zr) C, were present as rod- and ribbontypes, with a volume loading of about 8%. A blocky type of Ni3Al (γ′) precipitate, about 45% volume loading, was produced in the nickel-base matrix. The growth direction of both aligned carbide and matrix was parallel to 〈1 0 0〉. The effect of thermal cycling between 425 and 1100° C using a 2.5 min cycle time was examined. No microstructural degradation of the aligned carbide fibres occurred after 2000 cycles.

Steam film sampling of water for mass spectrometric analysis of the deuterium content.

The Leidenfrost effect, characterized by film boiling of a liquid adjacent to a hot metal surface, has been adapted in two forms for sampling water vapor for mass spectrometer analysis to determine the deuterium-to-hydrogen (D/H) ratio. Both a hot probe and a hot plate configuration convert liquid water to vapor without interference from dirt or dissolved material in the liquid phase. Automatic and semiautomatic analysis of the D/H ratio in water has been achieved with a precision of ±0.1 ppm at natural deuterium concentrations. A 2 min cycle time has been used for multiple sampling of bulk water and flowing stream samples.

Influence of motivation on physical work capacity and performance.

Influence of motivation on physical work capacity and performance.