Questions tagged [analytical-chemistry]

The branch of chemistry concerned with identifying and quantifying the chemical constituents of matter.

Filter by
Sorted by
Tagged with
-1
votes
0answers
17 views

Making a solution of 3.2M NH4OAc in HNO3

I'm working on a method for analyzing metal concentrations in soil samples. I'm going to use a sequential extraction process to find the proportion of easily exchangeable metals, those bound to ...
-2
votes
0answers
16 views

Fragmentation Pathway for 4'-Aminoacetophenone in Mass Spec

I was wondering if anyone would be able to help me draw the fragmentation pathway for this disubstituted benzene, I have never really encountered fragmentation in anything but very simple molecules ...
-1
votes
0answers
10 views

What does one mean by “Contact Interaction” in EPR (hyperfine splitting)? An intuitive picture would be helpful

While studying hyperfine interactions in EPR, I came across a term contact interaction, which roughly means interaction between nuclear and electronic spin angular moment. I don't know what does it ...
1
vote
1answer
12 views

Methods to quantify lead(II) concentration in water on the ppm/ppb level

While there are several ways to quantify metal concentrations in water, a lot of them are only specific to select metals. For example, there is the orthophenanthroline method for quantification of Fe(...
2
votes
1answer
18 views

Can o-phenanthroline be used as a complexing agent for lead(II)?

I’ve been trying to find a method to perform a spectrophotometric analysis to determine lead concentration (on the ppm level). This would require some chelator capable of forming a coloured complex ...
2
votes
2answers
48 views

Chemicals that form coloured complexes with Pb2+

I’m currently conducting a photo-spectrometric analysis of lead concentration in water and was looking into using Eriochrome Black t as an indicator for Pb2+ (due to the complex forming a reddish ...
0
votes
1answer
24 views

Should I relate the number of moles between substances when converting weight units?

Good day! I graduated from an undergrad degree of chemistry almost 3 years ago but I'm frustrated that I fail to reconcile these things: In gravimetric analysis, to get the correct amount for the ...
-2
votes
0answers
11 views

25,0 ml HNO3 with titration 0,006128 g/ml + 0,25 ml 0.1105H. NaOH. pH-? [closed]

25,0 ml HNO3 with titration 0,006128 g/ml + 0,25 ml 0.1105H. NaOH. Find pH
1
vote
2answers
43 views

Concentration of gas above aqueous ammonia

I am a physicist who has run into some chemistry in the lab (and unfortunately, I've completely evaded any formal training in chemistry). I have exposed some samples (I think details of the sample are ...
-4
votes
2answers
25 views

Checking how chemically plausible a molecular structure is? [closed]

I was working on a project, which dealt with the plausibility of a chemical structure. So i wanted to know on what basis can i check it? It would be nice if someone could list down all the features ...
2
votes
1answer
39 views

Can I use an acid other than sulfuric for hydrogen peroxide determination?

I would like to perform a permanganometric titration of hydrogen peroxide at home following a procedure similar to http://www.titrations.info/permanganate-titration-hydrogen-peroxide, i.e. the ...
-2
votes
1answer
26 views

How do I extract pure lactic acid from the mixture shown below? [closed]

How do I extract pure lactic acid from the mixture shown below?
0
votes
1answer
13 views

How to recalibrate qpCR reading when incorrect qty of solution is added during DNA elution step?

I have 20 viral DNA samples collected for 6 time points. The DNA content varies over time My DNA extraction protocol step suggests that in the last step of the protocol during elution I had 100uL of ...
1
vote
0answers
36 views

Spectrophotometry: shifting absorbance curves vertically so isosbestic points match

We're measuring reaction kinetic parameters of a hydration reaction (Co complex) by measuring the absorption spectrum a different time intervals, and calculating the ratio of product to reactant by ...
0
votes
0answers
25 views

SPE recovery greater than 100%?

I am evaluating a paper Gan et. al. 2013 (https://doi.org/10.1016/j.chroma.2012.11.081) Table S4 (see image below) and I am focusing on evaluating the percent recovery for using different solid-phase ...
0
votes
3answers
79 views

Is it possible to measure light absorbance for analysis of lead concentration without photospectrophotmeter

I’m designing an experiment which requires I measure final and initial lead concentrations for the determination of aqueous lead uptake by different mediums. Because lead concentrations would be ...
5
votes
1answer
89 views

What is “dithreitol”?

The article by Hu et al. [1] mentions a compound "dithreitol" in the Saliva Proteome Analysis section (emphasis mine): For the "shotgun" approach, saliva samples (1 mL) were pre-fractionated with ...
0
votes
2answers
51 views

Effect of the counterion on the colour emitted by a metalic salt

Could someone please enlighten me on what would be the theoretical effect of a counter ion on the colour of the flame emitted by a metallic salt in a flame test? Eg. NaCl - what would be the effect of ...
2
votes
1answer
28 views

How concentrated does the analyte solution need to be in order to perform a (chelatometric) titration

I’m currently investigating a method to chemically pretreat cellulosic waste as bisorbents for enhanced uptake of lead in water. I intend to measure the initial and final concentration of water to ...
0
votes
1answer
40 views

Cause of m/z = 56 peak in 4-methyl-1-pentanol

This is the mass spectrum for 4-methylpentan-1-ol: From its structural formula, what could be the fragmentation which results in a peak at $m/z = 56?$ I was considering a few possibilities; could it ...
-2
votes
1answer
27 views

Problem with determining the mass value of a soil sample for gravimetric calculations [closed]

I'm having some trouble with how to determine the representative mass value of a prepared soil sample for calculating its $\ce{Cl-}$ concentration in ppm (mg/kg). Recently I carried out a gravimetric ...
0
votes
0answers
18 views

When an electron is excited to a singlet state, must it flip its spin state to enter the triplet state and flip once more to the ground state?

I understand the Jablonski diagram in that it has intersystem crossing from the singlet state to the triplet state, but how many spin switches are necessary to complete to phosphores? When an electron ...
0
votes
0answers
15 views

Application of ISO/DIS 18219 Leather - Determination of chlorinated hydrocarbons in leather?

The following norm is for the analysis of leather: ISO/DIS 18219 Leather - Determination of chlorinated hydrocarbons in leather This regulation allows to measure short-chain chlorinated paraffins (...
0
votes
0answers
34 views

Writing mass balance equations of solution containing EDTA, metal, and other ligand

I am a first-year undergraduate student so my knowledge of analytical chemistry is limited but we are given a homework question that seems too difficult to me. Here is the question. EDTA is a ...
2
votes
1answer
82 views

Why is absorbance in UV-VIS spectrometer negative even after calibration?

I was collecting data to plot a calibration curve using pure beta-carotene sample. Prepared 5 different concentrations of beta-carotene dissolved in methanol. Pure methanol was used as blank. However, ...
2
votes
1answer
43 views

Why can zwitterions be difficult detect by HPLC-MS?

I understand that to separate molecules by HPLC (or SFC) you commonly adjust the pH of the mobile phase to get preferable charges (i.e. negative charges) on the molecules - so that they interact with ...
3
votes
2answers
51 views

Where do the percents in empirical formula questions come from?

A typical empirical formula problem reads something like this: Determine the empirical formula for a compound that contains 35.98% aluminum and 64.02% sulfur. source How would those percentages be ...
3
votes
1answer
78 views

Is there a list of must-have columns for LC-MS/MS used in biochemistry/clinical lab setting?

Considering a wide variety of chromatographic columns used for (U)HPLC based on phase type (normal or reverse); column dimensions (geometry, length, inner diameter); particle material $(\ce{SiO2},$ $\...
0
votes
1answer
44 views

Why does the concentration of the acid equals that of the base at the mid-point of titration? [closed]

Consider this graph of the titration of a weak acid and a strong base: The buffering region is strongest at the midpoint of titration because there is equal concentrations of acetic acid and its ...
1
vote
2answers
89 views

Why is H⁺ ion considered the source of acidity, and OH⁻ considered the source of basicity? [closed]

As the title implies, what caused the association between $\ce{H+}$ and acidity, and between $\ce{OH-}$ and basicity?
2
votes
0answers
50 views

What are common solvent removal methods?

In a laboratory setting, the most common solvent removal method is rotary vacuum distillation. This is something I have performed many times, starting in organic chemistry labs. However, I am ...
0
votes
1answer
51 views

Spectrum Of Metals [closed]

Recently, I've read that when metals are exposed to a high voltage source, metals produce a spectrum. I am curious on what is the minimum value of that 'high voltage'? Is the spectrum due to the high ...
1
vote
1answer
42 views

Setup for Sensing change in concentration of NaCl

I am making a sensor to sense the change in concentration of NaCl. My background is in electronics and chemistry is not my strong area. I got some screen printed electrodes, with Silver (Working ...
2
votes
0answers
26 views

UV-spectrophotometer analytical method for doxycycline hyclate and tylosin tartrate powder [closed]

I am trying to detect tylosin tartrate from the mixture of doxycycline hyclate using $\pu{0.01 M}$ $\ce{HCl}$ as solvent, and waveleghth of $\pu{290 nm}$ for detecting tylosin tartrate in UV-...
-2
votes
2answers
36 views

Solubility and wetting of substances in water [closed]

We have seen that, when we pour salt in water then it gets dissolved, that means it is soluble in water. But when we pour sand into water then it doesn't dissolve in water, that means it is insoluble, ...
-1
votes
1answer
33 views

What causes the differences in price in home testing kits for lead in water? [closed]

The price differences between home testing kits to test tap-water for lead are huge. 20 dollar will either buy 1 test kit or 100 test strips. Both are intended to test drinking-water safety. What ...
0
votes
0answers
13 views

Extraction of Chitosan

Does the temperature and duration during oven drying will affect the chemical properties and the quality of the chitosan that will be yield after deacetylation? Any help is highly appreciated. Thank ...
0
votes
1answer
66 views

Is it safe to touch salts given to you for analysis? [closed]

In our chemistry practical paper (High school level), Inorganic salt analysis is one of the questions asked. We are given a petri dish with a sample of salt and are asked to find the cation and anion ...
1
vote
0answers
28 views

Risks of using organic mercury compounds in analytical chemistry

I'm interested in speciation analysis. Hearing of fatal accidents with organic mercury compounds made me wonder about the risks for the analytical chemist trying to determine Hg species in foodstuff. ...
0
votes
0answers
17 views

How to account for the common ion effect on osmolarity quantitatively?

In adjusting the osmolarity of a solution of Benzalknonium Cl, Disodium Editate, and Disodium borate/boric acid buffer to be isotonic (about 290 mOsm), the addition of NaCl showed unexpected behavior, ...
-1
votes
2answers
84 views

What is the principle of RP-HPLC? [duplicate]

Is the following statement the correct way to explain principle of RP-HPLC? It works on the principle of hydrophobic interactions hence the more nonpolar the material is, the longer it will be ...
0
votes
0answers
32 views

How can a DPPH assay to measure antioxidant activity of beta carotene be conducted?

I am currently doing some research regarding beta-carotene. With reference to other sources and their methodoloy for DPPH assay, I conducted my experiment but failed to find any significant peak in ...
0
votes
0answers
23 views

Ideal characterization technique to study behavior of heated metal nitrates

I have 3-4 metal nitrates as precursors for my coprecipitation reaction. I need to study the behavior of each individual nitrate and also of various combinations at 60 degrees Celsius, which is my ...
1
vote
0answers
15 views

LIF spectrum with laser-coupled levels lines as the strongest

Why, if I excited the OH molecule Q-branch transition, my LIF spectrum (recorded during and after the laser pulse) does not result in only Q line being the most prominent, but also P and R lines with $...
0
votes
1answer
49 views

Is it possible to obtain the amount of air required for a combustion analysis?

I'm not very sure if the required amount of oxygen (I assume) can be found by only knowing the amounts of the produced subtances after a combustion. To illustrate this I found this problem: $1.14\,...
2
votes
1answer
83 views

Conditions for choosing quantifying and qualifying ion in LC-MS/MS

In my PhD-work, we are trying to develop LC-MS/MS methods for targeted analysis. Usually, I determine my quantifying ion/fragment based on a few different criteria: If there is a 13C internal ...
3
votes
1answer
80 views

Why is high molar molar mass a requirement of good primary standards for volumetric analysis? [closed]

I have been taught that using primary standards with a relatively high molar mass will reduce the error between the equivalence point and the end point during titration. However, I am unsure as to why ...
1
vote
2answers
57 views

Separation and qualitative identification of cations

A liquid problem may contain the following cations: $\ce{Pb^{2+}}$, $\ce{Cr^{3+}}$, $\ce{Fe^{2+}}$, $\ce{Ca^{2+}}$, $\ce{Fe^{3+}}$, $\ce{Ag^{+}}$, $\ce{Au^{3+}}$, $\ce{Co^{2+}}$. I need to devise a ...
3
votes
2answers
69 views

Electron Ionization and the Franck-Condon Diagram: vibrationally excited and vibrationally ground states

I am currently studying Mass Spectrometry: A Textbook, third edition, by Jürgen H. Gross. On page 41, the author says the following: As explained by the Franck-Condon diagram, hardly any molecular ...
2
votes
1answer
196 views

Can 2‐chloropropane and acetyl chloride give the iodoform test?

Can $\ce{CH3-CHCl-CH3}$ and $\ce{CH3COCl}$ give the iodoform test? I thought $\ce{CH3COCl}$ having the keto-methyl group would show the iodoform test, while $\ce{CH3-CHCl-CH3}$ will not since it's ...

1
2 3 4 5
16