TDS TOC COD Spectral Water Quality Detector (Banggood, Aliexpress: Battery: built-in 200mAh Li-ion battery, Duration of use: standby for 20 days, Charging time: 2 hours, continuous use more than 500 times, Product material: ABS and PC (the best price with coupon)).
Go down and check coupons out. Remember to check price history if it is available. Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There are no coupons available at this moment in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): TTxBG10, aff7off, bgssaff9, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for TDS TOC COD Spectral Water Quality Detector? There we go. The lowest price was: $39.09.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).