http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Article/list/535 Valuable advice on how to improve your LC methods from industry expert John Dolan 2012-05-17T17:20:24Z http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Calibration-Curves-Part-5-Curve-Weighting/ArticleStandard/Article/detail/624978?contextCategoryId=535&ref=25 When is curve weighting a good idea? 2009-09-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/372009/624978/lctrouble_thumbnail.jpg http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/372009/624978/lctroublets_flash.jpg XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Calibration-Curves-Part-4-Choosing-the-Appropriate/ArticleStandard/Article/detail/610622?contextCategoryId=535&ref=25 The best results depend on the correct choice of the calibration model. 2009-07-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/292009/610622/lctrouble_thumbnail.jpg http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/292009/610622/lctroublets_flash.jpg XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Calibration-Curves-Part-3-A-Different-View/ArticleStandard/Article/detail/602405?contextCategoryId=535&ref=25 It's all in the perspective. 2009-06-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/242009/602405null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Calibration-Curves-Part-2-What-are-the-Limits/ArticleStandard/Article/detail/598395?contextCategoryId=535&ref=25 How are the signal-to-noise ratio and imprecision related? 2009-05-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/202009/598395null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Calibration-Curves-Part-1-To-b-or-Not-to-b/ArticleStandard/Article/detail/592892?contextCategoryId=535&ref=25 Deciding on a zero intercept. 2009-04-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/152009/592892null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Testing-Method-Performance/ArticleStandard/Article/detail/585581?contextCategoryId=535&ref=25 What measurements are required for system suitability? 2009-03-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/102009/585581null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Drip-Drip-Drip/ArticleStandard/Article/detail/581573?contextCategoryId=535&ref=25 Some things never change. 2009-02-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/072009/581573null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Odds-and-Ends-from-the-Inbox/ArticleStandard/Article/detail/575277?contextCategoryId=535&ref=25 I regularly receive e-mails from readers with a wide variety of questions. Some of these blossom into full-blown columns, but many are answered with just a short response. As I cleaned out my inbox recently, I chose a few of these to share. There is no central theme this month, but hopefully you will pick up some useful information from these topics related to practical operation of the liquid chromatography (LC) system. 2009-01-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/032009/575277null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Column-Care/ArticleStandard/Article/detail/572712?contextCategoryId=535&ref=25 Another precaution I recommend is not to shut off the LC system for more than an hour or so if it or the column contains buffer. 2008-12-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/512008/572712null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Peak-Shape-Problems/ArticleStandard/Article/detail/572447?contextCategoryId=535&ref=25 What causes split or fronting peaks? 2008-11-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/512008/572447null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Check-Valves-and-Acetonitrile/ArticleStandard/Article/detail/565820?contextCategoryId=535&ref=25 Do sticky check valves have you discouraged? 2008-10-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/462008/565820null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/How-Do-I/ArticleStandard/Article/detail/565827?contextCategoryId=535&ref=25 Are you stuck on which step to take next? 2008-09-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/462008/565827null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Method-Transfer-Problems/ArticleStandard/Article/detail/525660?contextCategoryId=535&ref=25 What do you do when the method can't be reproduced? 2008-06-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/262008/525660null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Ion-Pairing-mdash-Blessing-or-Curse/ArticleStandard/Article/detail/513715?contextCategoryId=535&ref=25 Ion-pair chromatography can be your best friend or your worst enemy. 2008-05-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/182008/513715null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Flow-Rate-Adjustment-and-System-Suitability/ArticleStandard/Article/detail/504707?contextCategoryId=535&ref=25 If the problem source cannot be found or if found, cannot be corrected, an adjustment in flow-rate is justified. 2008-04-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/132008/504707null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-7-The-Gradient-Shortcut/ArticleStandard/Article/detail/503021?contextCategoryId=535&ref=25 A very efficient way to start an isocratic method development project is to make the first run as a scouting gradient run. 2008-03-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/112008/503021null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-6-Make-It-Faster/ArticleStandard/Article/detail/490130?contextCategoryId=535&ref=25 Trade extra resolution for speed. 2008-02-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/062008/490130null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-5-Changing-Column-Selectiv/ArticleStandard/Article/detail/493124?contextCategoryId=535&ref=25 How to avoid an expensive shot in the dark. 2008-01-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/082008/493124null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-4-Controlling-Peak-Spacing/ArticleStandard/Article/detail/501993?contextCategoryId=535&ref=25 How do I get the most out of my efforts? 2007-12-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/112008/501993null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-3-Adjusting-Retention/ArticleStandard/Article/detail/473127?contextCategoryId=535&ref=25 Faster isn't always better. 2007-11-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/462007/473127null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-II-Where-to-Start/ArticleStandard/Article/detail/466844?contextCategoryId=535&ref=25 Getting started on the right foot is important for efficient method development. 2007-10-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/432007/466844null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Perfect-Method-Part-1-What-Is-Your-Goal/ArticleStandard/Article/detail/457018?contextCategoryId=535&ref=25 Different methods require different strategies. 2007-09-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/372007/457018null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/How-Does-Temperature-Affect-Selectivity/ArticleStandard/Article/detail/441439?contextCategoryId=535&ref=25 Column temperature plays an important role in controlling peak spacing (selectivity) in reversed-phase liquid chromatography (LC) separations. Temperature has long been known to affect retention time, and more recently, its use in adjusting selectivity has gained popularity (see reference 1 for a review of temperature selectivity). In preparation of a paper for the most recent Pittsburgh Conference, I had an opportunity to reexamine some data that compare temperature selectivity with other variables used to control selectivity in LC separation. This month's instalment of "LC Troubleshooting" examines temperature selectivity and its relationship to pH selectivity. 2007-07-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/282007/441439null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Variability-mdash-How-to-Control-It/ArticleStandard/Article/detail/434921?contextCategoryId=535&ref=25 The topic of this month's instalment of "LC Troubleshooting" was prompted by a manuscript I recently reviewed and a question I received from a reader of this column. Both inputs related to the variability of retention times observed in liquid chromatography (LC) methods. Variable retention is a topic that has been touched on many times over the history of this column, sometimes just in passing and other times in depth. Yet, it seems to be a problem that keeps recurring, so I think it is worth considering again. 2007-06-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/242007/434921null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Solvent-Conservation/ArticleStandard/Article/detail/429137?contextCategoryId=535&ref=25 ...it is important to acknowledge that environmental concerns can be more important than the economics of the reduction of solvent consumption. 2007-05-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/212007/429137null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/How-Little-Can-I-See/ArticleStandard/Article/detail/414750?contextCategoryId=535&ref=25 Detector selection for a method should be made on a case-by-case basis. 2007-04-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/132007/414750null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Questions-from-India/ArticleStandard/Article/detail/409535?contextCategoryId=535&ref=25 A reluctance to make any changes to a validated or compendial method is common, and often well founded. 2007-03-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/102007/409535null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Method-Reproducibility-mdash-A-Case-Study/ArticleStandard/Article/detail/402244?contextCategoryId=535&ref=25 Excess variability is not acceptable in a pharmaceutical method. 2007-02-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/062007/402244null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/On-Column-Sample-Degradation/ArticleStandard/Article/detail/397280?contextCategoryId=535&ref=25 This month's instalment of "LC Troubleshooting" presents two examples of sample degradation inside the liquid chromatography (LC) column. Depending upon the type of samples you analyse, sample degradation might or might not be a problem that you encounter regularly. However, most of us run a sufficiently wide variety of sample types over our careers that we will probably run into some samples that do not behave as expected. 2007-01-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/022007/397280null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Making-Connections/ArticleStandard/Article/detail/389576?contextCategoryId=535&ref=25 Sometimes it is easy to ignore the fittings and tubing that are used to connect various parts of the liquid chromatography (LC) system. After all, it's the pump, injector, column and detector that do all the work — right? Well, yes and no. It is possible to compromise an otherwise excellent separation by the improper use of fittings, but with reasonable care, you should not have problems with most applications. This month's instalment of "LC Troubleshooting" takes a look at the important components that are used to connect various parts of the LC system and how to use them wisely. 2006-12-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/492006/389576null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Whats-Happening-to-My-Column/ArticleStandard/Article/detail/382208?contextCategoryId=535&ref=25 This month's instalment of "LC Troubleshooting" focuses on two column-related problems reported by readers. The first deals with a column that takes several injections to "settle down" for each batch of samples. The second relates to short column life as a result of early fouling of the column. Although both of these problems are not encountered with most liquid chromatography (LC) methods, they both appear often enough that we all should be aware of them. It is only a matter of time before you meet one of these problem types with one of your methods. 2006-11-01T05:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/432006/382208null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Autosampler-Carryover/ArticleStandard/Article/detail/377221?contextCategoryId=535&ref=25 Because each sample is unique, you will need to check for carryover under the conditions of each method. 2006-10-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/402006/377221null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Gradient-Performance-Problems-mdash-A-Case-Study/ArticleStandard/Article/detail/371550?contextCategoryId=535&ref=25 The gradient linearity and step tests are two of the most useful performance tests that can be made for a liquid chromatography (LC) system. These check the linearity of gradient generation and the accuracy of mobile phase proportioning. These tests, and examples of problems detected as a result of these tests, have been the subject of at least seven "LC Troubleshooting" columns over the last 18 years.1–7 We strongly recommend that every LC system undergo these tests at least on an annual basis, and preferably semiannually. When a new and different example of a problem detected by these tests is discovered, it is hard to bypass the opportunity to share it with our readers. So this month, you get yet another example of how an LC system can fail. 2006-09-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/372006/371550null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Power-of-Mobile-Phase-Strength/ArticleStandard/Article/detail/357954?contextCategoryId=535&ref=25 After you have worked with liquid chromatography (LC) for several years, adjustment of the mobile phase to move peaks around comes almost as second nature. To the newcomer, however, such changes border on magic. One of the rules of thumb that I teach in my short courses is "nothing's magic". This is meant to remind us that chromatography is a very systematic process — study it carefully and you will minimize your surprises. In this month's instalment of "LC Troubleshooting," we'll look at solvent strength and see how we can use it to make predictable changes in the peak movement for reversed-phase LC separations. Hopefully, you will be able to make some practical use out of the principles presented here the next time you need to develop or adjust a method. 2006-07-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/282006/357954null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Dwell-Volume-Revisited/ArticleStandard/Article/detail/333244?contextCategoryId=535&ref=25 In terms of practical use of the results, resolution is generally more critical than retention. 2006-06-01T04:00:00Z http://www.lcgceurope.com/lcgceurope/data/articlestandard/lcgceurope/232006/333244null XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Its-Going-to-Break/ArticleStandard/Article/detail/323291?contextCategoryId=535&ref=25 Testing helps you identify the soft spots in the method, select the best conditions for operation and develop troubleshooting strategies to correct problems when they do occur. 2006-05-01T04:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Chromatography-Forum-151-Use-the-Braintrust/ArticleStandard/Article/detail/317229?contextCategoryId=535&ref=25 When a problem is not solved quickly, it is a good idea to go back to basics and determine if the equipment is functioning properly or not. 2006-04-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Check-Valve-Problems/ArticleStandard/Article/detail/311442?contextCategoryId=535&ref=25 Check valves can be replaced with new ones, but often a simple cleaning procedure is sufficient to restore normal operation. 2006-03-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Obtaining-More-Consistent-Results/ArticleStandard/Article/detail/303365?contextCategoryId=535&ref=25 A more practical parameter for system suitability would be to use the peak width for a reference peak... 2006-02-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Role-of-the-Signal-to-Noise-Ratio-in-Precision/ArticleStandard/Article/detail/284453?contextCategoryId=535&ref=25 Improvement of detection and quantification limits for LC methods is a result of taking advantage of all the tools you have at your disposal. 2006-01-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Extending-Column-Life/ArticleStandard/Article/detail/211486?contextCategoryId=535&ref=25 There are two types of contamination that will ruin a column — physical and chemical. 2005-12-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/LC-Troubleshooting-The-Basics/ArticleStandard/Article/detail/196694?contextCategoryId=535&ref=25 Once the visual problems have been eliminated as problem sources, you are left with problems related to system performance. 2005-11-01T05:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Broad-Peaks/ArticleStandard/Article/detail/183843?contextCategoryId=535&ref=25 A problem that is encountered occasionally in liquid chromatography (LC) separations is the presence of unusually broad peaks in the chromatogram. This problem is seen most often in isocratic separations, but it can occur with gradients as well. This month's instalment of "LC Troubleshooting" will cover some techniques to help determine the reason these wide peaks are seen. 2005-10-01T04:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Reader-Questions-Mobile-Phase/ArticleStandard/Article/detail/177449?contextCategoryId=535&ref=25 Sometimes the mobile phase conditions selected for reversed-phase and ion-pairing methods seem either arbitrary or mysterious. 2005-09-01T04:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Peak-Fronting-Column-Life-and-Column-Conditioning/ArticleStandard/Article/detail/165452?contextCategoryId=535&ref=25 In this month’s column, various problems related to column performance are addressed with suggestions on how to resolve them. 2005-07-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Peak-Fronting-Column-Life-and-Column-Conditioning/ArticleStandard/Article/detail/167307?contextCategoryId=535&ref=25 Although there are other possible causes, the most common source of fronting peaks is a disturbance in the column packing bed. The fix is straightforward: replace the column. 2005-07-01T04:00:00Z XML http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Overload-or-Minor-Peak/ArticleStandard/Article/detail/162386?contextCategoryId=535&ref=25 This month, John Dolan offers some suggestions for distinguishing between overload and the presence of a minor peak. 2005-06-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Bermuda-Triangle/ArticleStandard/Article/detail/159009?contextCategoryId=535&ref=25 This month, John Dolan turns his attention to the unexplained forces that seem to inhabit laboratories in spite of the most ardent troubleshooting efforts. 2005-05-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Split-Peaks-mdash-A-Case-Study/ArticleStandard/Article/detail/152909?contextCategoryId=535&ref=25 In this month’s column, John Dolan addresses a reader’s peak-splitting problem and suggests ways to avoid such occurrences in the future. 2005-04-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Extracolumn-Effects/ArticleStandard/Article/detail/149733?contextCategoryId=535&ref=25 John Dolan concentrates on the impact plumbing can have on column performance and offers his advice on tubing selection. 2005-03-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Stay-Away-from-the-Cliffs/ArticleStandard/Article/detail/147490?contextCategoryId=535&ref=25 This month, John Dolan underlines the importance of building safety factors into laboratory methods so that costly and frustrating problems that can arise during routine operation can be avoided. 2005-02-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Retention-Time-Changes/ArticleStandard/Article/detail/143655?contextCategoryId=535&ref=25 This month, John Dolan looks at how changes in retention time can help to identify the source of some LC problems and demonstrates what can be learned from observing how the retention varies. 2005-01-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/My-Favourite-Shortcuts/ArticleStandard/Article/detail/137274?contextCategoryId=535&ref=25 In this month's column, John Dolan reveals a number of simple and useful shortcuts or rules of thumb that he has acquired over the years that allow quick estimates to guide method development or help solve a problem. 2004-12-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Gradient-Performance-Checks/ArticleStandard/Article/detail/133033?contextCategoryId=535&ref=25 In this month's column the authors present a case study to outline several gradient quality checks that can be performed periodically to ensure proper performance of LC instrumentation. The example shows how by taking the time to perform such tests, potential problems can be identified before they reach a critical point. 2004-11-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Grandmas-Ham/ArticleStandard/Article/detail/128468?contextCategoryId=535&ref=25 Are you guilty of strange troubleshooting and maintenance habits that have been passed on to you from predecessors? John Dolan looks at some such practices, which were once acceptable, but don’t make sense in today’s lab. 2004-10-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Divide-and-Conquer/ArticleStandard/Article/detail/115209?contextCategoryId=535&ref=25 Column author, John Dolan, presents a simple but powerful isolation technique for identifying problems with LC methods and equipment. 2004-09-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/System-Suitability/ArticleStandard/Article/detail/98295?contextCategoryId=535&ref=25 In this month's column, John Dolan addresses some of the guidelines regarding system suitability tests and comments on their significance for those developing chromatographic methods. 2004-06-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Parallel-Chromatography-151-Double-Your-Money/ArticleStandard/Article/detail/94653?contextCategoryId=535&ref=25 In this month's instalment, the authors cover the topics of column-switching techniques and parallel chromatography for LC?MS?MS methods, and describe the time benefits that can be achieved using such systems. An example set-up is presented and the authors outline the various steps required to perform such analyses routinely. 2004-05-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Success-with-Evaporative-Light-Scattering-Detectio/ArticleStandard/Article/detail/92335?contextCategoryId=535&ref=25 Following on from a previous instalment, this month's column assesses evaporative light-scattering detection as a complementary detection mode and builds upon the previous discussion in terms of detector applications. 2004-04-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Selecting-the-Best-Curve-Fit/ArticleStandard/Article/detail/88258?contextCategoryId=535&ref=25 In this month's column, the authors present a relatively simple method for selecting the appropriate curve-fitting function and thus ensure that the requirements of current guidelines can be met. 2004-03-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Broad-Peaks/ArticleStandard/Article/detail/84887?contextCategoryId=535&ref=25 Peaks that are too broad can mean that analysts are not using their LC columns very efficiently. In this month's column, John Dolan describes how to determine if peaks are broader than they should be and highlights some of the common system-related causes of peak broadening. 2004-02-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Understanding-Split-Peaks/ArticleStandard/Article/detail/82562?contextCategoryId=535&ref=25 This month's column examines several possible causes of peak splitting and presents some guidelines for isolating the problem source. 2004-01-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Extracolumn-Effects/ArticleStandard/Article/detail/75774?contextCategoryId=535&ref=25 This month, the authors try to determine whether a problem, originally attributed to extracolumn effects, was also the result of other contributing factors. 2003-11-28T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/How-Much-is-Enough/ArticleStandard/Article/detail/74305?contextCategoryId=535&ref=25 John Dolan answers questions about two LC practices: column regeneration after a reversed-phase gradient has been run, and which degassing technique is best. 2003-10-31T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Why-Do-Peaks-Tail/ArticleStandard/Article/detail/69793?contextCategoryId=535&ref=25 Truly symmetrical peaks are rare? 2003-09-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Now-Whats-Going-On/ArticleStandard/Article/detail/61436?contextCategoryId=535&ref=25 Column editor John Dolan answers questions posed by readers pertaining to negative peaks, column pressure . . . 2003-07-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Not-Another-Leak/ArticleStandard/Article/detail/58428?contextCategoryId=535&ref=25 John Dolan discusses LC system leaks, what information they provide and how to best avoid them. 2003-06-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Flow-Rate-and-Peak-Spacing/ArticleStandard/Article/detail/55592?contextCategoryId=535&ref=25 Column editor John Dolan examines the rights and wrongs of changing flow-rate as a means to . . . 2003-05-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/LC-Columns-151-Top-10-List/ArticleStandard/Article/detail/52466?contextCategoryId=535&ref=25 In this month's column, John Dolan lists his top-10 tips for improving column life in liquid chromatography. Hints on in-line filters, guard columns, temperature control and column retirement are all included. 2003-04-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Success-with-Evaporative-Light-Scattering-Detectio/ArticleStandard/Article/detail/47198?contextCategoryId=535&ref=25 In this month's column, tips and techniques are provided for optimizing evaporative light-scattering detection and practical aspects of the technique given for those considering its use in their laboratories. Advantages and limitations of ELSD are discussed, and common misconceptions about the technique addressed. 2003-03-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Mobile-Phase-Buffers-Part-III-151-Preparation-of-B/ArticleStandard/Article/detail/45009?contextCategoryId=535&ref=25 In the final instalment of this series, the concepts and limitations discussed in Parts I and II are used to propose strategies for buffer preparation. In addition, guidelines for reporting buffer procedures are suggested. 2003-02-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Mobile-Phase-Buffers-Part-II-151-Buffer-Selection-/ArticleStandard/Article/detail/41697?contextCategoryId=535&ref=25 In the second part of this series, the selection of buffers for use in partially aqueous mobile phases is discussed. 2003-01-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Mobile-Phase-Buffers-Part-I-151-The-Interpretation/ArticleStandard/Article/detail/39692?contextCategoryId=535&ref=25 In the first part of this series the significance of pH in partially aqueous mobile phases is discussed as a means of understanding buffer behaviour. 2002-12-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Hazards-of-Adjusting-Gradients/ArticleStandard/Article/detail/36582?contextCategoryId=535&ref=25 In this month's column, John Dolan examines how simple changes to gradients can yield unexpected results and consequently stresses the importance of tracking the influence of each parameter. 2002-11-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Performance-Qualification-of-LC-Systems/ArticleStandard/Article/detail/32967?contextCategoryId=535&ref=25 This month's column discusses a performance qualification test that can be applied to most, if not all, LC systems. A series of simple checks are described to ensure that risk of data loss from non-conformance is minimized. 2002-10-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Resolving-Minor-Peaks/ArticleStandard/Article/detail/30187?contextCategoryId=535&ref=25 Is a small peak hiding under that tail? 2002-09-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Importance-of-Temperature/ArticleStandard/Article/detail/23766?contextCategoryId=535&ref=25 In this month's column, John Dolan examines the role of temperature as an important variable to control in LC separations and describes how it can be used to improve chromatographic performance. 2002-07-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Peak-Tailing-and-Resolution/ArticleStandard/Article/detail/19199?contextCategoryId=535&ref=25 Column editor John Dolan describes how resolution can be affected significantly by peak size and shape... 2002-05-17T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Quiet-Please/ArticleStandard/Article/detail/19099?contextCategoryId=535&ref=25 This month's column looks at some chemical, physical and electronic sources of baseline noise and suggests how to reduce or eliminate them. 2002-05-16T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Stability-Indicating-Assays/ArticleStandard/Article/detail/17642?contextCategoryId=535&ref=25 Dolan explains what these assays are all about, and demonstrates that developing them requires consideration of three important aspects... 2002-05-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/The-Future-of-LC-Troubleshooting-151-10-Years-Late/ArticleStandard/Article/detail/17296?contextCategoryId=535&ref=25 In this month's column, John Dolan revisits 10-year old predictions, reflects on some of the changes and makes some more predictions for the next decade. 2002-04-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Ion-Suppression-in-LC150MS150MS-151-A-Case-Study/ArticleStandard/Article/detail/9103?contextCategoryId=535&ref=25 This month's column examines a case in which ion suppression compromised method performance in LC-tandem MS and shows how the strategy for eliminating ion suppression differs little from addressing other chromatographic interferences. 2002-02-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/From-the-e-Mail-Bag/ArticleStandard/Article/detail/18158?contextCategoryId=535&ref=25 Dolan tackles a selection of readers' questions and offers advice on solving problems related to columns and methods... 2002-01-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Retaining-Polar-Compounds/ArticleStandard/Article/detail/18145?contextCategoryId=535&ref=25 Dolan examines techniques that can be used to increase retention of polar compounds and provides his recommendations in order of preference... 2001-12-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Attacking-Carryover-Problems/ArticleStandard/Article/detail/18135?contextCategoryId=535&ref=25 This column provides guidelines for a systematic approach to solving carryover problems. The method described helps to locate and correct problems much more quickly in the future... 2001-11-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/When-Ideal-Isnt-Practical/ArticleStandard/Article/detail/18125?contextCategoryId=535&ref=25 Dolan and guest author Harrington look at situations that arise with hyphenations of LC with MS, when analysis speed is a major concern... 2001-10-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Communicating-with-the-Baseline/ArticleStandard/Article/detail/18114?contextCategoryId=535&ref=25 Dolan describes how looking at a magnified baseline can help diagnose problems. Several examples will demonstrate the information that can be obtained about the source of baseline disturbances... 2001-09-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Buffers-and-Baselines/ArticleStandard/Article/detail/18106?contextCategoryId=535&ref=25 How do common LC buffers affect the baseline characteristics of your chromatograms? This column lets you know and discusses means of minimizing drift... 2001-07-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Autosamplers-Part-II-151-Problems-and-Solutions/ArticleStandard/Article/detail/18099?contextCategoryId=535&ref=25 In the second part of this series, the author considers some of the common problems associated with autosamplers... 2001-06-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Autosamplers-Part-I-151-Design-Features/ArticleStandard/Article/detail/18089?contextCategoryId=535&ref=25 Column editor, John Dolan, looks at three common autosampler designs and evaluates their functions and features... 2001-05-01T04:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Reproducibility-and-Carryover-A-Case-Study/ArticleStandard/Article/detail/7663?contextCategoryId=535&ref=25 Reproducibility and carryover problems encountered during the development of methods for verifying analysts' proficiency are discussed... 2001-04-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Autosampler-Carryover/ArticleStandard/Article/detail/7657?contextCategoryId=535&ref=25 Where did that peak come from? No sample was injected! 2001-03-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Unexpected-Peaks/ArticleStandard/Article/detail/7465?contextCategoryId=535&ref=25 Dolan concentrates on problems arising from late-eluting peaks, and provides answers for overcoming them. 2001-02-01T05:00:00Z PDF http://www.lcgceurope.com/lcgceurope/Column%3A+LC+Troubleshooting/Reducing-Column-Diameter-in-Gradient-Elution---A-C/ArticleStandard/Article/detail/7351?contextCategoryId=535&ref=25 Dolan answers a reader's question on adjusting a gradient elution LC method... 2001-01-01T05:00:00Z PDF