Note: Lots of information in this post is outdated.
You can find updated version, many new findings and more companies compared on ELR website.
Long time lurker, first time poster. This website helped me so much and i felt that i need to contribute somehow (since i can't be of much help with my mixes yet). Note: I posted this same info on ELR already (hoping that even more vapers can find it useful + to create more pressure on manufacturers to be more transparent, which is always good for us/customers + more vapers can contribute and help make this info better and updated).
There are two reasons for this post:
1. to help vapers find basic information about diketones, oils, syrups in flavors of different companies on a single page; it's easier to find anything and to compare flavors of different manufacturers.
2. to help make companies become more transparent regarding the use of diketones, oils, sugars, syrups, GMO, aspartame, etc publicly. It is a health question and some vapers / their customers want to avoid those flavors, so why not give all the info, if there's nothing to hide?

Note: 6 most popular DIY companies are highlighted for easy following. TFA/TPA – The Flavor Apprentice/The Perfume Apprentice, FLV – Flavorah, FW – Flavor West, CAP – Capella, FA – Flavour Art, INW – Inawera, MB – Molinberry, LB – Liquid Barn, OoO – One on One, LA – LorAnn, DIYFS – DIY Flavor Shack, HG – Hangsen, RF – Real Flavors, JF – Jungle Flavors, WF – Wonder Flavours, GF – German Flavors, DEL – Delosi, MF – Medicine Flower
This list will be updated with any new findings (i ask for your help here; i wish one day this page will have all the info about flavors of premium liquid companies as well). I also hope the bottom listed companies in the table will soon figure out that they need to be more transparent if they want to gain vaping community's support.
TFA/TPA – The Flavor Apprentice / The Perfumers Apprentice

Note: shown are only flavors with the highest levels of A or AP (over 10,000 ppm = 1%). You can find more info about each of their flavors here:
http://shop.perfumersapprentice.com/specsheetlist.aspx?cas=600-14-6 – flavors with AP (40+ flavors)
http://shop.perfumersapprentice.com/specsheetlist.aspx?cas=513-86-0 – flavors with A (60+ flavors)
http://shop.perfumersapprentice.com/specsheetlist.aspx - all flavors
Their DX line contains zero diketones.
MB - Molinberry

Note: Very low levels of Acetoin were found in 6 of their flavors only (all other 68 flavorings are completely D-A-AP free).
More info on their website.
FLV – Flavorah

Note: Shown are only flavors with more than 1,000 ppm of Acetoin.
More info about diketons in their flavors: www.flavorah.com/safety/
RF - Real Flavors

Note: Listed are flavors with more than 1000ppm.
They say 'Testing done at recommended usage levels' (testing mixed juice, not liquid in a bottle). Since recommended usage levels are 1-2.5%, their 'less than 25ppm' means up to 1000-2500ppm.
Find more info on their website. (thx @Mattp169)
LB – Liquid Barn

Note: Shown are only flavors with more than 1000 ppm of A/AP.
Find more detailed info about their other flavors at www.liquidbarn.com/pages/quality
OoO – One on One

Note: Shown are only flavors with more than 10,000 ppm (1%) of A/AP.
Detailed info about diketones in their flavors https://cdn.shopify.com/s/files/1/0261/1345/files/OOO_Usage_File.pdf?13036354632880998590
FA – Flavour Arts
The information on their website is quite confusing and they cannot list their vaping and kitchen flavors separately due to legal reasons (blame regulators, not a company for that). Here is how you can find everything:
FA's official site is here (all flavorings listed).
Find out which their vaping flavors are here (all D/AP testings are there as well; about 130 flavors).
All flavors not on that list are NOT suitable for vaping. This includes flavors like Butter, Cream Whipped, Milk, Pandoro, and about 30 other flavors. You can find these flavors here.
FA says those flavors are some oil-based flavourings, and some that contain ingredients which are deemed unsuitable for vaping (besides oils, this may mean D/AP and/or other baddies and i would believe their researchers who are one of the best in the industry, so it is probably cool to avoid those flavors).
The black spot remains hiding information about Acetoin levels in any of their flavorings, which is unacceptable. (thx @AndriaD and others for clearing some things)
DEL – Delosi (Nicotine Labs)

Find more info at nicotinelabs.com or delosi.com
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