Detectors lamps

Capillary overheating Detector lamp either is not on or is weak. Also, poor selected optical wavelength Light Intensity through cell is low... 

Improve temperature regulation Repl ace detector lamp If... 

CE instruments are thermostated to dissipate excessive Joule heat. Generally that covers only the main part of the capillary, and not, e.g., the autosampler with the buffer and sample vials. In some instruments, it is difficult to control the autosampler temperature due to the near presence of extraneous heating sources such as the detector lamp. Also, some labs... 

Instruments, or at least detector lamps Age of analytical solutions Temperature... 

The most commonly reported symptom of a bad system is baseline drift the second is a noisy baseline. Baselines that drift up and down are almost always due to peaks coming off the column. Baselines that drift up continuously can be garbage, a bad detector lamp, or decomposition on the flow cell window. Noise can come from almost anywhere in the system. 

Treatment Replace detector lamp. Record new intensity value, if it can be measured, for later reference. 

Problem 11 Baseline increases with no solvent flow and detector lamp on. 

Continuous-detector lamp problem or dirty flow cell Replace UV lamp (each should last 2000 hr) clean and flush flow-cell... 

Detector lamp failing. Replace detector lamp. 

Spikes in chromatograms can come from many sources, such as aging detector lamps or bubbles in the flow cell both can be easily corrected. External electrical noise sources, such as ovens, refrigerators, cellular telephones, and fluorescent lights, and other possible noise sources such as system electronics or from external electronic sources, and laboratory power feed may be beyond a chromatographer s control. 

Having an unused spare detector lamp available makes checking the problems attributed to the lamp performance an easy task. 

The characteristics of an equipment may change over time, e.g., LfV detector lamps lose intensity, or pump piston seals abrade, or short-term noise affecting the LOD is increased because of flow cell contamination. These changes will have a direct impact on the performance of... 

The complicated nature of the instrumentation required for these experiments may also result in artifacts which may cause the fluorescence quenching to not conform to the model. Fluctuations in the proportioning of solutions A and B in the post-column reagent pump may result in error in the total Cu concentration reported as well as variation in concentration of Cu " in the post-column system throughout an experiment. Likewise, fluctuations in pump flow rate of both the eluent and post-column reagent pumps may also effect the total Cu concentration in the post-column system. Since each experiment was conducted over nine to twelve hours, temperature of the system and the fluorescence detector lamp output may also have contributed to variations in fluorescence quenching. A decreased run time for the chromatographic method and a decrease in the number of sample runs for each experiment may help to reduce this artifact. 

However, some elements of an automated solid-phase instrument do experience more accelerated degradation. These items should be easily accessible to the user and replaced at appropriate intervals. Examples of some of these disposable elements are O-rings for sealing reagent bottles, filter frits for the reagents and reaction vessel, and the detector lamp. 

Detector Lamp energy Accuracy of wavelength Measure the actual response factor at the detection limit Read energy values with a diagnostic function and compare with the value of a newly installed lamp Using solutes with sharp maximum of the extinction coefficient, e.g. terbium perchlorate 218.5 nm, erbium perchlorate 254.6 nm ... 

Ionization potentials are given as a guideline for the selection of photoionization detector lamps used in some direct-reading instruments.)... 

Just as the bulb in a table lamp has a finite lifetime, so do the ultraviolet/ visible (UV/Vis) detector lamps (tungsten and deuterium see Chapter 4) in HPLC systems. Light intensity decreases with time due to the evaporation of internal metal components and coatings. Lamps deteriorate with age and use according to most manufacturers, lamps have a lifetime of about 1,000 hours. The lifetime is defined as being the time at which 50% of the light intensity remains. After this time has elapsed, the lamp should be replaced. 

Spikes in chromatograms can come from many sources, such as aging detector lamps or bubbles in the flow cell both... 

The characteristics of an equipment may change over time, e.g., UV detector lamps lose intensity, or pump piston seals abrade, or short-term noise affecting the LOD is increased because of flow cell contamination. These changes will have a direct impact on the performance of the HPLC instrument. The frequency of performance tests will be determined by experience and is based on need, type, and history of equipment performance. Intervals between the checks should be shorter than the time the instrument drifts outside acceptable limits. New instruments need to be checked more frequently, and, if the instrument meets the performance specifications, the time interval can be increased. 

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