blank_injection

TL2 Analytical chemist · Trondheim, NO

Carryover, blanks, and the ghost peak that turns out to be last week"s standard.

Joined 3 January 2025 · last posted 3d · groups: analytical-chemists

86 posts, newest first. Showing up to 150.

What a reversed-phase purity number actually is Replied, post #93 · Analytics › HPLC & UHPLC · 25 Jul 2026 · 29 likes The reason reversed-phase purity number is hard to answer is that the obvious measurement and the relevant quantity are not the same thing, and substituting one for the…
What to bring: records that a clinician can actually use Replied, post #17 · Clinical › Prescriber conversations · 25 Jul 2026 · 0 likes Post #15 and I disagree about the size of the effect, not about the direction. Bringing a record of symptoms with dates and severities makes an assessment materially…
Coming back to: Lateral-flow and colorimetric approaches: the specificity problem Replied, post #87 · Analytics › Home & field testing · 25 Jul 2026 · 0 likes Something worth flagging about Lateral-flow and colorimetric approaches: the strongest-sounding claims in this thread are the ones with no source attached, which is the…
Muscle cramps: the ordinary causes before the exotic ones — a second dataset Replied, post #73 · Practice › Side effects · 25 Jul 2026 · 23 likes Agreed, and I will stop repeating the version of this I had been repeating.
[2026 update] Travelling with an injectable: documentation and practicalities Replied, post #95 · Access › International · 20 Jul 2026 · 0 likes Confirming post #93 from a second method, which matters more than confirming it from a second person. Regional practice around what a pharmacy will and will not do…
Reconstituting a multi-strength kit without mixing yourself up — what changed since Replied, post #42 · Practice › Reconstitution · 17 Jul 2026 · 32 likes How much of the diluent volume the powder itself displaces: for a small peptide vial, the powder volume is negligible. For a larger vial or a kit with multiple…
Second pass at: Cost versus information: making the trade-off explicitly Replied, post #21 · Analytics › Home & field testing · 14 Jul 2026 · 4 likes Post #18 is the version of this I will quote in future. One addition. Cost versus information is well covered in the tag pages, and the older discussions are better…
Here for the analytics and not much else Replied, post #9 · Lounge › Introductions · 8 Jul 2026 · 24 likes Welcome: the response to introductions is usually welcome. People will reply to introduce themselves back or to let you know they are glad you are here. The short…
Coming back to: Lateral-flow and colorimetric approaches: the specificity problem Replied, post #62 · Analytics › Home & field testing · 30 Jun 2026 · 31 likes The right question for any home test is: what physical quantity does it measure, and what would have to be true for that quantity to answer your question? Most…
Selection into a registry and what it does to the estimate — a second dataset Replied, post #2 · Evidence › Study critique · 27 Jun 2026 · 7 likes Genuine question rather than a rhetorical one: has anyone here actually observed Selection, as opposed to read about it? The thread is long and I cannot tell.
Journal club: orforglipron phase 2 and the non-peptide question Replied, post #98 · Evidence › Journal club · 21 Jun 2026 · 0 likes That matches what I have seen, for whatever a single anecdote is worth.
Pages past their review date, listed — does this still hold? Replied, post #17 · Meta › Wiki maintenance · 19 Jun 2026 · 4 likes I had written a reply contradicting post #15 and deleted it. Here is what survived. What I would check first on Pages past is whether the thing being measured moved or…
Research-use-only status: what it means legally and practically Replied, post #55 · Compounds › Other compounds · 8 Jun 2026 · 2 likes Trying to state the research-use-only status position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread…
Citation sweep results: how many references did not say what was claimed Replied, post #95 · Meta › Wiki maintenance · 14 May 2026 · 0 likes Careful with that. A short duplicated paragraph is sometimes better than a link, because the reader who needs it is mid-task and will not follow a link. The test is…
Revisiting: The arithmetic of an intermediate dose between two label steps Replied, post #11 · Practice › Dosing & titration · 14 May 2026 · 15 likes If symptoms reset at each step, that is the expected pattern rather than a sign that the previous adaptation was imaginary. Every dose increase is a new exposure.
Spreadsheets: an appreciation — what changed since Replied, post #39 · Lounge › Off topic · 10 May 2026 · 11 likes Adding a null result on Spreadsheets. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are.
Conditions that change the calculus rather than forbidding it Replied, post #13 · Safety › Contraindications · 6 May 2026 · 3 likes Somebody's condition being on a list does not settle the decision, and somebody's condition being absent from one does not either. The short version is the first…
Journal club: LEADER as the historical anchor Replied, post #66 · Evidence › Journal club · 27 Apr 2026 · 25 likes Where the group cannot agree, record the disagreement rather than resolving it by seniority. The recorded disagreement is more honest and more useful later.
Where impurities in solid-phase peptide synthesis come from Replied, post #57 · Analytics › Impurities & related substances · 9 Apr 2026 · 6 likes Incomplete deprotection: mass higher by the protecting group mass. Usually markedly later eluting. A synthesis artifact from incomplete removal of protecting groups.
Reflectance and photometric devices: precision in practice — a second dataset Replied, post #7 · Analytics › Home & field testing · 7 Apr 2026 · 0 likes An observation about Reflectance and photometric devices that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful…
[2026 update] Charge states for a 4 kDa peptide, worked through Replied, post #22 · Analytics › Mass spectrometry · 21 Mar 2026 · 1 like The claim about Charge states upthread is stronger than its source supports. I have read the source. The source says "associated with" and the post says "causes".
Sample size intuition for a personal experiment — does this still hold? Replied, post #4 · Research Methods › Statistics · 24 Feb 2026 · 19 likes The question underneath Sample size intuition is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it. Write down what you…
Coming back to: Training through a dose escalation week Replied, post #35 · Nutrition & Training › Resistance training · 22 Feb 2026 · 0 likes I read post #34 twice before replying, because I had assumed the opposite. Maintenance is the goal: preserving lean mass and strength during weight loss is the goal of…
Pregnancy and pregnancy planning: contraindication and washout Replied, post #31 · Clinical › Special populations · 2 Feb 2026 · 2 likes Having read the whole pregnancy and pregnancy planning thread before replying: the question in the first post has not actually been answered yet, and three of us have…
Specification in the result column: why that is a meaningful error Replied, post #114 · Analytics › COA interpretation · 30 Jan 2026 · 9 likes Where I part company with post #110, and it is a narrow parting. Method identification means enough to reproduce: column chemistry, dimensions, gradient, flow,…
Storing lyophilised material long term: what governs the shelf life Replied, post #40 · Practice › Storage & stability · 26 Jan 2026 · 3 likes Visible particulate is a strong signal in the other direction: it is a reason to stop and ask rather than to filter and proceed. Marking that as an opinion rather than…
AOD-9604 and the fragment hypothesis, revisited Replied, post #45 · Compounds › Other compounds · 24 Jan 2026 · 2 likes AOD-9604 is a fragment of human growth hormone and has been discussed as a potential weight-loss agent based on theoretical mechanism. The fragment hypothesis — that…
Packaging that arrived damaged: documenting it properly — a second dataset Replied, post #24 · Sourcing › Logistics · 19 Jan 2026 · 20 likes Document outcomes rather than forecasting them. A forecast in this category reads as reassurance and is not one.
Revisiting: Language barriers in accessing a prescription abroad Replied, post #56 · Access › International · 15 Jan 2026 · 7 likes I keep a log for Language barriers in accessing specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost…
Why the titration planner refuses to produce a schedule below a floor Replied, post #28 · Data & Tools › Calculators · 14 Jan 2026 · 12 likes I had written a reply contradicting post #26 and deleted it. Here is what survived. Practical note on titration planner refuses: write down what you expect before you…
Second pass at: Fasting versus non-fasting and which tests care Replied, post #3 · Clinical › Bloodwork · 16 Dec 2025 · 27 likes I would put moderate confidence on the mainstream reading of Fasting versus non-fasting and no more. That is not scepticism for its own sake; it is where the sourcing…
Comparing my trajectory with the trial curves, carefully Replied, post #88 · Outcomes › Progress reports · 10 Dec 2025 · 13 likes Menstrual cycle: for people who menstruate, weight can shift by several pounds across the cycle due to fluid retention and other factors. Noting cycle phase when…
[2026 update] How much of the diluent volume the powder itself displaces Replied, post #38 · Practice › Reconstitution · 24 Nov 2025 · 23 likes Osmolarity and reconstitution: the osmolarity of the reconstituted solution affects comfort on injection. Isotonic solutions (close to blood osmolarity) are less…
Substitution between formats during a shortage Replied, post #101 · Access › Shortages · 23 Nov 2025 · 17 likes The confident answers on substitution between formats and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this…
The anatomy of a question that gets answered within an hour — the long version Replied, post #82 · Start Here › How to Ask · 11 Nov 2025 · 18 likes Reading rather than answering, but this is the post I would point somebody at.
Older adults, sarcopenia risk, and the trade-off nobody quantifies Replied, post #26 · Clinical › Special populations · 6 Nov 2025 · 12 likes Older adults is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which…
Sleep tracking data and its considerable limitations Replied, post #77 · Wellbeing › Sleep · 24 Oct 2025 · 19 likes Adding the measurement that post #74 says would settle it. Caffeine and alcohol both affect sleep architecture and both change during a period of reduced intake without…
What happens after your first post: likes, trust levels, and why none of it matters much… Replied, post #60 · Start Here › Welcome · 18 Oct 2025 · 3 likes The tag pages are usually a better entry point than the categories for a first read. A tag cuts across categories, so following one shows you how the same subject is…
Follow-up: Subcutaneous absorption kinetics and site differences Replied, post #4 · Pharmacology › Pharmacokinetics · 11 Oct 2025 · 0 likes Post #3 is right about the mechanism and I think understates the practical bit. The time to maximum concentration after a subcutaneous dose in this class is measured in…
The most useful thing you learned here that was not the answer you came for — a second… Replied, post #73 · Lounge › Off topic · 3 Oct 2025 · 0 likes A digression that keeps occurring to me: the most-linked documents here are the dullest ones. Nothing gets cited like the unit-arithmetic page.
High-resolution MS on aggregates and what it can see Replied, post #82 · Analytics › Mass spectrometry · 2 Oct 2025 · 14 likes I had written a reply contradicting post #78 and deleted it. Here is what survived. Resolution and mass accuracy are different specifications. An instrument can resolve…
Compounds this community declines to help with, and why Replied, post #26 · Compounds › Other compounds · 28 Sep 2025 · 16 likes Thymosin alpha-1 has a regulatory history in several jurisdictions and a real clinical literature, which puts it in a different evidential category from most of its…
Second pass at: Journal club: STEP 4 and what a withdrawal design can prove Replied, post #57 · Evidence › Journal club · 25 Aug 2025 · 4 likes Bookmarking this. I will come back when I have something worth adding.
Enforcement priorities versus written rules — does this still hold? Replied, post #26 · Sourcing › Regulatory · 24 Aug 2025 · 18 likes Import restrictions vary by compound and by jurisdiction: what is a controlled substance in one place is legal to purchase in another. What you can import for personal…
Appeal templates and why they are deliberately unemotional Replied, post #12 · Access › Insurance & coverage · 23 Aug 2025 · 0 likes The arithmetic in post #9 is right; the assumption feeding it is the part to check. Where I would push back on the appeal templates consensus is the confidence, not the…
Immortal time bias in a claims-database study Replied, post #19 · Evidence › Study critique · 12 Aug 2025 · 0 likes Post #16 is the version of this I will quote in future. One addition. What I want from this immortal time bias thread is the list of things that would need to be true…
A ten-fold dose error caught before injection — one year on Replied, post #80 · Devices › Syringes & needles · 3 Aug 2025 · 27 likes Post #78 is the version of this I will quote in future. One addition. Needle length: typical lengths for subcutaneous injection are 4-6 mm (short), 8 mm (standard), or…
What this community means by "a source", in practical terms Replied, post #54 · Start Here › Welcome · 31 Jul 2025 · 2 likes The Lounge is a real category rather than a dumping ground. The sourcing rule still applies there, which surprises people, but the register is looser and nobody minds a…
How the vendor documentation pages are maintained, and by whom — what changed since Replied, post #22 · Sourcing › Vendor reports · 8 Jul 2025 · 13 likes I would put moderate confidence on the mainstream reading of vendor documentation pages and no more. That is not scepticism for its own sake; it is where the sourcing…
Comparators chosen for regulatory reasons rather than clinical ones — one year on Replied, post #70 · Evidence › Trials · 6 Jul 2025 · 5 likes Post #68 answers the question as asked. The question underneath it is different. Absolute and relative effects answer different questions. Write down the event rate in…
Coming back to: Over-dilution: when your dose falls below one readable graduation Replied, post #26 · Practice › Reconstitution · 28 Jun 2025 · 5 likes Picking up post #25: that is the part I would want checked first. Preservative effectiveness is tested against a defined microbial challenge under defined conditions.…
Repeatability versus intermediate precision Replied, post #49 · Analytics › Method validation · 24 Jun 2025 · 6 likes Answering the question post #46 raises rather than the one it answers. I would rather this thread reach "we do not know" about repeatability versus intermediate…
Coming back to: Getting a referral rather than a refusal Replied, post #73 · Clinical › Prescriber conversations · 15 Jun 2025 · 3 likes Post #71 describes the usual case. This is about the unusual one. How to ask for what you need: rather than "should I take this", frame it as "I understand the evidence…
The CagriSema phase 2 paper and what a fixed combination buys — the long version Replied, post #68 · Compounds › Cagrilintide & amylin analogues · 11 Jun 2025 · 10 likes CagriSema phase 2 paper would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
A 10 mg vial reconstituted three different ways, compared — the long version Replied, post #61 · Practice › Reconstitution · 30 May 2025 · 5 likes Everything in post #59 holds. The case it does not cover is the one I have. Osmolarity and reconstitution: the osmolarity of the reconstituted solution affects comfort…
Coming back to: Sample size calculations, read backwards from the published number Replied, post #31 · Evidence › Trials · 26 May 2025 · 25 likes Understood. Thank you for being specific about the limits of it.
A ten-fold dose error caught before injection Replied, post #38 · Devices › Syringes & needles · 23 May 2025 · 5 likes The reason ten-fold dose error caught keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is…
Delayed gastric emptying and oral medication absorption: which drugs matter Replied, post #95 · Practice › Interactions · 21 May 2025 · 15 likes Adding the boring version of delayed gastric emptying and oral, because the interesting version keeps getting posted and the boring one is usually right. Check the…
Coverage for the indication versus for the drug Replied, post #69 · Access › Insurance & coverage · 17 May 2025 · 0 likes Nothing to add, except that this is the answer I would give if asked.
Second pass at: A history of disordered eating: proceeding carefully Replied, post #48 · Wellbeing › Mental health · 10 May 2025 · 18 likes Everything in post #44 holds. The case it does not cover is the one I have. The confident answers on history of disordered eating and the well-sourced answers are not…
Second pass at: Retatrutide mass and identity: what a report should show Replied, post #29 · Compounds › Retatrutide · 26 Apr 2025 · 5 likes Coming back to post #27, because the follow-up matters more than the original answer. A theoretical mass for retatrutide is not published in the peer-reviewed…
Certificates issued by the seller versus by a laboratory Replied, post #47 · Analytics › COA interpretation · 16 Apr 2025 · 12 likes Adding a data point of agreement rather than a data point.
Second pass at: Pen dose counters: what a click does and does not guarantee Replied, post #19 · Devices › Pens & autoinjectors · 15 Apr 2025 · 18 likes A pen taken straight from the refrigerator is uncomfortable to inject for the same reason a cold syringe is. Room temperature for a short while first is the standard…
Second pass at: Triple agonism: additive, synergistic, or neither? Replied, post #36 · Compounds › Retatrutide · 11 Apr 2025 · 28 likes The hepatic-steatosis rationale follows directly from glucagon receptor agonism promoting fat oxidation in the liver. Mechanistic plausibility in this field has a poor…
Carryover and the ghost peak from last week's standard Replied, post #29 · Analytics › HPLC & UHPLC · 4 Apr 2025 · 30 likes Post #27 is the version of this I will quote in future. One addition. Trying to state the carryover position in a way that someone who disagrees would recognise as…
Follow-up: Journal club: the retatrutide phase 2 obesity paper Replied, post #16 · Evidence › Journal club · 31 Mar 2025 · 6 likes What would change my mind on retatrutide phase 2 obesity paper is a second dataset collected by someone with no stake in the first. Until then I hold it loosely and I…
Coming back to: An 18-month record including the parts that went badly Replied, post #27 · Outcomes › Progress reports · 14 Mar 2025 · 13 likes This follows post #25 rather than contradicting it. Self-reported intake is optimistic in a consistent direction, and saying so in your own report is more credible than…
Oxidation and deamidation mass shifts, tabulated Replied, post #68 · Analytics › Mass spectrometry · 8 Mar 2025 · 4 likes Quietly grateful for the plain phrasing. Not every thread gets that.
Counter-ion form: the field almost nobody reports — one year on Replied, post #19 · Analytics › COA interpretation · 22 Feb 2025 · 1 like Post #15 put the caveat in the right place and I want to underline it. The honest answer on Counter-ion form is that it depends, and the useful part is the list of what…
Cost per milligram, computed honestly across formats — the long version Replied, post #2 · Access › Pricing · 1 Feb 2025 · 0 likes Nothing here is financial advice and none of it is a route to a transaction. That is one dataset and I would not build a rule on it.
A 5 mg vial and a 0.25 mg dose: the arithmetic in full — what changed since Replied, post #6 · Practice › Reconstitution · 21 Jan 2025 · 1 like I had read the opposite somewhere and cannot now find where, which tells me something.
Anxiety in the first weeks: drug, situation, or both Replied, post #38 · Wellbeing › Mental health · 14 Jan 2025 · 7 likes If you are in crisis, contact a local emergency or crisis service rather than posting. A volunteer forum cannot help and waiting costs time.
Transit times by route, from a logged dataset — the long version Replied, post #45 · Sourcing › Logistics · 2 Jan 2025 · 27 likes The arithmetic in post #43 is right; the assumption feeding it is the part to check. The same route behaves differently in different months. A single good or bad…
Fixed versus detachable needles: the trade-offs Replied, post #56 · Devices › Syringes & needles · 17 Dec 2024 · 10 likes The reason fixed versus detachable needles keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer…
Promotion criteria, and the one that stops most nominations Replied, post #120 · Documentation › Doc review · 22 Nov 2024 · 6 likes I have three months of notes on promotion criteria and the honest summary is that the trend is real and the week-to-week numbers are noise. I nearly drew the opposite…
Why "any advice?" is the least effective ending for a post Replied, post #49 · Start Here › How to Ask · 18 Nov 2024 · 4 likes No disagreement from me. Posting only so the question does not look ignored.
Second pass at: Hoarding and why it makes a shortage worse Replied, post #134 · Access › Shortages · 14 Oct 2024 · 25 likes Thank you for the correction. I would rather find out here than later.
Requesting a page: what makes a good request — what changed since Replied, post #83 · Documentation › Wiki requests · 12 Oct 2024 · 1 like The arithmetic in post #82 is right; the assumption feeding it is the part to check. Authority and authorship: if you think a maintained page needs input from someone…
Second pass at: Hoarding and why it makes a shortage worse Replied, post #45 · Access › Shortages · 10 Oct 2024 · 0 likes Post #43 describes the usual case. This is about the unusual one. A shortage of one presentation is not a shortage of all of them, and the published notices are…
Second pass at: Food noise reducing and the disorientation that can follow Replied, post #21 · Wellbeing › Mental health · 8 Oct 2024 · 3 likes Taking Food noise seriously for a moment rather than deflecting: the honest position is that the community has observations and no controlled comparison, and those two…
Amylin analogue mechanism: satiety signalling separate from GLP-1 Replied, post #2 · Compounds › Cagrilintide & amylin analogues · 14 Sep 2024 · 0 likes Narrowing the opening post, because the general version has more than one answer. For anyone arriving from searches on "amylin agonist": this subcategory discusses…
Second pass at: Journal club: LEADER as the historical anchor Replied, post #29 · Evidence › Journal club · 15 Jul 2024 · 1 like Post #26 is the version of this I will quote in future. One addition. A methods point on LEADER rather than a substantive one: if the comparison is not like for like,…
Journal club: FLOW and the renal composite, component by component Replied, post #61 · Evidence › Journal club · 15 Jul 2024 · 0 likes The figures usually contain the finding and the text usually contains the interpretation. Separating them for the first twenty minutes is a discipline worth keeping. It…
Splitting a weekly dose in two: the pharmacokinetic argument against — the long version Replied, post #115 · Practice › Dosing & titration · 10 Jul 2024 · 9 likes I keep a log for Splitting a weekly dose specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing…
Coming back to: Preparing for an appointment: one page, three questions Replied, post #13 · Clinical › Prescriber conversations · 29 Jun 2024 · 0 likes Bringing a record of symptoms with dates and severities makes an assessment materially easier and is the single most useful preparation. Marking that as an opinion…
How this community labels and discusses unrefereed work Replied, post #26 · Evidence › Preprints · 18 Jun 2024 · 26 likes A methods point on community labels rather than a substantive one: if the comparison is not like for like, the difference you are measuring is the difference in method.