4

The primary reference for this type of data is the article by Li [1]. Snyder cites this paper as the primary source for UV cutoff values ("Ref 7" on the screenshot below) [2, p. 299]: References Li, J. B. Signal-to-Noise Optimization in HPLC UV Detection. LC GC 1992, 10 (11), 856–864. Snyder, L. R.; Kirkland, J. J.; Glajch, J. L. Practical HPLC ...


4

I will add one thing that may be the reason behind why (C) is an acceptable answer choice. Yes, both $\ce{PbS}$ and $\ce{PbSO_4}$ are insoluble. However, if you look at the $\ce{K_{sp}}$ for both compounds, $\ce{PbS}$ is about $\pu{3.2 x10^-28}$ while the $\ce{K_{sp}}$ for $\ce{PbSO_4}$ is $\pu{1.3 x 10^-8}$. When you have a mixture of ions, the resulting ...


3

The test for Chloride ion is silver nitrite in an Acidified solution [with nitric acid]. This removes carbonate (as carbonic acid), cyanide[careful] and sulfide (as hydrogen sulfide). Sulfate must be absent, if present it can be removed with barium nitrate (as barium sulfate). The silver chloride formed is solubilized by addition of ammonia; insoluble ...


3

Please don't apply the reversible CV diagram on something which is clearly a non-classical cyclic voltammogram. When you experimentally don't get the shape as predicted by the theory, it means it that particular theoretical model does not apply in your case. Look at three different types of voltammograms in this picture. Does your CV look like a reversible ...


2

Home science optical absorption test for approximate caffeine quantity in coffee? Yes..., except that for "...in coffee?" it's No. AAI Solutions' Measuring Caffeine Concentration; Applied Analytics Application Note No. AN-019 front artwork certainly looks hopeful... (click for larger) After all an Optical Multichannel Analyzer (OMA) in this case,...


2

Third edition (latest offline edition) of the ACS Style Guide (currently known as The ACS Guide to Scholarly Communication) has a section devoted to reporting analytical data, including mass-spectrometry and EIMS in particular [1, p. 275]: Mass Spectrometry MS $m/z$ (relative intensity): $238.2058~(44.8\%),$ $195.1487~(100\%),$ $153.1034 ~(21.2\%).$ GC–MS $...


2

Wow. This is a very bad question (the exam/assignment, not the OP's). There is no way that you can categorically determine the structure of this based only on the information given. This would have to be open-book providing access to chemical shift tables in the very least. Peaks are poorly labelled and what's more, I believe the molecular mass is incorrect. ...


2

Interesting Problem and quite a nailbiter. I will try to sort some of my ideas, even thought this won't be a full answer. This looks like a question from an exam. Did you have any reactions during study with hydrochloric acid and propanoyl chloride (acid chloride of propionic acid). So maybe look into different reactions of acid chlorides. As @...


1

[ This is a short answer, as a complete answer would require going through multiple references and books on the topic. ] First of all, the ESI process does not require the pH to be acidic : positive ESI is routinely done in ammonium acetate or ammonium bicarbonate media, which have a pH of 7.4 or 8.1. But indeed, to produce protonated analytes it indeed ...


1

I offer the following explanation for the fragments of the mass spectrum of methyl salicylate (1, m/z 152). Loss of methoxy radical affords acylium ion 2 (m/z 121). Subsequent loss of a proton from 2 gives rise to the base peak 6-oxomethylidenecyclohexa-2,4-dien-1-one (3). Loss of carbon monoxide from 3 produces carbene 4, which rearranges to cyclopenta-2,4-...


1

The short answer: Do not rely on the SIM trace alone. Amplify the representation of the trace about the TIC (total ion current) until you see a reasonable peak intensity at the same retention time as in your SIM traces (perhaps a time spectrum, but not a mass spectrum). Then integrate with the peak-shaped cursor (currently shown in the magenta coloured ...


1

My interpretation of the first spectrum: I would say that the 3517 band belongs to OH group. This is a typical shape OH group. Amines look more like two bands with a shoulder. However secondary amine is also a possibility. Other bands of OH should be the broad band between 1400 and 1300 from which the sharp bands arise. Than probably 1166, which seems to be ...


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